broken rings or chiped valve?

[mmaleney]

So I picked up a 87 venture but turns out it has 40 lbs when hot in one cylinder, front right, put oil in spark plug hole and on re test reading went up to 60 lbs , the other three are good, yesterday I pulled the motor, put some oil down the spark plug hole and with the comp tester on hand turned the motor and the oil pushed out a valve on the exhaust side, so what do you thing ? chiped valve ? bent valve, bad rings ? I did not test any other cylinder with the oil I do have clearance between camshaft and shim. thanks Mike.

[SilvrT]

So I picked up a 87 venture but turns out it has 40 lbs when hot in one cylinder, front right, put oil in spark plug hole and on re test reading went up to 60 lbs , the other three are good, yesterday I pulled the motor, put some oil down the spark plug hole and with the comp tester on hand turned the motor and the oil pushed out a valve on the exhaust side, so what do you thing ? chiped valve ? bent valve, bad rings ? I did not test any other cylinder with the oil I do have clearance between camshaft and shim. thanks Mike.

 

generally speaking if the compression goes up after putting oil into the cylinder then it's associated to rings but from what you've described, it could be all of the above (rings and valves). If you gotta get down to a ring job, then you should be doing the valves as well and you'll know exactly what the state of them are when you pull the heads.

[skydoc_17]

Hey Mike,

I am thinking you have a valve problem in that cylinder. The compression didn't go up enough when you added the oil to make me think that the rings are the problem. Broken rings are not unheard of in these motors but I have seen way more valve related problems with these motors than ring problems. For what it is worth, since you live in Pa. as I do, I have a 50,000 mile 86'MKII VR motor that has good compression on all 4 cylinders, the only thing that is wrong with the motor is the battery drain tube came loose from the battery and acid dripped down the right side of the cylinder area. Nothing a little paint wouldn't cure. $100.00 and it's yours. If you need help with transporting the motor, I can help. You would need to transfer your water pump Carbs., and clutch discs to this motor, but other than that, this may be a cheaper fix than pulling the heads and reringing your motor because of the price of the gasket set. If you are interested, PM me.

Earl

[SilvrT]

I am thinking you have a valve problem in that cylinder. The compression didn't go up enough when you added the oil to make me think that the rings are the problem.

 

If compression dry was 40 and wet was 60, that's a 50% increase .... seems quite a lot to me. ... but, what do I know??? could a chipped or leaky valve alone produce this much increase on a wet compression???

[bkuhr]

Hey Mike,

I am thinking you have a valve problem in that cylinder. The compression didn't go up enough when you added the oil to make me think that the rings are the problem. Earl

item #8 of the following thread is some old readings I took of direct air pressure on top of cylinders minus heads to test suspect rings. Turns out I had bent valve. The bad cylinder had bad ignition problems and had not fired in a long time, and PO had abused MC with dead cyl for long time.

http://www.venturerider.org/forum/showthread.php?t=46640

 

[skydoc_17]

Hey Rick,

Because the rings on a piston have multible layers, even with a broken ring, I would expect to see the compression raise close to 100 PSI with the oil added. I said a valve problem because with a burnt valve or an obstruction keeping the valve from closing all the way (like a piece of a slider stuck in the valve, or a valve shimmed to tight) the valve is always open somewhat and not affected by the oil. An easy check would be to pump some compressed air into that cylinder and see where the air ends up going. Without a few tests, we are just guessing here. If the compressed air comes out the intake, it would be an intake valve stuck open, if it exits the exhaust, then you would have a burnt or stuck exhaust valve. If you hear the air coming from the oil fill port, then the rings are leaking. Without an answer to this question, everything we suggest is speculation.

You could very well be right, but as you well know, tearing down one of these motors is VERY costly for ring replacement and is at the upper end of mechanical knowledge. The gasket set alone is in the $300.00 range plus a ring set and valve job. Plus if I was going to replace the rings on one piston, I would be tempted to replace the rings on all 4 cylinders. But that's just me. The point I was trying to make is a used motor is most times a better financial solution with a lot less down time, no matter where he gets the motor from. Out of the 50 or so motors I have gotten into this deep, I have seen broken rings twice. I have seen valve related problems 30 or more times. Because I have not personally inspected this motorcycle and run a series of tests to try to pinpoint the problem, I am only offering up a history of motors I have worked on.

Earl

[SilvrT]

Hey Rick,

Because the rings on a piston have multible layers, even with a broken ring, I would expect to see the compression raise close to 100 PSI with the oil added. I said a valve problem because with a burnt valve or an obstruction keeping the valve from closing all the way (like a piece of a slider stuck in the valve, or a valve shimmed to tight) the valve is always open somewhat and not affected by the oil. An easy check would be to pump some compressed air into that cylinder and see where the air ends up going. Without a few tests, we are just guessing here. If the compressed air comes out the intake, it would be an intake valve stuck open, if it exits the exhaust, then you would have a burnt or stuck exhaust valve. If you hear the air coming from the oil fill port, then the rings are leaking. Without an answer to this question, everything we suggest is speculation.

