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i whould run the stock flywheel those lightend ones are to light and throws off the balance factor by alot

but i guess onley 11.59$

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Re: Pit Bike

Looking good, dude. This starter system has a lot of leverage, over stock, and you use the older stock flywheel, and different type starter housing they come as a set. You should look at www. banggood .com and search under 49cc pocket bike parts, cheap, direct from China, or www. aliexpress ,com
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Last edited by EPR; 12-31-2019 at 10:50 PM.
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Re: Pit Bike

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i whould run the stock flywheel those lightend ones are to light and throws off the balance factor by alot

but i guess onley 11.59$
If the piston is at TDC with the crank counterweight sitting oppositely at BDC and balance factor of the build is set at say 55-60% at the factory before the flywheel is ever installed or even a factor,,;-Where is the heaviest part of the flywheel at this point and how does that throw off balance factor if the weight of the magnet doesn't change whereas the only thing that actually changed is simply the rotational weight of the flywheel..?

If the way an engine is mounted also affects balance factor how can there be a balance factor on an engine that's taken from a brushcutter / auger and mounted way differently and operated with multi directional useage?

Explain how my balance factor was affected when I simply popped the flywheel off my 125cc 4 stroke Honda clone pitbike engine and replaced it with a much lighter inner rotor kit to increase throttle response and revs yet it idles perfectly , vibrates normally and revs like lightning...?

In my T-Maxx with .27 Sirio midblock...I just simply popped the flywheel off of the Traxxas 3.3 [.20] smallblock engine and put the .20 engine flywheel on my bigger .27 midblock engine....How badly did I throw off balance factor by using a Traxxas flywheel on a Sirio engine that's going on its 4th repinch of its second sleeve and still kicking azz over 12 years later?




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Last edited by CAM2; 01-01-2020 at 09:58 AM.
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Re: Pit Bike

You can buy just the center part of the starter housing and replace it with any pulley you need.

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Re: Pit Bike

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Originally Posted by BlackReef View Post
Just checkin here, alot of you have been very helpful. The pull starter came, didn't fit, and so I sent it back to Amazon. The carb came and I just immediately sent it back. I figure I will just do it right the first time and order the right parts. Waiting for my Amazon refund and will go from there. Thanks

I have everything in my cart, ready to go when payday hits!
You do know that on those ratchet pawl type pullstarters you must pull the pullrope while setting the pullstarter or the fully sprung pawls wont allow the center to pass through...….;- Right?

Its easier to remove the pullstarter part from the aluminum case..set the pullstarter case to the engine using the 3 screws then install the pull mechanism by pressing the ratchet to the pawls then pulling the rope to set it then reinstalling the 3 screws used to attach that.......

The pulling action flicks the pawls to allow the pullstarter to be set in place...

In any event its good that you actually got a better pullstarter………….…….

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Last edited by CAM2; 01-01-2020 at 09:37 AM.
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Re: Pit Bike

Quick update, finally had the funds to order the parts. I installed the new carb, pull start assembly, "rocket key" and flywheel. I also installed the new fuel lines. I drilled a hole on the bottom of the fuel tank to run both lines in, and then connected the other end of the lines to the new carb. There is no fuel shutoff valve now. Should I purchase a fuel shutoff valve? Im not familiar with this 'fuel return' type carb, it's rather interesting.

Anyways, I still can't get the bike started. I am getting good fuel flow on both in/out fuel lines. I thought for a minute that the new flywheel was not in the correct position in regards to the magnetos but there is a rocket key in there to make sure it stays aligned, so I guess that isn't the issue? I dont know, Im tired at the end of a long day lol.

Notice the flywheel, it appears it is scraping when it turns over:




Also, does this look correct for the 'rocket key'?



Here is a better picture. Notice the extra slack in the fuel lines, I will address that later once everything is running:




Another (minor) issue is that the throttle cable sticks a little bit with the new throttle cable attachment setup with the new carb. It kind of attaches at a sharper angle now, and the throttle cable runs real close to the exhaust pipe with new carb setup:




So right now I just need to figure out why the bike isn't starting. I do have the NGK spark plug in there, I didn't gap it but I figure that the bike would atleast crank when I turn it over.

Also the choke is on the opposite side of the carb, and nearly impossible to manipulate with the exhaust pipe being in the way, kind of sucks

Last edited by BlackReef; 01-12-2020 at 08:52 PM.
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Re: Pit Bike

First off, the key is backwards, the offset always faces the exhaust port even on the piston port engine, facing backwards, yours is 10 degrees retarded. When you change the flywheel you have to adjust your coil clearance, .020" then make sure it clears all around afterwards. Your cable needs an extra coil spring between the brass swivel and the cable holder bracket, hardware store, or, we all do that.
Can you post a photo of the choke and pipe??

