XR400: Wont start without blocking air intake...HELP !!!

[DoubleXR]

I have a 96 XR400. It's had the snorkle removed and that's the only mod. If it's been sitting for over 2 days it won't start unless I put a rag in the air box to shut off the air. I thought it had a vacuum leak, but when it's running you can stick the rag back in the airbox and it dies immediately.It's like it's not pulling the fuel out of the bowl during a normal start up. When it's cold I can kick and kick and it's dry as a bone. I can use the rag and there is fuel present. Once it starts it runs great. Once it gets warmed up it starts on the first or second kick. My riding buddies say I'm getting a little puff of smoke on de-acceleration but none on acceleration. Is it a carb problem or valve train not drawing enough vacuum to pull the fuel from the carb...I've been told both. What do you think ????

[dwade277]

Check and clean any fuel filters.

My 2 cents

[NORTEXED]

Have you checked to see if you have fuel in the bowl when trying to start it? It almost sounds like a sticking float or a partially clogged slow jet. The clogged jet would explain the success with the rag on the intake, as could no choke plate (or missing partial plate. For some reason, it's taking a tremendous amount of vacum to pull gas up into the charge stream. If it starts O.K. warm, I would think Choke plate problem.

[Tubo]

Partially clogged pilot jet or pilot too small?

[fishbone1]

I am with NORTEXED on this one. I am betting on something wrong with the choke plate. Just because the bike runs and idles normally after warmed up.

[hxr400]

Yes I think the choke plate.

When the bike is hot, turn the choke on full, to see what happens. If it runs fine, there musnt be a choke plate in there! But if it conk's out straight away and dies, like it should, it may well be somthing else! ?

[NORTEXED]

Man hxr, I like those blinkers and small dual headlight. I wanna put mine on the street soooo bad ?

[hxr400]

Thanks NORTEXED! ? I think it looks pretty damn good too!

The indicators come standard on the Australian road registed Xr's. And the little dual head lights are made by UFO.

Notice the number plate? HXR-400. The H stands for Honda, in case somone didnt realise.

[DoubleXR]

I tried closing the choke with it running. It dies immediately.If it dosen't have enough vacuum, could it be in the valve train ??

[NORTEXED]

Expert is NOT in my title, but I just don't see how it could be a valve train problem. An air leak in the system (adaptor to head, adaptor to carb, or carb to airbox) might be a possibility, but it shouldn't run well warm either. What size slow jet does it have in it?

ps: mine came with a 42 slow jet, and untill I "Gordonized" it, it was a B---- to start cold, but would start and run fine warm.

[NORTEXED]

Hey Man, I just had a brain flash (or fau-- as the case may be). If you had an air leak in the "manifold" between the carb and head, putting a rag in the air box would definately cause more vacum in the carb and possibly draw more fuel in. At the same time, putting the rag in after warmed up (or closing the choke), might cause it to draw more air in through the leaking spot and lean out the mixture below the combustable concentration. This would be more of a problem if the system was already too lean (ie. too small a slow jet). Sound reasonable??? ?

[DoubleXR]

I'll check for a leak there and check on that slow jet. Thanks Guys !!!