ive got a YAMAHA NIGHTMARE on my hands!!!!

[MikDee]

Re: ive got a YAMAHA NIGHTMARE on my hands!!!!

When replacing piston rings, the ring end gap should be placed about 120* apart from the next, meaning 1/3 of the way around the piston, away from the next if there's 3 rings on a piston, So that you get the least compression leakage between rings. If you placed all the ring gaps in the same spot on the piston, you'd lose considerable compression. Plus, you really need to Mic everything up when doing this, you didn't say if you reused the old rings, or new ones? There are limited specs for ring gaps, if you're old rings were reused, they maybe too worn, and the gap may be too big? Or your cylinder maybe too worn, as to be within specs. Besides, every time you remove rings from a cylinder you're supposed to re-hone it with a special stone, & leaving a crosshatch pattern, (or the rings won't seat properly, causing compression, and oil leaks). Was all this done after you took it apart, & put it back together???

 

[JustJason]

Re: ive got a YAMAHA NIGHTMARE on my hands!!!!

I'm gonna disagree with mikedee,
on a 4 stroke it doesn't really matter if the ring gaps all line up or are staggered. Rings on a 4 stroke float and are not held in place by a pin like on a 2 stroke. When the motor is running the rings will spin a bit on the piston anyways. And it certainly won't make an engine that's supposed to have over 100psi minimum and drop a reading to 15....
the 3 most important things with the piston to consider are;
1. is the piston directional
2. piston to cylinder wall clearence
3. ring end gap (size... not location)

 

[oonighttrain]

Re: ive got a YAMAHA NIGHTMARE on my hands!!!!

When replacing piston rings, the ring end gap should be placed about 120* apart from the next, meaning 1/3 of the way around the piston, away from the next if there's 3 rings on a piston, So that you get the least compression leakage between rings. If you placed all the ring gaps in the same spot on the piston, you'd lose considerable compression. Plus, you really need to Mic everything up when doing this, you didn't say if you reused the old rings, or new ones? There are limited specs for ring gaps, if you're old rings were reused, they maybe too worn, and the gap may be too big? Or your cylinder maybe too worn, as to be within specs. Besides, every time you remove rings from a cylinder you're supposed to re-hone it with a special stone, & leaving a crosshatch pattern, (or the rings won't seat properly, causing compression, and oil leaks). Was all this done after you took it apart, & put it back together???

we honed the cylinders to a perfect cross hatch pattern, used new rings and aligned the rings precisely how the manual instructed..

 

[oonighttrain]

Re: ive got a YAMAHA NIGHTMARE on my hands!!!!

/rings.
but ya cant do a compression test using a wrench on the flywheel,aint gonna happen.
.

no,
this is with the motor installed... pulled the kill switch tether and turned the motor over... got 15 psi, then after a few squirts of oil in the cylinder, i got over 100 psi...

 

[MikDee]

Re: ive got a YAMAHA NIGHTMARE on my hands!!!!

we honed the cylinders to a perfect cross hatch pattern, used new rings and aligned the rings precisely how the manual instructed..

Nice to see this part was well done.

 

[MikDee]

Re: ive got a YAMAHA NIGHTMARE on my hands!!!!

I'm gonna disagree with mikedee,
on a 4 stroke it doesn't really matter if the ring gaps all line up or are staggered. Rings on a 4 stroke float and are not held in place by a pin like on a 2 stroke. When the motor is running the rings will spin a bit on the piston anyways. And it certainly won't make an engine that's supposed to have over 100psi minimum and drop a reading to 15....
the 3 most important things with the piston to consider are;
1. is the piston directional
2. piston to cylinder wall clearence
3. ring end gap (size... not location)

Yeah Right Jason, Then why is there a recommened procedure for putting the rings on a piston, either 2 stroke or 4 stroke? Apparently you know more then the manufacturer, or think you do!

 

[JustJason]

Re: ive got a YAMAHA NIGHTMARE on my hands!!!!

