Transmission removal method

[georgesgiralt]

IMHO, the valve stem damage was not,per se, caused by the rocker but by a seizure in the guide and, a following very hot valve which got pounded by the rocker.
The questions remains, what caused the valve to seize in it's guide ? Was it bent during installation ? Or a bad guide installation, making it not perpendicular to the guide ?
If you said that the head was properly oiled, we can rule that out.
As per the rockers, I had a couple worn and having a "step" making noise on their contact surface. A local BMW  Guru restored the proper shape and hardened them back. They are still on the bike since 1999 .....  So maybe inquire with mechanics around you ....
Lastly, check if the push rod are strait and not damaged because they had a very harder job to do. Same goes for the cam operating this valve...

[tunnelrider]

Had a little time a week ago to get the valve out of the guide, it wasnt that hard to tap out with a normal hammer, after blunting down the stem tip mushrooming with sandpaper and spraying a bit of aerosol lube up and down the guide.

Turns out you are right george, the valve did bind in the guide, it seems to have built up a carbon layer on the stem, above the valve head, that interrupts the return of the valve to full seated position.

I'm thinking the valve might get hot by the extra friction of the rocker arm, attracting oil to carbonise (or stick) to the valve in the exhaust port, eventually building up the stem to where sits in the valve guide at full seat position.

The valve hasn't bent and is still straight, but I need a new valve guide, or K'insert, and sort out the rocker arm/ or find a new post 1985 one.  Whether the valve can be reused, I'm not sure.  It may just need the tip re-smoothed.

[georgesgiralt]

Hi !
IMHO, your valve is beyond hope. The top stem is very special. Once hurt, it is dead. I bet it has lost it's hardness so wont last long if the valve is reused.
This goes also for the valve guide, because as the valve has seized into it, there had been metal removal inside the tube, and this will deter proper function with a new valve....
Your analysis is not totally correct I think. The valve seized first into the guide then the carbon build up took place because the valve stayed partially open. You where lucky because it closed enough not to hurt the piston...
Sorry to write this...

[tunnelrider]

Ah yep, makes sense to me, except I'm not sure the exhaust valve was not seated properly for long, as there was no difference in performance until the sign of obvious problem, which was a loud valve ting ting ting...

Agree, it'd worth the extra money to get a new valve also.

[Tony Smith]

Re gearbox removal.

I remove the swingarm and for the extra 5 minutes work involved I also remove the rear subframe and battery box. Nothing like having room to work comfortably I reckon.

[Tony Smith]

Re seized valve.

I think you are not looking far enough back in the failure chain.

I strongly suspect the problem is lack of oil.

A reduction in oil flow would account for both the damage to the rocker axle and the seized valve.

When all is operating correctly a very large amount of oil is pumped via the upper cylinder studs. As a rule of thumb cranking the engine over for 20secs should see around 150ml in tins positioned under the head.

If not, why not?

Static testing is really only valuable in gross terms given the cold pressure capability of the airhead piping system - but do connect a direct reading gauge in place of the warning switch.

Less than 80psi with cold oil and you have one of:-

The wrong oil
Stuffed pump
Failed pressure regulator
Stuffed bearings.

Inspection will confirm which.

If oil pressure is good then you have probably restricted oil flow up the studs - the usual reason for this is the use of too much "goop" when fitting cylinder/head. The only thing to use is minute amounts of hylomar and preferably nothing at all.

If you are lucky enough to not need oversized valve guides ( for which the only sources are OEM or make them yourself) pattern guides from Motobins are good quality and cheap.

Motobins also sell Intervalve valves, these are superior quality.ifci am correct regarding oil starvation you are going to be replacing bearings in the rockers and having the lash faces rebuilt. This will cost but you should probably have all four done.

I have assumed you didn't put the the clear shafts in upside down.

[tunnelrider]

Hey thanks Tony for your thoughts and tips on the possible cause of the valve seize, great to hear from you again too.

You're hot on the trail of georges thoughts too, about a lack of oil, so that's really helpful to start looking a bit deeper, thanks guys.

