Lightweight 1000cc piston & cylinder longevity

In 2012 Dave Watsons 1000cc Norton with JS lightweight pistons won all its races in the 1300cc open UK classic. Recently I asked Gordon Humphreys the tuner about wear on the pistons and cylinders, see his answer below.

Hi Jim, checked bore wear, no wear, 6 thou clearance, in fact the engine was perfect .... By the way we used to have problems with bore wear when we used fully synthetic race oil but since we changed to Caster R40 oil we have had no problems, regards Gordon

.006" clearance was the original clearance to allow for expansion of the forged pistons. The earlier bore wear problems Gordon mentions with synthetic oil happened before the JS lightweight pistons were installed. When they switched to the lightweight pistons they were able to get an additional 1000+RPM and "power was up." It looks like Caster oil is the way to go to avoid cylinder wear in race bikes (not compatible with other oils). Another way to eliminate or reduce bore would be to have the soft cast iron cylinders or liners Nikasil coated (Millenium technologies) or impregnated with carbide (Bore tech). Street bikes can develop a ring ridge because of the rings and the cylinder coating should help avoid or delay this.

Photo below is Champion Gary Thwaites on the 1000cc Norton.

Re: Lightweight JS 1000cc piston & cylinder longevity

I'm the one who 1st brought forum attention to short skirt piston rocking and bore wear issues after 2 smoke builders brought to my attention a few years ago. Comnoz filled me in on a racer let down when I brought this up at 2013 Texas LOP. Road users can not use Caster bean oil as it congeals on cooling so must be emptied while hot or leaves very tough deposits. Btw Castor oil is absolute best lube to ram-jam interference fit metal items together, but not to pull apart again. Your pistons basically saved Ms Peel project for a number of reasopns CR to rpm needed for decent sport bike spanking boost. I will have Ken Canga or me send barrels off to bore treat and I will take apart often enough to catch wear and replace before much damage done and then slow up for longer term use after Peel point is proven or blown away by digi controlled balloon tire appliances. I want Peel to be able to take 8000-ish loads with ~3x's heat flow than a factory engine.

Peel's base line balance factor is in upper 50's after Canga drilled out flywheel balanced to "light wt." Cosworth pistons, so would like to lighten your pistons a bit more to raise BF into mid 60's, so ask if you could do em or instruct us on how to DIY w/o bothering your many commitments.

Not only is that one seriously quick Norton, I think you'll find it is also currently up for sale...

More news from UK

Jim When changing on to caster oil from mineral oil [petroleum] all the mineral oil must be got rid of, I had already stripped the motor for winter rebuild when we decided to go caster because of extreme wear on bores and cam, so it was quite easy to wash everything off and clean oil tank and lines, this was about 4 years ago before we got your goodies. Squish clearance is 40 thou. you may have heard the big Norton is for sale Dave has already sold the 750. ... Regards Gordon
P.S the pistons will be coming up to their third season

Will be interesting to see what they can get out of used up race bikes vs what they put in, though winning races is priceless for a time. Not that good of news to hear on short skirt pistons in long term street bikes, similar to non DOT race compound tires if ya can't run so hard to remove chicken strips their centers dissolve under 2000 miles with just normal upright low throttle never engine draging timid legal upright operation, ugh. I'm concerned enough to delay and spend on Peel for carbide bore treament but not so concerned I'm sorry JMS pistons installed. Here's some low down on racer solution vs real life with caster bean oil, which is also a poison if ya eat the beans. Mc-engine famous list of builders covered caster oil uses to report its by far the best lube for tight interference hard to press together parts mating. If ya carried a bucket to dump caster into on each parking stop it'd be practical to extend bore and skirt life. A dash smells nice in the gas tank.
http://www.penriteoil.com.au/tech_pdfs/ ... CASTOR.pdf

Back in the late sixties early seventies, I used R40 on my road bike without any problem internally. Where it leaked (they all do that, Sir) it baked to a nice brown tone.

Not having used the JS engineering pistons in question, but having built lots of hipo car and bike engines, pretty much all of which use short skirts. I have not noticed any problems on strip down. Or had any reports back (so far... fingers crossed!).
Pretty much all modern production engines use short skirts too - and often with a shorter stroke/rod ratio. With higher specific output quite likely, and possibly higher engine speeds.
Why the concern? Is there any documented proof or is this just the internet chit chat?

Whilst I am no expert I think the problem may be with the larger clearances required in our old air cooled iron cylinders. This I am informed allows more rock at TDC/BDC. Most modern engines are water cooled. The air cooled motors still made are mostly using Nikasil bores or similar. Both run tighter clearances. I would like to run Jims rods/pistons in the engine I am currently building but, until I am certain about their lifespan I'm holding fire.
Martyn.

Martyn,

what is the known or expected wear of the pistons you are considering that are not made by JS?

what maker/manufacturer are you considering otherwise then?

Matchless said:

Whilst I am no expert I think the problem may be with the larger clearances required in our old air cooled iron cylinders. This I am informed allows more rock at TDC/BDC. Most modern engines are water cooled. The air cooled motors still made are mostly using Nikasil bores or similar. Both run tighter clearances. I would like to run Jims rods/pistons in the engine I am currently building but, until I am certain about their lifespan I'm holding fire.
Martyn.

