Compression question PEASE HELP: KZ1000 E 1980

KZ Riders,
Been reading this forum for a while while working on the resurrection of this 1980 KZ1000E2. Been a great resource-- and now I have to ask a question:

A buddy gave me this bike. It has 51K on the odometer and had sat for an even 20 years (in a garage) before I decided to fix it up. It is stock, except that it now has KN air pods and a four into one exhaust with a Cherry Bomb glass pack muffler. The main jets are now 120 and the pilots are at 22.5 (air screws out one full turn). The bike runs well, except for some mysterious oddness that sounds like a carb/carbs out of synch-- seems to appear most frequently when I'm in fifth gear, running at about 4,800 RPM. I am fairly confident that this is a carb synching issue, so I am not overly concerned about it.

The issue is this: when the bike is idling, it will start producing bursts of blue smoke when I hit the throttle hard (bring it up to maybe 6K RPM ) and let off. It only smokes when I let off the throttle-- not when I am applying the throttle.

I have also been getting a black plug (number four). The blackness is somewhere between flat and glossy-- let's call it a 'satin' finish (and it will stay this 'satin' way-- never totally dry, never totally shiny-- eve after 200 miles of riding). The rest of the plugs come up varying degrees of golden brown. In any event, I am pretty sure the bike is burning oil (though I haven't seen any oil loss when checking the level, and I did an experiment where I leaned all the carbs way out and let the bike idle a while-- all plugs came up white, but the bike still smoked when I hammered on the throttle). If I am burning oil, I really want to know what the source is.

My concern is that there may be piston ring issues that need to be dealt with sooner, rather than later. So, I did a compression check. With the engine cold, I got: 1.) 122, 2.) 102, 3.) 114, 4.) 130 (and this is the cylinder whose plug always comes up black-- and here's another interesting detail: the plug in second cylinder-- the cylinder with the weakest compression-- always comes up looking the lightest/healthiest).

With the engine hot (I let it sit and idle for about 20 minutes), I got: 1.) 130, 2.) 112, 3.) 125, 4.) 132.

I then let the engine cool down some (let it sit for may 10-15 minutes) and rechecked the compression of each cylinder with a little Marvel Mystery Oil in each. Uniformly, the MMO caused a 20 psi increase in readings-- on all cylinders. I have read that, if compression increases dramatically when oil is added to cylinders, loss of compression is likely due to rings-- but the fact that compression in each cylinder increased by exactly 20 psi (regardless of its base compression reading) seems to indicate to me that this problem is not rings. Would you all consider a 20 psi increase with some MMO added to the cylinder to be a dramatic enough increase to indicate bad rings? What do you all think about the uniform 20 psi increase across all four cylinders? What does this indicate to you?

Also, am I correct in thinking that the cylinder compression should come in at 128-156, with no more than a 14 psi variation between cylinders? And 100 psi is as low as you can go without having to tear into the engine? Eventually, I'd like to do a full top end rebuild, but would rather do it when I have more time/money to deal with it.

I have not checked the valve clearance yet, but all this has got me thinking that the low compression and possible oil entry in cylinder/cylinders is likely due to valves and valve guide seals. Please tell me if you all think this conclusion is correct-- I definitely appreciate any/all thoughts on this.

This project is driving me out of my damn tree-- it's been fun, but I look forward to hang the tools up and just enjoying this beast.

Thanks.

Sounds like worn rings, and at least one valve guide seal. The compression increase with MMO suggests rings, and the blue smoke on decel is oil being sucked down the valve guide and past the valve stem seal. I've seen bikes with worse compression run a good many miles so you have a decision to make. You didn't mention adjusting the valves, so needless to say you should tend to that. If the valves are tight, fix the problem and consider retesting the compression.

Good luck

Nesim,
Thanks very much-- I really appreciate the thoughts.

If the rings are good, would there be any increase in compression at all? I keep wondering if the uniform 20 psi increase across all cylinders wouldn't just be cause by the fact that there is oil in the cylinder (like displacement caused by the oil itself). How much of an increase would you expect to see if the rings are worn, versus good? I've seen threads that state that a "substantial" increase in compression readings after adding oil indicates rings, but I've also seen threads that indicate that an increase of 20 psi would be expected and negligible when adding oil to check rings.

Also, I do plan on hitting the valves next. If they are tight, how do you loosen them?

Thanks again.

Change the shims. You should do this before messing with a compression check, because if the valves are hanging open you are just wasting your time.

Thanks-- I appreciate it. Sounds like a good plan.

My manual does not seem to discuss this. In order to change out the shims, do I just remove the cams?

Also, I figure I'll change out the valve guide seals while I'm in there-- since they are a very likely culprit. Does the head need to come off the cylinders for the replacement of these, or can the job be done with only the valve cover and cams removed?

Again-- thanks for the help-- and thanks for your patience with all the questions.

Because you're pulling the head to replace the valve seals. check the valves and your exhaust guides for wear. Since the head will be off, why not also pull the jugs, hone them and install new rings if the wear is not too bad. It's really not a lot of work and you'll be all set for years of riding. You'll need a top end gasket set and maybe some new intake manifolds to do it right.

It is highly unlikely that the valve guides are worn, they are extremely hard. But I would certainly lap the valves.

50,000 miles in a J1000 motor. I'll bet the exhaust valves are as wobbly as loose teeth in thier guides. I seldom see worn out intake guides, but the exhausts.....common. They're also not too difficult to replace, but must then be reamed to size. No problem if you have the tooling. The replacements are solid bronze that also have a lubricating property that the sintered metal originals lack.

Zero, Koolaid Kid,
Thanks-- I appreciate the words of wisdom. I would like to go in there and essentially rebuild the top end-- since this seems due, and since it will clear this all up for years to come. But, the problem is that the bike is also my only transportation tight now and I can't afford to have it off the road too long. Basically trying to figure out what I can get away with to improve conditions (and decrease chances of damaging the engine), without going too deeply into the engine, until I get a chance to rebuild the whole top end-- which I figure I should be able to pull off sometime within the year, but not now.

So, for right now, I'm thinking a healthy valve inspection and adjustment is in order, as well as new valve guide seals-- but, I'm not sure if the head needs to come off for this, or if it can just be done with the valve cover off. Any thoughts on this are appreciated.

Changing valve stem seals without pulling the engine apart is tricky, but it can be done. You need to pull the cams, then make a tool of some sort that will compress the valve spring so the keepers can be removed, and the seal changed. Good luck with that; it's no trivial task.

Since the bike is transportation, I'd adjust the valves and ride. A little blue smoke isn't going to hurt anything unless you are fouling plugs. Look for a replacement head and prepare it while you ride the bike as is. When the time comes, swap on the new head in one day.

Nessim,
Thanks-- great idea. I'll see what I can find on Ebay-- if anyone out there has a head for an 79-80 E1/E2 Shaft, please let me know.

By adjusting the valves, you mean re-shimming? Is changing out the shims the only way adjustments can be made? Sorry if this is an obvious question, but I've never messed with valves before.

Thanks.

Yes, to adjust the valves you would need to change out the shims. You need a metric feeler gauge to check the clearances, along with a manual to know where to set the cams for checking each lobe.
And I agree with Nessism about leaving the head alone. As he mentioned, the valve seals can be changed out without removing the head, but it is not a trivial task.
Sending you a PM.