GY6 49cc needs rebuild, HOW BIG CAN I GO By billwgol (Read 3,481 times)

[ctpgs]

81.2889

[billwgol]

All I wanted to know is if I could put a 100 cc or larger crank in my 49 cc gy6 scooter I don't care if you know how to do math or not just let me know if the crank will fit thank you..

[billwgol]

P.S. I'm not interested in any of these monster big bore kits you all claim a bigger than they are!!! I think of the problem and some men think things are bigger than they really are!!! I'm just interested in putting a longer stroke crank in my scooter, 100 cc or larger crank in my 49cc gy6 engine

[ctpgs]

don't think it would without modifications but here is a heavier one
www.racingplanetusa.com/crankshaft-with-tooth-pump-driven-sprocket-139qmbqma-p-2856-1.html?cPath=27987_27989_27995&sessID=48f6a74b33a52132cbf909d5c10e2578
or
www.monstergy6.com/product_crankshaft.htm

[frmrwiseguy]

Sept 5, 2013 10:00:47 GMT -6 billwgol said:

All I wanted to know is if I could put a 100 cc or larger crank in my 49 cc gy6 scooter I don't care if you know how to do math or not just let me know if the crank will fit thank you..

With such a long stroke to obtain the desired CC's beware of the Harsh rod angle of the stock length connecting rod.
Crank Works can prolly make any stroke you want.
I left out with such a long stroke to obtain desired cc's, being a noob I have not had the pleasure of measuring the piston for wristpin offset.
A straight up pin would be a real bad buzz with a stock rod and long stroke. should require 1mm pin offset.
research Rod to Stroke ratio's.
Good Day!

[scooterbob]

What happens if you install a dished piston. Flat top or a domed piston. If you take 350 CI engine and bore it .030 you end up with a 355 CI engine. CI and CC is just one part of building HP. You need to add other parts to achieve horsepower and horse power is what your looking for. Forget CC size and add components that build HP. If you build it right you could add a little nitro to bump up the HP a lot.

[frmrwiseguy]

Sept 5, 2013 19:45:19 GMT -6 scooterbob said:

What happens if you install a dished piston. Flat top or a domed piston. If you take 350 CI engine and bore it .030 you end up with a 355 CI engine. CI and CC is just one part of building HP. You need to add other parts to achieve horsepower and horse power is what your looking for. Forget CC size and add components that build HP. If you build it right you could add a little nitro to bump up the HP a lot.

No replacement for Displacement!
This going way off topic for the guy just wanting to know how big a stroke he can stuff in his Fiddy.
Piston volume in terms of cc's either + or - only is effecting compression ratio, not bore size and swept volume (stroke). Same with combustion chamber volume,Head gasket thickness.
With the Plethora of aftermarket heads on the market you can pick and choose a combination for you specific application. This generally will be dictated by the cam shaft your going to run as it has comp.ratio and rpm range it will work in. Flat top piston=best flame travel, Mini dome(+.110 Brodix NASCAR) yields the best flow. Give and take.
For a national event in my KT100 on Methanol I obtained from Funny
car driver Mark Oswald, a gallon of the Nitromethane (the POP) in this application was a very high rpm motor but low 9:0-1 comp. ratio.
1989 was $70. per gallon. Holly Schmolly was it the POP! Very weather Sensitive ran it in a morning heat race and had to turn the main out during (Walbro) the race to keep the engine cool, skipped it in afternoon heat race, Put it back for the final and spanked e'm
Cost a ring as the heat made it lose its temper by the end of the race. But for a National win was worth it.
Good day.