22 replies to this topic

[ads7]

My 850 must have blown the head gasket eight times in the last few years. It's just gone again after 3000 miles which is pretty good going for this particular engine.

I've been very carefully following the advice on the forum regarding correct fitting procedure. Admittedly I do use cheap gaskets from minimine.

Is it worth spending money on the following or am I wasting my hard-earned ?

victor reinz gasket

New head bolts

Head skim (it's been checked and found to be true last time I did the HG

Finally there are some tiny signs of pitting due to water ingress property from previous head gasket failures. Is it worth applying a spot of hylomar?

Sorry to post on this subject but I'm at my wits end

Edited by ads7, 16 March 2021 - 09:55 PM.

[lordcakes]

I too had problems with small bore head gaskets, blowing at least 3 over a 2 year period with quite small mileage. This was using high quality gaskets and following all of the advice out there. In the end I got a mechanic to look at it and he replaced it with a cheap gasket and it stayed on there until the clutch died 8 years later.

I reckon it was to do with filling the cooling system with antifreeze from the off because that seemed to be the only difference in what I did compared to the mechanic.

I have recently done my gasket on a 1275 and I followed the advice of running it up to temperature the first time with plain water only and it has been 6 months now without any issues. This was using the minispares own gasket.

Best advice is not to use hylomar on the head hasket, make sure everything is really clean, don't overtighten the head bolts.

Use a good quality gasket. You probably don't need new head bolts unless they have been overtightened in the past - I'm sure you will get some more specific advice on that from others on here.

Edited by lordcakes, 16 March 2021 - 10:18 PM.

[MiniMadRacer]

Use a decent accurate torque wrench, I tighten them down in 3 stages following the workshop  manual sequence.... once the engine is fully warmed up and cooled i open the Rad cap, retorque them, cracking them off half a turn first, again following the sequence.. then re torgue again after 500 miles..

[nicklouse]

Er..... no head bolts. (Strange Aus builds excepted) they are studs. They are reusable as the are not stretch items. Old ones are often better quality than the new ones.

 

inspect and if not in a serviceable condition then consider replacing.

 

check block for readied threads where the studs go in. Dress if needed.

 

I don’t do small bore so can’t say if there have been gasket issues.

[Spider]

Respectfully, there must be something more to this. On an 850, even in mild tune, it should hold even a cheap gasket, though granted, copper composite head gaskets can be tricky

 

What gaskets have you been using and where have they failed ?

[goudoogje]

did you check the deck and the head with a ruler and a small flashlight? 

Edited by goudoogje, 17 March 2021 - 09:20 AM.

[ads7]

https://www.ebay.co....4.m46890.l49292

Link above to gasket I normally use above

Below is link to Instagram post showing condition of block and head surfaces pre install


https://www.instagra...id=1sqqwua5mc3r

Gasket usually blows between the middle cylinders

I've had issues with crankcase pressure and a recent cloud of blue smoke indicating worn rings and bores that need re honing in future, perhaps this is a contributing factor to the gasket issue?

Edited by ads7, 17 March 2021 - 09:23 AM.

[ads7]

did you check the deck and the head with a ruler and a small flashlight? No

Yes a steel ruler and torch

[nicklouse]

https://www.ebay.co....4.m46890.l49292

Link above to gasket I normally use above

Below is link to Instagram post showing condition of block and head surfaces pre install


https://www.instagra...id=1sqqwua5mc3r

Gasket usually blows between the middle cylinders

I've had issues with crankcase pressure and a recent cloud of blue smoke indicating worn rings and bores that need re honing in future, perhaps this is a contributing factor to the gasket issue?

I guess the picture was taken before you cleaned the block? If it is shown before assembly I would say could do better. Pull the studs and then check for pulled threads. get rid of the rust and carbon deposits. But don’t rub in one place to much. More of an all over application. Then Then check for flatness. 10 thou is a permitted amount before machining is needed IIRC.

 

Worn rings etc don’t really cause head gasket failure as they reduce the pressure in the cylinder.

[ads7]

Ok thanks I'll do all of this

[GraemeC]

The comment about the torque wrench is very valid - especially if you've had it a while and/or don't know its history.

 

As a minimum I'd suggest borrowing one so you can at least do a comparison check - maybe take yours to a friendly mechanic and see if they'd compare it to theirs for you.

[ads7]

The comment about the torque wrench is very valid - especially if you've had it a while and/or don't know its history.

As a minimum I'd suggest borrowing one so you can at least do a comparison check - maybe take yours to a friendly mechanic and see if they'd compare it to theirs for you.

Will do . I was using a cheap 'bendy' one if you know what I mean.

Edited by ads7, 17 March 2021 - 12:52 PM.

[GraemeC]

Treat yourself
https://www.halfords...200-488711.html

[Dusky]

Nothing wrong with those bendy torque wrenches. Just check it’s calibration with a Vice and a bucket of water.

[ads7]

Nothing wrong with those bendy torque wrenches. Just check it’s calibration with a Vice and a bucket of water.

???