hybrid chinese motors and performance tuning
- Thread starter foureasy
- Start date
Is it possible for you to cut the bottom of the cylinder? Seems if you cut it "more than you had to", then set a final timing for the transfers using base gasket(s), and finally modifying the exhaust timing you could use the short rod.
hey four easy thanx for this thread again i just ordered the athena kit 70cc and high comp head i hope it works as well as yours once again thanks !!!!!!!!!!!!!!!!!!!!!!!!!
this one? did you get a carb? about time someone else drops some dough
puch athena 70cc 45mm reed cylinder
puch athena 70cc 45mm reed cylinder
I live in australia and worked in a motor cycle wrecking yard for 10 years and i collected some late 60s through to 1977 Garelli 50 cc mini bikes .they are 50 cc and suposed to be a 40 mm bore with a 39 mm stroke. they are a simple 4 port design and the chinese bicycle engine almost looks like a detuned copy of the cylinder ie the transfer ports are int he right place . the fins are massive ,they run 13 to 1 compression ratio and they run a 20 mm delorto carby. " Road and Race Garelli parts " in australia sell parts for them . i havent tried to swap a cylinder head carby and exhaust yet but they look like they will fit with out too much trouble , these engines were GP 50 road race engines from the 60s even used at bonnieville for speed trials .also used in canadian mini bikes and detuned with washers in the inlet and exhaust for the english mopeds in the early 70s .they make a claimed 7.7 to 11 hp and rev beyond 10,000 rpm . i think they would make a great cylinder conversion .they use a crowded rollers on the little end ,not sure about the big end as we broke a 50 ton press at toyota trying to get the pin out .
one other thing i wondered is why no one makes an adaptor to put between the rectangle exhaust port of the chinese bicycle engine and the round pipe ? the barrels have huge rectangle exhaust blocked by a gasket going to a tiny round pipe. surely if you made an adaptor it would increase the hp ,it would be cheap to make and you would sell thousands of them . if you made an adaptor to smooth out the exhaust flow it has to make more hp or alternativly if you replace your engine pipe and cylinder flange matched to the exhaust port with a larger diameter pipe using the origional muffler at the end and youll have to gain HP with out any added noise yet no one seems to have tried it . ?? ill let you know if the early garelli chrome bore 50cc cylinder will fit easily when i re ring my 50 .i notice some of the older engines seem to be made from seconds where as if you buy a generic from china youll get the latest models. why buy old stock from australia or the USA when you can buy the latest ex china dirt cheap ? the generic cost under $200 au and was so much better than the local cheapo engine. that said the cheapo in australia had the early bushed rod with a roller little end but the big end was a crowded roller funny enough so there is lots of variations in the engines out there.
one other thing i wondered is why no one makes an adaptor to put between the rectangle exhaust port of the chinese bicycle engine and the round pipe ? the barrels have huge rectangle exhaust blocked by a gasket going to a tiny round pipe. surely if you made an adaptor it would increase the hp ,it would be cheap to make and you would sell thousands of them . if you made an adaptor to smooth out the exhaust flow it has to make more hp or alternativly if you replace your engine pipe and cylinder flange matched to the exhaust port with a larger diameter pipe using the origional muffler at the end and youll have to gain HP with out any added noise yet no one seems to have tried it . ?? ill let you know if the early garelli chrome bore 50cc cylinder will fit easily when i re ring my 50 .i notice some of the older engines seem to be made from seconds where as if you buy a generic from china youll get the latest models. why buy old stock from australia or the USA when you can buy the latest ex china dirt cheap ? the generic cost under $200 au and was so much better than the local cheapo engine. that said the cheapo in australia had the early bushed rod with a roller little end but the big end was a crowded roller funny enough so there is lots of variations in the engines out there.
hey 4easy, check this out...
harley/aermacchi M50 head. dunno what year, or what the heck an aermacchi is, but it fits. just need to clean it up and buy a longer spark plug and studs.
harley/aermacchi M50 head. dunno what year, or what the heck an aermacchi is, but it fits. just need to clean it up and buy a longer spark plug and studs.
Attachments
as much as possible without overheating.
only the big end bearing has gone bad. actually, the flywheels separated on my 50mm crank, it just started vibrating real bad and didn't quite run right. just true the wheels to under .002" and balance it correctly.
so far 10k hasn't done it.
safety? on a bicycle that does 50?
only the big end bearing has gone bad. actually, the flywheels separated on my 50mm crank, it just started vibrating real bad and didn't quite run right. just true the wheels to under .002" and balance it correctly.
so far 10k hasn't done it.
safety? on a bicycle that does 50?
i put the 24mm flat mikuni on and switched back to 91 octane and this thing is an animal. i think i need a 44t sprocket cause im hitting 46-47 with the 41t, a little bottom end was lost with the new port timing. 180 exh and 116 on the transfers. this thing hits hard in the middle and revs to the moon. no noticable heat fade on the test hill, but the compression is still way low. i will need to weld up the head to fix the 2mm squish band. the crank is perfectly balanced as well. i can finally call this motor a win.
