Problem turning engine over - cant start - help


I ran into a mechanical problem this weekend for the first time with my 98 WR400 engine. I thought I would see if anyone else has expereinced this before I start diagnostic surgery.

Bike has been running great, no probs. While riding this weekend we stopped at a trail crossroads to decide what way to go and I shut the bike off. I then restarted it, put it in gear and proceeded to take off and as I let the clutch out I stalled it, or at least I think I did. After that I couldnt restart it... better yet I cant kick it thru a complete revolution.

As you go down with the kicker it turns over a bit and then makes a light metalic clink and will not turn over any more. putting the bike and gear and backing up a tiny bit you can feel the engine turn backwards a bit (I know this is bad to rotate it backwards cause of timing chain jump possibility). you can then proceed to kick it a bit until you hit that "spot". You can also feel this spot by doing the same thing in gear, roll back a bit then forward and it hits it.

The one thing that seems a bit odd is the compression release lever doesnt seem to have as much tension on it, almost as if internally it is still released, however the external actuator on the head is moving its full range of motion.

Has anyone experienced anything like this and could save me some time exploring? I havent found anything else on the board that describes this situation.


this doesnt sound good. what is the maintinance history of the bike, when was the last time the valve shim's adj'd. how many km's has it done etc.

I just got the bike from a dealership about 3 months ago and have probably ridden a total of 20 hours or so on it. I am a maintenance slacker (at least I admit it!). So ntothing has been done other then some minor stuff such as check fluid levels, lube chain, tighten spokes. Valve clearances have not been checked, but if I had any really tight valves I am pretty sure it would not start as easily as it does (or used to) considering I had a Yamaha FZR600 that lost its valve clearance and was ridiculous to start cold.

Your exhaust valve is stuck open. You need to find out why. The compression release works by opening it; is something stuck? Worst case is you dropped the valve and I doubt that.Whatever you do, DO NOT force your piston up against it anymore!!! You will cause greater damage. Good luck and keep us posted.

[ March 31, 2002: Message edited by: Chaindrive ]

sounds like broken rod

I'll check the valvetrain first... I should get to it towards the end of this week, so I will let you all know what it was...

Anything is possible, but how would a broken rod affect the feel of the compression release? Valvetrain. Out on a limb: bent valve. I've always wondered if accidently hitting the comp release with the engine running would do that. Could that have happened r6roadracer?

sometimes rod breaks and piston gets jammed in cylinder. broken rod will then run into jammed piston.thats why he can only turn crank a little bit.when you try and turn crank over backwards will it make a complete revolution?

I guess it is possible I could have hit the release while the engine is running when I pulled in the clutch, but I have a friend who uses his compression release to kill his engine as his kill switch is broken and he has never had any probs...

I havent tried to turn the engine over back wards until it hits that spot, so I dont know about the rod possibility. I have had rods break before on a running engine and you defintely heard it, there was no noise accompanying the "stall".

Will be interesting to see what it is... maybe even something in the tranny?? but the wierd feel of the compression release I guess points to valvetrain (unless of course that wierd feel is just me).

And to think I went four stroke for reliability! :)

it's not a rod. rods break at high speed on engine braking usually.

it'll be the valvetrain.


over the years ive had about 10 connecting rods break.most of them broke like taffy said,but a few broke after i had already pulled in clutch and was coming to a stop. im not saying thats the problem with your bike,im just saying its a could also be that your piston broke and a piece is binding in crank.then again its most likely you valve train.

[ April 01, 2002: Message edited by: freestyle111 ]

We're a big help here, aren't we? :)

Now that the NCAA is winding down, maybe we can start a pool. I'm betting an exhaust valve dropped.


r6, did you ever find the problem? Suspense is killing me! Hope it was some minor glitch.

I might have been one of the first people that ever had a catistrophic failure on a 98 YZ400f around the middle of 1998.

I had tightened up the slack in the compression release cable before riding and after a very short period of time the bike locked up very similar to what you are talking about.

Because it was a new bike and just slightly out of warranty Yamaha was willing to take care of it. It only took a month to get the back ordered new head. The service manager admitted to me that he heard from Yamaha there was a clearance problem on the first few heads that came out and they determined that was the problem. Apparently at that time there had been 15-20 bikes that had suffered that same problem. I never told him that I had taken the slack out of the compression release cable. Truth is, I didn't realize or even consider that to be the problem at the time. Soon after I got the bike back there was a tech update released on leaving slack in the cable.

Maybe you can use that angle with the dealer if it turnes out to be the exhaust valve. ( that is also my bet by the way.

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