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Ebay 47 or 49cc motors?

9K views 44 replies 4 participants last post by  CAM2 
#1 ·
Hi, does anyone use any of the Ebay 47cc or 49cc motors? And if so how are they? And I did search the forums for awhile and didn't find this listing. So if its already been asked a bunch of times before sorry. I'm a new guy here and just try to figure some stuff out.

And a second question is what pumper carb are most of you using for the MTA2 bikes. Are you buying the $50+ name brand carb or one of the knock offs?

Thanks in advance.
 

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#2 · (Edited)
Amazon , ebay it doesnt really matter. The engines are manufactured in china shipped in a huge box with minimal packing between each...

The difference in 40cc,43cc,47cc and 49cc is the mystery.....Some claim that the 40cc and 47cc are made up numbers to get the 44mm bore bikes into the country faster by qouting the engine power as being 2cc less...Some say its to give merit to those bigbore kits and Big Bore kits with FCC crank that was supposed to boost an engine to 52cc's......lol

Others say that the engine had a 32mm stroke back in the earlier years and now the engines are bumped up to a 34mm stroke to make them 49cc which makes zero sense to me because then there would be different cylinders sold for 32mm and 34mm stroke engines yet there isnt....

For aslong as I can remember theres no difference in strokes from 2003 and now and whats funny is you have one of the older 2004 engines that would definitely hold that fabled 32mm stroke crank inside the crankcase of the original engine.....

To me its just an identifier between reeded and piston ported engines.....



Theres no way to tell if youre getting a 40mm bore with 10mm pin or a 44mm bore with 10 or 12mm pin reedported engine without measuring the piston,pin and the cylinder too.Although there are some identifiers that differentiate the two if youre good at attention to detail and knowing what to look for.......

Heres a 40mm 10mm pin crank versus a 44mm 12mm pin hd ctank..In the background amongst the many pistons across the workbench in my hobbyroom on the upper righthand part of the pic is the 10mm journal and rod of the 43cc/49cc piston ported engine...….




Some Chinese made 2 stroke tool engines are a lil better than others but its very hard to know whos got the best but back in the day I used to hunt down The TM casted and SanRen built engines / TM and SanRen casted cylinders are the better ones IMO as the chrome on those cylinders are the toughest and they were casted with a lil extra power too.

The best and easiest carb to tune that offers the best benefits is buying the WYK192 15mm pumper carb setup for $20-25 bux...…

This is the pumper carb setup........Youll also need a fuelline kit from Home Depot

https://www.ebay.com/itm/Racing-Car...695055?hash=item23baac14cf:g:8KQAAOSw0w1ct9y6

For the engine I'd buy this one because the transmission is an extra bonus that you can resell for $25-30 bux to recoup back money....Best part is it comes with an aluminum pullstarter with aluminum claw too

https://www.ebay.com/itm/49CC-2-STR...b:g:GnEAAOSwOrpbwAYV:sc:UPSGround!11207!US!-1

cheap hp engine......

https://www.ebay.com/itm/52-49cc-Bi...918620&hash=item340553fc4b:g:zBIAAOSwMhVcDi-I

Heres what the engine looks like when its utilized as a tool based engine...……




Good Luck
 

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#3 ·
CAM2, your awesome, thanks again for all of the great information. If I get one of the pumper carbs that you showed me do I need to get a different throttle cable assembly? Or will the stock one work?

And you said that I should replace my crank seals since the motor is 15 years old and had been sitting for so long. Is there a easy way for me to check them to see if they are bad before I pull this little motor apart?

I fired the bike up yesterday with the choke on and let it run for a minute or so then turned the choke off and just let it idle for a few minutes. Then i just blipped the throttle and let it run for a bit and it seemed fine. I think my oil to gas ratio is still to high.

It was smoking a lot and took out those mosquitos. I'm going to drain the tank and go get some fresh super today and use a ratio jug to measure the oil to gas more accurately this time. I'm using Yamaha semi synthetic oil now. Is there any problem with using this or is a non synthetic oil better?
 
#5 · (Edited)
Just like EPR stated the throttle cable will work just fine...Just make sure you get a pusher spring.....

The pusher spring makes the throttle snap back really quick......



