Blown headgasket is never a problem in itself. Is usually just side-effect or result of real problem. Without actually identifying and fixing that problem, new headgasket will blow just like previous one. In troubleshooting cooling system, did you:

• measure ECT at 25c and 100c and confirm it matches response-curve from manual?
• confirm that ECU activated cooling fan at proper temperature?

Doesn’t appear to be any breaches in heatgasket. Need to:

1. measure flatness of head and block deck.

2. Repair stripped thread with solid metal insert such as Time-sert. Do not use
helicoil, they will let you down.

3. change to studs in block rather than head bolts. Much, much more secure and doesn’t loose tension over time like bolts. Also less chance of stripping threads in block.

4. use copper exhaust header nuts to avoid yanking out studs and stripping holes in head.

 

Thanks for the insight. What I've gotten so far is someone's loaded the parts cannon and fired off a head gasket job without checking for warping, as evident by a brand new HG with obvious signs of exhaust going between cylinders 1-2 and 3-4 along with the existing overheating.

Good shout on the timesert, I have helicoils already but will take the advice and look at those along with studs (though getting the head back on in situ may be challenging).

Anything else to rule out? As the thermostat was gutted so couldn't be stuck, pump/radiator are fine and no sign of blockage. Given it was tracked earlier in life all I can get to is warpage/head gasket. Can't see any evidence of cracks in the head or cylinder walls either

Also, given the HG currently in barely looks bothered, is it safe to re-install?

EDIT: I did confirm fan comes on when it should, can't check ECT now as the head is off. Pretty obvious it's not that though as it's overheating with. Thermostat blanked so fully open, coolant clearly over-pressured as it pushes coolant into the res and not pulling into the system along with the presence of exhaust bubbles (can smell the exhaust in them)

 

Remaining possibilities:

- clogged radiator. Needs reverse flush to get stuff out

- clogged block. You mentioned corrosion from tap-water, might be scale build-up internally. Use something like CLR to remove deposits and reverse-flush block

- water-pump vanes, check blades and make sure they haven’t been chewed away by corrosion

- coolant, do not use propylene-glycol based coolants. They only have 1/2 thermal-conductivity of regular ethylene glycol. In non-freezing summer, use distilled-water + Water Wetter for maximum thermal transfer. In winter, use just 25% ethylene-glycol for freezing protection. Fill rest with distilled-water + Water Wetter.

- bubbles in cooling system, need to burp with running with cap off until thermostat opens, squeezing hoses and blipping throttle to get bubbles out. Top off, put cap on.

- manual fan switch, last ditch effort many people use. Switch grounds activation terminal of fan relay just like ECU would. Use it in stop-n-go traffic to keep fan on full-time. Anticipate traffic lights and turn on when approaching stop.

Measure raised compression-ridges around headgasket. If they’re 0,1mm or more thicker and than flat sections of gasket, can probably re-use. Spray 3-layers of spray Coppercoat on each side with complete drying in between. This seals against surface scratches rougher than RA=80 which may weep coolant through.

 

Thanks, good to keep in mind especially for the coolant to use.

Thermostat was permanently open as it had been gutted, burping failed. Water pump was pristine. Rules that out. Radiator tested off the bike as well. Seems only reason for the bubbles is exhaust gases along with the smell and evidence of exhaust gas migration on the mating surfaces.

 

All makes sense now, the gasket 'looked OK' but between the layers it's pretty evident where the issue lies. Getting the head machined today, happy with the deck (which I've also had to helicoil) so hopefully she'll be back together by tomorrow afternoon 😎

 

Only just ended up getting the head back. Also noticed the new head gasket has 3 layers vs the old one having 2. Anyone able to weigh in there?

Went to put her back together, turns out every other head bolt had weak threads so ended up doing 9 more of those. Never want to see a helicoil again lol.

Got her torqued down and timed up so now just have to do the valve clearances before putting the rest back on.

 

Did both 3-layer & 2-layer gaskets end up with same thickness? What's part# of 3-layer one you got?

Might be 2-layer one is wrong part with incorrect thickness and that's why it failed?

 

This one is aftermarket (Athena brand) and no markings on the old one so assuming that is aftermarket too. It was a track bike at some point in life so could be to do with that. Doubt it's the reason but wouldn't have helped.

Currently trying to get her started, seems it might just be that I've had the tank in the shed for 2 weeks now and might have moisture so gonna sort that

 

Finally back together with fresh fluids. Took her on a 60mi round trip without a hiccup, stays around 80C cruising so no concerns any more. Cracking piece of kit