Compression stumper

Ok, background:

replaced the valve seals, cleaned up the valves and lapped the head. Had a problems getting it to run so I discovered that I had the timing off by 1 link.

Fixed the link problem, but still would not run. Messed around with some input from the good folks here and ended up checking the compression and found that across the board the compression had dropped across the board in all cylinders and down to 75 psi in number 2.

So tonight I tore it all down again to see:
1. Did I damage anything by being off 1 pin.
2. Did I not clean up the valve seats well enough thereby allowing leakage and lowering the compression.

What I found: No Damage :woohoo:
But also found that the valves are not leaking (checked the exhaust and then the intake with solvent, no leakage).

Bad news, I messed up the head gaskets so now I need to replace them. Worse, in my haste, I failed to notice that I didn't remove one of the little metal plates under the top idler wheel and of course when I was taking off the head bolts it fell into the oil pan, so now I get to change the oil, drop the pan and buy another gasket.

Haste makes waste.

I am letting the intake sit with solvent for a little longer, but it looks like no leaks.

So: if the valves are not leaking and the compression is low, it must be the rings, right? except I didn't touch the pistons or the rings.

Any ideas where else to look? Am I forgetting something? Thanks for listening.

fill the ports with solvent then blow compressed air around valve and seat on each cylinder,watch for bubbles in solvent.flip head and do rest of the ports. did you check the valve clearances before you pulled head back off, could #2 of been hanging open?

I'll try the compressed air, good idea. I didn't check the valve to see if it was hanging. I did check the clearances and they were all in spec, but some on the low side of the tolerances.

thanks for the tip.

did the compressed air trick and low and behold, 3 out of 4 intake valves had bubbles. they are the 3 that had the lowest compression.

getting late, so I'll check the exhaust valves tomorrow. Seriously considering letting the local shop machine the valves.

This would be an easy one, to just sit back, watch and listen. However I am going to throw in my 2 cents, for whatever it's worth.

Going by the little, that you stated in the begaining. I could be wrong here, so please don't hold my feet to the fire.

You replaced the valve seals and lapped the valves, Why?
I would guess that it was smoking or using oil? What was the valve guide clearance? If you have alot of clearance, the seals will not last very long. Have the shop check the clearance, when they do the valve job.

Now not knowing the mileage? Or, how many people have owned it? You are now at an age old "cross Roads"
You are getting ready to install a rebuilt head on old pistons and rings. How long before you will have blow-by? Good sealing valves with old rings, isn't a good mix.

Who knows, You may beat the odds? But on other hand, you will be mad, if your rebuild, is short term.

If the valve seats are leaking, why? Bent valves or bad valve job?

Have you had the cylinder off, the bike?

I would strongly suggest, that you take your time, and check everything, a few times. When you think that you have it all figured out, check it again.

You may have work or money, ahead of you. Whatever it takes, to do it right...................It would be easy for me, to tell you, to just do a valve job. That would get you by on the cheap, but thats all.

Good questions Kzz1p. I replaced the valve seals because I was using a little oil, had oily plugs and it was not running real well. I had good compression so I thought that the oil was probably from the seals and not the rings.

When I had the head off, there was a fair amount of buildup so I lapped the valves to clean off the buildup and to get a good seal (guess I didn't to a very good job). I didn't measure the valve guide clearance beyond the finger wiggle, and there was very little wiggle, so I thought it was ok.

As far as mileage, I have around 32k. I am the 2nd owner and the 1st didn't do any mods other than cosmetic and a 4-1 exhaust.

I realize I might be looking at a ring job in the near future, hope not but it's possible. I'm a novice wrencher on a limited budget so I decided to do what I could afford and hope it get's me to next summer.

when I got into the head, the valve seals were pretty hard and broke apart instead of pulling off the guides so they not flexible any more.

I have not had the cylinders off the bike. Appreciate the advice to check everything and recheck. I'll keep pluging away and hopefully I'll get it running again before the snow flies.

IowaKZ wrote:

did the compressed air trick and low and behold, 3 out of 4 intake valves had bubbles. they are the 3 that had the lowest compression.

getting late, so I'll check the exhaust valves tomorrow. Seriously considering letting the local shop machine the valves.

ive never been a fan of lapping valves,once youre that far in even having the valves and seats ground minimal amount to clean them up should show better results.i use the simple and crude technique of sticking bare valve part way into guide and try to wiggle it,if it moves side to side time to replace guides(valve stems are usually ok unless theyre bent).also measure your valve springs

valve stems on my bike wore 2 or more thou from one end t the other. I used them to ream new guides because of the taper. Fill the chamber up with water, hold the valve down with a finger and wrap a rag around the air nozzle to blow air into the port. Tis much easy that way. Then just how many bubbles are coming out> remember this is or isn't the fix for your troubles. I always lap and have great compression so I totally believe in doing it every time, that way there isnt any issues. You should have no bubbles, none. check every valve. Check and double check that timing make darn sure it's on. If can't get the bubbles to stop, you have bent valves or the seats are not cut straight. If the valves don't form a nice concentric margin, and wont seal dont keep lapping or youll end up with a reciever groove into the valve face. geterdone