4 - stroke Schwinn Stingray Chopper occ

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Related to this post: https://motoredbikes.com/threads/pr...chopper-and-im-looking-for-some-advice.50872/

Donnor bike:
IMG_20171001_111755.jpg


Since this is not being an standard build (as expected) I'm going to describe how I'm solving the issues that I'm having, I hope it will be useful for someone.

First thing, choosing the motor kit: after digging and asking around I decided to go for
I ordered this kit: http://www.bicycle-engines.com/49cc-4G-T-Belt-Drive-Complete-Gas-Powered-Engine-Kit.html
I didn't know if to get the 100 or the 80 tooth pulley, I asked on the chat that they have and.... I believe the person behind didn't know much about what she was talking about... I asked which configuration will be faster and she told me the 100 tooth... After checking the manual that comes with the engine, that is wrong, 80 has a "faster" ratio, 100 is for better hill climbing and torque. Because of this I ordered a smaller sprocket (36 tooth), I'll get a Engine rpm to bike wheel rpm ratio of 18, close to what you get with the 80 on the transmission and a 44 on the wheel (17.6).
[UPDATE]
After contacting BE, they are sending me a 80 tooth transmission to exchange with the 100 one, I don't have to pay for anything, amazing customer service!

IMG-20171006-WA0006.jpg


Pieces I've ordering so far (updated on Apr 2018):
- 49cc 4G T Belt Drive Complete Gas Powered Engine Kit - 80 tooth transmission (from Bicicle-engines) (firt transmission was a 100 tooth by mistake, exchanged with a 80 tooth)
- 2 Piece Muffler "Poo Poo Pipe" Deluxe For 4 Strokes
- Flexible muffler tube (eBay)
- 36 tooth sprocket (Amazon)
- 40 tooth sprocket (Amazon) <- using this one
- Sunlite D-Cruiser Handlebar, 32" W x 13.5" H x 7/8" - Hi-Rise handlebar
- 2 x 2,5 inch U-clamps with nuts and washers
- Front wheel, being a 24'' back wheel with free-wheel to install disk brake
- Disk brake kit for free-wheel (BlueSunshine Front and Back Disk Brake Kit - 160mm For 80cc Gas Motorized Bicycle - Amazon)
- Front fork with suspension

First thing is holding the motor to the bike, the engine bracket that comes with the motor si not compatible with the frame, and indeed, there is no much room to play around in the frame, so I have to remove pedals, bike chain and the chain cover, after that still, really tight, so I cut a portion of the chain cover holder, like in the picture:

IMG_20171007_153759.jpg


After thinking about different options, I come up with a solution, using the central part of the bracket drilling 4 holes (picture only has the first two) on each side of it, so I can use 2 u-clamps to hold it to the bottom part of the frame of the bike

IMG_20171008_214141.jpg


After first try, looks like it is gonna make the trick, the round part of the u-clamp is kind of the same round that the frame, so it adjust well, on the other side, part of the unthreaded u is coming out of the bracket, so I need some washes or something, and of course, I'll have to cut the u, it is way too long.

So far Is what I did (as October 8th). I'll keep updating as I work on it.

November 5th update -> https://motoredbikes.com/threads/4-stroke-schwinn-stingray-chopper-occ.51001/#post-451003

Video of the first start of the motor (Nov/05) -> https://motoredbikes.com/threads/4-stroke-schwinn-stingray-chopper-occ.51001/page-2#post-451198
 
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I adjusted valves on it, no mayor change, they where not really offset, but I realized I was loosing pressure on the junctions between the flex tube and the other parts of the exhaust, so I ordered two of these heavy duty clamps: https://www.amazon.com/gp/product/B00H7YMSES/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

It now bugs less on high RPM just installing one of these clamp, the other one broke while installing, so I'm waiting for the second one to arrive.

I tough that on 4-stroke the exhaust was not that important, just a way of putting gas out of the cylinder... Anyone can explain to me if this is really a thing or I'm just wrong?
 
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I adjusted valves on it, no mayor change, they where not really offset, but I realized I was loosing pressure on the junctions between the flex tube and the other parts of the exhaust, so I ordered two of these heavy duty clamps: https://www.amazon.com/gp/product/B00H7YMSES/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

It now bugs less on high RPM just installing one of these clamp, the other one broke while installing, so I'm waiting for the second one to arrive.

I tough that on 4-stroke the exhaust was not that important, just a way of putting gas out of the cylinder... Anyone can explain to me if this is really a thing or I'm just wrong?
Well.. Less leaks means more backpressure, which in a 4 stroke means it should be worse on gas, but that means nothing in terms of performance, maybe without the restriction the engine was spinning too fast for its cdi and just plain acting out, much like a bad 2 stroke cdi behaves beyond a certain rpm. The extra pressure may just be keeping the engine within a sort of governed state, which is likely better for it than letting it get spooky at top speed.. I would use muffler clamps, while they are larger and uglier they really seal up nicely. If not then welding is always a good idea, it's much smoother and relatively air tight.