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Last edited by EPR; 01-12-2020 at 11:38 PM.
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First off, the key is backwards, the offset always faces the exhaust port even on the piston port engine, facing backwards, yours is 10 degrees retarded. When you change the flywheel you have to adjust your coil clearance, .020" then make sure it clears all around afterwards. Your cable needs an extra coil spring between the brass swivel and the cable holder bracket
Can you post a photo of the choke and pipe??
Pic attached of choke. It's actually the front sprocket/clutch assembly that's in the way.

I will flip the rocket key. What do you mean that it is 10 degrees retarded? I notice the key moves quite a bit as well when I slide the flywheel on. I have to hold it down with a flat head screwdriver to keep it in place while I install the flywheel.

I read that I can apply two layers of electrical tape on the flywheel during install to create separation between the coil. Maybe because it is rubbing is the reason the bike won't start?
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Re: Pit Bike

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Originally Posted by BlackReef View Post
Pic attached of choke. It's actually the front sprocket/clutch assembly that's in the way.

I will flip the rocket key. What do you mean that it is 10 degrees retarded? I notice the key moves quite a bit as well when I slide the flywheel on. I have to hold it down with a flat head screwdriver to keep it in place while I install the flywheel.

I read that I can apply two layers of electrical tape on the flywheel during install to create separation between the coil. Maybe because it is rubbing is the reason the bike won't start?
The air gap between the coil and the flywheel is indeed a problem and expect some more problems with the coil too because when a coil makes contact with a magnet the coil or the flywheel magnets usually becomes compromised.....Ive seen magnets morph and the poles on a magneto flip because of it...…….I had to flip the pickup on one too [XR100]which worked for only so long before it went kaput for good......…….

The airgap is .020"...…...Tapes come in various thicknesses...I use a sliver of cardboard from a cereal box that's like 3/8" wide by 3-4" long...…...You sandwich the cereal box sliver between the coil and magnet..tighten the coil mount screws and pull out the cereal box sliver..

The pusher spring for the throttle EPR stated looks like this...………..



And yes the rocket key is placed in the crank slot in the "retarded" position......Not the worst case as it will enhance topend revs a lot more than it will enhance bottomend takeoff power and thats ok too with a lightweight 6year old rider under 100lbs riding it...…

Stock woodruff key sets the timing at a neutral Zero timing point...…..

When the raised offset is oriented to the right ;- its set advanced...[advanced gives more takeoff uumph].

When the raised offset set to the left on a reed inducted engine its set retarded...………[retarded gives more topend revs]

On some of my builds I have a 6.0volt auto advancing/retarding CDI ignition system which still retains the stock woodruff key..




On my twin turbo 5.3 LS powered Range Rover my boost timing master retards the timing for each pound of boost applied...Its pushing 16lbs of total boost so at full boost the computer is supposed to be retarding the beasty a full 16 degrees..Im going 20degres for safety...LOL.….This is done with a power programmer but essentially the same principal..If you apply too much boost without properly retarding the timing it can be quite detrimental for the crank and the whole engine at WOT,,,LOL

With your setup and level of where youre at the only thing I see wrong is the fact you set the airgap wrong...The engine has no porting or power mods and hasn't been degree'd to see where it actually stands so theres no real right and wrong in your case....Its when you start building stouter power with tighter squish tolerances and higher compression or having an adult rider aboard as a rider is when the choice of how the rocket key is set becomes a lot more critical.....

For the choke ….Flip the V-stack with choke arm 180 degrees...I usually put a slight bend in the choke flap so it makes slight pressure of the choke plate between the V-stack slot to keep the choke from dropping into the hole......……..

Good Luck

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Last edited by CAM2; 01-13-2020 at 11:28 AM.
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Quote:
Originally Posted by BlackReef View Post
Pic attached of choke. It's actually the front sprocket/clutch assembly that's in the way.

I will flip the rocket key. What do you mean that it is 10 degrees retarded? I notice the key moves quite a bit as well when I slide the flywheel on. I have to hold it down with a flat head screwdriver to keep it in place while I install the flywheel.

I read that I can apply two layers of electrical tape on the flywheel during install to create separation between the coil. Maybe because it is rubbing is the reason the bike won't start?
The air gap between the coil and the flywheel is indeed a problem and expect some more problems with the coil too because when a coil makes contact with a magnet the coil or the flywheel magnets usually becomes compromised.....Ive seen magnets morph and the poles on a magneto flip because of it...…….I had to flip the pickup on one too [XR100]which worked for only so long before it went kaput for good......…….

