HillBilly Needs Help! Engine Dying!

Today was not good for me. I went riding but here is what happened after about 1 1/2 hours of tight woods riding (using 2nd and 3rd gear; allowing to idle down long hills and up to 1/2 throttle everywhere else). My bike began backfiring when I would let off the throttle. It soon quit completely. I figured that I had fouled a plug. I waited about 5 minutes, pulled out the hot start and eventually cranked the bike up. I went straight back to the truck.

I then changed the plug (Splitfire SF 430C). I inspected the plug taken out. Although it was black and sooty around the outside, near the electrode was brown and had a few specks of white. Assuming problem fixed, I cranked back up, went 200 yards and yes, it quit. I could not get the bike cranked with the hot start in or out. I finally pulled out the choke in desperation and it cranked. I got back to the truck, pushed in the choke, and it quit. Riding over for today!

After I got home, I washed my bike off (had been pretty muddy) and thought that quite possibly the vent hoses from the carb were plugged with mud. I cleaned them off well and then tried to crank the bike. It fired up with the choke out. I rode down the street and back (About 100 yards) and my bike quit in the driveway. Have not check the plug yet. So a long story made short, MY BIKE'S FALLEN AND IT CAN'T GET UP!!!


'98 WR 400

WB E-series, 10 discs

Snorkel removed

WB Power Filter

WR timing

180 main jet

50 pilot jet (at least dealer was supposed to move it to a 50)

Air screw 1 1/2 turns

Elevation @ 800 feet

Rode about 3 weeks ago after getting the bike serviced and it ran superb. Help would definitely be appreciated.

Hey Richard, I am no expert, but I would check the following;

1. Fuel level and fuel filter

2. Oil level, color, etc.....

3. Air filter. Is it clogged?

4. Carb intake. Any dirt?

I dont think it has anyhthing to do with the plu, particularly as it was serviced. When it was serviced, did they do anything apart from the service? Did they install everything associated with the carb correctly?

You mentioned riding in deep mud and such and you checked the hoses. As the main hose "blows" rather than sucks, I do not feel that would be the problem. But, is there any possibility of anything getting stuck in the hose? Running on choke but not normally?

I recall a post some time back that looked at the rubber seal around the hot start button being frayed and not closing correctly. Can you check to make sure the hot start closes correctly? If all else fails, take it to the shop and remind them that they serviced it three weeks ago and that if there was a problem, they had the responsibility of letting you know.

Good luck


At first it sounded like you fouled the plug... changed it... and forgot to turn the gas back on, going about 200 yards is the right distance, but restarting only with the choke is making it look more like an intermittent problem.

Aside from that, the #50 pilot sounds too rich for slow mud riding regardless of the needle and clip position.

The '00WR has a fuel screen hidden above the carb float needle, does the '98? maybe check if it does and make sure it's clean. Could the tank vent be clogged? Was your bike low on gas and needed to be on reserve? (You wouldn't be the first person to have missed that)

James Dean

Clean up the accelerator pump. Similar situation happened to me when riding in Arizona earlier this year. Would be worth a try, worked for me.


99 WR400





The same thing happened to me....and i mean everything you described. Well I tried everything to no evail. So I took the bike in to the local shop. Just before I got in my truck to leave, the mechanic came running out with a grin on his face.....After checking the plug earlier in the week I accidentaly left the piece of plastic/rubber that goes between the tank and seat on top of the airbox holes. Boy did I feel like a jackass...check it..stranger things have happened.

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