[Dan Diego]

Below 1000ft, my stock 2015 150r was always tough to start. Once started, I would have to play with idle screw to get a decent idle speed. After it was fully warmed up, the idle rpms were too fast so would require adjusting the idle screw again to slow it to acceptable rpm. Once there, bike ran great. All was stock, i just recently swapped a #42 pilot jet for the stock #38. It now starts much easier. I have not have it out for an extended ride yet. Just running in garage and up and down block. I cannot yet verify that I will still have to continue to adjust idle screw but I have already noticed this. If I put in gear and let out clutch and then clutch in, the idle will stay at acceptable level. If I then put the bike in neutral, twist and return throttle, and the idle rpms noticeably higher. As I am educating myself on how these carburetors work, I am wondering what is responsible to the noticeably higher idle rpms.

[Aussiecrf230]

Have you tried adjusting the fuel screw or just the idle speed?
If the idle mixture is not right it can idle poorly.
Have you made sure the cable is free and lubed along with the throttle tube on the handle bar.
Also make sure the cable is routed properly as this can cause issues as well depending on where the steering is angled too.
Hope that helps.

[Bretmaxwell]

I am having the same exact issue on my 2007 CRF150RB. I have re-jetted to Pro-Circuit specs which seems to have eliminated the bog I was experiencing, but I am still stuck with this idle speed issue. It doesn’t seem to matter where I adjust the Air/Fuel screw. Still does the same thing. It idles high after warming up until you let the clutch out a little and pull it back in. ‍♂️ Any help would be great.

[Mxcat]

Following this one. Ours is the same... idles high once warm

[Aussiecrf230]

A few possibilities here.

The slide is not fully returning because it is catching on the body or catching by the cable/throttle tube. Routing can cause an issue.

The mixture is slightly rich and an air leak happens once warmed up.

The mixture is slightly lean and extra fuel is being added once warmed up.

Processs of elimination starting from the top.