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Discussion Starter · #1 ·
Hello everyone. Gotta say this is a very informative forum.

I'm not a pocket bike owner though I really do like them. I do have a 49cc piston ported engine that I recently acquired and am looking to modify it. LOL, it was a freebie from the neighbor who was throwing a scooter to the trash and I happens to be passing by. Picked it up, cleaned the engine and the spark plug real nice and checked the carb to see if any gunk was present. Made sure everything was in check and put some new gas in it. Three pulls later, it was purring like a little kitty. And to think that I was about to shell out a pretty penny for a GP460 from DDM!!!



Well, it will be going into this...



It my custom built (by me) cruiser trike. It's inspired on the drift trikes that are making it big into the scene. I just love to modify things and saw those cool looking big wheels and gave me a really cool idea for the weekend trips (in style!!!) to the beach and some cold ones.

Well, I've been reading a lot on two stroke engines and more so on how to mod this specific ones. Gotta say this forum is well informed and most everyone is willing to help any way they can. That is just fabulous!!!

So at the moment I'm interested in slightly modding the engine to give it a bit of a snappy feel to it. Just want to get the trike running with an engine that can at least move me from one place to the other without much effort. I am settled on a velocity stack and timing key. Already reworked the carb throttle linkage to make it open full by filing the derlin material on the linkage stopper. Also disassembled the engine and filed down most all the excess aluminum from the ports and the excess welds on the inner part of the exhaust flange. In the meantime, I think it'll stay like this until I finish the project. But I do want to order a nice exhaust.

I've been looking at some that I could modify to suite my project right. Narrowed it to these...





So what you buys think? Which should I go with or which do you think will be easier to mod and be most effective after modding?
 

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Git R Dun PBracer
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Welcome the planet!

Very nice frame. I like the rear end setup.
 

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French Fries N Cheese
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Welcome to the planet! nice trike you got there, I really like it.. the first pipe you posted is probably the most easy to deal with since it is bolt on. you can find it for like 45 bucks on ebay too, brand new from china.

I recommend you get a Walbro WT603 rebuilt kit from ebay aswell to get the most out of that carb. that will run you about 18 bucks shipped.

another thing you could to if you feel comfortable working with a dremmel, is put a 3rd port in the cylinder, and window the piston and index the exhaust port, and you will be getting the maximum out of your headkit.

The flywheel and clutch can be lightened to increase lockup RPM, and the crank can be change to a fullcircle crank.

These are just ideas, it really depends on how far you want to take this project, how reliable you want your engine to be.

dont forget Loctite, yamabond and high temp RTV gasket maker...

Hope this helps.
 

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Discussion Starter · #5 ·
Welcome the planet!

Very nice frame. I like the rear end setup.
Thanks Repo. It's a 1" live axle setup rolling on kart bearing hangers. Almost all of the parts are kart parts but did have to modify some to fit my needs. Tube cuts where made using a tube notcher. Angles, measurements, parts, etc, all I sourced locally or bought through the web (eBay and major karting sites). The front end is a basic 1 1/8" thread-less box setup on 20" wheel. Vintage Shimano Via high flange hub that I will be modifying to accept bearings. It's been a very cool project to do, though a very slow moving one.

Hey, can you shine some light on the exhaust thing? I'm unsure of what would be the best option, being less of a hassle to modify and still yielding great results.

I'm thinking the first option would be the best as it's been proven to be a nice flowing exhaust giving good performance (as to what I've read). Will not be so much of a hassle to mod either. But I prefer the second option as it is the best looking and will almost be a direct fit. The website says it will need "extensive mods" to the manifold (flange?) in order to fit into the 43/49cc engines, but it will bolt right up to the lesser cc'd engines. Could this be bolt holes not lignin up or port dimensions being different (nothing a little dremelimg wouldn't fix)? And also, will it actually flow as much exhaust gas as the 49cc will need? The exhaust outlets seems a bit small to me (maybe I'm just wrong here). The third option would be the coolest and looks like it would deliver the best performance when completely modded to suit my build. The problem is that I would have to basically make a complete manifold from scratch or buy an existing one and modifying it to work properly. So, this will end up being the most expensive.

Well, what would be your choice based on experience (or anyone else's)? Or any other mod that you would suggest other than porting and blueprinting (I will be doing this once the project is up and running)?
 

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Discussion Starter · #6 ·
Welcome to the planet! nice trike you got there, I really like it.. the first pipe you posted is probably the most easy to deal with since it is bolt on. you can find it for like 45 bucks on ebay too, brand new from china.

