Kenny's lightweight Piston

jseng1 · Sep 9, 2010

Here's a shot of Kenny Cummings 74mm lightweight racing piston (200 grams) after a series of wins until the old used crank went BOOM.

The dark areas on the skirt are from the molly coating which is mostly worn off. The underside of the dome looks clean without any sign of overheating. DLC pin also looks cherry.

Look up Kenny at the next race event (Barbers). Kenny will be bringing these items and a bushless Carrillo rod for everyone to see.

more details at www.jsmotorsport.com

Jim Schmidt
more details at:

swooshdave · Sep 9, 2010

jseng1 said:
The dark areas on the skirt are from the molly coating which is mostly worn off.

Is that good or bad. Can they get recoated? Will he reuse these or put new stuff in?

comnoz · Sep 9, 2010

Dave, The ceramic-moly coating was applied by me. It is sacrificial and the majority of it wears away pretty quickly. I really helps most during break -in. The piston is measured and fit before the coating is applied. It helps avoid those little scratches and sieze marks common when new pistons are wearing in. I have found pistons broken in with this coating loose less diameter during the break-in. Jim

jseng1 · Sep 9, 2010

When the crank broke, one piston hit the head and suffered some minor damage - so reuse isn't a good idea. They would have gone back in otherwise.

Hortons Norton · Sep 9, 2010

The condition of the pin is amazing! What rings is he using? The top ring dosen't look like a total seal ring? Thanks for the pictures.

comnoz · Sep 9, 2010

They are JE rings. Chrome or "red ring.
Total seal rings are of no benefit at higher engine speeds. Jim

CptKelly · Sep 9, 2010

Does Kenny make them in 77mm?

Mike

comnoz · Sep 9, 2010

The pistons are from Jim Schmidt Engineering. I believe he has 77mm kits. They must be used with the long rods. Jim

Hortons Norton · Sep 9, 2010

Yes he does, You can see his products here: http://users.gotsky.com/jimschmidt/jsmo ... oducts.asp

Hobot · Sep 9, 2010

Thanks for the show and tell. Educational to me to see the color and texture of the crown carbon to shoot for. Interesting data point TS rings no benefit near 7000 rpm which ain't exactly hi rpm in moderns. But sure is more fun for all of us to see hunks of money burnt up in exciting entertainment than just tossed directly on a fire.

Hortons Norton · Sep 9, 2010

I guess anything is a matter of opinon, I know a few people in racing that use them and also have their pistons custom made. They are used by some of the top race teams in the world. http://www.totalseal.com/TechPage.aspx :wink:

Hobot · Sep 9, 2010

Jim said no extra hi rpm advantage not they wouldn't work in hi rpm. I assume at some rpm the bleed through time is so short not much can get through ring gaps.
Peel gets what ever rings Jim sent with the piston/rod kit. I'm just happy I've learned enough this decade to even discuss this stuff let alone attempt a special weird configuration of engine and chassis. Hurts a bit more though knowing what is happening hearing those vintage engines roaring their hearts out. I have to get in a angry don't giveashit state of mind to let past Peel's hair out over red line. I want a bullet proof bike of course so trying to build it stronger than i'll ever dare run it but maybe once for a dyno test. Racers are so hard hearted a bunch.

comnoz · Sep 10, 2010

Hortons Norton said:
I guess anything is a matter of opinon, I know a few people in racing that use them and also have their pistons custom made. They are used by some of the top race teams in the world. http://www.totalseal.com/TechPage.aspx :wink:

The last few years engine builders have found that better sealing is available if the second ring leaks more than the top ring. This causes a larger pressure differential over the top ring which makes it seal tighter. Total seal has devoted their development to gappless top rings instead of second rings for the past several years because of that finding. I recently talked to Total Seal and they would not supply a gapless top ring set for an air cooled engine because of durability problems stemming from high temperatures and cylinder wall distortion.
I used to run Total seal rings in my racebike with the gapless second ring. I never saw any advantage once the rpm got over 3000. Below that speed I did see a slight increase in torque with the gapless.
I have seen the top ring in a gapless second ring set that was collapsed and stuck in the groove after only 7000 miles on a streetbike that was ridden very easy. [too easy] It had never seated the top ring and the second ring was doing all the work. I have never had any problems with their rings on any of my personal bikes. Jim

splatt · Sep 10, 2010

I believe most ring manufactures went that way, some piston makers also machine a groove around the piston between top and second groove to lower the pressure between the two, it helps lessen ring flutter.

jseng1 · Sep 10, 2010

Kenny is getting gapless 2nd rings this time in his new rebuild. Why? Well - why not? They do seem to seal better and keep the oil cleaner (and burn less of it). If you want them, they are an option at a slightly increased cost. If low end torque is improved then that is at least something. They are an improvement for street bikes in my opinion. Especially if you are of the mind that corrosive gasses leaking through the ring gaps contaminates the oil and is bad for the bottom end. There were lots of comments on that subject in the one way breather discussions. In any case - its reassuring and impressive to stand on the kickstart and count 30 seconds or more waiting for it to leak down.

more details at http://www.jsmotorsport.com

xbacksideslider · Sep 10, 2010

The picture shows that the rings were sealing very well and that the crowns never got hot enough to burn oil onto their undersides. I see good parts, a good build, and good tuning.