You do realize as 2 stroke mix sits the oil and gas seperate in the tank or gas can its sitting in and all the oil goes to the bottom being the heaviest between the two...It even seperates in the floatbowl and the fuellines…...LOL

That's another reason why I love pumper carbs ….You can shake the tank up then circulate the separated fuel back to get mixed also to get the proper mix with-in seconds after starting up...

Im sure that you can fathom whats going into the carb when you open the fuel valve so Im very sure your ratio was a lil off until the vibes of the running 2 stroker re-mixed the two in the tank for you....

With 2 stroke bikes you have to shake them up a lil before opening the fuel valve and starting it up.........

Im also sure theres a pretty nice collection of gas n oil in the j-bend of the exhaust pipe that needs to be blasted out....

Bone stock cag vid...…..This is an older model....Listen to it wheeze and sputter until I clean it out by flogging the throttle with that floater carb…...Listen to the idle run higher then lower

bone stock cag by Dizzy Gillespie, on Flickr

Modified cag with race porting and pumper carb vid...stock 43cc engine...

trophy cag modded exhaust 1 by Dizzy Gillespie, on Flickr

Stinger removed to reduce backpressure...Notice how the bike just stays running pretty consistent.....?

That's the magic of the pumper carb also pretty good tuning..

trophy cag modded exhaust 2 by Dizzy Gillespie, on Flickr

Heres the same cag with dual chamber rev pipe and frame remodel.....It needed an exhaust tone adjustment as it was super obnoxiously loud also needed a lil seating comfort for getting the rider weight over the frontwheel a lot better to keep it planted...Unicycles are fun but not at 35mph 18" off the asphalt….LOL

trophy cag modded exhaust 3rp by Dizzy Gillespie, on Flickr
 
#4 ·
Your throttle cable should work fine, changed my piston carbs to pumper carbs on Cags, never had a problem, yet, lol.
A China WT-603 pumper is about $35, a real Walbro is about $50. Intake manifold $18, V-stack $9, swivel $2, and throttle cable arm to hold cable $10 and then an air filter. The best place is Dave's Discount Motors, in Utah. davesmotors.com, they carry scooter and gas RC cars, parts, carbs and engines. Got an Walbro HDA48B 16mm carb for $30 on sell, best for the Cag cause it does not have a return line only an gas inlet. Similar to these photos.
 

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#6 ·
I worked on my bike again today. I drained the fuel and went and got some fresh super and mixed the oil 50.1 for the first time. It took long time to get it started. I just put the chock on and didn't give it any throttle. After it finally started I ran it for a minute or so on the choke and then turned it off and let it idle for a minute. Then it did the rev up and die thing again. I tried to get it to run again. And after bunch of sweating and cussing I drained the fuel again and pulled off that new Amazon carb.

I pulled my old stock carb apart again and cleaned it and blew it all out again. I reinstalled it on my bike added fuel again. And after about 3 pulls it fired up. I ran it on the chock for a minute then let it idle for about 2 minute or so.

Then me and my son rode it for about 20 minutes. It lives again!! My new plug comes in on Monday so I will install that and see how it goes. Hopefully I can ride it for awhile and then put my body work back on and post a video on this old little bike.

Everyone has been super cool on this site and helpful!
 
#7 · (Edited)
Awesome to hear you didnt give up and got it running...Thats a pretty clean looking bike.........

This engine had low runtime of about 25 minutes before it stalled and they couldn't get it started then chucked it in the shed and forgot about it until they sold the house and were cleaning out the shed but as you can see it kinda sat in the wrong spot for those 10 years he said it was in there..........

The old owner was surprised when I didnt care of it ran of not I just needed it as a whole to revive and modify........Had it been started it wouldve ran very crappy..


 
#8 ·
Don't think that clutch would work very well either, lol. I have a bunch of new alum arm clutches that I was putting hp springs on, for some new hp engines I am building from parts. Some of them were hard to move, that's why CAM2 tells you to take them apart and make it work right. New parts don't always work right, sounds like the engine kept going lean which makes it rev high. If its hot you need a bigger main jet, stock is about .64, you probably need a .70mm jet to get enough gas. They have jet kits with a .66, .68, .70, .72, .75mm. The new carbs float level could be very low, which could run the float bowl dry. Or you could have had an air leak behind the carb, which would make run lean w/ high RPMs. On any carb, you have to remove the brass main jet, and the atomizer tube, and run a small wire thru w/ cleaner to get crap out that even air pressure won't remove. I would modified the new carb, many things you can do to make it better.
 
