hybrid chinese motors and performance tuning

the main problem with getting 6 to 10 hp from a chinese bicycle engine is the heat build up problem. the garelli has cooling fins over double the size of the bicycle engine and if you want to make big HP reliably you will have to go to methanol or ethanol and castor oil to get the cooling effect for a reliable engine .if your happy with a short engine life then petrol in a modified engine is fine. the other bonus with alcohol fuel is you can safely raise the compression to double the normal and gain HP at the same time . sadly this means you have to drill out all the fuel passages and jets and it will use more fuel but fuel is cheaper than new pistons rings and barrels .
 
Here's a alcohol conversion kit for 49cc pocket bikes that would prolly work! Someone just needs to build a custom liquid cooling system for these china girl's! :P

ALCHY.jpg


ALCOHOLCARBKIT
 
what happened ? is that a piston pin clip or did the big end bearing cage break up ? you can see bits of metal have been bouncing around in there but its not clear what the piece of metal is from the picture .mind you the colour of the piston sugests there was some detonation happening perhaps from a lean fuel air mix maybe . we saw a lot of this in the motocross bikes at the motor cycle wreckers when the roller bearings in the big end failed .a very sad end to the day
 
john_the_great
The carby above looks good. we often use the go kart carbys or even chainsaw carbys when we modify the bicycle engines as they are easily tunable ,no mess jets to fiddle with .you can see the high and low speed mixture screws on the methanol carby above .tuned right we have never seized a engine yet .might be cheaper to search for a second hand go kart carby perhaps though . the other bonus with chainsaw and go kart carbys is they have a in built fuel pump so when you make a manifold adaptor you have to drill a small hole so the action of the piston going up and down ie vacume then no vacume works the fuel pump so you can use almost anything for a fuel tank then.
 
all those nicks were from a previous wreck that broke the intake off and sucked some of 4th ave. into the chamber.
the head gasket (silicone) leaked and caused a major lean condition which ventillated my piston. the cylinder is fine, nikasil is very hardy. new piston ordered yesterday. i did some port work on the transfers also last night.


oh yeah, when i switched to the flatslide mikuni, i stuck with gas for now. 110 vp and klotz at 32:1
 
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i went a little too far with the portwork which, in turn, had me running too many rpms for the big end roller. so i picked up a new motor from bgf and ripped it apart. i also had a gilardoni 70cc kit for a puch project that ate the last piston and rod it had in it
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i cleaned up the cylinder and intake port and now i have this
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and this
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this kit has a bore of 47mm which not only gives me the same displace ment as stock, but also enables me to run the stock 10mm wristpin and a roller bearing instead of the 12mm and a bushing. only time will tell if this piston will survive.
i had to weld up the outside of the transfers before i ported the cases

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what i had to match
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also balanced the crank
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maybe the crank bearings will last a little longer
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bdc with a 6.75mm cylinder spacer to give me 114 on my transfers
 
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