cylinder head reliability

[kawaman]

Hello all
Most ZXR400 owners around me have had at least once some troubles with the cylinder head + gasket
Do you have any hint about what could be the cause? I mean this could not be coincidence, there should be something wrong somewhere that may be corrected to prevent the head from overheating...
Thanks

[bendog66]

Do you have any hint about what could be the cause?

20 year old head gaskets?

[zimm]

my feeling is that its a design/assembley flaw.. seems more mileage related than age related .. the gaskets just seem to give up after a while, no overheating required...

combination of poor gasket design/material, flexy block, poor coolant flow creating "hotspots", high rpm .. work hardening of the gasket material ?

the recommended torque for the head bolts isn't much compared to other engines either which has always struck me as.. well.. as something that may be related.


its not really a problem.. they seem to fail every 25000 miles or so.. in which time something else has usually failed and necessitated a strip down anyway.

[kawaman]

It's a pity, the 750 is so strong comparativelly... engines doesn't require to be oppened before nearly 100.000kms
My friend bought the 400 a couple of month ago and after making 500km with it he detect a leak of coolant from the headgasket towards the exterior (coolant was spraying outside, incredible!), by this time the engine has stopped running so fine. We all knew that the head gasket was the defetct of these 400, but we didn't thought it was so immediate!!!

I will try to get a 400 repair manual to have a closer idea about the problem, if I am not wrong it happened equally on H or L models, isn't it?
If I understand well your answer, it is a problem of the gasket itself rather than a overheating problem of the cylinder head, thus repairing the engine doesn't require to rectify the cylinder head...

I have been looking on the forum through the search tool, but I didn't find: Does anybody know if a reinforced head gasket exists and where to buy it?
Does anybody tried to tight the cylinder head to a higher torque?

Thanks for sharing your knowledge

[AFM327]

I've had two heads develop cracks between the the sparkplug hole and the coolant port. Both were very small and only leaked when the temps got high enough for the crack to expand allowing the coolant system to become pressurized. I've heard early ZX7r's had similar issues as well. You can put stronger studs in to torque the head to a higher torque spec. The stock ones can and do stretch more than they should if you torque them too high.

[kawaman]

OK, so I have seen on the forum that the zxr4 has a rather oversized coolant radiator, so I guess cylinder head problems has nothing to see with cooling capacity.
I will try to find out where to buy a reinforced gasket and stronger studs, as the problems might rather comes from a mechanical issue.
Thanks to everybody for answer me, this has been a great help