#9 · (Edited)
You're absolutely right about that one EPR...The clutcharms were very sticky from rust and oxidized aluminum...….The clutcharms would've engaged got stuck and the bike would've kept going or stalled..LOL

Funny part was the people selling the cag were only asking $30 bux for it too.....LOL

The older engines didn't have EPA strangleholds like restricted carbs and restricted exhausts also had a better casted carb with a slightly bigger mainjet so your theory about it being too lean seems to be spot on.....

You'll never get one of the older carbs brand new at this point seeings the carbs are so cheap to just replace when they give problems...

The rubber in the newer petcocks are a lot more reactive to ethanol now than they were in the older carbs too so they swell up and restrict fuel a lot lesser...….



I hope you don't think I magically cut the pipe in the right spot...I used a scope to find the restriction then gauged it with a rod...…..LOL
 
#11 · (Edited)
Yep...They used slightly better magnets in them.........

You have an old crank from a reed ported engine Im almost positively sure.....


There was a debate years back when i first joined about the stroke of a FCC to the stroke of a regular crank...

Get a small cardboard box or a flat piece of cardboard...Take one of your stock cranks and cut a 15mm hole for the crank arm to poke through....

Stretch the crankrod out to its furthest point and put a mark with a sharpie dead center of the rodhole..

Rotate the crank down 180 degrees to retract the rod and take the sharpie and make another mark dead center..

Pull crank up and measure the distance between the two marks..
Those of you all that have a crank laying around and want to give some input do the countrywide experiment and post up what you all get...

You should get a measurement of roughly 1.26" or 32mm's........
 
#12 ·
I might try that EPR, since I have 2 now. I have no idea what size main jet came in the Amazon carb. It is super hot here now I think its suppose to be 103 today so i'm sure that leans it out a bit.

The main jet on the new carb is a different style then the stock carb. It is just 1 piece that screws out and the old carb has the main jet and the base. I didn't see a size or # on either one.

I got my new NGK plug in the mail yesterday after noon so i'll install that and give it a go.

How fast should these old MTA2 bikes go with a 200 + pound adult on them? I'm going to try one of the gps speedometer apps.
 
#13 · (Edited)
Hotter doesnt always mean its gonna run leaner especially if you live in a place with high humidity....Water vapor takes place of air.....

If you live in a place with low humidity you would be correct........

The best and absolute way to tell how your engine is liking the tune is to pull the sparkplug and read it...Its been a common practice since the start of the combustion engine...…

2 stroke engines require a special kind of give and take tune to get the most power out of them aswell as overall useage...

The way the condition of the sparkplug looks gives you an indication of which way to go with the tune of the engine as in 2 stroke what seems too lean could be too rich and fogging the plug at wide open throttle instead of the engine sucking more air less fuel...…


With fixed mainjet carbs its harder to get that perfect give and take balance so they run on basically a flatplane powerband......

Soon if you get deeper into this hobby and do alot more riding youre gonna realize why I choose the streetfighter look....With the amount of plug pulling and carb tuning I have to do the lower half and front part of the body would be sitting on the bench anyways seeings it takes atmost 10-15 minutes just to remove the fairing and same time to reinstall not adding the time to fix the problem......That's ridetime lost...….Youre also gonna learn if youre gonna ride a lot more too you need to start buying more sparkplugs than 1 at a time... I buy my 2 stroke engine sparkplugs 5-10 at a time and always get the bulk buy discount too...

An older Mt-A2 went between 26-30mph without mods with a rider weight between 180-200lbs...Like I stated in many threads and probably here too that top speed depended on who manufactured the engine as some engines were alot more powerful than some others...

When I did my Cag cag cag build thread here back in 2011 when I was searching for build materials I ran across an ad for a cag that said it went 40mph.....I was looking at the pics and said to myself theres no way even though it had 7/55 gearing too.....



