79' GS 850G Valve clearance not readable??

[svahnm]

Hi, I recently bought original 1979 GS850G bike. Just 60kms driven by me...Odometer says approx. 4000km, but camshaft was looking good, so 104 000km doesn't look like right..

It seems that all the cylinders (#2 and #3) are not active all the time. Headers are rather cold sometime. I have changed spark plugs at first 60kms ago (maybe should do again?). While driving it the acceleration feels normal, so it must work normally while and while at least high rpms.

Anyway, yesterday I decided to check valve clearances, because of strange sound (although more clank from the engine - piston rod or something??). Sound appears only FULL HOT idle or below 2000rpm. I suspect that it is heard only when one or two of those cylinders are dead. So that sound might be even normal?? I scare exhaust valve too tight and would loose compression makes idling rough.

Back to question:
How clearance should be measured, because Haynes and Clymer advices to rotate cam pointing up or head surface level - two alternatives. While my cam is pointing to the side clearance is eg. 0.07mm which is fine. But when I rotate it few degrees it won't fit anymore even 0.04mm (smallest feeler I got). Also cam pointing up it is under 0.04mm!!? So basically cam is not round behind? Is this normal? Which is the position I should measure? If I take smallest gap I need to expand clearaces and then another position is over 0.08mm eg. intake valve not good.

more information:
First day compression was poor on cylinder #2 compare to others after driving. Later cold engine it was better!, so I thought valve (too tight at hot). Anyway now after valve check compression was quite equal to other cylinders (maybe carbon buildup between valve has been while plug was dead?). Surely there is something also carburators idling jets or something, but valves concern me first..

I would appreciate any help on this case.

[NickNoo]

If you have cylinders 2 and 3 not firing, you probably have an ignition problem. I would suspect a faulty coil, or maybe a problem with the points/CDI or whatever ignition system is on the bike.

Those engine noises are probably due to non-firing cylinders - but there could be other reasons.
It may be that your timing chain has skipped a tooth on the cam, which could cause major engine damage - I would not start the bike up again until it has been properly checked ! The manual will show you how to do this. When you are happy with this, check the timing and adjust as necessary.

As your valve clearance is correct at the side position (0.03 to 0.08mm according to the Haynes manual), it is probably OK. There will always be some variation when you measure the clearances at different angles (+ or - 0.05mm is a little high, but not unusual).
You may be able to swap around the other shims if you want to get serious about clearances, but you will need to remove and accurately measure all 8 of them with a micrometer. It is not a 5-minute job !

[ptm]

Yes, you can get different measurement in each of the 'proper' cam lobe positions. Good advice I got from others on this site is to follow the procedure in the manual exactly. Even though it should be the same with the lobe in either position, it doesn't always seem to be the case. If you use the approved procedure consistently, you can't go wrong and it's easier to figure out what to do when you have one consistent measurement per valve. On my '78 750 and the '82 850, (which should be the same for your '79 850) the procedure is:

----------------------------------
turn crank until
#1 exhaust cam lobe pointing forward parallel with the top of the head
- check #1 exhaust
- check #2 exhaust

rotate crank 180 degrees
#1 intake cam lobe pointing up perpendicular to the top of the head
- check #1 intake
- check #2 intake

rotate crank 180 degrees
#4 exhaust cam lobe pointing forward parallel to the top of the head
- check #3 exhaust
- check #4 exhaust

rotate crank 180 degrees
#4 intake came lobe pointing up perpendicular to the top of the head
- check #3 intake
- check #4 intake

[svahnm]

Thanks for replies.

Actually I bought that bike from one guy who is importing and restoring those and he has checked the bike (just driving and listening, I guess). So first day I told him problems with non-firing, he just adviced me to ride some hundred kilometers first. Also he claimed that non-firing cylinders are normal after winter break and I should ride and change spark plugs until it works fine.

Power of the engine feels normal (77hp), because our Kawasaki GPZ500 feels quite same with 60hp and just 190kg. Isn't the timing chain then in place?

Some update for the case:

That metallic clanking noise could anyway come from the camshaft area (more from the right side) , It feels like exhaust pipes are transporting knocking/clanking down under engine and that makes it hard to locate. It sounds like headers would be clicking to the frame or engine, but I tested with piece of metal twist them and no change while idling. Frequency is like one cylinder goes up and down.
Clanking appears time and time below 2000rpm. It feels little bit oil pressure related, because it appears when revolution decreases under 2000rpm, but to quieten the noise needs maybe some 2500rpm?? Just guess.
Clutch makes no difference. It has no specific temperature to occur. Sometimes full hot and sometimes half hot. In addition, clanking doesn't seem to affect power or character of the engine.
When I was checking valve clearances I tested to press tappets twisting screw driver between camshaft and tappet I noticed camshaft was moving slightly. I just didn't realize to check bolt tightness.. Could that little play cause the noise like that?

Is there good way to test carburetors and ignition corcerning about that non-firing and bad hot idling? I have manuals, but total adjustment/sync carbs is maybe too difficult for me at first (if carbs were fine I would just screw them up). So I thought that I could first try to spray something to carburetor of "dead" cylinder and see if it changes anything? What about ignition? Wouldn't timing lamp show something? Outside spark plug seems fine and sparks are equal each other, but compression make difference, right? Also cylinder #2 became hot after that valve check I started first time. So, ignition would be the case like NickNoo suspected. Also plugs seems to get wet if cranking.

Does dead cylinder produce slightly blue oily smoke when gassing the bike? Just looked when idling was poor and and I gassed the engine from the right pipe came some blue. It happened also left pipe day before, so it is only temporary.

I need to begin thorough trouble shooting (including that timing also) and close out everything I can. Tips and comments are welcome!

Sorry about long message and going OFF TOPIC, but I thought that it is natural to continue here..

[NickNoo]

OK - I think you need to spend a few hours studying the manual before running this engine again, otherwise you are going to do some serious damage !

You mention the camshaft moving (up/down I guess?) when depressing the valves. Of course there must be NO visible movement.
You need to torque down the bolts on the cam bearings (the manual tells you how to do it). THEN check timing chain position on the cams, check the timing and finally, check the valve clearances.
Dont rush it - just take your time and dont force anything. Those bolts are easy to overtighten and they can break !

Then report back !