Help Needed - Hanging Revs

My '98 WR400 has a problem: when warmed up and in first or second gear (at least thats when I notice it) when I close the throttle from about 1/4 - 1/3 turn, revs come down but then hang at a very high idle and dont come down until I very slightly blip the throttle, then it settles to normal idle. This is the only way I have so far found to get rid of it. Doesnt do it all the time, but most of the time.

Anybody any ideas what might be going on ?

My thoughts so far...

- I cleaned and lubed the throttle cables very recently so I dont think it is that but if anybody thinks different let me know - I did find it a PITA to adjust the cables so the throttle rolls/snaps back easily, which it still does by the way.

- A high hanging idle is a sign of lean on the pilots (I think) but my understanding was that revs eventually drop on their own if this is the case.

Carb slide problem ?

Jetting is not what it says in my signature, its now stock (EURO) with JD blue needle and a slightly smaller start jet but still de-octopussed!

Read this thread. It sounds just like what's happened to my bike. The rings, and possibly the piston, are shot on mine. I haven't gotten mine back together yet because I'm going to be measuring the piston and cylinder tonight to see if they are within specs, so I can't say for sure yet all that needs to be done. But the nice thing is that I now have something concrete that I can fix istead of endlessly messing with the jetting.

I'll be looking very closely at that very soon.

I did the valve timing switch to YZ myself and found it pretty straightforward. Is the piston ring thing something equally or more challenging or should I get a shop to look at it ? I only have the clymer manual.

doing the rings is no harder than the valve timing, just takes a lot longer. It's a good idea to leave the head bolted to the barrel and remove the 2 as 1, saves disturbing the head gasket. Not sure if this is possible if doing it in the frame. Make sure u check the ring end gap, regardless of how many people tell you that 'it'll be right'. After you put it back together check, check and check again the cam timing. If you get that bit wrong, it's all over.

my $0.02 worth


Jetting is not what it says in my signature, its now stock (EURO) with JD blue needle and a slightly smaller start jet but still de-octopussed!

There's the problem. The DRZ guys have discussed this problem in

detail...The fact that the carbs are nearly identical to the WR400

FCR I think you're lean. My DRZ440 was fine until I de-octopussed it.

Now I have the same trouble. Hanging idle. If you lower the idle, it

tends to pop and stall.

That indicates a lean condition on the pilot/slow air circuit.

Mine is way too lean. I replaced the slow air jet with an adjustible

air screw which makes that part of the circuit infinitely adjustible.

I'd take a hard look at jetting before a major engine problem...

Just my $.02 worth. YMMV :)


Have a leakdown test performed before any major teardown. It may save you $$$ in the long run.

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