Valve clearance too tight on exhaust

[saints]

Hello,

Question, i got all the other valve clearances in check, but the exhaust valves for 4th cylinder are both too tight, even with the 2.50mm cam follower which is the smallest you can get. Barely 0.05mm feeler goes under.. What is the next step? If i need to remove cylinder head, then i am afraid it is a job for a real mechanic..

[Ingo]

Sounds like the valve seat (where it seals in the head) is worn down, stretched valve stem is highly unlikely. Means you'd have to pull the head and take to a shop...
Probably have to pull the head in any case just to figure out what's up...
If I'm not mistaken the seat is a ring that's inserted into the aluminum head. 

 11 12 1 461 301    VALVE SEAT RING EXHAUST   0.02    8     $66.76   From MAX BMW parts fiche...  I believe that's for a set of 8

[The Mighty Gryphon]

11 12 1 461 301    VALVE SEAT RING EXHAUST   0.02    8     $66.76   From MAX BMW parts fiche...  I believe that's for a set of 8

Means there are eight of them and they are $66.76 each.  I am pretty sure if you take the head to a machine shop they can get generic seats a lot cheaper. 

If you do decide to pull the head, make sure you use the correct Torx bit.  You need the T50 1/2" impact bit.  It is a lot heavier and will fit better than the standard Torx bit.  The head bolts are a bitch.  High torque, and the ones back by cylinder #4 usually have corrosion as an added bonus.  I broke one off in the block when I pulled the head on my '92 RS. 

https://www.ebay.com/itm/404590465510?

[Ingo]

^  Agree with Gryphon, 66+ a PIECE is heavy, but what else do we expect?! Machine shop can likely source cheaper.
And :  Head bolts are BRUTAL. Just to get them to brake loose, once there the rest is fine. As above stated, make sure to have the best tool possible for this.

[The Mighty Gryphon]

I would advise using an impact wrench to loosen up the head bolts before going after them with a big breaker bar.  You don't want to break one off in the block.  It will definitely ruin way more than one of your days.   

[Ingo]

I just remembered: I turned my craftsman torx socket into a corkscrew on the head bolts, had to buy a set of impact rated sockets from HF...
But at least the new head gasket is made of stainless steel, I feel it's much improved over the old style that left a lot of hardened material on the aluminum of head and cylinder block and was hard to remove without hurting the surfaces.    At any rate, this is likely to be a somewhat bigger job...

[saints]

Ok, so valve seats might be the problem. I doubt i can change them with my tools, so i will give this assignment to the local shop. Thanks for rapid answers!

[Duckbubbles]

The head bolts are "Torque To Yield" type and are one time use.  When installed they are torqued to a spec and then angle torqued another 90 deg. if I remember correctly.  You can feel them stretch during the angle torque- an uneasy feeling.  Your problem is probably a combination of valve seat wear and valve head wear.  I know of a couple of valve failures on K1100's.

Frank

[The Mighty Gryphon]

YIKES!!!  I reused them on my '92 RS!!!  The head is going to fall off!!!

Boy, am I glad I don't own that bike anymore.

[Laitch]

The head bolts are "Torque To Yield" type and are one time use.

Consider also that torque-to-yield bolts don't always have an angle spec in tightening. Another prominent use of them by BMW is in attaching the clutch pack assembly to the clutch housing.

[Ingo]

I dunno know, I think I reused also ( would likely recall "how friggin expensive..."), ooops. Been a while so it's prolly ok.
As far as valve: yes, it's entirely possible that the affected exhaust valve is fried from gases blowing by...  There's another 100 or 200 gone...
Depending on mechanical inclination and tools available I'd suggest to work the bike and just turn the head into a machine shop. Of course would have to go and buy gaskets and stuff, still a lot cheaper than having a BMW shop remove all the plastic and dismantle the engine top then put all that stuff back together.

In any case: good luck with this, and remember: the only stupid question is the one that wasn't asked...

