My Coolster Dbl is still running real lean. I put a 145 Main and a 42.5 Pilot, and the exhaust still glows red hot and the sparkplug is white as a ghost. What is the deal? I am wondering if the combo Uni filter and MRP exhaust is just too much? In fact I really haven't noticed any difference in performance fro a 130 main to 145? I am totally at a loss?

do you have the uni clamped right on the carb? I would double check the intake for cracks, put the stock cdi back in. does both water hoses get wqarm? I have seen the plug left in the water pump outlet

I agree. Something aint right. If you need that much fuel your probly sucking air

The Uni filter is attached directly to the carb. I have checked, rechecked and triple checked for leaks. There are none. Intake boot is solid. Sprayed carb cleaner all over the outside of the carb and intake boot...nothing. No change. I am about 99% sure water is circulating through the engine, but I will double check that tonight.

I think it might be time to put the OEM CDI back in, and install the factory exhaust. Maybe my airflow in and out of the engine is too good. Maybe a little more back preasure is just what the doctor ordered.

I've never heard of 'too much' air flow unless there is a vacuum leak. The rules of thumb for jetting that are advised here at BN should definitely get you in the ballpark.

I have heard of glowing exhausts from timing issues.

Also, at least on some dirt bikes, an air pocket can happen inside of the head that might cause overheating issues. My KX500 has a screw on the head to bleed out air.

It would be interesting if you had the chance to put another carb on it. Maybe there's an obstruction somewhere.

Just tossing out wild ideas here...............

Just out of curiosity (I may have missed it somewhere in your posts), have you checked for exhaust leaks at the cylinder head or elsewhere?

Anywhere that air is leaking where it shouldn't be is going to throw it off.

I like ideas I highly doubt there is anything wrong with the carb. The auto-choke works great, and the engine responds to idle mixture adjustments. I think the MRP CDI maybe advancing the timing too much.

Also I like your air pocket idea. Not because I have an air pocket in the head, but because I have hooked the crankcase breather hose to the CVT filter. This is how it came from the factory, with the stock airbox setup. However, this doesn’t make a whole lot of sense to me, because the CVT is blowing air into the breather tube.

On the other hand, it is fairly common to have positive pressure for crankcase breathers on diesels, because compression is so high. However, I don’t think it is common on gasoline engines, is it?

Positive crankcase pressure isn't good. I let my vent dangle down and open. I've done that on race cars, race bikes, street cars, and street bikes. I can't image that causing your problem.

When you put the stock ignition back on, don't change the exhaust back. Only make one adjustment at a time so you can track the results.

I'd say at this point disconnect that crankcase breather from the CVT, and see if your lean condition goes away!

The CDI is likely a different issue altogether. Deal with that once the air/fuel thing is sorted.

I just remembered a test I use sometimes for jetting... at least at idle. Remove a vacuum line and see what happens to the idle speed. If it goes up, you're rich. If it goes down, you're lean.

Probably doesn't help here though...........