I gave the kid my GPS and told him to take a blast on it.....He did,,I read the results and he went 39.7mph on a bone stock 40mm bore engine with 7/55 gearing..Only mod was a stinger delete..LOL

I was gonna buy it anyway and even though there was no debating his claims the overall condition of the bike was quite rough so he accepted half of what he was asking which was $20;-he was asking $40.....LOL


I also built a 2004 Ziemini Mt-A2 cag with a 5 port 2pc cylinder engine with a 7/49 gearing plus a modded stock exhaust with 6" belly extension and a 19mm Del rep carb that nobody else could ever get tuned on a cag until I achieved it...

I just put the engine together like an average joe would and with my 160lb brother on it and got 49.3 mph out of it but it didn't last very long..…..After a rebuild and refinements I got an extra 3.7mph out of it...….

3.7mph seems like a small number but if you compare the difference between 32 & 34mm stroke engines you're only discussing 1/16 of an inch also to mention if two cags raced and one was 3.7mph faster than the other after running wide open for an hour the faster cag would be over 3.5 miles further...…

That's quite a lengthy distance for such a puny variable...…...LOL

 
#15 · (Edited)
For $10 you can buy a Stihl MS250 16mm pumper carb, clone WT-813 w/ accel pump and choke plate that can be removed and use a Dave's 19 x 44mm V-stack with choke arm for more air flow. Best part is there is only a gas inlet, no return, perfect for a reed port engine. It will bolt up to a piston or reed port engine manifold. The hardest part was making & installing a throttle arm and swivel for the throttle cable.
DDM has a V-stack with built in choke plate now, 1 piece $10, swivel $2, throttle arm $10, about $35.
ADA racing .com has closeout on pocket bike parts. Billet alum throttle arms for $3
 
#16 ·
Hello gentlemen and ladies? I took pictures of my old carb to show you but my iPhone and my iMac aren't speaking to each other right now.

I put the new NGK plug in and got the bike started fairly easy. I ran it on the choke for a minute and then let it idle for about 2 minutes. and took it out foe a run.

It seemed to run good and it was pulling good. I got a short full throttle run and then backed off a bit. Then I went down the next street which is slightly down hill. And got a good full throttle pull.

I think that was the best run I've ever gotten on this bike. Then I just slowed down a bit and the motor just cut out. I checked to make sure I had gas in the tank and tried to start it a bunch of times but it didn't fire off.

It seemed like it wanted a few times but it didn't start again so I gave it a rest for tonight.

I think i'm going to replace the 15 year old coil like CAM 2 suggested.

What do you guys think?
 
#18 · (Edited)
I also think you should buy the new crankseals and replace them...…Theyre $7 bux and cheap insurance against any airleaks occurring at the crank at wide open throttle....

All of this isn't unfounded and part of the end of building a 2 stroke engine is doing a process called "Doing a Leakdown / Pressure test" which is something the Chinese never do when they build their engines...


A leakdown test tells if all your sealing points are correctly sealed on a 2 stroke engine and able to handle the pressure exerted under engine operation without a failure.....….I call it proofreading your build...LOL



Pull the sparkplug and see what it says.....Ive had engines run on the cusp of being too lean and killed the sparkplugs from thermal overload or even fouled it from "Glazing".......

If the sparkplug tip is white or gray in color you lean fouled/killed the sparkplug....

You might want to switch to a cooler tip sparkplug too if it is lean fouled /glazed....If youre running a NGK BM6A run the Autolite equivalent of the NGK BM7A

If the sparkplug tip is black in color you have a jetting issue or a coil going/gone bad......


Like EPR stated about possible culprit to the problem and Ill also add its a great idea and practice to always change the coil and cheap insurance too also to mention that the coil should always be changed when doing a small engine tune-up where the engine is over 5 years old or you're doing a topend rebuild...........


Too bad you didn't have a short vid of how it was running...Musicians have an ear for the tone whereas my dad used to say I have an ear for the tune..Airleaks too...LOL

Good Luck
 
#20 · (Edited)
Theres no video I know of but alls Ill say is its not very hard at all....Alls needed to do the job the easiest way would be to purchase a cheap steering wheel puller set from the local autoparts store.

https://www.ebay.com/itm/New-11pc-U...438985&hash=item5d3e1c5e47:g:rAoAAOSw~kVbn~JS

The process is simple after you remove the clutch,flywheel and woodruff keys from the crank...


