piston ring tight fitting - rebuild

[fishfeatures]

I am rebuilding a 1990 60hp Johnson, alarm went off and upon inspection it needed honing.

Anyway, I have all pieces ready to put this motor back together, but yesterday as i was replacing the rings (re-ringing only not new pistons) I found that the bottom one wouldn't compress too well in the groove.
they are OEM .0030 rings and the ring gap was measured and is within spec. The issue seems to be the the ring doesn't slide/ move freely when in the groove. No issue with the old one and i am putting the rings on with the pin in the gap.

I thought that maybe a build up of carbon was the issue so, I broke an old ring and used that to clean the gap (found this tip on an old post), got a bit of carbon but not alot out adn the ring still seems to be sticking at the LHS of the gap.

Top ones no issues it's only the bottom ones.. is it a case that the piston is not OEM and so the groove and ring won't fit ? Is it uncommon for rings not to be an exact fit?
the old rings look shinier than the new ones so maybe they are different .

 

[gm280]

Re: piston ring tight fitting - rebuild

I am rebuilding a 1990 60hp Johnson, alarm went off and upon inspection it needed honing.

Anyway, I have all pieces ready to put this motor back together, but yesterday as i was replacing the rings (re-ringing only not new pistons) I found that the bottom one wouldn't compress too well in the groove.
they are OEM .0030 rings and the ring gap was measured and is within spec. The issue seems to be the the ring doesn't slide/ move freely when in the groove. No issue with the old one and i am putting the rings on with the pin in the gap.

I thought that maybe a build up of carbon was the issue so, I broke an old ring and used that to clean the gap (found this tip on an old post), got a bit of carbon but not alot out adn the ring still seems to be sticking at the LHS of the gap.

Top ones no issues it's only the bottom ones.. is it a case that the piston is not OEM and so the groove and ring won't fit ? Is it uncommon for rings not to be an exact fit?
the old rings look shinier than the new ones so maybe they are different .

Am I understanding you that you bought oversized rings for a standard piston? I guess I don't understand what you are try to say... If your pistons are OEM standard, you have to replace the rings with standard size as well. You can't go to oversize rings on standard pistons and have them fit properly and work... I could be confused from your comment though.

 

[fishfeatures]

Re: piston ring tight fitting - rebuild

Oh the pistons are OS 0.0030 too.... sorry meant to inc that as well.

I didn't do the last rebuild, I bought it liek that and only discovered when i stripped it down that it was bored out to oversize..

 

[orbanp]

Re: piston ring tight fitting - rebuild

You are correct, a stuck ring does not bode well for engine durability!
Measure the ring thickness, and its uniformity, both the old ring and new ring.
The ring groove clearance (not the end gap clearance) on a '70 60HP (3-cylinder engine) is between 0.0045" - 0.0015".
Yours should be similar!
You could also try to "dress" the side of the new ring by rubbing it on a flat surface with emery paper on it. While you do that, keep measuring/checking the ring thickness!
You could also measure the rings for the other cylinders (I assume all three cylinders got new rings), and mix and match the rings to the pistons, as there is variation in ring/groove dimensions. If you only honed one cylinder, and got only one new ring set, than this obviously would not work!

Good luck, Peter

 

[gm280]

Re: piston ring tight fitting - rebuild

Oh the pistons are OS 0.0030 too.... sorry meant to inc that as well.

I didn't do the last rebuild, I bought it liek that and only discovered when i stripped it down that it was bored out to oversize..

Okay that makes a huge difference. And I think you mean .030” and not .0030” oversize. Either way did you do the honing (deglazing) for the new rings? Since someone else rebuilt this engine before, they may have not bore or cross-hatched the cylinder correctly and filed the end gaps on the .030” over rings the first time. Now that isn't a bad thing because you now have the opportunity to deglaze and hone the walls until you get your new ring’s end gaps into spec. If you can see any carbon on the ring grooves at all, they need to be cleaned out to the aluminum before reassembling... And if you still can’t get the fit to go properly, you need to figure out what brand pistons the PO used or...I hate to say it...purchase known pistons that fit the rings you purchased. Are you sure your new rings are for the engine and not some after-market type? It seems hard to believe that you have correct ring end gap tolerances but won’t fit the piston correctly. Something isn’t right with those two items... Before you locate the problem, DON’T file the rings to fit... Being the pin is in the end gap on the piston, they will work once everything is fitted correctly. Also, if I’m not mistaken, the rings have a top and bottom profile that needs to be followed to fit properly. I know the top ring is tapered. Not sure if your second rings are or not... Check for the carbon again and clean the ring groove out CAREFULLY until all the carbon is gone. Keep us posted...

