Topic: oil rings help needed

[turboguzzi]

dear racing bros,

motor is apart now for a refreshment and general check as it was smoking pretty heavily in the last race. The kit 57mm (motor's a 500) pistons  ive used held well but seemingly the quality of the thin oil rings (it's a three piece oil ring setup) is a bit low. Under high racing stress they seem to have lost all tension, there's hardly any gap now!

the compression rings seem to have done fine, no signs of blow by and the motor felt strong.

so am in need of oil rings that are 0.3mm X 1.6mm (0.12" X .063"), width is a bit less critical, groove's pretty deep. Obviously these dimensions are totally different from stock CB500 four rings.

tried to coantact total seal but the only 57mm oil rings thye had were 0.6mm thick.

can anybody think of another source for them? the most important parmeters are the 57mm bore and 0.3mm thicknes.

I can eventually go for 0.6mm rings but hate the idea of messing with the ring grooves in a lathe, leaving that option for last.

thanks in advance

TG

[simon#42]

tg  dont worry to much about cutting the ring grooves in a lathe , thats how the 0.3 ring grooves got there in the first place . also have you checked the grooves ? if they are worn that could be your problem .

[mick7504]

TG
I don't know if these people can help with rings.
http://www.scafutopistoni.it/
Mick

[Big Jay]

What is the total width of the oil ring groove?

[turboguzzi]

hei guys

thanks for the tips,


scafuto is a dealer for asso and vertex, should give these a try even if i believe that they just buy rings somewhere else. the only 57's in the scafuto catalog are scooter pistons with a one piece oil ring.

will take some measurements and pics later today

ciao

TG

[turboguzzi]

OK, here are the latest developments on the oil rings saga

the reasons I thought that my motor was smoking too much on fresh pistons was the too small free ring gap.

something like 1.6-1.8mm against 2.2-2.4mm in the oil rings of my previous pistons, see pic ("problem ring" on the left, stock CB500 in the middle, last season's kit piston ring on the right)

but thank god i went down to measure them cause its only now that I discovered that my tasty pistons (graphite coating, Slipper skirt design, 142 grams complete) just dont have the second row of oil holes in the skirt! they do have the regular oil holes behind the spring ring, but could the missing holes be the reason that oil was getting into the CC?

Planning on adding them now, maybe the problem wasnt the rings at all.

What do you guys say?

Thanks, TG

Howell, Big Jay, the total oil ring height (2 scrappers X expander) is 1.4mm, scrapper ring section is 0.3mm X 1.7mm,

[Howell]

OK, here are the latest developments on the oil rings saga

the reasons I thought that my motor was smoking too much on fresh pistons was the too small free ring gap.

something like 1.6-1.8mm against 2.2-2.4mm in the oil rings of my previous pistons, see pic ("problem ring" on the left, stock CB500 in the middle, last season's kit piston ring on the right)

but thank god i went down to measure them cause its only now that I discovered that my tasty pistons (graphite coating, Slipper skirt design, 142 grams complete) just dont have the second row of oil holes in the skirt! they do have the regular oil holes behind the spring ring, but could the missing holes be the reason that oil was getting into the CC?

Planning on adding them now, maybe the problem wasnt the rings at all.

What do you guys say?

Thanks, TG

Howell, Big Jay, the total oil ring height (2 scrappers X expander) is 1.4mm, scrapper ring section is 0.3mm X 1.7mm,

I don't think that the oilholes gives the problem , have you measured the valve guides ?
The pistons we use don't have also these oilholes.

[Rod]

OK, here are the latest developments on the oil rings saga

the reasons I thought that my motor was smoking too much on fresh pistons was the too small free ring gap.

something like 1.6-1.8mm against 2.2-2.4mm in the oil rings of my previous pistons, see pic ("problem ring" on the left, stock CB500 in the middle, last season's kit piston ring on the right)

but thank god i went down to measure them cause its only now that I discovered that my tasty pistons (graphite coating, Slipper skirt design, 142 grams complete) just dont have the second row of oil holes in the skirt! they do have the regular oil holes behind the spring ring, but could the missing holes be the reason that oil was getting into the CC?

Planning on adding them now, maybe the problem wasnt the rings at all.

What do you guys say?

Thanks, TG

Howell, Big Jay, the total oil ring height (2 scrappers X expander) is 1.4mm, scrapper ring section is 0.3mm X 1.7mm,

I don't think that the oilholes gives the problem , have you measured the valve guides ?
The pistons we use don't have also these oilholes.

+1 important thing is when does it smoke? - if its worn guides it will smoke when throttle is shut rapidly (from medium/high revs), but not under acceleration.

[turboguzzi]

Rod, Howell, motor is of course very fresh, new valve seals, no play in valve guides, new rebore, look at the left piston and there's no blow by whatsoever. Indeed it smokes steadily, not only when shutting the throttle off.

that's why when I saw the small free gap of the rings my initial thoughts were about the oil rings "tiring" and losing tension

Then, when I realised the missing holes under the rings, my thoughts went there, it does make sense, no? this piston has extra thin oil groove so the holes behind the ring are maybe 1.2mm.

look at the holes in these Wiseco CB750 pistons, I am now thinking about doing the same. just enlarging the existing ones in the groove down.

Howell, What is the free gap in your oil rings?

My second thought is that both our pistons are kit pistons for small 125 motors that usually dont see 12,000 rpm so maybe that's why they dont have those holes. Hope you will not have this problem too....

[bwaller]

I think you're probably on to something TG. It has to help evacuate oil....can't hurt.

[turboguzzi]

I think you're probably on to something TG. It has to help evacuate oil....can't hurt.

got that feeling too, specially wiht the oil ring groove being so thin

engine was running fine other wise, so gonna give it a try and see if situation improves.

cheers

TG

[paulages]

TG-

I think you're on the right track with the oil holes. I contacted hastings to see if they'd have anything for you, and they were very confused about your dimensions.. must be a very short groove. The .063" measurement is the thickness or depth? I thought I read it as the depth, but she seemed to think it would be the height. In any case, they didn't seem to have anything, but could you clarify those dimensions?

[paulages]

Looking at your ring pictures, the larger dimension is obviously the depth of the groove. ok, let me know if I can help with any phone calls over here.

[turboguzzi]

Looking at your ring pictures, the larger dimension is obviously the depth of the groove. ok, let me know if I can help with any phone calls over here.

thanks P, the dimensions of each ring are 57mm (bore) X 1.6mm X 0.3mm so yes, 0.063" is the width of the thin ring section, and 0.012" the thickness of the ring.

I tend to believe that the story was the lack of drain holes, started to drill them today, will close the motor next week.

still, if you get around to ask hastings, then by all means.

thanks

TG

[MRieck]

Looking at your ring pictures, the larger dimension is obviously the depth of the groove. ok, let me know if I can help with any phone calls over here.

thanks P, the dimensions of each ring are 57mm (bore) X 1.6mm X 0.3mm so yes, 0.063" is the width of the thin ring section, and 0.012" the thickness of the ring.

I tend to believe that the story was the lack of drain holes, started to drill them today, will close the motor next week.

still, if you get around to ask hastings, then by all means.

thanks

TG

Lack of hole holes....... especially on throttle chop and high vacuum....will create a lot of problems IMO.