Yeah Right Jason, Then why is there a recommened procedure for putting the rings on a piston, either 2 stroke or 4 stroke? Apparently you know more then the manufacturer, or think you do!

huh???
We'll... obviously there is always going to be some sort of procedure for installing rings.

On a 2 stroke, (which is not this motor) the rings will only fit on a piston 1 way. there is a locating pin in the ring land of the piston. The rings do not freely rotate on a 2 stroke piston. If they did the end gap would eventually find its way over a port and you would chew the rings out. 90+% of 2 stroke rings are champhered at the ends of the ring gap to accept the locating pin... so you can't even put them on upside down.

Now on a 4 stroke... most rings are directional, and have an "up" side and a "down" side. And on some, the 2 compression rings may be not the same. But the biggest difference is they do not have a locating pin, and are therefor able to spin freely on the piston. When that motor is running those rings do move around a bit. And because it's normal for them to move around in a running engine, you really do not need to stagger them. 1 end gap directly above another isn't going to drop compression 85lbs... (he say's he's only getting 15psi, and we know 100psi to be bare minimum) Heck i'd even say if he's got his rings on upside down he'd get more than 15psi.... until it runs, heats up, and breaks

piston direction.....
and piston to cylinder wall clearence, and ring end gap measured at 3 places (top, middle and bottom) on both axis is what determines how well a bottom end is going to seal. (assuming the bore is true)
I've seen running engines that have massive detonation damage on the edges of the piston, i've also seen engines with aweful gouges on the cylinder walls (which always happens when chunks of burning piston are flying around everywhere...) that have decent (over 100psi) compression. They just blow through alot of oil.

This whole thing is either here nor there though. As this guys needs to do a leakdown test first, and to my knowledge, hasn't done so.

oonighttrain, post a serial for your engine. on the head does it use rocker arms or is it shim over bucket???? if you aren't gonna do a leakdown... check your valve clearences. (do it cold) if it's buckets... did you remove any and not put them all back in the same spot???

 

[oonighttrain]

Re: ive got a YAMAHA NIGHTMARE on my hands!!!!

oonighttrain, post a serial for your engine. on the head does it use rocker arms or is it shim over bucket???? if you aren't gonna do a leakdown... check your valve clearences. (do it cold) if it's buckets... did you remove any and not put them all back in the same spot???

its a rocker arm set up.. im convinced that my problem is someting in the cylinders/rings.. my #1 will not get above 15 psi unless i squirt oil in the cylinder.. i plan on taking the engine to the outboard machine shop on monday..

there is 1 of the 5 rings that must be placed in the exact spot, it does have a keeper pin. that would be the upper oil ring.. the book says which direction to put them all but also has a little note that says they can move around a bit..

again, i have no problem with a leak down test but, im fairly convinced that i have a definate cylinder problem..

ill just take it to the guy and see what hes got to say.. he already tole me it would be about $125 to bore the cylinders.. the way i see it is, ill give him the whole damm thing and it should be good as new when i get it back for a rather reasonable price..

 

[oonighttrain]

Re: ive got a YAMAHA NIGHTMARE on my hands!!!!

captjason,
my motor is a j50tlrw.. 98 yami 50 hp 4 stroke...

 

[MikDee]

Re: ive got a YAMAHA NIGHTMARE on my hands!!!!

huh???
We'll... obviously there is always going to be some sort of procedure for installing rings.

On a 2 stroke, (which is not this motor) the rings will only fit on a piston 1 way. there is a locating pin in the ring land of the piston. The rings do not freely rotate on a 2 stroke piston. If they did the end gap would eventually find its way over a port and you would chew the rings out. 90+% of 2 stroke rings are champhered at the ends of the ring gap to accept the locating pin... so you can't even put them on upside down.

Yep, I learned this about 30yrs ago when I rebuilt the powerhead of my 69'- 115hp Evinrude V4, but the 2cycle locating pin design actually mometarily slipped my mind I was thinking 4cycle.