Tell me if you can weld that flexible exhaust tube, I've had odd difficulty with it, namely it wants to melt away before the arc and pool even approaches, maybe I needed to use a weaker welder..
 
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Well.. Less leaks means more backpressure, which in a 4 stroke means it should be worse on gas, but that means nothing in terms of performance, maybe without the restriction the engine was spinning too fast for its cdi and just plain acting out, much like a bad 2 stroke cdi behaves beyond a certain rpm. The extra pressure may just be keeping the engine within a sort of governed state, which is likely better for it than letting it get spooky at top speed.. I would use muffler clamps, while they are larger and uglier they really seal up nicely. If not then welding is always a good idea, it's much smoother and relatively air tight.

Tell me if you can weld that flexible exhaust tube, I've had odd difficulty with it, namely it wants to melt away before the arc and pool even approaches, maybe I needed to use a weaker welder..

Thank you for your comments. Welding is not an option so far, I don't have the skills neither the tools... These clamps I'm using now are made for exhausts, so I hope they are enough.

Any other idea why it could be bugging on the top RPMs? something else to check?
 
Thank you for your comments. Welding is not an option so far, I don't have the skills neither the tools... These clamps I'm using now are made for exhausts, so I hope they are enough.

Any other idea why it could be bugging on the top RPMs? something else to check?
No I don't, I just haven't played with these 4 strokes enough, though it is very likely they just aren't tuned up for high rpm out of the factory, hell most normal car engines arent really meant to top out, they don't need to either, they have transmissions to get the speed up there.

If you look at go kart sites that specialize in the harbor freight 212 you'll see there are quite a lot of mods and aftermarket parts to drag the top speed out of a motor. Maybe give higher octane fuel a shot, check your plug and exhaust for carbon, sometimes you just need a slight carb adjustment of the engine components are at peak adjustment. Hey at least if you screw up you don't need an engine lift to find out what you did wrong, and if you drop a part down the crankcase you don't have to pull an oil pan hoping youll find it, just turn it upside down, one hand!
 
No I don't, I just haven't played with these 4 strokes enough, though it is very likely they just aren't tuned up for high rpm out of the factory, hell most normal car engines arent really meant to top out, they don't need to either, they have transmissions to get the speed up there.

If you look at go kart sites that specialize in the harbor freight 212 you'll see there are quite a lot of mods and aftermarket parts to drag the top speed out of a motor. Maybe give higher octane fuel a shot, check your plug and exhaust for carbon, sometimes you just need a slight carb adjustment of the engine components are at peak adjustment. Hey at least if you screw up you don't need an engine lift to find out what you did wrong, and if you drop a part down the crankcase you don't have to pull an oil pan hoping youll find it, just turn it upside down, one hand!

Well, I was playing yesterday with it. I add the second clamp to the exhaust, so now it is properly set up, after that, I removed the air filter and played with the air/fuel mix screw and looks like there is a configuration where it doesn't bug on the high RPMs, so I ordered a new air filter that is less restrictive, and a tachometer to know exactly how I am on the RPMs, I feel like I get to the max RPM too fast.

Right now I'm getting a max speed or 26-27mph which is not bad, but I would like to cruise at 25mph without having to max out the motor, maybe it's time to change the sprocket (again) for something a little bit smaller, I'm running on a 40t, I tried 36t and the acceleration was too poor, maybe now with all the improvements on the exhaust, valves, gas/air mix and air filter, works just fine, but I'm afraid I'll have to order a 38t soon.

That's all so far!
 
Well, I was playing yesterday with it. I add the second clamp to the exhaust, so now it is properly set up, after that, I removed the air filter and played with the air/fuel mix screw and looks like there is a configuration where it doesn't bug on the high RPMs, so I ordered a new air filter that is less restrictive, and a tachometer to know exactly how I am on the RPMs, I feel like I get to the max RPM too fast.

Right now I'm getting a max speed or 26-27mph which is not bad, but I would like to cruise at 25mph without having to max out the motor, maybe it's time to change the sprocket (again) for something a little bit smaller, I'm running on a 40t, I tried 36t and the acceleration was too poor, maybe now with all the improvements on the exhaust, valves, gas/air mix and air filter, works just fine, but I'm afraid I'll have to order a 38t soon.

That's all so far!
I just realized I have a 10t pulley around and I believe I'm using the 9t, so that may give me the little more speed I'm looking for...
 
I just realized I have a 10t pulley around and I believe I'm using the 9t, so that may give me the little more speed I'm looking for...
Yeah! 10t does the trick! I was able to get 29mph while I still have a decent low speed torque.

Screenshot_20180623-173332.png
 
I'm starting my first build on a OCC Srltingray. Is there a special motor mount for the 4 strokes? Anything special needed? Debating on 2 or 4 stroke. Like the dependability of 4 stroke.
 
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