Need some help with engine mods......
 

Hey all,

I need some help with my engine, it's just a basic sport engine which came with my Ultima RB.



Anyway, i disassembled the carb to clean it out, and noticed that the barrel in the carb has a 4mm throat (!!). The inlet of the carb is 6mm....but the throat is tiny!!

I see this as a big restriction, and i plan to bore it out to 5-5.5mm......can anybody give me any tips or suggestions as to how i should go about this, and any problems i may get from doing it?? I'm also going to remove 1 head shim to try and raise compression, will i need a different glow plug if i do this??

I have added a tuned pipe, and matched andpolished the exhaust manifold. I also added a higher flow filter than the stock one, and oil and clean it regularly.

I am starting an offroad buggy club (we have an unused BMX track to race on) and i will be racing mainly agains other RTR's such as Evaders (.18 O.S.), and want to better my chances of keeping up.

Thanks in advance,

Jamie

BTW its a kyosho GX15 CRG

bump

The carb hole is suppose to taper, if you drill it out to the same bore with no taper you will hurt performance. The taper is called a venturi, the air speed increases as it enters the carb becasue of this taper, leave it alone.

Sounds like you are about to mess up a good motor.

The thing is it doesn't taper......it goes from 5.5mm, to 4mm (barrel)instantly, like a big step, then the bottom part of the throat between the engine and barrel is 4.5-5mm. so this means that the air accelerates through the barrel (4mm) then loses velocity when it goes into the tube leading to the crankcase.....

I haven't done anything yet.....

Are you sure you are not missing the insert (restrictor)?

There is no restrictor for this carb...