30% of the way there...

You are on the right track. Readings are good. Try it at factory pressures.

 

The tester doesn't go that high.

As I understand it, the pressure itself isn't important for testing, but rather the pressure loss.

I'm only losing 3-4%, well within the 10-15% allowable.

Every test says I'm not losing pressure, they all indicate that I'm just not building pressure, which is weird because the cylinders are, for all intents and purposes, airtight.

It's completely baffling... and maddening.

 

I probably a mile off here but can there be any leakage via the YICS system? What are the gaskets in the YICS port plugs like? I know the YICS holes are tiny where the o rings are, just a idea.

 

I get that you are confident there's no carb issues, but you've posted a couple videos where everything runs and sounds normal when dumping fuel in it by hand. Then it exhausts the load of fuel and dies. Everything about that indicates the carbs are not delivering fuel...for whatever reason I don't know. If my bike was doing that, I'd be digging into the carbs.

The leakdown test looks like everything is tight. Clearly you did a good job on lapping the valves. I don't know the reason for the compression test results...it still feels like something is wonky with the test.

Regardless, even an old tired motor will still run. It might smoke and burn oil and make shit horsepower, but with the basics of fuel, air, spark it will run. And your bike does run when hand feeding fuel. So you know it has spark, its timed, it has compression, everything is working. Seems like fuel is the issue.

 

is there an echo here?

 

Some pics would be good - cams with engine at tdc, carbs - butterfly positions, jets, including air jets, floats with carbs semi inverted. The answer is there I believe...

 

Have you verified that the pilot jets are OEM?
Have you verified that the pilot jets are the correct size?

 

I can guarantee with 47 trillion percent accuracy that it is not a carb issue.

I'm leaning towards the manual being wrong... again. Not the first time on this project.

I'm going to set the timing the way I think it should be, and not according to the manual, and see what happens.

Everything is as airtight as it should be. And as it's not reaching the compression that is should be, I'm inclined to suspect the valves aren't opening and closing when they should be.

I'm going to advance the cams a few degrees and see how it goes.

 

How do you account for those times when you ran it by dumping gas in though? The bike sounded good. It wasn't popping or missing or doing anything you would expect with timing messed up. Whatever the compression was, it was plenty to make it run then. I guess I'm lost as to why compression would have anything to do with not running on the carbs, but runs when hand feeding gas.

And how will you advance the cam a few degrees? The cam sprockets have maybe 30 teeth on them. That's 12 degrees per tooth (or 6 crank degrees I suppose). There is no adjustment other than right or wrong and the dots are cast right into the cams, as is the big "E" and "I". The crank pointer is not cast in, but you said you already double checked it for TDC.

 

I agree with you @Zoot_Suit - one war at a time. Until you get this compression issue sorted out no point worrying about carbs - cross that bridge when you get to it, as they say.

I was thinking about it last night - seems like you should be able to pop the valve cover off, slowly turn the crank manually, and look at when the cams are moving valves, maybe focus on cyl #1.

 

And some pictures of the timing marks on the cams and crank might help.

I could easily see being off by one tooth on the cam timing - those marks dont seem all that precise. Definitely something I would do.

I could also see accidentally swapping the cams. Also definitely something I would do.

 

As posted above....
If you don't check this out you are wasting your time..
Engines are just air pumps really, with a bit of fuel sucked in, and a spark. The inlet valve should open just before tdc, close just after it. The exhaust should open just before bdc. At tdc, not on firing point, the inlet opens before the exhaust closes ie there is some overlap - why not share some pics?

 

I tried advancing and retarding the timing (by about 6 degrees), with no change. Then YET AGAIN followed the manual, to the letter, and it still has not changed anything.

 

Could the problem be piston rings need to bed in a bit on the bores? Mabe just needs run. Are the ring angles like this?

 

How long are you cranking it when doing the compression test? Does the needle slowly climb to 80?

 

Engine looks really clean on top, by chance do you have a bore scope? Know nothing of the engine life and if the valves are seating right or not? There is space under each lope of the cam when each cylinder on the compression stroke? Just trying to weed out anything that could cause this.

I would guess if all the cylinder as the same, then I might put the 50/50 solution in each cylinder and let it soak a week to see if the rings are the issue? Either the bike was run a lot and each cylinder is indeed that low of compression, or it was sitting for a long time and the rings have frozen on the cylinder groves.

From what else you have shown us, it looks like you are right on the money for timing and the top of the engine looks clean and undamaged. Would be nice to take a set of known working carbs off another bike and slap them on this one and see what happens. For now your 47 trillion present sure they are not the issue I will go with.

 

Rings are perfect and installed correctly. Cylinder walls are perfect.

It hits 80psi within 2-4 revolutions, but I crank it for at least 10 seconds.

I hot tanked and cleaned the engine, inside and out. Then soda blasted it. Polished the pistons. I lapped the valves. For all intents and purposes, this is a brand new engine.

At this point, carbs aren't relevant. Simply because the cylinders aren't reaching the required pressure. No matter the condition of the carbs, it's not going to run right if it's not hitting the right pressure inside of the cylinders.

 

Try another gauge. Harbor Freight = maybe not good.

 

A while back you were going to test that compression gage on another motor. Did you confirm the gage is good? With your leakdown test results, everything timed and valves adjusted, the only way it would have compression that low is if you put a stack of gaskets under the jugs to raise them up.

And I'm still thinking about your videos when it DID run. It sounded normal. It sounded and acted like a good motor that was getting gas dumped in it by hand.

 

This is nonsense my friend. You are basing everything on one compression gauge, probably made in China and never callibrated. Ignore it, get another one, or get it cross checked. Engine will still run without the compression, just won't make much power, but ultimately, if your cams valves and rings are right, CR will be.