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compression diminishes to nothing from 1 to 4

  • Thread starter Thread starter Paul's Zuki
  • Start date Start date
Sure. Just a few drops. If you can get it to fire even for a single turn, you'll know 100% that compression is not your problem; at least not completely. Full choke? Throttles closed?

I don't think the intake stroke is as prone to reduction in efficacy by a leaky cylinder as compression is. It should still move air...
 
well, turns out and let me excuse myself again as this is my first build. I purchased a carb rebuild kit, which wasn't so complete. all of the jets were clogged up. So i pulled them off and they are sitting in carb cleaner as i type this. they will be there till sometime tomorrow this time as. What next?:(
 
Paul's Zuki said:
well, turns out and let me excuse myself again as this is my first build. I purchased a carb rebuild kit, which wasn't so complete. all of the jets were clogged up. So i pulled them off and they are sitting in carb cleaner as i type this. they will be there till sometime tomorrow this time as. What next?:(
Click to expand...

Paul, Do you have o-rings in the kit? If not try Robert Barr's cycleorings.com . He has them. Did you put the bodies in the cleaner, or just the jets? "The bodies need cleaning also. Ray
 
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Ghostgs1 said:
Paul, Do you have o-rings in the kit? If not try Robert Barr's cycleorings.com . He has them. Did you put the bodies in the cleaner, or just the jets? "The bodies need cleaning also. Ray
Click to expand...
no, I have to get some new o-rings. I am dipping the bodies in the cleaner tomorrow. I have the jets in now and will have to do the bodies 2 at a time. can isn't that big, although I had dipped them previously, but will do again for safe measure.
 
Read the carb tutorial with pic's at BikeCliff's site. Might want to gently stick a fine wire thru the jets to confirm they're open and spray carb cleaner to confirm it will make it thru the passages. The good thing is, when you do all that, the bike will probably run great considering all you have done for it.
 
one other question. Do any of the vacuum hoses need to be installed to test and start. I have an aftermarket petcock with only one outlet that leads to fuel supply. What of the other nipples that need hoses?
 
The carbs have one vacuum port that normally connects to the petcock. If your petcock doesn't have a vacuum port you will have to plug the carb vacuum port in some way otherwise you will have a massive vacuum leak. The carbs also have breather ports that connect to vent tubes. Those need to stay open.
 
sounds familiar...

sounds familiar...

Years ago I had a similar low compression problem with an '82 GS750E. Mine was a result of moving where the moving company crated up my bike and then shipped it on end standing on it's front wheel (no kidding!)! Most of the oil ran up past the pistons, into the combustion chambers, and then out whatever exhaust valves were open. When it was delivered it was a real mess. To make matters worse, the upper fork tubes were bent back towards the engine from supporting all the weight and the battery acid leaked and ate whatever it came in contact with.

Anyway, got it all fixed up and went to start it. After a lot of cranking she finally caught and started to run. However, due to all of the residual oil in the upper cylinders, combustion chambers and exhaust, it created a huge oil smoke cloud causing the bike to virtually disappear within it's own smoke screen! Put a couple of fans on her to blow the smoke out of my garage and to keep her from overheating. Let it run for a while until all the smoke finally cleared out and then took it around the block a time or two.

All seemed fine until I went to restart it. It wouldn't start for anything. The only way I could get it to start was to dribble a little bit of gas down each spark plug hole using an eye-dropper. Everything checked out except for the dry/wet compression check which was now low, something like 60 psi across the board. I then did a LEAK DOWN CHECK at 80 psi and confirmed that I was loosing compression pressure past all the piston rings.

Had no choice but to take the engine apart. When I did, I discovered that the upper cylinders where mirror smooth and most of the piston rings were kind of stuck in the ring lands. When she started the engine burned off some of the residual oil and as the engine heated up the rest created a "glaze" upon the cylinders, pistons and rings making it so they couldn't create the necessary seal to achieve normal combustion pressures.

