Went to pass a car today and the bike fell to one cylinder than died.  Fuel pressure is good so I pulled the plugs. Back plug fouled. Middle two wet with fuel. Replaced plugs but no go. Checked compression and have zero on the back three cylinders. Any ideas on what may have happened?

Head gasket?
Seems the most likely when three cylinders go at the same time.
Not to difficult or expensive to fix.

No compression on three cylinders all at same time? Sounds strange. Are you happy with the tester you used?

Loss of compression on two adjoining cylinders is often put down to head gasket failing between two adjoining cylinders. Not the end of the world. Could it happen between three? Not sure but the fact that its three and not all 4 seems to point this way. I wondered if the timing chain might have jumped but I think it would take out all 4.

Pulled the valve cover and stared awhile. All looked good to me. Until I noticed the intake cam is broken in two just past the first cylinder. Maybe I got lucky. 

Lucky if it broke by itself, unlucky if it broke because something it presses on wouldn't move.. Any marks on the pistons if you can see inside through the plug holes? Maybe even try tapping the tops of the valves, see if one sounds more solid than the rest? Or maybe the other end of the cam seized? All of these are totally bizarre of course!

That happened in my [diesel] car a few years ago and did a lot of damage. I still have the car and it was only when I was doing some work under it that I noticed the sump had been off at some point. I asked the garage when I was next out there, as it was covered by warranty they had stripped and rebuilt the engine. I am curious as to why the camshaft broke in the first place but absence of compression suggests three bent intake valves meaning head off. If the timing hear and exhaust camshaft are all ok you need to check of the two broken camshaft pieces have dumped metal filings or swarf where the two faces were rubbing off each other.

Cam actually was broke in to three pieces! Tops of pistons look okay. No signs of the camshaft seizing. Going to purchase a leak down tester to see if cylinders are holding pressure. 

I may have missed a gear and over revved. 

Very strange!! The inlet camshaft on my spares bike was broken in the middle of the bearing between cylinders 1 and 2, but the cause was very obviously a lack of oil. The cam lobes and shims were blue from heat, and the shaft had picked up on the bearings. I started it before I opened it and there was some racket out of the engine.

Hi, as I see it, maybe the camshaft was not properly settled, and being what seems to bee some kind of cast iron, will not tolerate fatigue stress and hence has almost no tolerance to misalignment.
That explains why the camshaft bearings on the head are machined as one piece and the upper half moons are not supplied as spares.
Best regards
JAP

Number two cylinder bad. Leak down test shows 100% leakage. Bad news.

I'd buy a lottery ticket...

Air leaking out the air intake valve. Can hear the air blowing out the throttle body on leak down test. Piston top looks okay. Now hoping for just a head rebuild.  Tear down time.

in the past i have seen cars the blew head gaskets because of overheating.
the head was planed down at a machine shop to make it flat again.
but, the head was warped and with miles and time the cam had to flex.
eventualy the cam broke.
something else is wrong there.
you can't over rev it, the controler won't allow it ....
i'd replace the head, e bay is full of them at a reasonable cost.

Kartoo has sound advice. Either a complete head including the valves, springs and camshaft assembly from eBay or even a complete engine. Plenty of them out there. I would expect the inlet valves on all 3 cylinders to be gone as well. Unlikely to have piston damage.

I am still curious as to the cause, but if you figure over revving because of missing a gear then that's fine. But according to the Clymer it shouldn't over rev unless a missed gear is too quick for it to cut the engine revs.

Kartoo has sound advice. Either a complete head including the valves, springs and camshaft assembly from eBay or even a complete engine. Plenty of them out there. I would expect the inlet valves on all 3 cylinders to be gone as well. Unlikely to have piston damage.

I am still curious as to the cause, but if you figure over revving because of missing a gear then that's fine. But according to the Clymer it shouldn't over rev unless a missed gear is too quick for it to cut the engine revs.

I have a spare engine near Santa Barbara from a 85 K100RS
Contact me if you need some parts.

