98 WR400 won't kick start...HELP!

My 98 WR decided to make me a little crazy today. It will not start by kick-starting, but if I push/pull start it then it starts and runs fine. It does not make any difference hot or cold. I have been trail riding this bike for over a year and never had starting issues, in fact I have never had any issues. But today that changed....

Last week it was acting a little temperamental about starting, but it did and ran good. So I went ahead and cleaned/oiled the air filter and changed the oil. Today when it would not start my first thought was spark plug, so I put a new one in (at the trail head :) ) but it still would not start. So I fiddled some more and then it started (with the kick starter). I let it run for a minute and then shut it off to put the seat back on. Then it would not start again. So we pull started it and took off up the trail. It never did start with the kick starter the rest of the day. It ran well, most of the day, but just before we got back to the truck it started faltering unless I kept the RPM's up.

So, now I am about to go and start testing the ignition system, but if anyone has any ideas I would sure like to hear them....



check your valve clearance, not shure how those are setup, but on my bike i can remove two covers and check that i have a little clearance(roll the motor over to get the cams on there base circle.

this is not a substitute for using feeler guages,but rather a quick diagnostic check.

if you got a little clearance on all the valves (thats good), then next thing to do is a compression check. do it hot and cold (trust me on this).

Sounds like it's ignition related - check your coil for good spark then test the stator.

Sounds like it's ignition related - check your coil for good spark then test the stator.

+1 on this.

Okay, I did resistance tests on the CDI pickup, the coil and the TPS all check out fine. I am getting a nice blue spark at the plug. I checked the valves and they are good. I pulled the carb and cleaned all the jets and the accelerator pump is working just peachy. I pull started and checked for vacuum leaks and finally I drained all the gas and put in new stuff. The only thing I have not been able to do is a compression test, but I can stand on the kick starter (all 265lbs of me) and it will hold my weight, I can kick it w/o the compression release if I hop...

So, I am back to my original thought that it is a timing issue,which would point to the CDI, but I hate to buy something like that just on a hunch...

I would double check the cam timing and valve clearance, be sure to use feeler guages. If they are out of spec the bike will run but is hell to start.

I had a similar problem on an 06 wr450 and it turned out to be the CDI. There were diagnostic steps in the manual to check electrical components and hence pointed at the CDI by method of elimination. A sudden change of starting ability seems to be electrical where a gradual change would indicate valve clearance issues. The following thread details my experience:


I just finished double checking the valves and only one is slightly out of spec (.2 mm), as I was doing this I realized that I can turn the engine over using the crank nut fairly easy (probably not a good sign), but when I use the kick starter it will support my weight for a few seconds before bleeding off.

Is this possibly normal?

I know you said you cleaned your carb but I think you need to do it again. I had the same thing happen to me. Out of nowhere I started to hear popping and a slight bog off acceleration. It got worse very fast, I had to really keep the rpms up just to keep it runing. Luckily I was just able to get my bike back to the trailer before she died completely. I went through ALL of the trouble shooting you've described, I still even have the original CDI box which I replaced convinced that was the problem.:worthy:

On the advise from some folks here at TT I re-visited the carb.:D The thought being the pilot circut which has some tight spots and isn't really easy to get to, had a little crud in it that needed to soften up in order to be blown out. I yanked off all the plastic bits and soaked it over night. I used a combination of gas/paint thinner and carb cleaner (from what I understand Yamaha makes a solution for this exact purpose) I reassembled it and sure enough she fired right up, after some basic carb adjustment everything was back to normal. I think if I had better understood how the pilot circut works in the first place I may have saved myself a lot of time and trouble. The pilot circut has everything to do with the way your bike is going to start and perform off idle. Besides a good thorough carb cleaning can't hurt.:)

Thanks, I will give it a try. When you say paint thinner, did you use lacquer thinner or mineral spirits? (or something else?)



The can said paint thinner.

Well it looks like I am back to square one. Thanks to WR Dave I was able to get the valves in spec w/o having to drive all over the country. I disassembled the carb and soaked it in gas/lacquer thinner for about 5 hours and then carefully blew everything out and put it back together. I even put another new plug in just to make sure I did not have a fluke. All with the same results.

So my last bright idea is timing which points to the CDI...

Thanks for all your thoughts, I will post when I finally do get it going again.


I'm glad the shims worked out for you with the valve set. Make sure you check all the wiring to be sure that there is no rubbed through or shorted wires. Does the bike have good spark at the plug? I hate to say it , but on my 426 when this type of thing happened , I had to replace the CDI. My 426 started to backfire quite a lot and have intermitent low power before the CDI was done. If you go that route try E-Bay and if you go aftermarket, then you can't do any better than installing a Vortex X-10 CDI box. WR Dave.

Wiring and bad connections was the first thing I checked. The frustrating part is that it does have a very good spark, nice and blue and you can hear it snapping as you kick it over (with the plug out).


When my CDI went out I had very intermittent spark at the end but the problem occurred over a 2 week time so who knows. Sooner or later you'll figure it out......good luck

Well it looks like the problem is solved (without replacing the CDI). I went and bought a new compression tester (my old one is pushing 20 years old) just to be sure and it tested out at 160# cold. I decided to do a hot test so I pull started it and rode around in the field for a while and it ran better than it ever has since I have owned it--the carb cleaning I think made a big difference here. Anyway, once it was warm I turned it off and tried to kick it, same results. But it did sort of pop, so a few more kicks and it started. I ran it around a little more, killed it and tried again seemed like 100 kicks later it started again. Finally after going through this process a few times I decided to try holding the compression release longer than normal and get the engine spinning a little faster. Lo and behold it started first kick. I killed it and started it (easily) several times in a row. I let it sit over night and went out this morning and it started second kick. But I have to hold that compression release until the kick start is almost at the bottom.

My best guess is that the carb was plugged after all. The exhaust valve the compression release is on is the one that I switched shims on, so maybe that changed where it liked to start on the compression release.....

Any way, thanks to everyone for your advice!

So I am having to re-learn the timing of starting it! I am going out trail riding tomorrow so I will see how it does. I think I am going to put my KLR in the trailer just in case!


Glad to hear your running again. After reading how your starting I'm wondering if maybe your cam chain has stretched throwing the timing a little off? I'm really just guessing here but if you noticed the index marks being off when you where shimming the valves mayyybe...:)

I was thinking the same thing (chain stretch), I did not look real closely at the marks other than they were not lined up. I suspect that someone changed the timing from the original WR specs to the YZ specs. While tensioner is in place the chain seems nice and tight and I don't hear any slap.



I seem to recall reading that the cam sprockets can shift positions on the shaft. It seems odd they wouldn't key the 2 together( the shaft and the spocket). But if it did move that would explain alot. Again just guessing.

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