rs125 jetting ???

[dardappa2004]

hi there, basically i have bought a big bore kit for my rs125 its the polini 159cc one, its fitted and works okish (see theres the problem) it feels alot less responsive on the throttle and power. I have a 34mm carb with the standard jets it came with and was wondering will upjetting help increase reponsiveness and power as it does feels as if the engine is being starved when being pushed?

Many thanks

[dougon2wheels]

you'll find with big bore kits that you have to down jet...(more air drawn through the carb and across the jets,more fuel drawn through the jet,makeing the engine run rich).
does the bike feel like its,coughing/spluttering,misfireing ?
try dropping the needle by one notch and reducing the main by 5 points

i really would recommend dyno time with bb kits,they can be real trouble for little gain

[stevo as b4]

Id automatically be fitting a slightly bigger main jet than std, unless the kit manufactuer states otherwise. i'd never fit a smaller main jet unless i could see the effect on fueling, and EGT's when run on a dyno. Any advice regarding jetting without actually running the bike and logging the mixture ratio's is wild geuss work at best, and at worst an almost certain way to ruin or wreck the engine, possibly causing £££'s worth of damage!

[dardappa2004]

At the minute the plug is carbon fouling, i have checked the oil pump and it is at the normal adjustment? So would it be best to down jet or upjet as im a noob when it comes to jetting? Bike dont feel like it misfires , sputters or coughs.

Thanks for the help

[Kickstart]

Hi

Can you check what jets are in the 34mm carb. It should be about a 150 main jet. Also check the position of the clip on the needle valve.

Suspect the 34mm carb might have been bought 2nd hand and if so the jetting could be pretty random.

All the best

Keith
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