Tighter piston clearances

Hobots PII was built by USA NAVY development Engineers , From San Dieago , round 67 .
Was Returned to ' The shop ' Where it was purchased a a RECREATIONAL VEHICAL .
After the Project Commader Re Timed .

U S NAVY secret List . Do Not Disclose .anyalis of hydrosonic emanations from latest
propulsion set up , Non Harmonic materials .

Half the blokes were Ex Veterans . To stop them killing each other , waiting tests completion ,
The Norton was Remade from the offcuts fromthe shafts & supports ( alloy )

Ran 8.51 I believe it was ( near exact 1/2 the time of the second fastest car . Cross the State line .
Team Dispersed . Some experts in the automotive field . But Machinists as good as the best in the states.
One Puloined the experimental valve gear thatd been to expensive to use , ' production ' race engines .

Presume it was on Nitro . the photo the tyre smoke was still billowing out at 3/4 trip .
Comander had used the last two on the navy film roll for a few snaps of the bike .

The Dealer wasnt to keen to take it back . But a U S N Top Secuity Pass , and seeing it run
after being reset for pump gas , he allowed .

Obvious where Hobot got it , out the Mid West somewhere , from a ' Experimental Oil well Equipment ' cover outfit .

The Annual County Drag Meeting Report was from a local rag , Green deco on newsprint . 3 x A4 sheets . Marmalade ,
Wallpapering , Something about flowers .

So if any in the U S find in a antique Shop etc a old decorative cover local rag from around 67 ,

The Strip Picure across the bottom of the center page , is a P II pulling 8.51 ( check & confirm )

R H Page had a old jacked up 54 , and a Impala maybe . Think one ran 14.5 odd or 15.6 and the other 16.8 maybe . Other 4 were 18s / 20 .

So a P II with cases from the most drable alloy available to the U S Govt. and a Crank from the strongest most vibration resistent steel ,
Available to the U S Govt . Might just pull 9.000 , on pump gas , and lift the front the odd time past half revs , if one of the engineers
had been from a Top U S Racing Engine Company and had utilised secret experimental Hi Tech Valves , springs & Lifters etc .
Guess the rods mightve been the High Tech Shaft Support alloy too . Joined the Navy when the company folded . Machinist .

Theres a reciept for a $ 1000 payment for ' ANYLISIS in N.Z. , and a photo or two on the end of a film row of the navy Componentry
in the making . Two Machinists , a Foundryman , two fitter / dogsbodys . Some of these top flight blokes go PHYCO sitting around playing cards out in the wops , for secrecy .

So the ' recreational Vehical ' ( on the books San dieago , about $ 890 od , should come up , if one of our Nortoneers , is in the navy & in sandiago naval base .

Wonder if its still on the secrets list & if I should expect ' a visit ' . Wonder what the do to keep em inline these days .



Maybe it set a presedent , Pilot was Car Drag Racer from L A , who could ride .
When he wasnt rowing about sandieago Harbour .
Mazing wotta & yr old picks up , serving the coffees ,
Photo was explained the last evening , over beers . AFTER the case was sealed .
Tho He tossed us the rag , wouldnt let bro have the photo .

Maybe he was proud of his team . Nobody does anything like that THESE DAYS .

Shed musta bin Okey / ary way

Thanks for that Matt.

That’s really useful information regarding piston clearances.

Thanks for the nice clear writing style too.

Vauguely like this , Mayberry or shadey junction , maybe .

Well , bit like that . Work Site Town some highway crossroads village town

Likely Northern Ark Pine Lined on Rt. rural airstrip meet . Enyone Recognise it .
Couldve even been this car in it , rest were slow .

CLEARANCES . See Double Star . ZERO CLEARANCE satisfactory on alloy Sleeve . With Right Oil .
Or they scew up bad . Ingess of debri And Youre screwed .

Still Dunno the Liner Composition . will they blow apart like thos wellington motorcycles blokes bikes .

IS there a Crank , ( Or Bike ) that will match HOBOTs ' P II ' ( and a bit . U.S.N. Spec no cost spared )

Would you buy a used bike off this man .




Disquised to protect the guilty .

As YOU brought Hobot up , slamming Him ,
and Id seen photos of THAT bike as a kid , until I saw a PII picture in the right light from the right low angle , all Id remembered was a ' XR ' HD like RED tank , and the General shamoozzle .
However , after ' keeping out off the way ' The last evening we were abandoned . The Photo went to go back in the brief case . ( The Norton wasnt entirely classified - just the materials .
His opening move was to throw ' us ' the county rag . He'd thrown in , ' leaving town ' . a report on his crimes ! .
A few Beers were had .
What chance did he have , against two kids . ( Not to mention the old man . The U S Navy can be proud of him . No Alcohol USN policy , but the job was finished . A beer or two couldnt hurt .
After ' Boat Talk ' , and two Taxi Cancellations with a GUARANTEE from the Taxi Theyd get him to the Airport at 8 . ( 20:00 Hrs ! ) The Trapp was sprung .
ALL was revealed .
This is MOST PROBABLY Hobots ' P II ' . If it wasnt how would it try'n lift the front - cranked over - at 90 - in 3 rd . Pulling onto a freeway ?
Most Unlikly that it wasnt . Somebody mustve been suckered into buying that darn Navy Blokes Norton . Gees - These guys - Think they . . .
Andy Grifith probly turned a blind eye . After All .

Thus our friend Hobot was likely somewhat befuddled & bewildered , getting ' a new ' Norton 750 . after That . Later . And wondered how much He had imagined .
and took a bit of effort , to get a Commando ' going respectfully ' . It'd feel a bit dull . after an 8 second bike . But you know these 18 yr old student types .

