Low compression, could it be valves?

[oldmopars]

Well, my 82 GL1100I was running good I thought, then I replaced a cam seal and in my stupid rush I did not notice that I had the right cam off one tooth and I bent a valve. Yes I know better, not my first rodeo and I got cocky and screwed up.
However I wanted to verify before pulling the heads off so I did a compression test and found that I had 0 on the right as I thought and 90 psi on the left.
I was thinking that it should be around 125-130 (- the 2 with bent valves). So I pulled the head off the right side to fix it and the engine looks very good. There is still very strong cross-hatch in those cylinders. So I pulled the "good" side with only 90 psi and it looks the same. Very strong cross hatch almost like a new engine.
Now I have been a mechanic for over 20 years and rebuilt many engines, I know what cylinders look like with fresh cross-hatch and what worn out looks like where you see a few stray lines, but mostly smooth and shiny. These are like a fresh engine.
This lead me to look at the valves/head and head gasket. I found no breaks or leaks in the head gasket, everything looks good.
I poured some carb cleaner in the head and found that it ran out of one of the intake and exhaust valves, but only on one cylinder. I may have to do it again as I did it rather quick and ghetto.
So, 2 things. First it was good in a way that I screwed up and bent a valve, now I know that I have had at least one valve leaking and now I can fix it and redo the others.
Now, why? Is there something I can do to prevent this, valve leaks from happening again? The bike has 82K miles and seemed to run ok, but I have not had it long and have never had another Goldwing. Nothing to compare it to.
In the end, I was mad, but now I know that I was doomed to do this soon anyway and I found an alternator for my conversion and what better than now when it is all torn apart anyway. Might do a set of Neon coils and a new blade style fuse box over the winter also.

 

[slabghost]

82K miles the valves could have been too tight to seal properly. Which will give you low compression.

 

[dan filipi]

Just to verify, when you did the compression test were all 4 plugs out, wide open throttle, and spinning over fast with the starter?
Same method on all 4?

Every auto engine I've done valve jobs on I always had the heads surfaced flat and all the guides checked as well as lapped the valves, at a minimum along with new valve seals though lots of guys only lap the valves and many don't replace the seals on these engines and they run fine.
The last 2 I've done, a 1200 and my 1100, I had the full deal done.

With good cross hatch and sealing valves you should expect 160-165 compression.

 

[oldmopars]

I told you I was in a hurry, forgot to open the throttle. I plan to get a full gasket set and replace seals and all. I will also lap all the valves. I also question my tester. I could not find my screw in style and so I had to use the kind with the rubber tip and just hold it in, the reason I forgot to hold the throttle open.
Oh well, it would be stupid to buy a full head set and only do half the job.

 

[dan filipi]

I'd have to see what I get with throttle closed.
If you can wait til later in the week or weekend I'll post those numbers.
It will be a cold test.

 

[oldmopars]

I also pulled the valves out of the right head and found the exhaust valves are in bad shape, very crusty where they deal. Blessing in disguise that I screwed up.

 

[dan filipi]

oldmopars » Wed Oct 30, 2013 9:02 am[/url]":3en5t7b5]
I also pulled the valves out of the right head and found the exhaust valves are in bad shape, very crusty where they deal. Blessing in disguise that I screwed up.

Sounds like you had a few things going on causing the low compression.
If the exhaust valves are pitted at the seat they may be trash but might clean up while lapping.

 

[OldWrench]

Every auto engine I've done valve jobs on I always had the heads surfaced flat and all the guides checked as well as lapped the valves, at a minimum along with new valve seals

Dan is right on here. I know it is a little more money and work but with aluminum heads I always have them surfaced. Another thing many forget to check is valve spring height. For me, I would always replace the valve seals and magnaflux the head.

The plunger type compression gauges don't work well with the higher compression engines. Without the throttle open the engine can not get enough air into the cylinder to get an accurate compression reading. What happens is the cylinder actually creates a bit of a vacuum on the intake stroke.

 

[oldmopars]

I am just redoing everything on the heads. Seals, surface, lapping valves or grinding if needed, etc. It may be a slow go, money is tight right now, but the weather is bad so it is not too bad.

 

[dan filipi]

oldmopars » Thu Oct 31, 2013 11:38 am[/url]":2kqyfe3c]
I am just redoing everything on the heads. Seals, surface, lapping valves or grinding if needed, etc. It may be a slow go, money is tight right now, but the weather is bad so it is not too bad.

Are you having a head shop do the work?

Either way, make sure to only take enough material off to get a flat surface.
If a shop, tell them it's an interference engine then they won't grind any away.

 

[oldmopars]

Where I work we have a large flat granite slab for checking flat surfaces. I put some 320 paper on it and carefully sanded back and forth till it was even all over. Did not take long. I also have a full machine shop at work to play in. Water jets too.