I recommend you get a Walbro WT603 rebuilt kit from ebay aswell to get the most out of that carb. that will run you about 18 bucks shipped.

another thing you could to if you feel comfortable working with a dremmel, is put a 3rd port in the cylinder, and window the piston and index the exhaust port, and you will be getting the maximum out of your headkit.

The flywheel and clutch can be lightened to increase lockup RPM, and the crank can be change to a fullcircle crank.

These are just ideas, it really depends on how far you want to take this project, how reliable you want your engine to be.

dont forget Loctite, yamabond and high temp RTV gasket maker...

Hope this helps.
Thanks Mathieu on the trike comments and recommendations.

I plan on opening the engine and porting/blueprinting it as I've read on some posts, but for the moment I want to stay with external mods. They should make the engine feel a bit peppier without really having to get deep into modifications. The clutch arms mod seem good but if I take a tot of weight, will it stall too much on rpm's and burn too much clutch? I want the trike to have good power and move me reliably around town and nearby municipalities in around a 20 mile radius. Don't want a real racing engine that will need high octane fuel each time I want to ride. So, kins of hesitant on full circle crank and third ports and such. I do like the piston mod about raising the skits and drilling the holes on the upper part of the pin. It seems to be pretty straight forward and not too risky. Just as long as I clean edges and surfaces smooth.

So, for now:

V-stack
Rocket key
Piston mod (possibly in the very near future)
Exhaust pipe

So, you recommend the Pro Jet exhaust. Yes, I think that I can cut it on the last weld seam and rotate it so the muffler faces somewhat backwards and to the side. Should be fairly easy. But I really would like to use the second option. It will fit really nicely as I've seen pictures of it installed. The stated manifold modification does not scare me. I just want to know if it flows enough for a 49cc engine that will be modded in the future.
 

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French Fries N Cheese
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If you're ready to take on the task of moding it to fit, the second one will probably offer much better performance than the first. you might need to make your own flange from a piece of 1/4" aluminum or steel, then weld that to the pipe, or make a flange that fits inside the pipe.

If you're going to use this thing to commute you better get the real walbro carb rebuild kit, because the rep pumper carb is poorly built and doesent function quite like the real thing, the rebuild kit will make it alot better though, and all the parts fit. Also adjust the squish on the motor, and yamabond the head down so you dont get any compression leaks. Get a NGK iridium sparkplug, idk if your head takes 10 or 12mm plug, Im guessing 12. buy a few of them as you might fowl one up tuning the carburator. Replace ALL the hardware, and lubricate the crank shaft and bearings, piston, piston bearing and pin, cylinder. Lastly, replace all the hardware, and use high temp resistant loctite.

If you lighten your clutch lighten the flywheel to try and keep things balanced.

These things are assembled by kids somewhere in china, the quality is terrible, so unless you really make everything right yourself, they break down often. The more you put in, the more reliable it will be. if you're going to use it to commute, then you have alot to do to make this thing get you from A to B without having any worrys.

Also good idea to have a good ammount of replacement parts on hand, because you will hate waiting for something coming from china if and when it breaks haha.
 

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Thanks Mathieu on the trike comments and recommendations.

I plan on opening the engine and porting/blueprinting it as I've read on some posts, but for the moment I want to stay with external mods. They should make the engine feel a bit peppier without really having to get deep into modifications. The clutch arms mod seem good but if I take a tot of weight, will it stall too much on rpm's and burn too much clutch? I want the trike to have good power and move me reliably around town and nearby municipalities in around a 20 mile radius. Don't want a real racing engine that will need high octane fuel each time I want to ride. So, kins of hesitant on full circle crank and third ports and such. I do like the piston mod about raising the skits and drilling the holes on the upper part of the pin. It seems to be pretty straight forward and not too risky. Just as long as I clean edges and surfaces smooth.

So, for now:

V-stack
Rocket key
Piston mod (possibly in the very near future)
Exhaust pipe

So, you recommend the Pro Jet exhaust. Yes, I think that I can cut it on the last weld seam and rotate it so the muffler faces somewhat backwards and to the side. Should be fairly easy. But I really would like to use the second option. It will fit really nicely as I've seen pictures of it installed. The stated manifold modification does not scare me. I just want to know if it flows enough for a 49cc engine that will be modded in the future.
You can mod that beta50 exhaust....I put a similar exhaust on my Viza Viper scooter...It looks kind of spacey as told by me from other members but it works just fine.....



Heres another exhaust modification made by me...Its my Dual chamber rev pipe design and it works great

 

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Discussion Starter · #9 ·
If you're ready to take on the task of moding it to fit, the second one will probably offer much better performance than the first. you might need to make your own flange from a piece of 1/4" aluminum or steel, then weld that to the pipe, or make a flange that fits inside the pipe.

