I had my cylinder bored 20 over new reeds checked the piston to cylinder clearance .07 and the ring gab .3 put it all together then I leaked and vacum tested it that was great . So I wanted to test the comperssion before I put it back in the fram the comperssion is 90 . What did I do wrong ? . Did I miss a step somewhere .

did the rings seat on the wall? how did the jug slide on the piston when you installed. Sounds like too much piston to wall clearance if you mean .007-

Seventy thousandths (.070") piston to cylinder clearance or seven thousandths (.007")?

Even .007" is way too much piston to cylinder clearance. If you used a Weisco piston, clearance should have been .004".

Did you use the starter to turn the Engine over to check compression?


Rand

Sorry I had to get the book I write it all in . Piston to cylinder clearance is .005 . When I put the cylinder on it was a little rough at first but the piston seemed to slide in . Yes I used the starter for the test

I would check it again using the pull cord. I can usually always get 10 or 15 psi higher reading pulling the cord over the starter.

That woul still leave me way to low I think the comperssion should be around 130 . I think I will just take the cylinder off and double check it all .

I should have looked closer at the initial post, I didn't realize it was out out of the frame. Yes I would pull the cylinder back off and re inspect everything.

What kind of compression tester ?? Is it one of those cheap harbor freight ones ?? Check your compression again with another tester.

It is a harbor freight one but a couple of weeks ago I tested it against a snap on one they came back about the same so I don't think it is the tester . I used it on my sons 250 after honeing the cylinder and adding new rings and I get 135 on it . Could it be the rings not sitting wright . When I use the pull cord the piston seems to slide smooth in the cylinder . And if it was the gaskets wouldn't that show up in the leak test .

Which head gasket are you using?

The head gasket is a cosmetic and the base is a aluminum one .016 thickness . I can take a M249 SAW apart with my eyes closed but this thing is driving me nuts .

You have not run it right? So the rings haven't seated to the cylinder. So naturally the compression will be lower. Make sure your compression gauge is accurate. I had a cheap one that wouldn't read above 90-100 regardless of what I did.

So you think I should install it and get it running before I get into tearing open the motor (( Internal Combustion Engine ? )) to give the rings a chances to seat . And like I said I tested the comperssion tester against a snap on one and the tester workers fine on my sons 250 . He just tested his comperssion on his 250 this moring and it was 135lb . I'll get a different tester today just to make sure .

Checked the piston to cylinder clearance again .004 . So we're do I go from here

By the looks of your picture, if you can stick the feeler gauge that far down between the piston and cylinder, your gap is bigger than .004".

Without the rings on it, what is the gap at the top of the piston?

Rand

The top clearance is .005 bottom .004

Well from the looks of it right now it seems like the bore job is ok.
I actually had one of my cylinders bored at .007 clearance back when I was having Engine issues, and my compression came in at 125lbs with an American made good tester.
So here we have:
1) 90psi confirmed
2) tester good
3) .005 clearance
4) passes vacuum and pressure test so no leaks
So I guess my next three questions are:
1) what is the thickness of your head gasket ??
2) what is the squish ?? The stock Honda squish is excessive.
3) what is the thickness of your base gasket and is it the metal one or the paper one ??

The head gasket is a metal one .032 base is a aluminum one it's .016. The head gasket has three layers can I take one off our would that wreck it

A lot of us here use one layer of the original head gasket.
I do, but I put some red silicone on it to make sure I got a good seal.
I am a silicone homo and others here may attack me for it LOL.

Hummm ---- don't think we have solved the problem yet. I am stumped.
After a rebuild I haven't noticed the compression coming up any amount after the rings seat.
That's just my experience with oddy rebuilds.

What do your reeds and reed cage look like ??
Do they seal ??

Yes just put new ones on the old ones had a gap but these are tight

Could the reeds drop the compression that much if they weren't sealing wright?

Sure why not ??
You need to have a way of not letting the air/fuel mixture push back through the carb as the piston is on the up stroke. You would notice it spitting out the carb as it is running.
Not 100% sure right now if that was your problem but everything else seems to check out.

I just checked them again there is a small gap in them . But wouldn't that get closed in the up stroke of the piston