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.

 

Just read all the posts up to date. Wow, have you put the work into this bike! You can't let it go until you get her running as you like. I would guess you would really be mad at yourself if you did. When you first tried to start the bike, you said it ran on full throttle. So for now, don't worry about the compression, same across the board. The bike did run when you were feeding fuel through the air box. Have you tried an AUX fuel tank and bypass the gas tank? I would guess at this point you have checked the float bowls for fuel and each one has fuel running out of them when you crack the bowl screws?

Just a guess but still something with the fuel. Is the fuel or proper amount of fuel getting to the carbs? That is why I would set up an AUX fuel tank and see what happens. Having a clear fuel line so you can see it going to the carbs and filling them is a nice touch too. I don't know if you have done a fuel run test on the tank to see if it is passing fuel out of the petcock and running a good amount of fuel?

Bottom line, you do great work. Attention to detail is outstanding, guessing it is something very simple. If is runs with fuel being hand fed from the air box to the carbs, I would guess the carbs when hooked up to the bike fuel tank are not getting the correct amount of fuel to them.

Don't throw it in the trash, let the end loader have her or the contractor buy it. Take some time away from her and then come back to her. As you mentioned before, having a fresh set of eyes and hands might also help.

 

I went and read the reviews on this gage on the HF website. A unusually HUGE amount of the reviews mention incorrect, low readings saying things like "Caused me to misdiagnose a motor as bad".

 

Maybe, but for comparison sake, I just did the top end of an RJ engine - cyl hone and valve lap. That tested near the top of spec for compression right away.

 

Same here, with my Snap-On compression gauge. That, and the S-O timing light were two of the best things I ever bought from the damned van.

 

When I was getting suspected bogus readings from my cheap HB gauge, I 'borrowed' one from Advance Auto, and confirmed mine was bad.

My X had great compression directly after I honed the cylinders.

 

Why would glazed (or just deglazed for that matter) bores give you low compressions anyway? extra oil usage yes, but rings will seal (statically anyway) against any surface that's round...

 

Might be wrong but I thought the rings were pushed onto the bores with the compression, I am not an expert by any means.

 

But you did not change the piston rings?

 

No, I didn't. Why would that be needed with just a hone? The rings do not form to the cylinders, they can rotate around when the engine runs, so the mating surfaces aren't always the same.

 

Yes that is right only two strokes have pegs to stop piston ring rotation. Makes sense just wondered though.

 

Thanks for that reminder. I had forgotten what it was like honing the jugs on my old Kawasaki 500 H1 Mach III's.

 

Potentially, but for cranking pressures it's marginal at best, for cylinder leakage tests even less. Piston ports or grooves radially above the top ring are race mods usually.
Doesn't change my comment about rings sealing on shiny vs honed bores.

 

Yes, I checked flow from the tank, it's flowing very well.

As many others have suggested, it could be the HF compression guage. I'll test it, and if found to be faulty, I'll borrow another from a shop.

 

If found faulty I hope you'll put us all out our misery and get your carbs on the bench and take some pics...

 

I see that you must have painted your carb bodies? I see in the pics that all the mounting screws seem to be painted. Not too sure if you tested the sliding plunger on each of the carbs with compressed air?

You know the engine if fine, timing is one and no banging or hard knocking coming from the engine. Just a guess, but I would say you put her all together just fine. Timing is on and seeming like when it fired up, was running just fine. That only leaves fuel delivers to the engine.

There were no pics of you taking apart the carbs and going through them. I know this has been a long process, I think you mentioned 8 months from the time the engine came out until it went back in the bike. Did you take pics of the carb teardown and cleaning? Would be interesting to see how green or gummed up they were. If not, no big deal. I went through my first set of carbs six times before I got them clean. A ultrasonic cleaner didn't get the hard-to-reach areas and only with hand tools, Q tips, compressed air and lots of B-12 chem tool was I able to get them clean.

