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Pre Xflow jetting Help needed please

France North AR

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Hi everyone,

I'm currently trying to find the best jetting for my S2 (Pre Xflow with fast road cam on twin 40DCOE)
I found plenty of infos about Xflow jetting but nothing about Pre Xflow.

Trying Xflow jetting as basic set up is OK but far from perfect.
I will be very happy if you could share your jetting to help me to find the best set up.

At today best for me is:
Choke 30
fuel 125 / F16 / air 160
Pump 35
Idle jet 45F9

Thanks for your help !



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45 F9 should be fine for that spec,

You really need to get this on  set of rollers and see what your engine needs, rather than trying to copy someones else's spec, there are too many variables which could and will after performance, efficiency, and safety and longevity of your engine, including looking at your ignition curve / map depending what set up your running.

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It is my blue road S2 I'm just after a "round" tractable engine for road use.
It is a 120E block so 1499cc (I tried 32 choke but it is perhaps too much for this engine capacity?)

At the moment it is rough around 2500/3000rpm (no spitting carb or exhaust) but looks too rich (little black exhaust smoke at first pedal action and black sparks).
Problem is anything leaner is even worst.

Could you let me know value to check about float level ?
Also I'm interested about advice to set up idle screw.
Thanks !


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Assuming everything else is correct then the idles are straight forward, screw them all closed and then open each one 2 full turns and start up, adjust from there in 1/4 turn on each one in order to get a smooth idle.

If your using second hand jets make sure you check them which gauges as many jet are reamed or drilled oversize, some even soldered and re drilled don't rely on the numbers stamped on the jet alone.

If your needing to swap tubes (which it sounds like you need) then your best getting this done on the rollers.

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