M

Took it apart this morning. Cylinder and pistons look good. Now just need to find a machine shop and get the head checked out. Broken cam very hard to turn with timing chain removed. Can't see any cracks or signs of binding. Valves look okay to me but was leaking badly.

Looking at the pictures it looks like two valves hit the pistons.

9 on ebay right now at $99 or less with free shipping.
slap one on with a new head gasket and enjoy your summer.
you gonna pay that in labor at a machine shop.....

i bought a complete engine in the winter for $175 with trans/starter/alt

enzo wrote:Looking at the pictures it looks like two valves hit the pistons.

#2 intake for sure

kartooo wrote:9 on ebay right now at $99 or less with free shipping.
slap one on with a new head gasket and enjoy your summer.
you gonna pay that in labor at a machine shop.....

Good point. Looks like the best option.

I bought a complete 85 motor from a wrecked bike. 200$ from A And M cycle traders. They had three and all looked pretty beat. It was very tired looking and appears to have MANY more miles than mine. 


 I pulled it apart and took out the intake cam and a couple valves and rebuilt my head. Now I have some spare parts as well. Did not want to buy the valve compression tool so I cut and old socket and used a press. My first valve job was very educational! Cleaned up all the valves and lapped the seats. Now I am just waiting for a head gasket and bike will be back on the road. 
 

Hi there, lapping the seats changes the valve clearances, I would check them and get the required shims.
Hope this helps
Best regards
JAP

great !!
hall effect sensor still there ?
if so your ahead of the game.
looks like you got yourself a crankcase vent hose too.
like your valve spring compressor.

Before you even start it check the line bore of the cam journals. I will bet London to a brick the head is warped and that is what has broken the cam. Don't use the original head or you stand a very good chance of it happening again.
Put a cam into the head without the valves and try to turn the cam, more than likely it will be very hard to turn.  It should turn very freely with the caps tightened down.
Also check that the correct caps have been used as they are matched to the journal in the machining process and if they are mixed up it will bust a cam or chew a journal out.

RicK G wrote:Before you even start it check the line bore of the cam journals. I will bet London to a brick the head is warped and that is what has broken the cam. Don't use the original head or you stand a very good chance of it happening again.

that's what i stated in post #13

RicK G wrote:Before you even start it check the line bore of the cam journals. I will bet London to a brick the head is warped and that is what has broken the cam. Don't use the original head or you stand a very good chance of it happening again.
Put a cam into the head without the valves and try to turn the cam, more than likely it will be very hard to turn.  It should turn very freely with the caps tightened down.
Also check that the correct caps have been used as they are matched to the journal in the machining process and if they are mixed up it will bust a cam or chew a journal out.

Thank you, I will pull the valves tomorrow and check it out. Hope your wrong!!

You need to do as Rick G suggested. If the cams have any resistance to turning then you have a problem. They have no resistance to the stresses of a warped head.

Curiously I was having coffee on Tuesday with a friend who is ex BMW and working on bikes for about 45 years!. He jokingly slags me off about the K but when I asked him about engine reliabilty his comment was that the only time he had to work on the engines themselves was due to crash damage. Never an engine failure!

He was rebuilding a final drive on a GS. A very simple job if its done when the bearing starts to wear and not left until it breaks up.

It's warped. Intake cam has  resistance to turning. Not bad. But 10 times more than the exhaust which turns very freely. Binds at main journal by cam chain. Remove it and it spins fine. 

Time to do a valve job on the other cylinder. Thanks for the heads up guys.

probably overheated sometime in it's life.
after repeated flexing fatigue takes over and the cam breaks.
i've seen it with flywheels. trans to block missing a dowel.
or just a tab from a wire harness between the bell housing and block.
takes a few weeks, sometimes months and the flywheel develops cracks from flexing.

New Head gasket finally came from Germany, Got it all back together and was surprised that it runs perfectly!
I do have a new oil leak where you feed the wires down to the oil pressure sending switch. Have pulled the cover for the ignition pick up and it does not seem to be coming from the oil seal. Going to ride it a bit and see how it goes.

Thanks for the help Gentleman.

i love happy endings  

Well done    .

+1  
good result

happy riding !