You could very well be right, but as you well know, tearing down one of these motors is VERY costly for ring replacement and is at the upper end of mechanical knowledge. The gasket set alone is in the $300.00 range plus a ring set and valve job. Plus if I was going to replace the rings on one piston, I would be tempted to replace the rings on all 4 cylinders. But that's just me. The point I was trying to make is a used motor is most times a better financial solution with a lot less down time, no matter where he gets the motor from. Out of the 50 or so motors I have gotten into this deep, I have seen broken rings twice. I have seen valve related problems 30 or more times. Because I have not personally inspected this motorcycle and run a series of tests to try to pinpoint the problem, I am only offering up a history of motors I have worked on.

Earl

 

I'm always open to advance my knowledge so your points are well taken and I fully concur that popping in another engine might well be a better way to go. Frankly, it's been over 35 years since I was into diagnosing such problems and subsequent repair of same. As such my memory is somewhat ... ummm... diminished? LOL However, with what I do recall, having compression raise in the neighborhood of 50% on a wet test, regardless of what the actual value is was, in those days, a sure sign of the need for a ring job. I do agree tho that replacement vs repair may be the better way to go with these engines due to the work and cost involved in the repair. I also agree that more in-depth inspection/testing is necessary to "pinpoint" the actual problem before making a decision but at this stage, I'd be very suspicious of the rings. If it were me, I'd drop in the other motor and then rebuild the original one in my spare time (considering the price you're selling it for).

[mmaleney]

Thanks guys I may rent a leak down tester and see how long it will hold. That motor for $100 sounds good Will be in touch skydoc thanks again will let you know what I find.

[Monty]

When it's running, you can usually pinpoint a stuck/bent/burnt valve like this.

 

Intake valve will usually cause a backfire or pop thru the carbs during the compression stroke.

 

When holding a dollar bill back at the muffler outlets, an exhaust valve problem will usually try to suck in the dollar bill, whenever the piston is on its' intake stroke.

 

 

Just my 2 cents. Good luck.

[SilvrT]

When it's running, you can usually pinpoint a stuck/bent/burnt valve like this.

 

Intake valve will usually cause a backfire or pop thru the carbs during the compression stroke.

 

When holding a dollar bill back at the muffler outlets, an exhaust valve problem will usually try to suck in the dollar bill, whenever the piston is on its' intake stroke.

 

 

Just my 2 cents. Good luck.

 

only one problem to this theory ....

 

 

WHERE DOES ONE GET A DOLLAR BILL FROM ???

 

:sign20:

 

(us Canucks don't have 'em ... we jus` got "Looneys")

[Monty]

KInda hard to hold Marcarl up to the pipe, though.

[Condor]

Check the valve clearance. There was a discusssion a while back about clearance effecting the compression. You stated that oil came out the valve, and just maybe the valve is not seating.....

[98RoyalStar1]

I just joined the club after doing some reading on a problem I encountered with a newly acquired Royal Star. I had owned 2 Honda 750 Ace and a VStar 650 but was ready for the big move, and when the opportunity knocked I went for it!

 

I just bought a 98 Royal Star that only has 3300 Miles and thought it was a great deal however after getting it home I discovered I may have overlooked the possibility of a bad valve/ring when I noticed it was running bad. I thought I'll get it home and take the carbs appart to clean and off I go on the road. However after a carb cleaning the Front Right cylinder is still cold and it sucks the dollar bill at the tailpipe and in a not so funny way I'm begining to think it will want to suck a lot more dollars.

 

My next step was to try to do a compression test but I think is almost pointless from the postings above or am I wrong? The motorcycle was originally owned by a guy that knew about cycles but the guy I got it from inherited the bike about 8 years ago and only put 300 miles in the last 3 years, had no clue on proper maintenance or storage of a bike. BTW the fuel in it was nasty, from the miles on it I believe it had not gotten new gas in years.

 

To sum it up, I got the mistreated Royal Star home and changed the fuel, added techron, put new oil, new plugs, cleaned carbs, and amazingly it runs pretty good (iddle and accel) but can tell that the one cylinder is not getting hot / there is spark and is sucking in air at the tailpipe. Any adjustments in air/fuel mixture only cause a small rise in temperature at the tailpipe. I've only taken the bike to get gas after almost dumping all the gas in the tank and adding a small amount of new gas and it has run with techron for about a total of 1-2 hours at iddle/reving up some. I read that riding it couple of hours at high rpms on the highway may free up the suspected stuck exhaust valve. I don't want to damage the engine further, is it possible to damage it more? What with intereference engines? Is it like with cars? Has it already caused damage?