You just use a small screwdriver or sharpened pick to remove the seal from the crank then you lube the crank with a lil 2 stroke oil and push the seal on flush to the case with your fingers.....


Removing the flywheel affords the availability to also order a brand new aluminum clutch also a rocket key and do the flywheel mod...........



12fin flywheel mod...…...
 
#25 · (Edited)
It appears to me the engine was running very very hot judging by that blackened/blued strap....,,..Most likely from an airleak or improper jetting……..If you were running rich there would be a blacker ring around the metal base and the white insulator porcelain would be alot blacker too...…….

Overheated and glazed sparkplugs are the types you don't want to see at all in a 2 stroker…A blued strap like that shows the engine went into a Zone where engine damage has occurred....Sometimes the piston melts and traps the rings in the ring grooves killing compression...


How much or lil damage it suffered I cant say but if you want to know pull the exhaust pipe and get bright LED flashlight and look at the condition of the cylinder also roll the piston to TDC and inspect the condition of the side of the piston that faces the exhaust port..

Heres an example of dangerously lean high heat conditions...



It also appears when you installed the new sparkplug you really didn't crush the crush washer properly on the sparkplug by using proper torque....Unless its a photo enigma I see a an open spot in the crush washer bead that looks like a place for air to get in but the main part of the deal is the crush washer should be more compressed looking like the two sparkplugs posted below...…



Heres what sparkplugs that come from a perfectly tuned engine looks like and take into account that they're pretty old and worn out too.....….....The plug is supposed to take on a butterscotch brown color...…..



Are you running synthetic based or regular 2 stroke oil?
 

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#24 · (Edited)
Yes indeed..You have the 40mm 40.2cc engine barrel................


The three barrels on the bench are are 40mm barrels and 3 of the 5 different brands...



The engine on the left with the reddish-orange colored clutchpads has a 44mm 49cc barrel...The one on the right has a 40mm 40.2cc barrel and makes the 4th different kind of 40mm manufactured out of 5 poctured here that I knew of at the time...…

Can you spot the differences ?

If you can youll now be able to tell the difference between the two..........

The top left barrel of the trio on the bench is the same cylinder manufacturer as your engine....The middle one is the most powerful manufacturer and the top right is the second most powerful 40mm bore cylinder manufactured..



These engines above are both 44mm 49cc engines...Engine on the left has the 12mm pin and engine on the right has the 10mm pin....
 

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#26 ·
I’m using some Yamalube semi synthetic oil. I had always run the 25.1 ratio before since the hand book said to do that for the first 5 tanks. The last time I rode it I had mixed at the 50.1. So I’m not sure if that caused a problem or not.

The motor still turns over fine. And I didn’t tighten the plug much past 1/2 turn on contact of the washer so it may not have crushed it properly.

I didn’t want to go to tight on the plug for fear of stripping it out.

I did wipe the plug off before I took the picture. And I hope the motor didn’t lean out and seize the rings.

I’ve never had a 2 stroke bike before. I have many years of riding and working on 4 stroke sport bikes and I road raced for about 7 years. But never did anything with a 2 stroke race bike or pocket bike.

CAM2 if the motor got to hot would it detonate or do anything else before it crapped the bed? It seemed to be running really well before it died.

The new coil comes in next week, so I guess I’ll try that before I inspect the motor.

Thanks for all of the help. 👍
 
#27 · (Edited)
The wiped out engine I pictured spun over fine too....It just wouldn't start...…….

As far as the oil...Is the oil formulated for 2 stroke engine use like yamalube 2-S Pre-mix and not for 4 stroke engines or2 stroke engines with oil injection units..;-Right?...Post up a pic of the oil you're using...….

I have 4 cylinder Yamaha motorcycles and use Yamalube semi-synthetic oil in them too but its 10w/40 and for wetclutch crankcases which is entirely the wrong oil to mix with fuel and run through a 2 stroke engine......

You'd get way better results mixing transmission fluid and fuel together...I know it would because I run it with my backpack blower and have been for over 14 years...Its a 2004 model broken-in on regular 2 stroke at 32:1 but always run on 50:1 Dexron/MerconIII Synthetic transmission fluid after that with 93 octane fuel and its still kicking strong with zero engine/carb problems...