 

[fishfeatures]

Re: piston ring tight fitting - rebuild

let me do an overnight soak and clean and i'll report back tomorrow.. thx guys.

 

[fishfeatures]

Re: piston ring tight fitting - rebuild

let me do an overnight soak and clean and i'll report back tomorrow.. thx guys.

The soak seems to have worked, the bottom rings on two of the psitons move freely,other one is still binding or catching in one spot on the piston. I'll let this soak for another few hrs and see if it frees up.

 

[Greg_E]

Re: piston ring tight fitting - rebuild

Have you measured the ring thickness of the new rings with a micrometer and compared that reading to the old rings?
I seem to remember reading that the Wiseco pistons use different rings than what would be used on OE pistons. Are the pistons OE or aftermarket? I could be completely wrong on that, but I would measure them before I put everything back together.

 

[durban]

Re: piston ring tight fitting - rebuild

wot worked for me i dressed the ring groove with a file that fitted neatly in the groove did this very gently & was spot on atrer

 

[fishfeatures]

Re: piston ring tight fitting - rebuild

Have you measured the ring thickness of the new rings with a micrometer and compared that reading to the old rings?
I seem to remember reading that the Wiseco pistons use different rings than what would be used on OE pistons. Are the pistons OE or aftermarket? I could be completely wrong on that, but I would measure them before I put everything back together.

I don't have equipment that'll measure that small i.e. micrometer ....

 

[fishfeatures]

Re: piston ring tight fitting - rebuild

wot worked for me i dressed the ring groove with a file that fitted neatly in the groove did this very gently & was spot on atrer

What di dyou think the problem was Durban, different suppliers for the rings and pistons so they didn't fit as they should??

How tight was the ring fitting for you?

 

[Silvertip]

Re: piston ring tight fitting - rebuild

You can also insert just the ring into the cylinder, square it up by inserting the piston upside down. Now check the end gap. If it's tight, you have an incorrect ring. Iff too loose you have an incorrect ring or a bore that is excessively worn or bored differently than the others.

 

[gm280]

Re: piston ring tight fitting - rebuild

You can also insert just the ring into the cylinder, square it up by inserting the piston upside down. Now check the end gap. If it's tight, you have an incorrect ring. Iff too loose you have an incorrect ring or a bore that is excessively worn or bored differently than the others.

I agree that should have been the first thing done was to check the ring(s) end gaps for all rings and in all cylinders. And then if they were in the spec range move on to installing them on the pistons and see how they fit. I assumed that was what was done prior to this... I get the feeling that between the rings (from some supplier) and the pistons (from some other supplier but not the same as the rings) is a huge part of his problem. Maybe he needs to mic (measure precisely) the pistons AND the bores for a start only IF the ring end gaps fall into engine spec. Either measurement off is the problem...period! And if all the measurements are correct, you have to have carbon buildup in the ring groves or a simple mismatch of different supplier’s incompatibility. JMHO!

 

[fishfeatures]

Re: piston ring tight fitting - rebuild

You can also insert just the ring into the cylinder, square it up by inserting the piston upside down. Now check the end gap. If it's tight, you have an incorrect ring. Iff too loose you have an incorrect ring or a bore that is excessively worn or bored differently than the others.

Ring gap is within spec, it's not a gap problem....

I can't see any Name on the piston to see who made it, only part no., "UP" and "0.30" on the piston can't see anything else on skirt or underneath.

