951 ring gap

[Keith1000]

Hey all,
So I had my 98 GTX 951 carb bored .25 over. I had it done by a repitable company in Niagara Ontario, after getting it home i noticed the ring boxes were not even opened, so that concerned me a bit that ring gap wasn't set. So I opened them up and proceeded to check ring gap. (WSM piston) in the box it says all seadoo .010 to .018. I'm measuring .024 for the most part. .006 over the limit. Am I over thinking it and plop them in and send it or no chance?? And what do I do now? Is there such thing as over sized, over sized rings. And file them? Can I go .5 and file or is the ring radius different? I paid extra money to have them back for today and now I'm stumped till Tuesday (Holiday Monday) when i can speak to someone. Any thoughts

Thanks. Keith

 

[mikidymac]

You do not file fit two stroke rings ever! If you are out of spec then you need to talk to your machine shop. It sure sounds like they bored or honed too much.

This is why I never recommend local shops touching 2-stroke cylinders unless they do a lot of them.

 

[Keith1000]

You do not file fit two stroke rings ever! If you are out of spec then you need to talk to your machine shop. It sure sounds like they bored or honed too much.

This is why I never recommend local shops touching 2-stroke cylinders unless they do a lot of them.

I don't know their exact history of small engine but do know they had another seadoo engine there at the time. Now I don't have a 2000$ mic but do have a cheap digital one. And if standard bore is 88 my mic says 88.25 exactly.

 

[mikidymac]

You can only measure a bore correctly with a bore gauge.

 

[Keith1000]

You can only measure a bore correctly with a bore gauge.

Understandable. So i guess I've got a problem. The 024 gap is to big?

 

[mikidymac]

In my opinion yes, Seadoo says new bore is .016-.022. Wear limit is .039.

I would be more concerned with what your piston clearance is.

 

[Keith1000]

In my opinion yes, Seadoo says new bore is .016-.022. Wear limit is .039.

I would be more concerned with what your piston clearance is.

I was just about to quote the same thing with a picture i just read in a shop manual,
Is the gap over .022 yes. Is it under .039 hell ya.
I'll have to check into the clearance. Can that be done with a feeler gauge with the piston on the wall?
Thx again.

 

[mikidymac]

No, you don’t want a new ring over the .022.

It’s going to wear within a few hours as it wears into the cylinders and get bigger fast. That’s exactly why Seadoo says new ring maximum is .022.

You don’t measure ring gap with the piston in the cylinder. You install the ring in the cylinder then push it down about 3/4” with the piston to make sure it’s square then measure the gap with a feeler gauge.


You can’t measure piston clearance with a feeler gauge. You have to measure the bore with a bore gauge then subtract the actual measured piston diameter and subtract that number.

 

[Keith1000]

No, you don’t want a new ring over the .022.

It’s going to wear within a few hours as it wears into the cylinders and get bigger fast. That’s exactly why Seadoo says new ring maximum is .022.

You don’t measure ring gap with the piston in the cylinder. You install the ring in the cylinder then push it down about 3/4” with the piston to make sure it’s square then measure the gap with a feeler gauge.


You can’t measure piston clearance with a feeler gauge. You have to measure the bore with a bore gauge then subtract the actual measured piston diameter and subtract that number.

Ya that's how I measured the ring. Still 0.024

 

[etemplet]

Hey all,
So I had my 98 GTX 951 carb bored .25 over. I had it done by a repitable company in Niagara Ontario, after getting it home i noticed the ring boxes were not even opened, so that concerned me a bit that ring gap wasn't set. So I opened them up and proceeded to check ring gap. (WSM piston) in the box it says all seadoo .010 to .018. I'm measuring .024 for the most part. .006 over the limit. Am I over thinking it and plop them in and send it or no chance?? And what do I do now? Is there such thing as over sized, over sized rings. And file them? Can I go .5 and file or is the ring radius different? I paid extra money to have them back for today and now I'm stumped till Tuesday (Holiday Monday) when i can speak to someone. Any thoughts

Thanks. Keith

Don't worry about it, you'll be fine. Install the rings. You are looking at Seadoo specs, not WSM. Sometimes the difference in material causes components to grow at different rates so that must be accounted for. You don't change end gap with bore size. Bore is piston clearance.

I use WSM pistons and parts. I"ve never had them meet the Seadoo tolerance recommendations. Usually the 787 engine has .020 or more ring end gap. Compression is always fine. With WSM Pistons you should have about .005" piston to bore clearance. Be meticulous... make sure the ports are chamfered and clean the hell out of the cylinders. Get all the metal dust out of there. Good Luck !!

 

[Keith1000]

Don't worry about it, you'll be fine. Install the rings. You are looking at Seadoo specs, not WSM. Sometimes the difference in material causes components to grow at different rates so that must be accounted for. You don't change end gap with bore size. Bore is piston clearance.

I use WSM pistons and parts. I"ve never had them meet the Seadoo tolerance recommendations. Usually the 787 engine has .020 or more ring end gap. Compression is always fine. With WSM Pistons you should have about .005" piston to bore clearance. Be meticulous... make sure the ports are chamfered and clean the hell out of the cylinders. Get all the metal dust out of there. Good Luck !!

Problem is the wsm numbers are even lower than the brp, that's why I'm even more concerned. The instructions that came with the piston is the same piston to wall .0045-.005 and ring gap i believe was 0.010- 0.018
Keith

 

[etemplet]

All I can say is I have not had a problem and I guarantee WSM knows their rings and the end gap. Consistently the gap is .020" and perhaps a tad more at times. I've done 10 or more engines in the last two years... NONE have been in that .010" - .018" spec. Compression is alway where it should be. Gotta remember, all those internal parts "grow" as the engines heat up. I let the engineers worry about that. I'm more concerned with "too little" end gap. That is the show stopper.

If you would like more information on that perhaps you could call WSM and talk to one of the experts. You'll have to perservere though because I couldn't get a piston size them them. LOL

Again.... I'd put that engine together without hesitation. Good Luck !

 

[Keith1000]

All I can say is I have not had a problem and I guarantee WSM knows their rings and the end gap. Consistently the gap is .020" and perhaps a tad more at times. I've done 10 or more engines in the last two years... NONE have been in that .010" - .018" spec. Compression is alway where it should be. Gotta remember, all those internal parts "grow" as the engines heat up. I let the engineers worry about that. I'm more concerned with "too little" end gap. That is the show stopper.

If you would like more information on that perhaps you could call WSM and talk to one of the experts. You'll have to perservere though because I couldn't get a piston size them them. LOL

Again.... I'd put that engine together without hesitation. Good Luck !

Hi. If it was .20 i probably wouldn't hesitate, but it's not it ,24. My issue is that the company gave me the ok to return them for .5 if I send it and it goes wrong i won't be able to return.
I know this sucks but it's a decision I have to make. Besides I've still got some time Doug ford still has our camp closed until the 14th of June.

 

[mikidymac]

Like I said, more important is piston to cylinder clearance.
You really need to have that measured correctly and verify it is within spec. If it is then I wouldn't worry about the rings.

My concern would be that the cylinders were bored or honed too big and that is why the ring gap is too large and so will the cylinder clearance.