Now on a 4 stroke... most rings are directional, and have an "up" side and a "down" side. And on some, the 2 compression rings may be not the same. But the biggest difference is they do not have a locating pin, and are therefor able to spin freely on the piston. When that motor is running those rings do move around a bit.

I learned this also about 45yrs ago, when rebuilding a Chevy 327/300hp motor, and then a few yrs later a 426/415hp Plymouth Ramcharger engine.

And because it's normal for them to move around in a running engine, you really do not need to stagger them.

You're contradicting yourself with your first sentence here? We both know there's an engine manufacturers recommeded procedure to follow?

1 end gap directly above another isn't going to drop compression 85lbs... (he say's he's only getting 15psi, and we know 100psi to be bare minimum) Heck i'd even say if he's got his rings on upside down he'd get more than 15psi.... until it runs, heats up, and breaks

True if all the gaps lined up, I doubt you'd that lose much compression.

piston direction.....
and piston to cylinder wall clearence, and ring end gap measured at 3 places (top, middle and bottom) on both axis is what determines how well a bottom end is going to seal. (assuming the bore is true)
I've seen running engines that have massive detonation damage on the edges of the piston, i've also seen engines with aweful gouges on the cylinder walls (which always happens when chunks of burning piston are flying around everywhere...) that have decent (over 100psi) compression. They just blow through alot of oil.

Yes, This is the right way to measure, another factor to consider here is the taper, "the mushroom effect" of wear on the cylinder walls.

This whole thing is either here nor there though. As this guys needs to do a leakdown test first, and to my knowledge, hasn't done so.

oonighttrain, post a serial for your engine. on the head does it use rocker arms or is it shim over bucket???? if you aren't gonna do a leakdown... check your valve clearences. (do it cold) if it's buckets... did you remove any and not put them all back in the same spot???

Some good useful detail, & info here jason, even though you sometimes come on a bit strong.

 

[JustJason]

Re: ive got a YAMAHA NIGHTMARE on my hands!!!!

You're contradicting yourself with your first sentence here? We both know there's an engine manufacturers recommeded procedure to follow?

i hear ya on that. I always have a peek at the book before fitting rings (as i probably actually only do it 3 or 4 times a year). For me, the biggest thing i'm looking at/for is ring orientation (tip here: if its not specified its almost always number side up), and I want to see what type of ring it is. compression/sealing rings come in a couple of different styles. You have a keystone style (most common) bullnose (or barrellnose) dyke etc. Sometimes there may be a dyke style for the top groove but a keystone for the bottom. Always best to double check.
Is far as ring rotation goes. You actually want them to rotate, the bore will stay truer. I read in a hot rod magazine a few years back and they claimed a piston ring will rotate 1rpm for every 1000 engine rpm. Don't know how "true" that is, but it's not unreasonable to me so i go with it.

even though you sometimes come on a bit strong.

Ughhh I know!! It's my greatest strengh and biggest bane at the same time. People usually hate me at first, then warm up to me. In person i have a big personality and i often intimidate people, even though my intentions are always benevolent. After a while people see it's not that i'm cocky, just confident (even when i'm wrong). Part of why people never know what to think of me is because i'm always an "uppity" person... and not the normal grumpy know it all.
That's my phsycoselfanalysisapology!!
Sorry Mikdee and others if I come off like an ***** sometimes, i know it's percieved that way and i really mean no harm.

 

[MikDee]

Re: ive got a YAMAHA NIGHTMARE on my hands!!!!

Jason, I see you chilled some since when you first came on the forum, you definitly have a good bit of current usefull knowledge, but there are some things I've learned over my many years, from a lot of hands on knowledge that we may not agree on, but I just call it as I see it, or as I experienced it, if I say something it is not BS, I'm not here to BS anybody, but it's what I've found to the best of my experience, knowledge, or memory,,, and sometimes it's hard to fill in the blanks of what I try to remember Anyway, Peace! and good night.

