BMW K1200RS - Possible supercharger conversion
Turbo Mini Forums

Cool, cheers!

I was going to say, I didnt think there was that much room in a round nose!

bad news . Suspected head gasket again!

Hasnt even moved under its own power or had any load on it this time. There seems to be something pretty fundamental going on that i'm at a loss as to what it could be.

Since rebuilding after dry deck, ive run it on idle up to temp for 5-10mins and then switched it off after an apparent successful test. Then started it a few days later to check exhaust leaks.

Switched on a few days later to check something and it sounded on 3 cylinders so switched it off. Came back to investigate at weekend and it wouldnt start. Checked compression on cylider 2 and it wasnt registering more than 40psi .

I told myself this would be the last time and would give up the turbo dream but the fact its done it at idle, with no load or boost has given me hope its not turbo related and something that has happened during the build, im just not sure what...

Will take the head off this week to have a look but i doubt i'll be any closer to diagnosis.

head off and get some pics up!

how are you torquing the head down? do you use the tightening sequence as BMW suggest? and what torque value do you use?

Using the middle and work your way out method as per the SC guide. 30ftlbs and the 45 after 15mins iirc.

Only took 1 pic. Will get more 2moro but gasket looks fine to me although it was stuck to the block where it has been visually damaged before.

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Is that a sealant around the head studs where they meet the block?

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

Well, time to get a straight edge and a feeler gauge on the block and the head.
I am somewhat surprised that with all the mods to fit the K-heads that the blocks don't warp more under the first few heat cycles.

The question you need to ask yourself is, why is there coolant there if you have 'dry' decked it?

I am not sure about the SC tightening sequence, as I have always used the one that BMW suggest, wich is not just a simple start at the middle and work out. I agree with both Graham and Dave, what's the sealer doing there and best check flatness

I will feeler gauge the block later this week. My setup isnt a fresh one, i ran the car in NA form for a few years with no issues, so i dont think its a problem with k head block work. The turbo may have done some damage when first run i guess and it hasnt recovered since, hence why its done it now under no boost or load.

@ sprocket - cylinder 2 in the pic, thats just oil and water from pipework that found its way there when i lifted the head off in a hurry if thats what you mean.

What is the BMW tightening sequence? Again, the NA setup was fine with this method previously.

Sealant on the studs, yes, a small amount was used when i put the studs back but its a tiny amount and the gasket has blown on 2 without me touching the studs previously.

ok, two things...

1) i cant see a blow on the gasket?

2) that looks like a LOT of block showing on the exhaust side of the gasket for a 73.5mm bore, hats the gasket overhang on the otherside?

1. neither could i. It was likely on the underneath side i would say, but again noting i could see. will take more pics tonight, but its not done any real work, so there isnt anything spectacular to see.

2. yes, that is a good point. i think i would have noticed that when it was fitted. Overhang is probably the inverse of that on the otherside. Actually, I think i remember seeing a slight impression of the cylinder on the underside of the firing ring when i took it off last night

check the deck height too, the pistons could be twatting the fire ring at high rpm,

you "could" be better going to the af460 copper gasket, as the bore is slightly larger in them.

will do, however its not done any high rpm, maybe one or 2 blips to 3k or so.

will look into gaskets but ive gone through an SC cometic, 2 MED MLS ones and now 2 BK450's

The gasket ring looks clean, how's your torque wrench?

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

Are you 100% sure its the gasket? Could be a slightly bent/sticking valve maybe.

I'm not sure of anything any more .

Torque wrench is 2 years old, is an expensive industrial one, and has been fine across other torque sensitive bolts around the car.

The previous gasket looked like this:




I think the damage will be much more subtle this time as its not been under any load or boost like the above one has (albeit only 2mins on track)

How would i diagnose a sticking or bent valve?

so,

looks like its blowing at the front where the gasket is overhanging the bore?

yes, (to clarify that picture is of the underneath of cylinder 2). Any ideas why the overhang is happening or what the solution is?

I seem to remember that when I bought a few new head studs, the plain section was a little longer than the original ones. Are the nuts definitely tightening down on the head and not bottoming on the threads?

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1/4mile in 13.2sec @ 111 terminal on 15psi

what gasket is it? looks MLS, Cometic?

in its std position the centre front stud should alighn the gasket to the bores. has that stud been moved?

try a std bk 450 on there and see what the alignments like?

or try this gasket against a 450...

the picture of the gasket i attached last night is a standard BK450 with the bmw stud pattern cut into it.

The damaged gasket picture from last year is an MED MLS one, suited for BMW stud pattern

or could the block have been bored on the piss?

Has the lastest gasket acutually failed? got a photo of the top of the piston crown, and signs of damage, smoke when running?