The weedeater I have is slightly younger 2007 model but runs on same transmission fluid/93 octane fuel mix as the backpack blower with zero problems too….




It appears in my years of doing it I can now come to the solid conclusion that mixing trans fluid with fuel kills the harsh effects ethanol has on a carb aswell as engine internals has no ill effects and also seems to elongate the engines life by quite a stretch..Its also a detergent aswell as a lubricant so that definitely helps and is a pretty big factor....LOL

The theory behind your reason about not wanting to strip the sparkplug hole threads when properly torqueing down the sparkplug crushwasher mainly occurs when youre removing a hot sparkplug from a hot engine also installing a cold plug into a hot engine...Rule says you must remove & install sparkplugs in an aluminum head when both are cool to the touch which is room temperature...…..

You'll possibly get whats better known as "Galling of the Threads" when you fail to adhere to the rule and also to mention its pretty easy to feel when a crush washer is fully seated and properly crushed...Especially with a torque wrench..

You'll be surprised how much air gets sucked in and also how much compression you lose having that sparkplug as loose as you had it also surprised to know that the pressure that escapes erodes the sparkplug hole threads.....?

If I remember right It takes almost 2 full turns to fully and properly crush a sealing washer on a brand new sparkplug from the time it starts to get snug with the cylinder...……

Ask any technician who works at a sparkplug company about the ill effects of leaving a 2 stroke sparkplug loose by almost a turn and a half then tell them it was also ran wide open and then send them a pic of the plug....I guarantee they'll say things that aren't good.....

Using a lil anti-seize on the sparkplug threads also helps a lot in successfully torqueing and removing them and also to mention a racers trick to extending the life of the plughole threads too...

You mentioned sportbikes and racing..I did a lil of that myself as a weekend warrior on bikes that also got ridden on the street.......Do you have a compression tester?

One thing about engines no matter 2 stroke 3 stroke 4 stroke 5 stroke or 6 stroke they all need compression to run and should be part of a racers toolbox along with a leakdown tester......…….

You've never owned or operated lawn equipment like a 2 stroke weedeater ,chainsaw, concrete saw or backpack blower ever in your life?..

Its the same principal and useage also FYI back in the 70's and early 80's they had floater carbs on them especially the Homelite models..You couldn't flip them around like the pumper carb models without getting bathed in fuel and flooding the engine.....

By the description of the things you mentioned happening during the ride Id pull the pipe and look up the cylinder because that's kinda the same similar story I got from the old owner of the pocketbike with the wiped out engine I posted a picture of when I bought it...…

I think it would suck to wait for the coil then install it then pull your brains out trying to get it to fire up just to find out the piston started melting down and you didn't have enough compression...Its literally two screws to remove and pull the pipe to the side....Its even quicker to do a compression test.

The old sparkplug was most likely insulated well with burnt oil and ash also to mention Chinese made Torch brand..When that happens to a plug it lessens the intensity of the spark which hinders engine performance and heat build-up...Main part is that it was most likely seated tightly like it should of been with crush washer properly crushed.....

Post a pic of the old plug if ya can....don't clean it either...…...

One thing you have to remember and never never forget is these are Chinese gimmicks kinda like the goldfish in a bowl at the carnival that dies in a day or two if you don't properly care for it....LOL..

They were $169.00 through a pocketbike store and $237.00 shipped to your door brand new in the box under the ruse they are actual purpose built racing bikes …

If you bought every part of one of those cheapie bikes and built one from the ground up it would cost you almost 3 times more money than buying one whole…..Back then it was cheaper to just buy another....LOL

Back then they even sold what was called a stronger beefier framed and more powerful cags for $300-350.00....I had a couple of those models too and they were better built aswell as slightly faster...…....

With the trials and tribulations you have going on with your bike right now would you get much racing in with it as it currently has been running?

It takes a pretty good chunk of money and time to do modifications to make a cag a viable racebike that by the time you're done you could've bought an entry level aircooled/watercooled euro knockoff for $500/650 and had a lot more power and extra power potential despite similar wrenchtime to iron out the bugs.....Those bikes are modeled more for racing...…..