If you're going to use this thing to commute you better get the real walbro carb rebuild kit, because the rep pumper carb is poorly built and doesent function quite like the real thing, the rebuild kit will make it alot better though, and all the parts fit. Also adjust the squish on the motor, and yamabond the head down so you dont get any compression leaks. Get a NGK iridium sparkplug, idk if your head takes 10 or 12mm plug, Im guessing 12. buy a few of them as you might fowl one up tuning the carburator. Replace ALL the hardware, and lubricate the crank shaft and bearings, piston, piston bearing and pin, cylinder. Lastly, replace all the hardware, and use high temp resistant loctite.

If you lighten your clutch lighten the flywheel to try and keep things balanced.

These things are assembled by kids somewhere in china, the quality is terrible, so unless you really make everything right yourself, they break down often. The more you put in, the more reliable it will be. if you're going to use it to commute, then you have alot to do to make this thing get you from A to B without having any worrys.

Also good idea to have a good ammount of replacement parts on hand, because you will hate waiting for something coming from china if and when it breaks haha.
Yes, the second one seems to be a better performing exhaust.
Will do the yamabond, got half a tube from my 2.0L Suzuki Sidekick Biild.
Think I'm gonna buy a new carb. The stock one is shot, or I killed it. I know it's the thin rubbery thing that has a rounded peace of metal that looks kinda like a diaphragm that pushes a valve under it. When I was installing the four lower bolts, one corner of it got pinched with the bolt and got broken. So when y pump the primer, the carb leaks right where that rubber goes.

So, what carb do you guys recommend for me? Is the walbro 603 copy a good choice? Should I just buy the rebuild kit which will be way cheaper? My carb at the Venturi as well as the entrance is 15mm and I understand that the 603 copy is 15mm also at the venturi though bigger at the entrance (16mm?).

Well, I'm looking forward to your opinions on the carb. Really need to fix this. Thanks for all the help so far. Nice to see people jumping in to help a newbie get it going.
 

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Discussion Starter · #10 · (Edited)
Cam, I've been reading a lot of your posts and they're veeeeery informative. You do now your ****.

Yeah, the beta50 pipe would certainly be the better project to have as it would be way cool and really perform well. The thing is that it will end up being the most expensive. The pipe itself I found a good price on it but shipping is almost double the price of the exhaust so that killed it for me. And to have it modified when it arrives... Naaahhhh to much $$$.

I'll go w the second choice. Exhaust seems to be a good performer and it is priced right including shipping and all. Still, the beta pipe could be on the future if I continue on this hobby, which really like.

Your modded exhausts are really cool. The dual chamber exhaust is really ingenious. Kinda has a Frankenstein look to it... Hahaha. Awesome...

Thanks for the suggestions.
 

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Discussion Starter · #12 ·

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Discussion Starter · #14 ·
Mathieu, what about the hda-223?

I was thinking, since I should go with brand parts and I will be spending the money, I should buy the best I can for the money. So the hda-223 and a ADA manifold (for the gp-460) will cost me around $100 w/ shipping. The 668 kit you suggested costs like $80 shipped. The 603 is a bit more. So for the money, the 223 and ADA manifold seem reasonable.

What do you think? Do all three have a 31mm mounting pattern?

Also, thought that the manifold is needed since non of the 3 Walbro options incorporate any vacuum(?) port for the pumping action as the china knockoffs do. So I nderstand that I need to drill a hole somewhere in the case or manifold to route a line towards the carb vacuum fitting. Is this correct or is there a better way to approach this? Maybe I can hold from buying the manifold and modifying the stock aluminum one the engine has.
 

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Mathieu, what about the hda-223?

I was thinking, since I should go with brand parts and I will be spending the money, I should buy the best I can for the money. So the hda-223 and a ADA manifold (for the gp-460) will cost me around $100 w/ shipping. The 668 kit you suggested costs like $80 shipped. The 603 is a bit more. So for the money, the 223 and ADA manifold seem reasonable.

What do you think? Do all three have a 31mm mounting pattern?

Also, thought that the manifold is needed since non of the 3 Walbro options incorporate any vacuum(?) port for the pumping action as the china knockoffs do. So I nderstand that I need to drill a hole somewhere in the case or manifold to route a line towards the carb vacuum fitting. Is this correct or is there a better way to approach this? Maybe I can hold from buying the manifold and modifying the stock aluminum one the engine has.
For the HDA223 your gonna need a remote pulse hole tapped into the engine case...The HDA183 is a big carb with pulse hole with two fuellines and comes on the GP450 engines that came on the Viza Viper Scooter back in 97........

