Moly vs Cast rings

[tinkerman]

Any opinions on pros and cons for Moly or Cast rings. Ordered a set of Hastings cast rings this morning with a bunch of other top end stuff and see in the confirmation on my email this evening that they sent the Moly ones.

I would have preferred to put the cast ones in as thats what came out and they worked just fine. (if it aint broke don't fix it)

Any input would be good. I'll likley just throw the moly ones back on the back of the bench and get a set of cast ones if someone doesn't convince me of a good reason to use them. This is just a puttin around scoot so not sure I need something as hard wearing as moly running up and down the cylinder walls.

Thanks,

Tink

[wfolarry]

Cast rings require a rougher finish to break in properly. That moly top ring breaks in 5 minutes after you get the bike running. One of the problems that I still see to this day is the wrong bore finish with the ring type used. Run the moly ring. You'll be better off.

[tinkerman]

Hey wfolarry

Do I still hone the cylinders in the normal manner?

Tink

[wfolarry]

Yes.

[fulldress79]

Cast rings are less costly but more "forgiving". If the bore in your cylinders is still nice and round,without taper,and of course within specs,your better off with moly rings as they last longer.

[tinkerman]

Great,

I have checked the cyilinder for out of round and taper and they are good. Only 40,000 miles on the cylinders and the bike has been well maintained and not thrashed for the most part. As well the engine set up is pretty tame.

Thanks for the input fellows, will use the moly with some confidence at this point.


Tink

[silvercab996]

The reason for the Moly faced top ring is because it's more impervious to heat but should be used with a fine honed finish in a fresh bore. Use cast for a re ring in a worn or already run cylinder. The Moly facing  is very tough and will not conform well to a worn cylinder, like the soft cast unplated ring will.

[PanHeadRed]

This does not imply that other finishes won't work.

IMO these are good guide lines

Moly - 250-280 Grit / Surface Finish 15-25 Ra (Roughness Average)

Chrome/Iron - 220-250 Grit / Surface Finish 25-35 Ra (Roughness Average)

[tinkerman]

Hmmmmm?

OK, a couple of diff opinions. No sweat. I need to do a more detailed check on taper and out of round on my cylinders but they only have 40,000 miles on them. A little cylinder skirt evidence on the cylinders but you can't feel it or measure it so I am feeling pretty good about the cylinder walls.

At this point I am not 100% comfortable using the moly top ring if some folk feel it won't break in to the used cylinder as readily as a cast.

No problem for me to pick up a set of cast rings. I bring most of the parts in from the States to Canada by snail mail so it's not really worth screwing around with customs sending back the moly rings. I'll just put them up on the shelf if I don't use them. Some one will have a need for them at some point.

Appreciate any addition info or opinions from you folk.

Thanks

Tinkerman

[PanHeadRed]

>Appreciate any addition info or opinions from you folk.<

IMO you have all the info you need right here, from WFO Larry.

"Cast rings require a rougher finish to break in properly. That moly top ring breaks in 5 minutes after you get the bike running. One of the problems that I still see to this day is the wrong bore finish with the ring type used. Run the moly ring. You'll be better off."


I could not agree more with his entire post. Surface finish is the key.

[tinkerman]

Hey PHD,

Appreciate the input. It's becoming clear that my cyl honing skills are a little basic relative to what's happening or available in the industry today. But with your fellows help and a little research I am coming up to speed. Since I read your previous post I spent an hour or so doing some research and discoverd some good info. About the only thing I was aware of to this point relative to honing a cylinder would be the different grits and styles of hones. Now I see that even with the same grit but changing the abrasive type, ie. diamond vs stone, can change the result or RA as you refer to it. As well never heard of brushing the cylinder after honing to plateau the tops of the rough edges in the honing pattern. Makes perfect sense when you hear it for the first time

http://www.youtube.com/watch?v=3O0XnA_fwyU was a good eye opener as well.

In any case I am a lot better informed now. I will look at getting my self set up to refinish the cyl. for the moly rings or if the cost is prohibitive to get the gear will find a shop to do it for me.

Thanks man,

Tinkerman

PS......Spoke to the shop that used to do a bit of machining when I was working on the Brit bikes. $25 /cylinder to refinish for the moly rings and $65/head to inspect and reseat the valves. I don't have to scratch my head to hard on that one.

Tink