100cc to 125cc conversion

[dirtbike]

I was wondering if there is a significant difference in the exhaust/carb setup if I wanted to mount a 125cc piston/cylinder on my 100cc engine?

This must have been done I assume. What can I expect from just switching the piston and cylinder keeping the pipe and carb?

I'm not interested in max HP's but some torque would be nice without seizing or other major drawbacks.

 

[john durrill]

dirtbike,
 we have done this conversion, it's just a cylinder, head and piston, then change the jets in the carb. same pipe and carb . the slide and needle are the same in both bikes.
 Just a difference in jets . the 125 can use 1 tooth  larger on the counter shaft sprocket.
John & Peter



Edited by - john durrill on 11/29/2002  7:43:45 PM

[Doug Wilford]

Going from a 100 to 125cc is going to give you more torgue, the pipe and carb are the same as John said but jetting must be changed all three-- Needle, idle, and main.



Edited by - Doug Wilford on 11/29/2002  10:28:39 PM

[DKWRACER]

I also have good results, went to a 28mm Mikuni, and also hogged out the carb inlet manifold to 28mm for better airflow, also cut the inlet manifold moving the carb closer to the intake tract, if you send SASE to:Tom Brosius
209 So Yates St
Denver, COl 80219
I have SACHS porting article avail...