Hanging Idle on Mojave 250. Need some help guys

[Warrior1996]

Alright guys, I know this isn't warrior related, (or even yamaha related, that's why I posted here in the general area), but I need some help here. My brother's mojave 250 is having a hanging idle issue. My dad and I can't seem to figure it out. First I thought intake boot was leaking. It was, but that is fixed now. We have two carbs that both have been cleaned and gone through, the bike idles high with both. In all the other rpms, the bike seems to run great, good throttle response and no popping/smoke. Both the idle screw and air/fuel mix screw have been messed with, still nothing. The bike will either idle really high, or stall out. If anybody has any ideas on how to fix this, it would be awesome. Someone my dad talked to said it could be out of time, but we haven't checked that yet. I'm not even sure if that can cause a hanging idle... We are now looking into buying a different carb for it, but if anyone else has an idea to what it could be, please tell me. Thanks guys

 

[2000]

Did you adjust the throttle cable slack?

 

[Warrior1996]

Yup, we have tried adjusting the cable and are now running it without a cable just cause it's easier to remove after a test run.

 

[alex456123]

Sounds like the choke is stuck.

 

[Warrior1996]

Choke seems to be functioning fine. Will start on choke and idle will drop when choke is disengaged. However, I'll take a look at the cable since it is a handlebar mounted choke. Thanks Alex

 

[alex456123]

Just disconnect the cable and try to start it. If it idles fine, ya found your issue.
It could be stuck internally too.
What kind of carb is on that bike?

 

[Warrior1996]

I don't know if you can remove the cable and run the bike as the choke cable and the entire choke valve/assembly comes out in one piece, leaving a open hole in the side of the carb. The carb is a keihin w/ a vacuum slide, not sure on the size.

 

[Gen1Pat]

Common problem with the Mojave. All of them will do it over time. The carb is plain worn out and needs replacing. When you adjust the base idle you are adjusting how far open the throttle plate is. That is what raises and lowers the idle. When the carb's bore is worn too far it lets more air/fuel past the throttle plate then necessary, and causes the high idle problem. As you have found, you can idle it down, but, it will eventually stall after about fifteen seconds.

That is pretty much the same carb that came on the Bayou 300. The Bayou 300 had terrible fuel leakage issues, and it didn't matter what you did the carb would always leak fuel. Quick, and best fix, is to swap a Honda TRX300 Fourtrax carb in there. Basically, it is the "high dollar" version of the carb that comes stock on the Bayou 300. Most things I have read say that jetting isn't necessary, but, that will differ machine to machine. In all my searching, I have not found if swapping in the Honda carb has been done on a Mojave, however I don't see why it won't work. After all, it is the same carb as the Bayou's. Will probably have to rejet, but that's not the worst. The choke and throttle cables should work without a problem. May have to use the Honda throttle cable.

 

[Warrior1996]

Thanks a bunch Pat, that's the answer I was looking for!

 

[Gen1Pat]

No problem. I know the Mojave well. If you ever do a timing chain to it, watch out for the timing marks that the manual doesn't specify.

 

[Warrior1996]

Good to know Pat. I'm sure I'll be asking you some questions in the future...

I think the carb they are looking at buying right now is a mikuni round slide. You think that carb would make a good replacement?