ZZR250 overheated, blew head gasket

[ducatilover]

Hmm sounds like you have two shitheap motors bro. If your original one was heat seizing, I would pretty much put that in the scrap metal pile. Same goes for the second one really, but we can have a looksie at some point.
Bogan is bloody good at measury thingies, I highly recommend his help. He will even give you bike parts to polish for a few years

[ducatilover]

Blowing a headgasket on them is impressive, I am fairly certain they have a multilayer gasket on them and you'll find everything bends and warps before the gasket goes, I'd say you're more likely to warp the head and snap a stud before the gasket lets go. Or shift/crack a liner.

[imthatguy]

Hello again all!

Thank you very much for all your helpful replies, suggestions and offers of help!
All much appreciated.

To the people saying get a new motor, I totally agree that would be the logical thing to do at this stage, but I enjoy pulling things apart so theres nothing to be lost and experience to be gained in pull this one to bits.

I spent the afternoon in the garage, and after must frustration and swearing Ive managed to get the head off. (Pictures attached) Theres a few interesting things of note; the head gasket is fine, but there was water in both the pots (unfortunately cleaned up before I had the presence of mind to photograph). No visible cracks in the cylinder lining.
From what I could roughly determine with a metal ruler I had on had, no head warpage, but measuring with a ruler is a very inexact science and it will need to be properly measured. Anyway if its not head warpage I don't know how else to explain the leak..?

03ducatilover:
your quite right head gasket looks fine

01ducatilover /bogan:
Yeah Ide really appreciate the help, cheers! Flick me a text 0278633603, might take a break for a few days to study as I have an exam on Friday, but Ill be back to this soon..

08mossy1200:
No disrespect taken haha, I totally understood what you meant. And your right, Ive got a few contacts who wreck bikes so Im sure a new engine will turn up soon.
Would you really recommend replacing all that for a warped head? The engine is relatively new (30k) given the rest of the body is a 1990.. Seems a bit silly to spend so much on it. I was thinking maybe just a cylinder head plane and wack it back on!

The Reibz:
I suspect your right.

[mossy1200]

Idd suggest take head in and get advice that's not reliant on some photos on KB.
Me idd get skim and checked for warp. New piston and ring set one size over. Check bottom end for any issues prior to doing anything else.
Is that old im looking at or slightly wet radiator water?
Whats the oil look like also?

[The Reibz]

Atleast there isn't any catastrophic damage visible in the photos.
If you get the head skimed you will also need it die tested for cracks and pressure tested for good measure.
Expect to pay atleast $200

[nzspokes]

Atleast there isn't any catastrophic damage visible in the photos.
If you get the head skimed you will also need it die tested for cracks and pressure tested for good measure.
Expect to pay atleast $200

This is spot on. At a guess the cracks will be in the valve seats or under them. But I would strip and clean the head first and look for obvious cracks.

Or just buy a good motor. And do a good clean out of the radiator.

[imthatguy]

Idd suggest take head in and get advice that's not reliant on some photos on KB.
Me idd get skim and checked for warp. New piston and ring set one size over. Check bottom end for any issues prior to doing anything else.
Is that old im looking at or slightly wet radiator water?
Whats the oil look like also?

Oh the photos were more for interest sake then anything, I will ask advice from the a bike mechanic tomorrow.
Oil looks fine no water in it and its the right viscosity.
Not quite sure what your asking re water? Remember that I put water into it after it lost almost all of it due to the pipe leak..

[imthatguy]

This is spot on. At a guess the cracks will be in the valve seats or under them. But I would strip and clean the head first and look for obvious cracks.

Or just buy a good motor. And do a good clean out of the radiator.

Definitely no cracks I can see, but Im guessing they would be so small I wouldn't be able to see them? Will definitely give it a clean and check in any case.

Are you suggesting that would explain the fact its leaking OUT of the head? Or would simply be another consequence of the head being overheated.

[nzspokes]

Definitely no cracks I can see, but Im guessing they would be so small I wouldn't be able to see them? Will definitely give it a clean and check in any case.

Are you suggesting that would explain the fact its leaking OUT of the head? Or would simply be another consequence of the head being overheated.

No, thats why they use dye to mark where it is. You will need to clean the carbon off to have any chance of seeing unless its a big crack. And pull the valves as it could be in the ports or seats. I would say the head is cracked, you just need to find where. Couple of pics of the gasket may help to.

[imthatguy]

No, thats why they use dye to mark where it is. You will need to clean the carbon off to have any chance of seeing unless its a big crack. And pull the valves as it could be in the ports or seats. I would say the head is cracked, you just need to find where. Couple of pics of the gasket may help to.

Ahk gotcha, Ill get you some pics soon.

[bogan]

Theres a few interesting things of note; the head gasket is fine, but there was water in both the pots (unfortunately cleaned up before I had the presence of mind to photograph). No visible cracks in the cylinder lining.
From what I could roughly determine with a metal ruler I had on had, no head warpage, but measuring with a ruler is a very inexact science and it will need to be properly measured. Anyway if its not head warpage I don't know how else to explain the leak..?

I wasn't run-off water from dissasembly? If not, figuring out where that came from should be the focus imo, any water in the intake/exhaust sides of valves?

[imthatguy]

I wasn't run-off water from dissasembly? If not, figuring out where that came from should be the focus imo, any water in the intake/exhaust sides of valves?

Well I figured it came in because the head was warped? No the valves were all dry and relatively clean.
As I mentioned, when it broke down, the coolant was running out of the join between the head and the rest of the block just underneath the exhausts, I suspected if its warped its also running into the cylinders too, hence why they had water in them.

[imthatguy]

I wasn't run-off water from dissasembly? If not, figuring out where that came from should be the focus imo, any water in the intake/exhaust sides of valves?

Although actually come to think of it, it could well have been from disassembly as the engine is on a lean and there could have been water still in the coolant jacket as I pulled it off.

[bogan]

Although actually come to think of it, it could well have been from disassembly as the engine is on a lean and there could have been water still in the coolant jacket as I pulled it off.

Yeh, reckon that could be the case; which would take water out of the equation (but in a good way this time). So after it stopped from overheating, did you try and run it again once things had cooled? if so what were symptoms, compression etc.

[ducatilover]

Chances are the head is fucked. Usually with little Jappas like this the heads go soft after overheating and they go wobbly too. But worth having it checked if you really want to play with the motor (nothing wrong with that idea spanner time is good)

You'll want to hone the bores and re-ring it. So you'll need a set of micrometers, feeler gauges and a decent vernier caliper. (probably cheaper to borrow), I hope it's a poor photo because that bore looks glazed and I cannot see any cross hatching at all

I'd pop the barrels off it and have a good look on the thrust side of the pistons for signs of seizing (nice tasty marking) which I imagine it has done. If it has, pistons are toast unless you want a hand grenade motor. Checking the bore size all the way down is nice and easy, just calculate it with the ring gap

You can buy forged pistons for these with a number of different compression and squish arrangements
Also if it has been seizing, there is a very, very high chance that it has damaged the mains and big ends, they're not huge fans of suddenly stopping.
The rods will have to be very carefully inspected too as they're very petite around the small ends and seizing never helps
And after going that far, I would be investing in some beer to pay a decent mechanic mate to split the cases, because you'll learn a lot if you do.


And that's just the beginning