HEADS UP!!!

Site upgrade in progress... Core site functions are working, but some non-critical features/functions will be temporarily unavailable while we work to restore them over the next couple of weeks.

Please post any bugs you encounter, but before you do, check to see if it's already listed.

Thanks for your patience while we work to improve the community.

Sign in to follow this  
Followers 0
robg

more tic tic boom snap pics

18 posts in this topic

Share this post


Link to post
Share on other sites

Was this a street ridden bike? Not much head damage except for the one bent valve. Considering how much lower end damage there is, I'd say the conn rod went first and it had to be revving pretty fast to spin enough times to do that much case damage. The clean break of the rod tends to back that up.

Share this post


Link to post
Share on other sites

My guess:

1. Something went amiss in the combustion / head area, at high RPM - stuck or bent valve, possibly due to detonation (messy combustion area!) , hence...

2. The con-rod suffered too much stress and - BINGO! Tic Tic ...

The rest is history :thumbsup:

Colin

Share this post


Link to post
Share on other sites

so how long you out for? How much $ is it gonna take to fix? Can u do it youself? Riding season is apon us. Good luck man!!

Share this post


Link to post
Share on other sites
My guess:

1. Something went amiss in the combustion / head area, at high RPM - stuck or bent valve, possibly due to detonation (messy combustion area!) , hence...

2. The con-rod suffered too much stress and - BINGO! Tic Tic ...

I dunno. I'd expect to see a lot more piston/head damage if the valve had hit the piston. Looking at the piston's valve pockets I just don't see enough there. As many times as the flywheels had to spin to do that much case damage, the piston had to have stopped moving almost immediately or there would be more damage to it and the valvetrain. I would expect to see a broken valve, not just a bent one, and a hole in the piston. The bent valve appears to be collateral damage after the initial rod failure that was perhaps caused by a seized wrist pin bearing. Catastrophic rod failure from prolonged and frequent over-revving, possibly exacerbated by an oil flow problem is my guess. Probably no way to know for sure, though. Pretty freaky whatever the cause. :thumbsup:

Share this post


Link to post
Share on other sites

My guess is When I rode a real wide open track (ice racing) this winter and there was a few spots where I was pinned to get the lead and then backed out of it because I didn't want to blow it up. I think that was where the damage was done. Then a few races later I was going around a corner and tapped it into 2nd from 3rd and she over revved. I thought I caught I but about 5 corners later she was done . So now I think I know the combination of all the bad things that might of lead to that ouch. I also have raced that bike 3 ice seasons and I think when a fellow does that kind of stuff to then it's time to re rod them every so often. I did the tranny and the head and a new piston and rings But the Rod looked good but for the price I should have done it. I have decide to rebuild it and I'll keep y'all posted on the final rebuild cost.

an expensive lesson learned

Share this post


Link to post
Share on other sites

Racing will do it every time. You kind of have to adapt a different attitude about replacement with a race bike. More of a do it anyway, rather than a wait until necessary attitude. With these modern 4-strokes it is important to replace things on a schedule instead of just hoping things will last. Sorry you're learning this the hard way. Good luck on the rebuild. :thumbsup:

Share this post


Link to post
Share on other sites

Hell if I ever need a motor grenaded I know who to look up. Damn!

Share this post


Link to post
Share on other sites
Here are some more pics of my 2000 wr400. Ugly

Lots of stuff broke. So what do you think went first ?

I'd guess the rod small end went south causing the rod to break.

The small end is the weak link on the old 400f's. I just replaced mine with a 426 rod.

Fixing it is not an option. You need to find a motor or sell the chassis.

If you sell the chassis, let me know and maybe I can use any salvagable parts out of that motor.

Was it ticking for a while before it blew up?

Share this post


Link to post
Share on other sites

I have never witnessed anything like that on a motorcycle, however I have seen a lot of this when we used to race cars, particularly in drag racing and circle track.

Usually something like this would happened upon deceleration after a high RPM run, I.e. the run out after 1/4 mile at the drags, or at the end of a straight decelerating into the corner in circle track.

I can't remember ever seeing this happen at a low RPM or under acceleration.

Share this post


Link to post
Share on other sites

Thanks for keeping us informed

My guess is When I rode a real wide open track (ice racing) ....then it's time to re rod them every so often. I did the tranny and the head and a new piston and rings But the Rod looked good but for the price I should have done it. I have decide to rebuild it and I'll keep y'all posted on the final rebuild cost.

an expensive lesson learned

:thumbsup:

Good luck with the rebuild. Just for info, a friend of mine built a high performance turbo motor and had the standard rods "shot peened" to add strength - a cheap alternative to buying beefed up rods when you dont want added weight.

Colin

Share this post


Link to post
Share on other sites

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
Sign in to follow this  
Followers 0