It's interesting, the comment that Total Seal does not recommend gapless rings for air cooled engines. I wonder if gapless rings have trouble following a less straight cylinder wall, does friction between the overlapping parts of the ring inhibit their expansion and contraction? Maybe a conventional gapped ring is more able to follow an imperfect surface? I could see where their expansion and contraction might be more dampend than that of the gapless.

Hobot · Sep 10, 2010

Total Seal ad text
http://www.aircooled.net/new-bin/viewpr ... d2=EPS0004

Genera article on rings and gap but no specifics to apply per application.
That's another subject line.
http://www.aircooled.net/gnrlsite/resou ... pcrops.htm

There are other piston rings on the market that offer an engineering solution to the problem of a large ring gap. The gap is "eliminated" by using two thin rings that fit in one groove, staggering the ring gaps. These "gapless" rings are available in a Top or 2nd ring version. Aircooled.Net recommends the Total Seal gapless 2nd ring for street use, and the Total Seal gapless Top ring for racecars. Never ever use gapless rings in BOTH the Top and 2nd position in the same engine! The Total Seal gapless ring design definitely helps in ring sealing, but don't expect it to eliminate all the other cylinder preparatory work! If you're just replacing your rings (and not buying a piston set which includes rings) the best quality replacement piston rings are Deves brand. They are really easy to install and break in quickly, without headaches.

Hortons Norton · Sep 10, 2010

I trust anyting Mr. Comstock says, The picture of the pin and piston look awesome. No leaks, I cannot tell you a whole lot about the bikes I watched race without making sure and asking the guy who built the motors. And to be honest these bikes only would run short distances before being torn down and checked, As they were land speed bikes that run at Bonneville. So really their findings may not transfer over to street use, I would just tag along with my brother (rider) and help with getting the bike to the line and picking him up at the other end. I do know they used total seal rings and the bikes would run in both fuel class and gas class. Burning Nitro in one bike and gas with nitrous in another and just gas in the other. A ton of fun for sure. I will try to find out more details about how the motors were built, But one thing I can say for sure is the engine builder has had a lot of succes at Bonneville and people call him the professer behind his back, LOL LOL. Keep up the GREAT work Mr. Comstock and Mr. Schmidt. You guys take these Norton's to the next level. And congrats to Kenny. Take care guys and ride safe. Chuck.

Hobot · Sep 10, 2010

Amen to the real extremist destructive innovators!

Here's more on down side of TS rings. RPM ain't the real issue its the piston speed, so long Norton strokers might well be too fast for TS rings to stand.

There appears to be a problem (my experience anyway) with the rail of the ring breaking-which compromises the integrity of that ring which in turn scratch up the cylinder walls. By design, rings tend to "flutter" in there machined piston grooves as the piston moves up and down in the cylinder. As they do this, they need to be able to flex or else they can break, with a traditional ring, the end gap provides this ability to a certain extent but the rail section in the total seal rings do not. I realize the claim Total Seal makes on their rings which are engine dynometer tested-not real world tested, and that they are excellent for "all applications" but I have not had the best of luck with them. They do perform as described in reference to blow-by elimination but for actual "load" conditions such as high RPM blasts, nitrous, etc. they have come up short for me. Also, think about this: the rail design is supposed to move or "slide" in and out of the low tension ring-now if you should have any piece of foreign debris get lodged in that crevice while the engine was running and it stays there after the engine has cooled....then on a cold start up if that ring has not "released" so to speak, then the damn ring itself will burr the cylinder wall like crazy. So all in all, I do not think they are for a street engine-at least that's my opinion on it. They may work for some but not for me

I used the gapless top ring with the slant cut ends in my current motor. Also used the TS quick seat powder and my machine shop uses TS gapless rings exclusivly in every motor they build, but they mostly build drag race and offshore boat motors - all of which use a vacuum pump. I don't believe the oil is coming from the guides or seals. I think its a phenomenon of the gapless design that requires a bit of vacuum in the crankcase under the rings at all times to prevent oil from getting past the oil rings and accumulating between the top and second rings. What's wierd is that I've had engines with TS gapless rings that never used or burned any oil.

http://www.pro-touring.com/forum/showthread.php?t=443

stockie1 · Sep 11, 2010

Jim,

You are right about standing on the kick starter. After installing your piston and rod kit, with total seal second set. Wow the kick started need some curry! I just got the engine going about an hour ago. The low speed vibes, or lack of them are mighty impressive. So far only ran the engine for a short cycle, but so smmmoootttthhh?
Thanx Jim.

Cheers Richard Stock

Kenny's lightweight Piston

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