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Discussion Starter · #1 ·
Hey guys,

Ive recently installed a 30.5cc big bore kit on my old 23cc Fulie crankcase, But im seeing no increase in power!

I am using the stock crab, have installed everything properly and have run the engine in too.

What I have found is that no matter what my high end adjustment is, It runs no faster, and low end is doing close to nothing at all!

Do i need to buy a new carb for her?

Cheers.
 

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Hi there, is it possible you are seeing more torque but no more top speed? or is it just plain no different at all?

Reason I say that is because with a 30.5, and the same size gears - you would potentially see no more top speed, because the 30.5 wont necessarily rev higher than the 23cc, itl just make more torque.

if you think you have had an increase in torque and no increase in top speed, you may need taller gears to take advantage of it.
 

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Discussion Starter · #3 ·
Thats true, But i used to be able pull some pretty quick take offs for a 23cc! and now i have to wait for it to speed up!!
 

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the 30.5 will take more time to get on to full revs than the 23cc.. if your after more topend get some bigger gears like 20/54

also check your clutch is not slipping..if also you want a better take of get a bigger clutch spring..

you might have on the 23cc a 6000 rpm spring .. either get a 8000 or atouch bigger as the engine will spool up more revs before taking off.
 

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With an increase in motor size to the degree you have gone (25~30% larger) you should be seeing a marked improvement in both Torque and Speed, 6.5cc is a huge increase from stock, and should be noticeable.

Many people still use the stock Walbro 668 (chocked carb) on their larger engines with minimal performance loss.

How have you got it set up?

Gearing:
Carb:
Pipe:
Clutch Spring:
Manifold:
 
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