What's wrong with this thing??

My friend has a 99 WR400 that has a problem. I know very little about thumpers. Here's the problem. The bike will not start without replacing the spark plug every time he rides. Once a new spark plug is installed, the bike runs great. During the ride, he can shut the bike off and restart it without a problem as long as he does it in a short period of time. If the bike sits for more than 15-20 minutes, however, the sparkplug must be replaced again.

Please... any ideas for the mechanically retarted?

It could be many things.

If it were my bike (or my friends) I would take the carb off the bike and clean it out really well with carb cleaner and blow out all of the passages with compressed air. Then, it wouldn't be a bad idea to jet the bike completely stock, needle and all, just follow the manual. It's my opinion to start with a clean slate. Put it back together with a fresh CR8E plug and fresh gas. If that doesn't take care of it you might have an electrical problem but try this first for piece of mind.

I wish I had friends like you!!

peace DL :)

[ March 12, 2002: Message edited by: Dan Lorenze ]

I had a similar problem with my 1999 WR400 when I bought it new in March 1999. The dealership couldn't help me and the local shops gave me bad information. In fact, this is why I started ThumperTalk. To be able to share such information.

Basically, I was replacing a plug after every ride. I ride in Colorado and all along felt it was an altitude jetting problem. On one very high altitude ride, I replaced it twice! The biggest problem was LONG downhills with little throttle but occasional blips to clear obsticles. Finally, I got the jetting right for Colorado (dropped the main a little, dropped the clip one position and dropped the pilot one size) and it ran great.

My other WR400 friends had to also drop the main and the clip, but for some reason, my bike was the only one that required a pilot jet change. But all the bikes are just a little different.

I don't know if this is your friends problem or what altitude he rides at. But I thought I'd share just in case.

Bryan (in Denver)...

Thanks for the advice Dan.

My buddy took the bike to a shop in town about 2 weeks ago and had the carb cleaned and his fork seals replaced. The next time we rode he ran VP gas in the bike and it ran great.

We had been out about 4-5 times after the bike shop and the bike ran fine. Then one day he went to start it in the morning and we discovered the problem of not starting.

With the new plug in place, the bike fires on the first kick. Then when the bike sits it won't fire at all. We pull the plug and it seems to be fouled (black color with a bad smell of gas.) One of several things that I don't understand is why the bike will run fine with the new plug but won't restart after sitting.

I guess it is possible that the shop did or did'nt do something they should have??

Echo, Im glad to see that you guys got the carb all cleaned out and jetted to stock. Now, I think it's time to take Bryan's advice since he knows the bikes and your altitude. These carbs a really sensitive, I can remember the smallest changes that I've done have easily fouled plugs. Don't get discouraged with the bike because im sure that when it was purchased new from the dealer it was set up for the altitude and ran great but who knows what changes that previous owner (s) has made.

Also, did you know that Bryan (that responded to your question) actually started the crazy website we know as "ThumperTalk"? Pretty cool....

Do as he says and get back to us.

DL :)

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