About the oil supply question, oil pressure valve and oil pump... the right cylinder valve train is pretty quiet in all situations comparatively to the left side that had the failure, so I hope the oil supply in general is sufficient but you're right, I need to get actual an reading of the oil pressure, since the engine has over 210K km on it now.

The last time I refitted the barrels I used a different engine case/barrel sealer than Hylomar, which I'd used for a couple of refits before then. it was CRC Red Gasket for high temp applications, because in the two or so refits previously using Hylomar the seal blew out pretty quickly with a fair amount of oil misting on both sides around the barrel base after long trips/ heavy use.  I guess my mating surfaces aren't great but for the cost and hassle of fixing that I haven't investigated improving it correctly engineering wise.

The sealant I used did work much better than Hylomar at stopping the oil misting from the stud passages for something like five years, although it didn't stop it coming back completely.
I've always been conscious of using a sparse amount of sealant around the top stud oil passages and return down the push rod tubes, so it will be interesting to take the (now loose) barrel off to see if perhaps I have caused a blockage. I'll take up the tip on testing the actual oil pressure when I'm able to, and measuring the amount of oil dripping from the rockers.

By the clear shafts I'm thinking you mean the rocker arm shafts?  Yes, I make sure I fit them with the dot facing the rocker cover side....

The head job I did just over 40K km ago involved an engine shop (of dubious experience on BMW heads) fitting new oversize valve guides and new Intervalve valves all round, plus new exhaust valves seats on both heads, supplied by me via Motobins.  The punished exhaust valve is an Intervalve.

Cheers for the tip on gearbox removal also, I'll probably do the swing arm method this time, and get a socket machined as mentioned by our friends ealier by a friend with the gear.

What size socket fits the swing arm nut? (just being lazy here, I could check the Clymer manual  )

[georgesgiralt]

Hi Guys,
I've replaced sealants like Hylomar (or similar) to anaerobic products like Permabond or Loctite which do not cure in presence of air, thus preventing clogging oil passage tubes. The Permabond product I use is soluble in oil so will disappear from the oil passages if there is some on them.
Two drawbacks, though,
the first one is that the Permabond product is pink when cured and can show at the sealing line. Only a cosmetic reason here.
The last one is more annoying. Once cured it is very very hard so cleaning the surfaces after dismantling is a quite long job.
But having sealing that do not leak and resist temperature variation without risking oil starvation make the drawbacks less of a concern.
This is the product I use (but there are others on different brands ) https://www.permabond.com/wp-content/uploads/2016/04/A136_TDS.pdf

[Tony Smith]

I do not use any sealant on cylinder bases that have o-rings.

I used to use Hylomar but over time I decided that sealing the oil way was the o-ring's job. I just saw too many engines where sealant was partially blo cking the oilways. If this results in oilmost around the cylinder bases so be it, that is why God invented degreaser.

I have built 2  stroke 6 engines in the last couple of years, these have neither o-rings or a paper gasket. Instead they have an alloy plate which can be bought in several thicknesses in case you need to reduce compression. I do use Hylomar on these as if the mating surface isn't perfect they pump oil.

I am going to do another stroke 5-6 shortly and I am going to machine it for o-rings.

[tunnelrider]

I'm thinking I won't use any sealant on my next cylinder refit either, to eliminate the chance of blocking those cylinder stud oil passages..

An update after taking off the barrel: There wasn't any obvious sign of blockage possibly caused by using too much sealant.  Both little o-rings had a little bit of sealant build up on the outside of the orings (see pic) but nothing more than that.  Would this be enough to reduce the flow down the oil passage, maybe by squeezing the oring out of its position?  I find it hard to think that would happen when its bolted up tight, as long as the orings were seated in their barrel groove ok.

BUT..  one of the oil passages was a bit drier than the other in the freshly taken out barrel (by that I mean oil sitting at the bottom of the passage).  It was the oil passage on the intake side, so not the side that failed, but maybe caused a lack of oil to the rocker arm area in general?

So, my plan is to put the donor heads on, measure the oil pressure and volume of oil coming from the rockers.

Maybe a dumb question and I don't think it happens but just to be sure, the pushrods don't supply oil to the rockers do they?