Ring clearances

[(F5)]

So we're pulling apart a mate's 07 EC300 last night. Done a bunch of hours, but probably less than mine I did a few months back.

Piston didn't look that worn, but it was a different make to the one I'd pulled out of mine. Very similar but
1. had black coating on some of the areas with silver (unplated) border
2. ribs under crown different
3. skirt was finished differently on the inside.

Otherwise it looked real damm close. I assume one of them was a Vertex

Mine was considerable more worn. Neither was a Woosner (which is what I put back in). No evidence it had been apart before.

ok so back to the queer part. Mine had worn rings, the closed end gap was like 1mm. Std for the 300 is 0.5-0.8mm

So slotted his in a reasonable ways. . . 0.3mm! Hells teeth!

I would have though being that tight they would have bound on each end & bulged the ring into the ex port. Can't see any scraping damage at all.

This makes a bit of a mockery of the ring end finishing I've done on other bikes. Who else has seen such close fitment on their GGs?

Surprised that it is so tight & not worn for the time he has put on it. Looked a very low hour bike when he got it.

[Jakobi]

I think my 2010 EC300 had 0.4mm ring gap after 75hrs on the stock piston. Strangely enough it had piston slap. Dropped a Wossner in with 0.5mm which did another 80 something hours before I went to the 250. Those rings came out at 0.55mm.

[(F5)]

The std Wiseco in my 200 came out looking mint, & the rings that the previous owner had put it (said it didn't need them, didn't believe him) came out as new spec after 3 years of my thrashing so started to believe him.

Still 0.3 seems super tight for a 72mm bore.

[Jakobi]

Its on spec with Wisecos recommendations for a top ring.

72 millimetres = 2.83464567 inches
2.84 x 0.004" = 0.01136 inches = 0.288544 millimetres

[(F5)]

Hmm, actually you're quite right. Still seems pretty tight. GG manual over cautious perhaps.

[Jakobi]

Yeah I went over cautious with the first top end on the 300 and set mine at 0.5mm. Even with the 250 I used Wiseco recommendations and then added a touch more.

If they came out at 0.3mm though depending on how many hours on the top end, you'd have to wonder how tight they were when they were fresh.

[(F5)]

well yeah exactly the question in my mind as I was measuring them. Too tight & they must bulge, or at least scrape the bore of oil. You'd think that would wear them a bit more. Sheesh I don't know.

[desertgasser300]

At the sake of sounding ignorant, how would I check my ring tolerences?

[Jakobi]

Originally Posted by desertgasser300

At the sake of sounding ignorant, how would I check my ring tolerences?

When you have the cylinder off the bike and the rings off the piston you carefully compress the ring and place it inside the cylinder. Turn the piston upside down and then use it to push the ring down an inch or two. The piston levels the ring. Then use feeler guages between the ends to measure the gap.

[Jakobi]

Originally Posted by (F5)

well yeah exactly the question in my mind as I was measuring them. Too tight & they must bulge, or at least scrape the bore of oil. You'd think that would wear them a bit more. Sheesh I don't know.

Mmm. Hows the clylinder look? Like I said, I went pretty tight on my 250 engine. Well just over wiseco recommendations.