Cylinder heads 85 interstate

[cftsi]

I had very low compression on the right bank and decided to do a valve job. The right side was so bad I had to replace the head. Reassembly went well on both heads and the right side is perfect. The left side however now has a problem. When examining the valves I noticed wear. The compression had been good, but out of caution I lapped the valves anyway. Once assembled turning the engine over the left side compression was good initially, but after checking all the cylinders, the left rear cylinder suddenly lost all compression. Leaving it for a minute, it came back for a few turns and then lost it again. This happened several more times. In assembly every part felt right. No sticking or anything unusual. It makes me wonder. By lapping the vales and the general wear from age have I got the hydraulic lifters too far out of spec to work properly? I know there are shims and the manual does say they may need to be looked at after a valve job, but I don't really understand mechanism well. Anyone have experience with this? I don't want to pull the head again unnecessarily.

[joecoolsuncle]

honda used to advise against lapping or grinding their valves. it sounds like you are losing the compression because they are too tight on clearance after lifters pump up. check em again hot and see. valves wear into the seat. usually intake side because it is heaviest. as it wears the seat, it narrows the clearance. also, when checking, you should make sure all oil is off the shims and the bucket, it WILL deduct clearances (tighten). when you do rebuild or replace the head(s) you will need to clean, check and adjust all over again.

[cftsi]

Thanks. Too tight is my guess. If it was a typical engine with lifters or even push rods, I would know what to do. These have me stumped. Read and reread everything I can find. Still missing details that would come with experience to get the adjustment right.

[joecoolsuncle]

think of it like lifters and pushrods. but the lifters are machined to hold shims for initial adjustments. everybody else went with straight up shim and bucket....honda made it weird.
BTW, just shim and bucket usually never required adjustment unless you abused the engine with high rpm. high rpm was over 10-20k rpm every day.

[cftsi]

Thanks again. I have the old set of lifters. I will take it apart and figure out step by step how it works. If I bend a spring or shape something, at least I will know what not to do the next time. It all seems so complicated, the manual calling for Honda tools and such.

[cftsi]

Postscript:
I did take the old cam assembly into pieces to see how it worked. I had thought the shims might be internal. They are on the retaining caps. The top adjusting shafts are different than the bottom. I found out how hard they can be to reassemble and the necessity for a special tool. In my case I used a very long screw to pull the shafts forward. I also found why it is best to do one lobe at a time. Good advice unless you like a pile of parts falling on the floor. Surprise! Finally was able to figure out whether to add shims or take them away. My case add them. None of this was clear in what I had downloaded for reading.

With the unit on the bike, I did find those tinny friction springs were broken and came out in two pieces. Interesting!