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The reason JS pistons have more clearance than 'normal' Norton pistons is that they are forged, and expand more than 'normal' cast pistons. The clearance WHEN COLD is therefore more, specifically in order to allow for the greater expansion when hot. Meaning, that at correct running temp, JS pistons should have no more, or less, clearance than a 'normal' Norton piston.
I personally therefore, do not really understand the theory that this increased clearance causes any issue other than more rock when cold. So, unless you want to thrash your motor from cold, I cannot see any issue.
I was also reassured when I compared a JS piston to a forged Omega piston out of my old 906cc, 80.5mm bore Nourish engine. The dimensional design, location of gudgeon pin, etc is all really very similar. They also run in iron barrels and have no issues.
So, in summary, I am quite happy with my JS pistons, although, I confess, I have yet to run them! But I intend to do so soon, this summer my bike will see some road miles, some track 'action' and some Dyno time.
I shall report back to y'all when its got some action under its belt!

The pistons I am considering are from the same person who is supplying the cases, crank, & barrel. Steve Maney. These are proven & apparently have a good lifespan. I think they are made by J.E. to Steves design.
As for they clearance only being bigger when cold, I think it might be bigger even when hot compared to a watercooled engine. But l am a precision engineer, not an engine development engineer. I would love to hear from someone with 25,000 hard road miles using Jims parts.
Martyn.

Matchless said:

The pistons I am considering are from the same person who is supplying the cases, crank, & barrel. Steve Maney. These are proven & apparently have a good lifespan. I think they are made by J.E. to Steves design.
As for they clearance only being bigger when cold, I think it might be bigger even when hot compared to a watercooled engine. But l am a precision engineer, not an engine development engineer. I would love to hear from someone with 25,000 hard road miles using Jims parts.
Martyn.

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Hey... I'm not 'dissing' Steves stuff Martyn, far from it actually, as you say, he has a proven track record and I'd be confident in using his stuff.
But as they say "there's more than one way to skin a cat" (although I've no idea where that saying comes from)! And whichever way you skin your cat, I think you're 'pushing the envalope' if you're hoping to build a high performance Norton engine AND do 25,000 miles between strip downs!
Even my lowly tuned, 7.6:1 CR standard bike with standard rods and standard pistons in a standard barrel was worn oversize at a little over 20,000 from new...
BTW, out of interest, what piston to bore clearance does Maney suggest when using his pistons in iron barrels Martyn, do you know?

Eddie,
Sorry if my previous post sounded like a rant. It wasn't meant to be. I would expect to get at least 30,000 miles from a stock set of barrels/pistons & I do like to hammer my engines ( once warmed up of course ). Were you using decent oil & an air filter?
As for the long rods & short pistons, Moorespeed offer a similar set up for airhead BMWs. Anybody heard any reports on those. Maybe Chasbmw might know ?

The .0055"clearances I give are measured 1/2 from the bottom of the skirt as specified by JE. If measured at the very bottom of the skirt the clearance is more like .0045" When hot the clearance in reduced to about .001" or 0. You don't want it any tighter. Surely no one out there wants to scuff or seize their pistons. The bottom line is that cast iron cylinders will wear out - depending on how hard you run them.

quote from Herb Becker:

" the factory short stroke barrel that the factory thought was nessesary to harden the bore. they must have encountered cylinder wear on there own race bikes ,perhaps it is a function of high rpm and high heat."

Herb Beckers own 10,000 RPM 500 short stroke wore the cylinders .003" in one race using his own piston design.

Dave Watson's 1000 Norton had severe cylinder wear problems with long skirted pistons before he switched to JS piston & Caster R40 oil.

Ouote from Norman Holland with lightweight pistons

"Hey Jim, Hope you are well, ....
Bike runs great.... no loss of compression
My wee body 70kg is able to kick the beast into life and runs sweet.
I have had big boys standin on KS and it drops very slowly"


Quote from Herbert Toscany
"I am going into my 4th season of racing with 2 bikes that use your long rods and short pistons. I have not opened any of the engines again since the rebuild with your parts 4 years ago. everything is still going strong. no need for replacement or service.
I am totally satisfied.
just wanted to let you know"

But another racer wore his bore out in 3 seasons racing. So everyone has a different experience. I have 15,000 on my test bike and it runs perfect. You can stand on the kickstart for 30 seconds with the total seal rings.

jseng1 said:

quote from Herb Becker:

" the factory short stroke barrel that the factory thought was nessesary to harden the bore. they must have encountered cylinder wear on there own race bikes ,perhaps it is a function of high rpm and high heat."

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Interesting comment. When I bought the ex-John Hately factory flat track bike to get the 750 short stroke engine from it, I was told that the cylinder bore had been surface hardened by nitriding. I'm not sure that was the process used, but the bore was certainly hardened somehow. I raced that engine in my roadracer for several years and it never seemed to wear significantly. That was with the original Omega pistons, and a 7500 rpm rev limit. When I eventually had to bore the cylinders (and sleeved it to 920 cc) after a rod broke and damaged the bore, I discovered that the surface really was harder than normal. The first cuts wwere arly through harder material, and the succeeding cuts were just like with a standard iron cylinder. It sounds like using one of the modern surface hardening processes, like the carbide process from Bore Tech, would be good insurance for an engine expected to rack up a lot of miles, or maybe just one that is run hard on the race track. If my memory is correct, Jim Comstock has had good things to say about that process. I'll probably try it on my next serious engine build.

Ken

Lookie here R40 new age hydrid caster bean based oil though only mentions racing as market. I assume with hard enough bore surfaces just renew pistons every 30g rand miles or so and substract some mileage for life time thrills spent in red line zone that these wonder jugs allow us. If ya do make it past riding age which times would ya most like to reflect on with shortening memory spans? VarRoOOOM!

http://www.opieoils.co.uk/p-776-silkole ... e-oil.aspx