The 603 is ok and the 668 is basically the same carb seeings they use the same carb rebuild kit.....[K20-WAT]
 

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Discussion Starter · #16 ·
Hey guys. Thanks for all the help you've given me so far. I really appreciate it.

I was checking the carb and it didn't seem to be too complicated to rebuild. I went looking for a low mower shop that I remembered back when I was a 13yo kid and had a minibike with a Honda clone engine on it. My dad used to take the bikes there when the engine gave trouble. So I looked till I remember well the rout we took to get there and to my surprise they were still open. I asked for a walbro rebuild kit and showed him the carb and he said it was not a WT carb, but a WYJ version. Well he had the rebuild kit and bought it. He was so kind as to mount all the parts, wich I was paying good attention, and set the jet adjustments. Only $18 including his work!!!

Got home and installed the carb. Gave it a couple of pulls but nothing. It seemed as if it was not getting good gas. I opened the low needle 1/2 turn and it wanted to start but died really fast. Kept doing the same proces and when if finally started and I adjusted the idle, I ended up having to give the low needle 3 full twists (from fully closed). Haven't fully adjusted the high needle but ****, isn't that low needle too open? It feels very loose and like could easily loose adjustment. Thinking of using a bit of blue locktite.

So since I got the carb running fairly well, knowing that it will need much fine tuning, I'm holding from buying the high performance carb. Will still buy the v-stack, rocket key and exhaust (second choice). Now, some suggestions were:

-no cilynder gasket and some yamabond/hondabond
-lightening the clutch and flywheel
-iridium spark plug

Anything else that could be done to increase reliability on this engines?
 

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Hey guys. Thanks for all the help you've given me so far. I really appreciate it.

I was checking the carb and it didn't seem to be too complicated to rebuild. I went looking for a low mower shop that I remembered back when I was a 13yo kid and had a minibike with a Honda clone engine on it. My dad used to take the bikes there when the engine gave trouble. So I looked till I remember well the rout we took to get there and to my surprise they were still open. I asked for a walbro rebuild kit and showed him the carb and he said it was not a WT carb, but a WYJ version. Well he had the rebuild kit and bought it. He was so kind as to mount all the parts, wich I was paying good attention, and set the jet adjustments. Only $18 including his work!!!

Got home and installed the carb. Gave it a couple of pulls but nothing. It seemed as if it was not getting good gas. I opened the low needle 1/2 turn and it wanted to start but died really fast. Kept doing the same proces and when if finally started and I adjusted the idle, I ended up having to give the low needle 3 full twists (from fully closed). Haven't fully adjusted the high needle but ****, isn't that low needle too open? It feels very loose and like could easily loose adjustment. Thinking of using a bit of blue locktite.

So since I got the carb running fairly well, knowing that it will need much fine tuning, I'm holding from buying the high performance carb. Will still buy the v-stack, rocket key and exhaust (second choice). Now, some suggestions were:

-no cilynder gasket and some yamabond/hondabond
-lightening the clutch and flywheel
-iridium spark plug

Anything else that could be done to increase reliability on this engines?

The stock piston ported pumper carbs are WYK series not WYJ.......
 

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That carb your looking at is a China WT-603, the venturi is 12.7mm and a 15.88 bore and you have a 15mm bore on the carb you have now. Put a boost fitting on top of your intake manifold and bottle. Rocket key for the flywheel, lighten it, and make a good exhaust.
I have an HDA223 19mm carb on a 20mm billet GS40 intake manifold or something like that and modded the holes to fit my piston port head. The manifold takes the pulse from the pulse hole in the head out a fitting to a tube & back to the bottom of the Walbro. See Photo
 

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Discussion Starter · #19 ·
Thanks guys. I already ordered the rocket key and v-stack. Will order the exhaust shortly after I get the trike completely finished and running as the motor has a muffler on it so I can use that in the meantime. I had to order some extra parts for the trike to make some changes as it is sitting way too low and will hit the road everywhere. So the parts are coming in and they should bring the frame up almost two more inches.

Will post a vid of the running engine as soon as possible.

EPR
Thanks for the insight on the 223 carb mod. I have good plans with this engine. In the near future I will be porting intake and exhaust. Loved the blueprinting cam2 does to his engines and I know I can do this too (have experience porting Suzuki 4cyl heads). Will do the piston mods to eliminate parachute effect and will be upgrading the carb to the 223 when I do these mods as I know he little WKY (thanks for the clarification cam2) will not supply the mix this engine will be asking for.

So, owe you the vid and I'll update you on the trike progress.
Thanks again.
 
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