 

Any suggestions would be greatly appreciated.

[Flyinfool]

These bikes run amazingly well on 3 cylinders.

 

I woulkd od all of the testing mentioned above that can be done while the motor is still in the bike to rule out all of the less bad things that could be wrong.

 

Good luck

[Marcarl]

KInda hard to hold Marcarl up to the pipe, though.

Are you trying to resemble me, or are you saying that I'm cheap,,, or are you saying I flop around a lot,,,,or just not very fat,,,, now just what are you trying to point out, inquiring minds need to know!!!

[MiCarl]

Here is how to make a poor mans leak down tester (requires a better compression gauge, the type where the gauge uncouples from the hose).

 

Take the gauge off and remove the Schrader valve from the engine end of the tester hose. Screw the hose into the suspect cylinder.

 

Set the pressure regulator on your air compressor to about 5PSI.

 

Remove the oil fill plug.

 

Turn the engine by hand until you're on the intake stroke of the cylinder you're testing.

 

Hook the air hose to the compressor hose. You should hear air escaping from the intake.

 

Turn the engine forward (counter clockwise, anticlockwise) by hand. When the intake valve closes you should not hear air leaking from anywhere. If it is listen at the oil fill, intake and exhaust to see where its coming from.

 

BTW, if you use too much oil on a wet compression test it'll raise the numbers even if rings aren't the problem.

[Dano]

 

(us Canucks don't have 'em ... we jus` got "Looneys")

 

KInda hard to hold Marcarl up to the pipe, though.

 

Are you trying to resemble me, or are you saying that I'm cheap,,, or are you saying I flop around a lot,,,,or just not very fat,,,, now just what are you trying to point out, inquiring minds need to know!!!

 

 

I believe putting these three posts together will help Carl out a bit.........

[bongobobny]

Yah!! Back in my old motorheading days, we made up a fitting that screwed into the spark plug hole and the other end had a schrader. You put the piston to top dead center on the compression stroke and hit it up with air then listened thru the carb, the oil filler, and the exhaust pipe for hissing air...

Here is how to make a poor mans leak down tester (requires a better compression gauge, the type where the gauge uncouples from the hose).

 

Take the gauge off and remove the Schrader valve from the engine end of the tester hose. Screw the hose into the suspect cylinder.

 

Set the pressure regulator on your air compressor to about 5PSI.

 

Remove the oil fill plug.

 

Turn the engine by hand until you're on the intake stroke of the cylinder you're testing.

 

Hook the air hose to the compressor hose. You should hear air escaping from the intake.

 

Turn the engine forward (counter clockwise, anticlockwise) by hand. When the intake valve closes you should not hear air leaking from anywhere. If it is listen at the oil fill, intake and exhaust to see where its coming from.

 

BTW, if you use too much oil on a wet compression test it'll raise the numbers even if rings aren't the problem.

[tazmocycle]

there has been a couple of guys i know that has had pieces of carbon on the valve and not had go compression on them. you can add a whole bottle of techron to a tank of gas and run it hard keeping it in thr upper rpms for the tank full and it''ll most times clear it out. we have done it to a lot of bikes and one that had over 31k on it after 60 miles or so, it was blowing out soot and sparks of the muffler and started to missing, he thought we had ruined his bike but we got him to get back on it and keep running thr heck out of it. after another 70 or so miles it was running smooth and faster than ever. with the bad gas we are getting and the de-tuned motors for passing epa requirement, it's just the nature of motors today. thats why opening up the airboxs and re-jetting the carbs and adding a dyna tech ign box gets these engines running awhole lots better is done to them. how many of the new ars do you see a cream colored exhaust pipe anymore, just a few ponitac sst a few yrs ago. nowadays they are all soot black, a sign of poor burning of fuel. REMEMBER WHEN!! YOU KNEW YOUR CAR WAS RUNNING AT PEAK PERFORMANCE- THE WHITE TAIL-PIPE!! or cream(i know some will say it's running too leanLOL!!@

[jasonm.]

So I picked up a 87 venture but turns out it has 40 lbs when hot in one cylinder, front right, put oil in spark plug hole and on re test reading went up to 60 lbs , the other three are good, yesterday I pulled the motor, put some oil down the spark plug hole and with the comp tester on hand turned the motor and the oil pushed out a valve on the exhaust side, so what do you thing ? chiped valve ? bent valve, bad rings ? I did not test any other cylinder with the oil I do have clearance between camshaft and shim. thanks Mike.

that valve may be too tight clearance..and likely burned too. pull valve cover, Check clearance