Ruckus FMF exhaust. 78 main jet. Idle mixture all the way in

[razorrust]

I bought a ruckus that wouldn't pull hills without bogging down and stalling.

I tried new carbs and everything I could think of. Eventually realized it had a FMF exhaust. Read I might need to jet the carb.

The original carb had a 75 jet and the long 06+ needle. I put a 78 jet in the carb and the ruckus runs great, from what I can tell.

I hooked a tach to the ruckus and stated adjusting the idle mixture screw. The problem is I get the highest RPM with the screw all the way in.

So it must be running too rich. Is the small jet completely shut off with the idle mix screw all the way in? I'm wondering if I need a smaller small jet?

[Baizy]

My ruck is the same when it comes to the idle screw setting. I'm running a 20mm carb meant for a GY6 engine on my 58cc with a Leo Vince exhaust. Running the screw all the way in doesn't completely cut off fuel otherwise it would die, it just restricts the flow severely. What I have done (since 35 is the smallest pilot jet I've found) is wound it in all the way and then out a single complete turn and it cold starts and idles when warm setup like that. I'd try that and see how it does over the course of a few days.

[razorrust]

Thats good to know. Yea looks like 35 is the smallest jet available. I got a chance to ride it today. I believe it is still a little lean when wide open. I pulled the plug and it's completely white. May try an 80 jet. I wonder if this will make it even richer at idle. It idles great with the mixture screw all the way in. Not sure if that can cause harm.

[Baizy]

In theory you could set idle without any main jet installed and it wouldn't change your idle adjustments. The idle shouldn't change as the needle jet is fully closed, keeping the fueling circuit separate, so your idle should stay stable. I do think you're on the right track taking the main jet up a notch since the plugs come out white, instead of a light brown. That will keep the cylinder temps lower and the engine happier. Have fun!