[Laitch]

I dunno know, I think I reused also ( would likely recall "how friggin expensive..."), ooops. Been a while so it's prolly ok.
As far as valve: yes, it's entirely possible that the affected exhaust valve is fried from gases blowing by... 

Probably many of us reuse those clutch bolts; I haven't found much negative feedback about that. Maybe the Bricks are sold on when owners encounter problems generated by that.  Did you do a compression test and a leak-down test yet? The results could be interesting.

[The Mighty Gryphon]

I put a good 20,000 miles on those reused head bolts.  They even went through a somewhat major fender bender and bike rebuild with another 2,000 miles.


In the median.jpg (43.83 kB . 432x576 - viewed 171 times)

Hey, who knows, maybe the head did fall off and I didn't notice. 

[Ingo]

Head must still be on, otherwise she'd lay lower, flatter!
 Still sucks!

[Duckbubbles]

Hey guys, a little bit of an apology here.  I was slightly mistaken about the torque to yield head bolts.  After consulting a couple of maintenance books I have (Clymer/Haynes) the angle torque method is used on K1200 engines.  K100/K1100 use a simple two step torque sequence with no mention of single use bolts.  The last engine I had the head off of was a 1200 so that's what I remembered.  Foremost in my mind was the feeling of the head bolts stretching.  If you've been a mechanic for a while you may know this feeling.  The bolt is turning but the feeling is that it is NOT getting tighter.  Earlier 1200's use an initial 20nm torque followed by a followed by a 76 deg. angle and then ANOTHER 76 deg. angle!  Later 1200's use an initial 20nm followed by 90 deg. angle.  Maybe the change was issued after some bolts snapped during the second angle torque.

It seems that re-use of the head bolts on K100/1100's is fine. 

Frank

[Ingo]

OK, we all can breathe easy now, no heads are coming off!   

[jbt]

Changing the valve seat is not an easy job. I've seen plenty of engines with new valve seats, supposed to be needed because of use of unleaded fuel, release the newly fitted seats into the combustion chamber.
The installation requires real machining skills, Nitrogen freeze, negative tolerances... The kind of skills you could acquire when it was common to change the valve seats on engines, that is to say the kind of skills that you can today almost only find  on retired mechanics.
Considering the price of a used head, and the chances of fail, I'd consider buying another head.
Maybe you could find shops specialised in overhauling K heads at Mini specialists, who love to adapt these heads on Mini engines.

[Chaos]

Maybe you could find shops specialised in overhauling K heads at Mini specialists, who love to adapt these heads on Mini engines.

That's the old 997 or 1275cc mini, not the new BMW/mini?  I remember reading about that conversion. 

[saints]

It wast easy to disassemble, with right tools, impact torx head and one meter steel pipe leverage.

With amateurs eyes it looks like it has been running +131000..have to take head to shop and be prepeared to pay many moneys..

[jbt]

Seems that there's signs of seat recess on cylinder 4 and 2 also...

[Ingo]

Good man, well done!
Now: I'd go and turn over the head with sparkplugs still in there. Put some motoroil into the combustion chamber and see how fast it runs out. This tells you how bad or good the valves seal. At 131K (miles or kilometers) it's probably pretty bad. Sometimes it's just the "rim" of the valve and a replacement valve and good lapping in does the trick...

[saints]

Estimated cost for head maintenance would have been at least 700€ ..got 52 000km driven spare motor for 600€ including shipping. I’ll take the head off that one and hope that is in good condition.

[saints]

Is it mandatory, or highly recommended to resurface Cylinder head, before installing it back? Because removal was not caused by gasket failure or so, i would like to assume that the mating surfaces are good. Have people just installed heads back with new gasket?

[jbt]

It is highly recommanded NOT to surface cylinder heads of K100/1100!
 .

[The Mighty Gryphon]

When I pulled mine to do the valve guide seals I just reinstalled it with a new head gasket.