A professional cylinder hone, piston clean-up and new piston rings eventually got her back to normal and going again. The point of my little story is to illustrate two points: 1) 60psi isn't going to create enough vacuum to draw the fuel up out of the float bowl and into the engine; and 2) use a Leak Down Check to pinpoint the exact location of where you are losing your compression pressure. A Leak Down Check is a lot more definitive of a diagnostic tool than just a regular compression check.
 
Well, she's popping out the exhaust and I can hear the carbs hissing. I am as close as finishing this thread to taking it to the stealer I'm so frustrated with this thing.
 
Typically after a topend rebuild what should the compression normally be at? Or better yet those that have rebuilt, what has your compression been after rebuild? I can't imagine it's my rings anymore, b/c I set the ring end gap to .004-.008". I honed the bore, but it's still felt smooth to the touch. Is it supposed to be a little rough? Could the gasket be leaking? I think I will perform a leak down test.
 
Hiss noise is normal when turning over the engine with a wrench. I wouldn't worry about that. Honestly now, if you did as you say the engine should have compression. Are you sure the cams are timed correctly? You sure the rings were installed properly? Sure the cam chain tensioner is installed correctly? If the answers are yes, focus your energy on something else.
 
Nessism said:
Hiss noise is normal when turning over the engine with a wrench. I wouldn't worry about that. Honestly now, if you did as you say the engine should have compression. Are you sure the cams are timed correctly? You sure the rings were installed properly? Sure the cam chain tensioner is installed correctly? If the answers are yes, focus your energy on something else.
Click to expand...

Actually the hissing was more a pffftttttt of air coming out of the carb part when trying to start the motor. I'm guessing it was ignitting the fuel?:confused:

Okay, Theoritically speaking, I have the TDC dead center, then pull my cam chain tight from the front of the motor, place my exhaust cam with the 1 even with the top of the cylinder head and 2 notch facing straight up, then count the 20 chain pins to the notch 3(facing straight up) on the intake cam. That is properly installed per book. i let loose the cam chain tensioner and spin it a few times to make sure everything looks good. I take it back to TDC after about 10 turns and make sure that my notch 2 & 3 have 20 chains pins between each other and they do. Could it still be off somehow? Just asking cause I dont know.

As far as the rings go. I put the chromed one on top, darker in the middle and oil rings at the bottom all with the ring end gap set to .004-.008". One thing that confuses me in the manual its talks about placing the middle ring right side up and but the rings i have don't look any different or have an angle as I've read on google searches. problem?
 
Paul's Zuki said:
As far as the rings go. I put the chromed one on top, darker in the middle and oil rings at the bottom all with the ring end gap set to .004-.008". One thing that confuses me in the manual its talks about placing the middle ring right side up and but the rings i have don't look any different or have an angle as I've read on google searches. problem?
Click to expand...

IIRC - the rings have a tiny letter stamped on them that should face up when you install them onto the piston. It is pretty hard to see, but you can find it right at the ring gap.
 
If I pull the head, can I still use the rings I just put in? Again it has not been turned on so they would have not seated.
 
chef1366 said:
With even compression who knows?
I'd love to see the hone on the cylinders
Click to expand...

I think I'm gonna pull the head one more time to inspect the rings (which are new and properly spaced) and make sure they are facing the right way. I'll also take a picture of the hone. that was probably the easiest part. I use to hone so it's not unfamiliar to me on how to properly crosshatch a bore.

Check this out though, when I filed down the rings to the proper spacing within the bore, and I did that by placing the rings in the bore and leveling within it, I then used a feeler gauge to see the gap space. However when I placed the rings on the piston, I noticed they stuck out quite a bit and would even come off of the piston making it hard to slip into the cylinder, so I took them off the piston and squeezed them in enough that they sat withing the grove, still popping out, but quite as dramatic as before and they slipped into the sleeve better. Is that how you guys do it or did i do something wrong by doing it that way.
 
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