There are a few folks on here that do carbs for a good price. If you are frustrated with that part of this project, just send them off. The attention to detail you have done on the rest of the bike is commendable. You really do enjoy your hobby.

 

From a month ago...

As with everything else, the carbs were gone through, meticulously, five times in a week.

(pic from June 6)

 

I think the only orifice we are concerned with is at the bottom of the float bowl.

 

I’d love to see a photo of the enrichment jets in the carb bowl with a light shining through them.

 

I'd like to see what jets are where, and where all the butterflies sit with the idle screw two turns in.

 

I have tested the HF compression guage. It's good.

 

Well crap. Now what?

 

By popular demand, I've pulled the carburetors apart, AGAIN... now for a seventh time...

Here are the butterflies, two turns out, all four are the same.



Here are the factory jets, all clear (on all four carbs), and the correct sizes, in the correct locations.



Here is the factory seat, inside and out. Perfectly clean.



Spraying carb cleaner through the orifices, ALL of them are flowing.





Now, can we, for the love of everything unholy, stop with the carbs?!?

 

As I've said before, the condition of the carburetors is absolutely, unequivocally, utterly, not relevant, to an infinite degree if the cylinders aren't reaching the required pressures/vacuum.

If the cylinders are not pulling a strong enough vacuum, they're not going to pull fuel from the idle circuit of the carbs to run at idle, but rather only at higher RPM'S. As is the case.

This is a cylinder/head issue... of which, I have zero clue. I've performed the leak down test, and they're only losing 3%, well within the 10-15% allowable. So that eliminates rings and valves.

There has to be something within the YICS that has gone awry. And unfortunately, I don't know enough about the YICS to test for or determine what that issue is.

 

I didn't see the jet in the float bowl....

 

YICS primer: https://www.xj4ever.com/catalog/yics.html

The punch line is that once the intake valve is closed, YICS is out of the equation. Should not mess with compression numbers.

At this point I am at a loss to even theorize why you are getting such low compression numbers but passing leakdown with flying colors and valvetrain timing is spot on.

 

Nope, not happy yet.
Can you screw the idle speed screw right off, then in to touch. Then in one turn only.
Then a pic of each butterfly at the position of the first progression hole. They should all be at the edge of that first hole - this is them bench synched, adjust each one to achieve this edge of hole. All things being correct the bike should run and idle here albeit fast.
Then I'd like to see the numbers on the idle jets, and the air jets.
Then I'd like to see you remove each idle mixture screw, open the butterfly of each carb in turn, put a finger over the air jet, and squirt carb cleaner in the jet mounting, watching for fuel coming out of the idle screw hole, and each progression hole, on all carbs. Then we will know that the passagways between the idle jet (not the air jet), and the idle and progression circuits is clear. Wear eye protection!
I'm being pedantic, but these simple settings are essential. I could add a test to check that the hole in the bottom of the enrichment chamber is clear also - in fact yes, please check each of these.

 

And another comment, on the pic you show the idle circuit being blasted, there are bubbles forming where I would expect a jet of fuel - this needs investigating.

 

It wasn't the carburetors.

 

Awesome! Don't keep us in suspense though....

 

The issue...

Chinese fuel line.

I figured that I would replace the 42 year old, half dry rotted factory fuel line with new.

There was however, a defect. There was a little flap of rubber on the inside acting like a reed valve. At low fuel demand it couldn't overcome the "reed", but at high demand it'd overcome the resistance and feed it fuel.

I reached in with the highly underrated and humble dental pick, ripped that flap out and she worked.

There's some more fine tuning to do, and a few more parts to replace, but this is huge progress.

When I tested the petcock, I pulled the fuel line off the petcock, cranked the engine a few times and fuel flowed. "Great, the petcock works. It's getting fuel..." or so I thought.

After shining a light into the fuel line, seeing some light at the othe end, and blowing air through it, I assumed, "Yep, it's a fuel line." So who would have ever thought to look deeper into it?