cheap 66cc engine mods

I am using a 40 tooth rear sprocket, and I can outrun my bud who has a 44. He weighs about 2/3 of what I do, so I feel pretty good wioth my combo. Yes, iot bogs a tiny bit on the longer steaper hills, but I canlive with that. I also have the 36 which I hope to try befor winter. Winter time?? Probablt down to a 44 or even a 50.

No matter what I use, it'll be fun. Motorized bicycles takes my mind off the upcoming test to determine if I have lung cancer or not.

Gary
 
I agree with the 40 tooth being bad under about 15mph. I go 10mph or so idling, so that's nowhere near the power band.

Mind you, no matter how much power you put out, with only a single fixed gearing, you're only going to get a fairly small usable range of speed. First gear is pedaling off the line. From there, you've got 10mph to 30mph. I am very hesitant to believe anyone who claims "I GET 40+MPH STOCK WITH A 44T OMG!!!11". It just doesn't happen. Even if it has the power, it's past the reasonable limit of the rpms these motors can spin. Check your speedometer calibration. On my Schwinn bike computer, the difference between the 26" preset wheel diameter and my actual measured wheel diameter was a 3-4mph difference.
 
I got 42mph with a 40 tooth sprocket according to my bike computer which was set up to the actual wheel diameter and that motor was not capable or reving any higher. I'm not saying I was doing 42 but that's what the computer read. There's no way I could get 40 mph with a 44tooth unless I had taller tires or something else that changed the gear ratio. With that said my bike and I are much happier at 25-30mph and that's why I geared down so I can cruise at that speed at a comfortable rpm and it still climbs most hills.
 
40 tooth sounds a little more reasonable, and certainly doable. But you'd likely need to have tuned the engine quite a bit.
 
im running high 30s on a 44t sprocket... 62 jet in the carb, no air filter, puch head, modified stock exhaust... the engine cant handle much more rpm. i have to back off going down hills
 
Pilotgeek said:
40 tooth sounds a little more reasonable, and certainly doable. But you'd likely need to have tuned the engine quite a bit.
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I didn't do a lot to it. I took the catalyst out of the stock muffler(I thought it was clogged) widened the exhaust,intake port, and matched all the sufaces up, ngk plug and cap. None of this helped top end performance or much in any other performance for that matter. The gearing was always and will always be the limiting factor. I stand corrected on my last post also. You could raise the exhaust port and make the motor run at a higher rpm but you'd lose bottom end and the motor likely wouldn't last very long. I'm still good with 25-30mph
 
decoherence said:
oh they are faster than you.
6 months ago they posted & you are just starting to catch up.
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no moron, ive only been on this forum for a month or two. and these engines arent that complicated, there actually a joke. try building up a car motor.
 
Nikko said:
try building up a car motor.
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i was just making fun.

but since you requested.
i have about 5 cylinders to a couple ww2 radial engines in the next room.
here i am using a micrometer to check sodium filled valves for engines that are most likely older than your father.
21460236.jpg

also built up a chevy 400 small block to a 420.
built up my own air cooled flat four.
i was also a mechanic @ a car lot.
i'm going to upgrade my et-4 4 stroke vespa from a 150cc to 187cc. i think i found a place that sells used titanium valves & springs from race cars. a lot of machining should make them fit a hotter cam well.
lol. what were we talking about again?
dance1
 
talking about how simple these toys are, and good for you on your knowledge. sounds like you know a thing or 2.
and im also into engine design, ive already dissasembled 2 engines down to removing the crankshaft and measured every part of the engine that was removable from valve spring tension to cylinder bore diameter.
anyways since your into engines too and seem to have more experience then me, have you ever considered shaving the block or head on these motorized bike engines to raise compression? if so how much would you take off ,i saw maniac sells a head thats supposed to raise compression but they charge 70 dollars or sum.
 
i don't have much experience with 2 strokes. i still prefer 4-strokes.
i havn't even pulled the jug of or (heavens forbid) not needed to touch the inner clutch or gearing. guess i was lucky.

i have read a few threads of people that have played with shaving.
i think the consensus is that engine life would not be a priority.
there is a thread here about using a Punch head for cheap.
http://motorbicycling.com/f13/ceiling-unlimited-build-performance-details-puch-30655.html
here is a thread about using a punch jug and head.
http://motorbicycling.com/f13/hybrid-chinese-motors-performance-tuning-14204.html
 
I'm running a 50cc, so my performance will be skewed. And I don't run a speedometer because I'm cheap.

But I'm pulling on a 36 tooth sprocket. And the 50cc revs a good bit higher than the 66 I built for my brother that's running a 41. Mind you, this motor has been almost totally altered.

My next maniac build will be a reed modded 66cc with a puch head, all new hardware, balanced crank, dellorto 16mm SHA, happy pipe, and experimental port job. Boost porting, boyesen ports, possibly exhaust boost ports. Possibly a puch piston. Going to take the stock china motor top end as far as it can go.
 
HEyy .. would any one recommend a shifter kit ? ... im still on my breakin perious .. dose it get much more power after breaking-in ?
 
I refuse to believe anyone that says that they can go 40mph with a 44t sprocket. PERIOD
If you go to the other site under"Wild in the streets" and use the gear ratio calculator and input the proper gears ,you will find that with a 26"rim with a 44t sprocket that the motor would have to acheive 9000 rpm to hit 40mph
Everybody would like to think they have the one Chineese Morini that can do this. Im sure there are a few members that could actually say that they could but with all the work , money and time into there motors you reaily couldnt call it a china ht anymore.
So To the others, with no disresepct, ITS YOUR STORY- TELL IT LIKE YOU WANNA
IF you think i dont know what im saying check out my bike:
http://motorbicycling.com/f42/29r-genisis-almost-done-34580.html
34 mph all day long,160 lb rider, 29" tires 40t sprocket 6500 rpm's
 
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I agree with you about speeds claimed with a 44 tooth. I have a forty and can hit about 34 on a very good day. Mind you, I am about 250, and with all the crap I have on my bike, we weigh about 330-340 and I am happy with that. I did buy a 36, but do not feel I will be able to pull the hills, and find that 20-25 is a very good speed. I don't want to fall going any faster than that anyway. I can hurt myself doing 20.

:-||
 
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When I had the 44 on my bike a cop here in town clocked me at 37MPH. So yes you can do alot even with the stock 44T, it's not as impossible as everyone thinks.
 
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