 

[bob johnson]

Re: piston ring tight fitting - rebuild

come on guys, he said in the first post that the RING GAP was within spec!!! soo it isn't a bore dia or ring OD issue!! its either the ID of the ring is too small or the OD of the ring groove on the piston is too large (or that they were not ment for each other!!!!) filing the end of the ring is a POOR fix here......you only do that when the ring end gap measure is too tight......and like has been mentioned here, that is don't with the ring in the bore and NOT ON THE PISTON. if you used an old ring to clean out the groove.. I cant imagine that soaking in anything would help....if you don't cut aluminum with the end of the broken ring while cleaning...you haven't cleaned enough.since you don't have an OD mike to measure the dia of the ring groove, nor a way to measure the wall thinkness of the ring and or the bore dia.......we are stuck..... so you KNOW it is 100% a fit of the ring to the piston issue......might be they wont work...(new rings with the old piston).....did you verify someone remark that your bore is really .030" over and not .003" over???......a bore for a 60 hp in 1989 is still in spec if it is .003" over size...but that's it..... 3.187-3.188 is standard.... so you can go up to 3.191....the ring end gap is .007-.017... that's a big gap!...bob

 

[gm280]

Re: piston ring tight fitting - rebuild

Maybe he needs to take it to a machine shop and have them measure both the pistons AND cylinders to seriously see what gives. He didn’t say if he had any snap gauges or micrometers. If both are in specs, he has to either buy rings to fit the pistons OR pistons to fit the rings. Either way it is not a cheap fix... I recently purchased two sets of standard rings for an old Johnson 40 HP and I was able to talk them down from $40 dollars a set to around $20 dollars a set (actual OMC parts). And that was only for two rings for each piston... If he has to buy new something, I’d make very sure they were compatible to the other product or replace both as matched sets... The rings he has now are in spec as far as end gap goes which means their ID (inside diameter) is too small and therefore when installed on the piston they are sticking out too far and won’t collapse enough to install in the cylinder correctly. I’d be interested to know just how much the end gaps spread once installed on the pistons. Because obviously there are not closing up to the end gap he read without the pistons, and that IS the total problem.

 

[out 2 launch]

Re: piston ring tight fitting - rebuild

Rectangular vs semi keystone? Could there be a mix up? If the ring in question is placed in another ring groove does the problem still exist?

 

[bob johnson]

Re: piston ring tight fitting - rebuild

well since he is using the old pistons it is highly likely they are no longer in spec..... pistons warp, and maybe be out of round more than tolerance allows... this may hinder an other wise good ring from letting the assy slide into the bore. I cant reme,mber if the OP mentioned wether he has measured the piston OD itself....( the ring grooves will obviously follow) bob

 

[fishfeatures]

Re: piston ring tight fitting - rebuild

Guys,

with no micrometer to hand i can't verify ring differences. All i can say is that all 3 new rings are having the same prob on one piston and in the same spot. The Upper rings are grand and no issues here. It's the lower grooves that are causing the prob. I suspect different rings and pistons from different suppliers.

What i'm considering at this stage, is to bring off the pistons to the machine shop (bear in mind that there are no marine machine shops here only automotive ones and there are only a few in the whole country, and the one near me has no idea of marine set up, hell he laughed at me and pretty much called me a liar when i said that only one cylinder could go larger on an outboard rebuild and not be out of balance). I'll get them to measure the pistons and rings and see if there are stark differences.

If all else fails then I'm not buying new rings, 2 of the 3 pistons are ok after the soak, so for the 3rd I'll put on one of the old rings and take a chance , put it all back together and see how the compression is... and hope to hell the ring will hold.

Without knowing whose pistons i have I am not going to take a chance and guess what rings will do, i did that once and am now in this mess because of it.

I can get a 2nd hand motor here, cheaper than the cost of new piston kits and postage to here so hence the reason for rings only in this job.

 

[nwcove]

Re: piston ring tight fitting - rebuild

not sure what the prices are like on the other side of the pond, but you should be able to pick up a micrometer that you can use to compare ring width and thickness to the other rings. i recently picked up digital mic for $30, it measures down to 0.001. im sure the machine shop will charge you more than $30, and you have a new tool in the box!!