 

[SgtMaj]

Re: ive got a YAMAHA NIGHTMARE on my hands!!!!

Easy you two... Lets address the real issue in this thread... if you two want to duke it out, there is a PM system for that.

Now, oonighttrain, you last said that you were able to get over 100psi with some oil in the piston... how long did that last, or is it still giving 100+?

 

[JustJason]

Re: ive got a YAMAHA NIGHTMARE on my hands!!!!

read the posts... it's going to a shop.

 

[JustJason]

Re: ive got a YAMAHA NIGHTMARE on my hands!!!!

I'm picking up what your putting down Mikdee.
I'm fairly tolerant of people... but i have a hard time with stupidity.

My teachers used to tell me when i was growing up, "there is no such thing as a dumb question".
I disagree... there's more dumb questions than educated questions out there.

I also used to hear... "there is no such thing as common sense, so expect everyone you talk to not to have any... and let them surprise you."
I also disagree..... and often do not have the patience to find out if a person has common sense.... unless of course there is money on the table... then i'm all ears and smiles.

I closely moniter people's perceptions of me when it comes to business. But when it comes to day to day stuff (like iboats forums among others) I stopped caring a long time ago what people think of me.... and I've always done ok... with little headaches.


What i've come to learn in this being my 396th post here.... is that for every 1post of actuall good info (be it right or wrong, as long as it makes sense and fits the symptom). There are 10 bad posts about the same thing.
I'm not scared of waiving my dirty laundry.

As far as keeping all this in PM. The originater said he's taking it to the shop... might as well be subject closed at this point... But i still would like to hear the verdict on the engine. So while the post is idle until the results are posted, i feel it's fairly ok to hijack a bit without going over the top.

As for the rest of this post regarding Mikdee. I do appreciate your candor. Although in the future we may disagree on techie stuff and common answers for common symptoms. I feel that we can now with respect agree and disagree on whatever the subject may be post by post. Again... no i'll will intended. Right or wrong, you are extremely honerable with the best of intentions, and I hope you can see the same about me someday.

A dozen cheers with 2 cases of beers...
Jason


ps~ post your results for us oonighttrain

 

[SgtMaj]

Re: ive got a YAMAHA NIGHTMARE on my hands!!!!

read the posts... it's going to a shop.

I saw that, but I didn't ask him if it was going to a shop. I asked him how long the sqirt of oil in the cylinder lasted for. Knowing that it's going to a shop doesn't really do anything to address my curiosity on the issue.

SgtMaj

 

[oonighttrain]

Re: ive got a YAMAHA NIGHTMARE on my hands!!!!

take it easy on each other guys...

and quit highjackin my thread...


SGTMAJ,
when i squirt some oil in the cylinder #1, it jumps from 15 psi to about 100 for only a short time.. say 2 compression test rounds..
2 and 3 cylinder go from 120 to over 150 when i squirt oil in them...

according to the book, this engine should be at 180 psi compression...

 

[rodbolt]

Re: ive got a YAMAHA NIGHTMARE on my hands!!!!

myself, I am done with this thread.
we have told him exactly how to trouble shoot yet he is stil a pokin and a hopeing.
I probably see more bored blocks and rings weekly than most posting here have seen in a lifetime.
but we cant help if the person simply refuses to do the correct test for an accurate diagnosis.

 

[MikDee]

Re: ive got a YAMAHA NIGHTMARE on my hands!!!!

Sorry to hijack the thread, but IMO The piston, or cylinder wall, has a minute hole, crack, or some porousity, in it somewhere, if the compression is not getting past the rings, or valves? It has to be going somewhere? and now I'm plum outta idea's?

 

[JustJason]

Re: ive got a YAMAHA NIGHTMARE on my hands!!!!

Any news on this thread? What was the outcome from the original poster?