holy moley!

[gixer400]

this is a nice little picture of a head and piston from a zxr400. it did belong to jon (racemeandsee). the little bits next to the (half) piston are what i found in the crank :? no wonder bits of metal were coming out of the exhaust. anybody have any idea how this could have happened, because it looks like the piston has been banging into the head, broke off 3 valves and squashed the spark plug. seems a bit odd to me.
http://images5.theimagehosting.com/zxrengine.JPG (http://www.theimagehosting.com)

[Lateshift]

ZXR400's are supposedly notorious for their cam chain tensioner problems.

If the cam chain tensioner had worn then there is a good chance that the valves are opening when they should be closing etc.

Thats pretty much the same picture you will see in most 4 stroke car engines when the cam belt goes ;)

The spark plug would have been squashed by all the metal throwing around in the cylinder, given that its relatively soft metal and hot at the time it wouldnt have taken much to damage it.

The picture to my mind shows that the camshaft or tensioner had given way, this has caused vibration in the shaft and in turn has shattered the valvetrain above that cylinder?

Was there any damage inside the top of the cylinderhead/camshaft housing?

[gixer400]

ive not really had a chance to have a good look around yet, but thanks for the tips. at least i know where to look now. you really are a fountain of knowledge.

[Lateshift]

Nah, i just used to be a mechanic before i joined the Army :D

I only wish i used to be a bike mechanic! :D


Generally speaking a "holed" piston like on a 4 stroke engine is only caused by a handful of things, valves (and the failure of the associated items) and detonation but this is more common in turbo engines and i dont really think its that common in sport's bikes simply because the quality of the piston tends to be up to the job.

Oh and lastly, some sort of damage to the piston that creates "swarf" or metal flaking off in the cylinder, this could be piston rings, but for it to have happened on such a scale to cause that damage there would be plenty of blue white smoke from the exhaust first ;)


My money will stay on the Cam chain problem, we have a ZXR400 sat here and that was the first bit of advice i was given when looking for one of these bikes, and that was from a guy that has been working as a bike mechanic on and off for the last 20 years :)

[Ride-or-die]

it looks normal to me, whats missing, a screw a bolt what?

[Spider]

told ya it was fooked

[Lateshift]

told ya it was fooked

I was trying to tell him that, but you put it so much better :D :D

[AndyC]

ZXR400's are supposedly notorious for their cam chain tensioner problems.

If the cam chain tensioner had worn then there is a good chance that the valves are opening when they should be closing etc.

Surely if this were the case then we would be seeingthe same damage on all 4 cylinders??

Looks more like a single valve failed and took the others with is as it was bouncing about in the pot.

Was there any warning before the failure, IE any strange noises?

[ProdigyPete]

Sod being behind him, with metal flying out the exhaust.

Something very James Bond about that

[gixer400]

ZXR400's are supposedly notorious for their cam chain tensioner problems.

If the cam chain tensioner had worn then there is a good chance that the valves are opening when they should be closing etc.

Surely if this were the case then we would be seeingthe same damage on all 4 cylinders??

Looks more like a single valve failed and took the others with is as it was bouncing about in the pot.

Was there any warning before the failure, IE any strange noises? ive no idea. it wasnt mine, but ill ask.

[Biker Dude]

yup, it was spitting metal for ages b4 he swaped lumps

[Lateshift]

I agree with that, i have been trying to do some digging about "harmonic vibrations" causing the valve assembly to shatter, its seemingly a problem but not as common, it may explain why its only happened to one cylinder.

The proof of that will be to check the cam housing to see if there is any debris knocking around in there, its got to be something that is common to all 4 valves, for one valve to have had a problem it would have only damaged the one valve in that way.

With it being a double camshaft (if i recall correctly) the problem will have been preceeded with a shed load of rattling in the top half of the engine before it finally started throwing shrapnel! :D

[Tark]

Doesn't look healthy!! Hope you get it sorted!