No/low idle on RMX250, HELP!

[MBgren]

Hi folks, first post here from me. I´m having some trouble with my old -91 RMX250. (Mikuni TMX38SS carb)
First it does´nt have any idle at all. When I let go of the throttle grip or clutches it dies within seconds. Very annoying!

Second it does´nt rev up like it shoud, and "bogs" a lot. Only when like in third gear and higher it rips on high revs. When starting in first and whacking the throttle, nothing really happens except bogging (4-stroking?).

But the idle problem is worst. When I have the bike running and shuts ot the fuel, it starts to rev like crazy. When turning fuel on again, this stops and it goes to die. I have set the float height according to my manual, original jetting, clean filter and so on. One thing I found out yesterday though, there should be a "lid" on the top of the air box. My bike does not have that. Can that really explain all my problems with my bike? Or do you guys have any other advice for me. I´ve turned both idle screw and air/fuel mixture screw but none of them really affects the idle issue. Carb has been cleaned several times as well.

Mixing gas 1:40 by the way. Sorry for my english as well.

Thanks,
/Regards, Peter (Sweden)

[psycho393]

Try adjusting the idle screw. That should at least make the bike idle. As far as the bike not having any top end in the first couple of gears, but having it in the rest. It doesn't make any sense to me at all. Try making sure that your air filter is clean, the spark plug shows that the jetting is correct and that your power valves isn't all gummed up.

[MBgren]

Idle screw dont do nothing. Filter is clean. I´ll be going for the power valve and see how that looks.
Thanks.

[DRGSin393]

Hey MBgren, welcome to . Is this bike new to you or have you had it for a while? Has the bike been sitting, not running, for a while? Have you checked the reeds?

[Halfast816]

Have you removed the pilot jet and checked for dirt. Just spraying carb cleaner in there won't work if it's plugged.

[MBgren]

I´ve had the bike for about a year.
Reeds are checked, they are fine.
All jets, float assy and all other stuff in there are removed, cleaned, and put back again. New jets and air screw btw.

I´m removing the engine from the frame and checking the powevalve as soon as I get the time. I´ll keep you posted on how that looks...

[Rotorranch]

Reeds maybe? I see you already checked that. But bad reeds could make it load up at idle, and have poor performance down low. That's what it sounds like to me.

Also, make sure the idle speed screw is actually moving the slide when you adjust it. It may be damaged/ broken and not moving the slide as it's supposed to.

Rotor