The airgap is .020"...…...Tapes come in various thicknesses...I use a sliver of cardboard from a cereal box that's like 3/8" wide by 3-4" long...…...You sandwich the cereal box sliver between the coil and magnet..tighten the coil mount screws and pull out the cereal box sliver..

The pusher spring for the throttle EPR stated looks like this...………..



And yes the rocket key is placed in the crank slot in the "retarded" position......Not the worst case as it will enhance topend revs a lot more than it will enhance bottomend takeoff power and thats ok too with a lightweight 6year old rider under 100lbs riding it...…

Stock woodruff key sets the timing at a neutral Zero timing point...…..

When the raised offset is oriented to the right ;- its set advanced...[advanced gives more takeoff uumph].

When the raised offset set to the left on a reed inducted engine its set retarded...………[retarded gives more topend revs]

On some of my builds I have a 6.0volt auto advancing/retarding CDI ignition system which still retains the stock woodruff key..




On my twin turbo 5.3 LS powered Range Rover my boost timing master retards the timing for each pound of boost applied...Its pushing 16lbs of total boost so at full boost the computer is supposed to be retarding the beasty a full 16 degrees..Im going 20degres for safety...LOL.….This is done with a power programmer but essentially the same principal..If you apply too much boost without properly retarding the timing it can be quite detrimental for the crank and the whole engine at WOT,,,LOL

With your setup and level of where youre at the only thing I see wrong is the fact you set the airgap wrong...The engine has no porting or power mods and hasn't been degree'd to see where it actually stands so theres no real right and wrong in your case....Its when you start building stouter power with tighter squish tolerances and higher compression or having an adult rider aboard as a rider is when the choice of how the rocket key is set becomes a lot more critical.....

For the choke ….Flip the V-stack with choke arm 180 degrees...I usually put a slight bend in the choke flap so it makes slight pressure of the choke plate between the V-stack slot to keep the choke from dropping into the hole......……..

Good Luck
Excellent post, thank you. well, worst case scenario, I have two other spare flywheels in the garage. I have the stock flywheel that came off the bike, and I also have the one that came with the new pull start assembly. Of course the one installed, is the lighter flywheel that you guys had recommended. and I guess if I have to get a new coil, it's not the end of the world. I think the only cost a few bucks.

So tonight, when I get home, I'm going to regap the coil and flywheel, and I'm also going to flip the choke to the other side of the carb. I guess I did not realize at the time that that was reversible. And then, we'll give it another go.

Thank you again for the very informative reply.
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Re: Pit Bike

Ok here is a quick update.

Came home from work tonight and went to work on the bike. I played with the tolerance between the coil and flywheel and did the 'cereal box cardboard' method and was able to get a nice good gap in there. I kept trying to start the bike but it wouldn't turn over. I was getting pretty frustrated. I pulled the spark plug out to take a look at it, and it was completely dry (not fouled). So I put it back in there and tried cranking again and again. I pressed the bulb on the carb another 5-10x and kept cranking. Then all of the sudden it turned over and sparked and idled for 2-3 seconds. It was awesome, then I cranked it again and it idled for maybe 5-6 seconds. By the next crank I had the bike idling. It idled for maybe 30 seconds then died again. The next crank and now it idles without dying. VERY satisfying and a huge win for me. I think maybe it just took several cranks to get fuel throughout the carb? I dont know, but it's idling now.

There are some issues, though. The throttle cable isn't calibrated at all and I put a spring in there but the twist throttle has a good 3/4 turn in it before the throttle cable even pulls on the carb throttle. Further the spring that I installed at the carb is actually pushing the throttle cable out of it's notch. I cut some spring OUT of it and it helped, but it still is sloppy and has no tight tolerance.

The bigger issue is, if I give the bike throttle at all, it dies. Complete opposite when I had the old carb. The old carb, bike wouldn't idle but you could keep it running my staying in the gas. This time, the bike seems to idle fine but immediately dies when you give it throttle. So I need to somehow figure out a way to 'tighten' the connection between twist throttle and throttle response (too much slack?). I don't know - is there an aftermarket throttle kit I can buy that includes twist grip and cable? I think the stock one is junk anyways.

Anyways, I went out there after a bit and tried starting it again. Its kind of real difficult to start if the motor isn't warm. Takes a good 20-25 pulls it seems like. Perhaps whatever is causing it to be difficult to start is the same issue with why I cant give it throttle?

Here are some videos for reference:

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Re: Pit Bike

Your coil might be bad, and or the flywheel. Your new carb may not be working right. Are you sure the gas lines are on right. Have you tried to adjust your low & high speed jets. L is on top of the carb in the brass hole next to the spring and the H is on the side of the carb. There is glue in the top jet, have to clean it out to turn the screw. Sounds like your not getting enough gas to run right.