The engines on the pocketbike you have comes from industrial based tools and were never designed for minibikes....The engines are a ripoff of Robin brand tool engines evenwhich a reputable pocketbike company like Blata also did years before the Chinese ever did with the Blata 2.5 which was $1000.00 brand new and I know because I bought one brand new in 1999 and found out that in 2004 that Blata used Robin NB-411 brushcutter engines in their pocketbikes that were designated entry level racing pocketbikes with 3.5hp….

Heres a picture below of the exact engine mounted in your pocketbike frame...Its a 40.2cc brushcutter engine made by TM or SanRen..They also use them for trashpumps and power winches.….


When you look at the engine posted above as it is as a tool engine it gives the answer as to why the sparkplug boot is so odd looking....Reason is because they remove the cooling shroud too which reduces effective cooling.. Some cags were actually sold with it and lots of members removed them....LOL

Just realize these small engines heat up quite well when being worked as plain old industrial tools....Now think about the extra heat stress the engine has to go through with the extra load of a weighted rider most likely at temps in the heatrange you mentioned the other day...[103*]

I dont take my aircooled bikes or nitro r/c vehicles out when temps exceed 90*.....Not even my Harley or my oldschool Yamaha motorcycles....You could literally smell the humidity sizzle off the engines like steam from a hot clothes iron after taking a nice healthy run.LOL



Heavily modded 1989 Honda CBR600 with engine built to AMA racebike specs , 2012 BMW S1000RR , 2005 R6 ,2012 GSXR 750 , 1985 Suzuki GS550E....That's just a few of the sportbikes Ive owned over the years....LOL
 

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#28 ·
Here is the old stock Torch plug. And your right about the plug being way to loose. I’ll have to loosen the pipe up and look inside later. I messed with it a bit last night and it tried to start and would run for a second but I didn’t get it to fire off.

This is the 2 stroke oil that I use. When I pulled the new plug and checked the spark while I pulled the starter the spark seems very small.

I’m not sure if it’s getting a good spark or not.

And I’ve never had any other 2 stroke bike or tool. Just electric lawn tools. Hahah.

I’m not sure yet if I should keep messing with this motor or just go buy a stock type or a Hp type from EBay and try that.
 

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#29 ·
Well unfortunately I think I have to pull the plug on this patient. I didn’t think she is going to come back to life.

My curiosity got to me so I just moved the pipe like you said and here is the cause of death.

But I guess I really don’t if it was the crank seals leaking and letting air in. Because it was doing the run a little while then rev up and die before I put the new plug or 50.1 fuel ratio.

Or it just burnt up from the new plug not being tight enough.

So do you think the cylinder will be bad also?
 

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#31 · (Edited)
We have a code blue attention we have a code blue.....

Only way to find out if the crankseals went bad would be to totally unbolt the engine remove the clutch the carb and the flywheel then make a capoff plate for the exhaust and a capoff plate for the carb then use a leakdown tester tool through the sparkplug hole to pressurize the engine with 10psi of pressure then use bubbled soapy water to trace the key areas for leaks by dabbing areas with the soappy water using an acid brush...….

Kinda like the way you find leaks in a tire or bike tube but judging by the top of the cylinder on one of your pictures it looks like you have the telltale signs of a loose sparkplug with burnt oily spooge...……



Like Kitty said you can get a cheap cylinder and a set of crankseals along with a pumper carb setup and you can do a rebuild on it or you can just cut your losses on it to use it as a learning tool and buy a new motor with a pumper carb setup and start over fresh...

Once you pull the cylinder you can see how much of the damage the cylinder dome endured and a distinct pattern if the loose sparkplug started the meltdown or by looking at the piston top to see if the crankseals or lean jetting caused it...…

I have a feeling its a combo of the two maybe even 3..Ive seen those...You already had an airleak or lean jetting and the loose sparkplug sent it into orbit quick...…...

You create a cylinder condtion similar to an acetylene torch when you get an airleak in the upper part of the cylinder either through the copper washer on a 2pc cylinder or through a loose sparkplug...…



Sorry for your loss...…….
 
#32 ·
Well one thing is for sure, i'm learning a lot more about these engines than I ever knew before and quickly. Hahaha.

I'm surprised that the motor didn't ping or detonate etc. on its way to Valhalla. It seemed to be really going good before it burnt up.

I tried to find the info on here about which crank seals to use, Size etc. but I didn't see it.

