98 won't idle

I just bought a 98 wr400 that was built up for racing and it's got all the power in the world but it won't idle except when cold with the choke on. Any guidance would be appreciated.

Your fuel screw and idle setting...

check ur carb pilot circuit..(fuel screw, idle screw n pilot jet)..oso check ur air-cleaner, make sure they're clean..

if you decide to open up your carb, there are two air jets that are prone to clog w/ oil from a freshly oiled filter.

These would be the Pilot Air Jet &

Main air jet.

They are inside the air horm on the airbox end of your carb.

Thanks for the info, I think I'll look at ripping the carb out this next week and check both jets.

If you are getting into the carb, make sure that you check the accel pump too. It won't effect the idle, but the shaft is prone to corrosion and the diaphram collects dirt. Both of these result in a shot shot.

And, as everyone knows, no one whats a shot shot> :)

Speaking of the AP, the 98 / 99's use either the Taffy Mod (less intrusive) or my KL Mod to limit diaphragm pump stroke. Stock, the stoke is ~ 4 seconds. 0.5 has been recommended by a Yamaha Pro Mechanic (the BK [ Brian ???] mod).

But something that could change the results is a power now installed. I don't know if it would help or hurt w/ such a long squirt duration...


maybe the carb slide is cracked???

better open up the carb b4 something serious happen,


Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now