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try backing out the hsn (high speed neddle) on the the side of the carb 1/8 th turn at a time untill it wants to run. then tune it from there Carburetor-tuning-flow-chart-ver-3-696x1049_1578979515635.png

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try backing out the hsn (high speed neddle) on the the side of the carb 1/8 th turn at a time untill it wants to run. then tune it from there Attachment 150959
So two things worth mentioning. The new carb has no reeds on it, but the old one did. I did not swap the reeds over as it didn't look like they were suppose to swap over. Also the choke feels real loose and flimsy and there appears to be a small amount of fuel coming out of the choke area when bike is idling. I guess I'll take the carb apart again when I get home and swap the choke to the other side and see if I can't tighten it down better. I also need to figure out how to tighten the throttle linkage/cable.


The black hose from the tank (fuel in) is attached to the larger nozzle on the carb. The clear line (fuel out) is attached to the smaller nozzle on carb

Last edited by BlackReef; 01-14-2020 at 11:52 AM.
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Re: Pit Bike

You need the reed plate behind the intake manifold and the cases, if you want it to run right, that's why they call in a reed port engine.

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my stuff is all modifyed but these are all the parts required to make it run...
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File Type: jpg 20180319_211509_1579047549405.jpg (202.6 KB, 3 views)
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Re: Pit Bike

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my stuff is all modifyed but these are all the parts required to make it run...

Thanks for the reply. Fortunately, it looks like the intake plenum on the old carb (that has the reeds attached) will fit with the new carb. So I'll have to take the new carb back off, swap the plenum and bolt it back up. I need to take the carb off anyways to swap the position on the choke. So I guess Ill drain all the fuel, once again, lol and get the carb off probably friday and re-do it. I can't believe I overlooked this, I think I have been more tired than I realize when I come home and try to work on the bike.


- Do I need a fuel shutoff valve?
- Can you guys recommend a better twist throttle+cable assembly that might work better with this setup? Or do you recommend I mess with the current setup to get it dialed in. Again, the throttle turns a full 1/2 or 3/4 before it even begins to suck up the slack in the cable and actually pull the throttle on the carb
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Re: Pit Bike

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Thanks for the reply. Fortunately, it looks like the intake plenum on the old carb (that has the reeds attached) will fit with the new carb. So I'll have to take the new carb back off, swap the plenum and bolt it back up. I need to take the carb off anyways to swap the position on the choke. So I guess Ill drain all the fuel, once again, lol and get the carb off probably friday and re-do it. I can't believe I overlooked this, I think I have been more tired than I realize when I come home and try to work on the bike.


- Do I need a fuel shutoff valve?
- Can you guys recommend a better twist throttle+cable assembly that might work better with this setup? Or do you recommend I mess with the current setup to get it dialed in. Again, the throttle turns a full 1/2 or 3/4 before it even begins to suck up the slack in the cable and actually pull the throttle on the carb
It seems they've made an all in one intake/reedplate for what you have...

You cannot put the stock intake back on and use the pumper carb...You need a purge port to pump the internal diaphragm.

You need to buy a $5 reedplate too unfortunately...…………


https://www.amazon.com/XLJOY-Engine-...4&sr=8-3-spell

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Last edited by CAM2; 01-14-2020 at 08:34 PM.
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Re: Pit Bike

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It seems they've made an all in one intake/reedplate for what you have...

You cannot put the stock intake back on and use the pumper carb...You need a purge port to pump the internal diaphragm.

You need to buy a $5 reedplate too unfortunately...…………


https://www.amazon.com/XLJOY-Engine-...4&sr=8-3-spell

Ok I dont mind purchasing the reedplate. Im assuming I just sandwich this new reedplate between the carb intake and the manifold? I think its safe to assume this is why the bike dies when I give it throttle LOL

I wonder if there are any other reed plates available on Amazon for this bike that wont take 3 weeks for delivery. ****.

Thanks again for the help man

Last edited by BlackReef; 01-14-2020 at 08:47 PM.
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Re: Pit Bike

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Ok I dont mind purchasing the reedplate. Im assuming I just sandwich this new reedplate between the carb intake and the manifold? I think its safe to assume this is why the bike dies when I give it throttle LOL

I wonder if there are any other reed plates available on Amazon for this bike that wont take 3 weeks for delivery. ****.

Thanks again for the help man
Youre welcome and try this link its a lil more but it has one of the needed gaskets too

https://www.amazon.com/Block-Gasket-...053505&sr=8-16


https://www.amazon.com/TC-Motor-Mani...9053356&sr=8-1

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Last edited by CAM2; 01-14-2020 at 08:59 PM.
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