I don't have a micrometer to measure them. So can any of you tell me what size I would need if you wouldn't mind?
 
#33 · (Edited)
The crank journal seals are both 25mm x 15mm x 7mm thick...Heres a link

https://www.ebay.com/itm/Engine-Cra...887587?hash=item239e5f1823:g:GhQAAOSws~pb7PVH

Heres a link for the topend kit...….

https://www.ebay.com/itm/Cylinder-K...m=182392383387&_trksid=p2047675.c100752.m1982

https://www.ebay.com/itm/40MM-BIG-B...04AAOSwrklVJYRu:sc:USPSFirstClass!11550!US!-1

Yes you definately are on a learning curve........One thing about 2 strokers is they do start to run really good before they give up the ghost prematurely...


Just be glad it happened to you with a cheap engine..


When I raced outlaw racekarts back in the early 80's that went 133mph with an IAME powered 137cc methanol huffing engine that had a 220 minute runtime between rebuilds and if the tune was just a lil off or an airleak developed the engine was a possible paperweight..

Thats why I had an rpm aswell as a pyrometer gauge on the steering wheel aswell as a leakdown tester tool to keep tabs on engine condition and be rest assured theres no airleaks.....


When I was racing I had to have 3 engines at 2 grand a pop....1 on the kart, 1 backup and one in Italy being rebuilt then airmailed back.......

I still have it too...........





I also have an oldschool 100cc Jr racekart ...

 
#35 ·
Wow!! Those carts look super fun. You have a wealth of knowledge. Thanks again for all of your help.

Now I just have to figure out if I go the small rebuild route for $30 or get the cheap hp motor for $110. Every one loves some extra performance.

CAM2 if I do the jug and seals what oil do you use inside the jug, rings and piston when you assemble it? A bit of the 2 stroke oil?
 
#37 · (Edited)
When I assemble my engines I use Lucas semi-synthetic. transmission fluid ……

IF youre gonna use 2 stroke oil get regular old Valvoline or gas station brand 2 stroke oil that's TCW-3 approved.That oil should be used for proper break-in too...



Like Kitty said those cheap HP motors are assembled and not built to be what they look like......

If you dont take them apart to blueprint and deburr the engine also to mention that if you get one with the Full Circle Crank youll have loads of harsh vibes aswell as whats known as touchy tuning problems especially with that 14/14 Del rep carb they put on them and it just may as last as long as the first engine..They don't even properly torque the headbolts down either which would cause a major airleak and another meltdown….

Id do the rebuild but Id also do mods to make improvements that change a tool engine into more of a real motorbike engine...

Using the old cylinder as practice material you can practice on grinding-in an extra 1 , 2 or 3 boost port channels into the cylinder to really increase power of what you were riding by up to 2 - 2.5hp and a lot more toque too...

Heres a 40mm stock cylinder I turned into a wicked lil beasty..If you notice something odd looking about the exhaust port...Its not odd its made to be that way..Not everything in life is conscentric identical parallel and even..

I even have one that's called the butterfly pattern....LOL





When you take the time to blueprint the fit and flow between the cylinder and the case halves you can slightly widen and polish the transferports and jug to enhance throttle response and snappiness........It also enhances power and revs..

 

Attachments

#40 ·
Ok, thanks again to everyone. Maybe i'll just get the cylinder kit and the new seals and try that.

I just want to have a little bit of fun riding and playing with the bike a bit. Not to race it, so the new kit may be the way to go.

What should the cylinder torque be and should I use some Yamabond on the cylinder gasket or just the gasket and the proper torque?
 
#41 · (Edited)
My racing days are pretty much over but my days of having things that are above the norm arent............LOL


These small engines with 40mm bore only have 1.6hp......These lil bikes start becoming fun at around 4hp..........


When you mod your first engine , get a good grasp on tuning and take it for a highly successful and satisfying ride youll feel like a god and pretty amazed too at how such a small engine could give so much....LOL

Best part is if you ever run across another with one and they have one of those 2pc headkits and you beat his azz with a stock appearing/looking engine...He will be none the wiser but highly dumbfounded....LOL

Lots of times Im all about teaching those types about the shock factor and to never judge a book by its cover...........LOL

Then sometimes that goes out the window too.....LOL


 
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