As for riding ability , out in the Wop wops , ( bar the Deer ) You do own the road . And if he wants to drift a Commando with the pipes dragging . whos to know .
Bar the deer . and are THEY gunna say anything . All these mags talk about dunlops & drifting & how the traction actually increases on the IF your drifting .
That you have to be up to it , and 35 % faster than a ' sane ' man , whose complaining . The Deer dont know . Nobody else knows . theres no ARMCO ,
neigbours and the cop car came through thursday last month . He's not due through for another quater ,Who's to know the mags wernt exactly representative ? .

Why anybody'd supercharge a Commando's beyond me . ( weight . Simplicity . lightness . impaired ) But I can see why HE would want to . After all . . .
He still aint got nothin that goes like that P II . or didee imagin itall . Somewhere in the U S N archives theres a film of low sonic emmisions componentry ,
with 2 of a red P II on the end .
And a county newsprint rag . High Tech . Both black AND green. on the cover anyway . With across the bottom of two pages , a P II pumping 300 yds of tyre smoke out past the ton easy there .

Some twit dragged it out of his dorm , and if the ' abandond vehical crew ' from Town didnt get it , the guys in the grey trench coats mustve been the commies . IF the commies shortly after
cloned that material , they mustve got onto it . But fates of mice & men , fastest single engine norton thereabouts - were a few other quick ones - went to the scrap depo
. Like mother threw the rag in the trash next day , on a ' tidy spree ' . Maybe she wanted to get rid of the evidance too .

So any Turkey know a down country Mid west Rural drag strip - pine wind break , back around 67 . Or someone into wallpapering , marmalade ( or was it Jam ? PRESERVES ! ) Remember the county
newsletter ( 5 cents ? ) and a few hillbilly ' race cars ' . Jacked uo 54 with Ex pipes through the hood . THAT we would have to presume . Was Hobots bike . It went back to the County M'Cycle Shop .
A pine Board town with a twist in the main street , corner cafe / tea rooms & greyhound ( interstate ) Bus Depo/ stop .

And WILL these fancey close clearance alloy barrels stay together on 80 / 90 % Nitro . Like Routt And TRIUMPH ENGINEERING ones do .? Thanks .

Did You say ' HOBOT ' . !

Matt what on Earth are you rambling on about now ??

You do know this thread is about piston to bore clearances, right ?

When I make a comment, I usually try to be helpful and constructive. I do not believe in much without a lot of evidence, but I believe in altruism. Hobot is a dill, but he is a force for good. Commandos are good things. I have never had another motor which was so responsive to tuning. You always know where you are with them, unless you get silly.

Matt is capable of making sensible comment- sometimes.

acotrel said:

Matt is capable of making sensible comment- sometimes.

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Wow, Al. Sometimes I think the only one who can make sense of your posts is you. Pot/kettle. Lol!

acotrel said:

When I make a comment, I usually try to be helpful and constructive.

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However, please try to stay on topic. For instance, I deleted two of your posts in the same thread within the last couple of days as they were way off-topic and if you happen to find one of your posts has been removed then that isn't your cue to post the same again.

lcrken said:

Indeed he does. All Jim's pistons, including JE and Wiseco, are custom made to his specs.

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Ken,

I can't comment about JE, but I find it unlikely for Wiseco to offer completely custom made pistons, given the assumed small number of pistons Jim's outfit sell each year.

It's more than likely Wiseco took a core product and modified it to fit Jim's specification. Wiseco will have hundreds if not thousands of cores to select from.
In the machining stage, the core will be adapted to meet customer's requirements with a specific skirt diameter, ring lands, valve pockets, internal machining, and the wrist pin bore.

The Wiseco pistons supplied by Jim are nicely made, the longevity is probably excellent, and I would like to express my thanks to Jim for his effort by making these pirtons available!

- Knut

This video shows the production process at Wiseco:

mdt-son said:

Ken,

I can't comment about JE, but I find it unlikely for Wiseco to offer completely custom made pistons, given the assumed small number of pistons Jim's outfit sell each year.

It's more than likely Wiseco took a core product and modified it to fit Jim's specification. Wiseco will have hundreds if not thousands of cores to select from.
In the machining stage, the core will be adapted to meet customer's requirements with a specific skirt diameter, ring lands, valve pockets, internal machining, and the wrist pin bore.

The Wiseco pistons supplied by Jim are nicely made, the longevity is probably excellent, and I would like to express my thanks to Jim for his effort by making these pistons available!

- Knut

View attachment 86273

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Not to start an argument, Knut, and maybe this is just a semantics issue, but by JE standards this is the definition of a custom piston. It doesn't need to be a completely new forging design to be called a custom piston. For example, the Norton pistons I used to have JE make for me used different basic forgings as starting points, depending on bore size (from 73 mm to 83 mm), but were still considered full custom designs. On the other hand, with the help of an inventive sales rep, we were able to get JE to classifiy some of the pistons as modified Kawasaki pistons, with a subsequently lower price. Others were still considered custom designs, and priced accordingly.

For example, this is the spec for my 74 mm pistons. Note the motor type listed as Kawasaki Misc.



But this one for 78.5 mm long rod, short stroke 750 pistons, shows the motor type only as Misc., and they were classified by JE as a custom design.



Regarding Jim's Wiseco pistons, he does indeed deserve thanks for making them available. JE was easy to deal with for small quantities of special designs, compared to Wiseco, who were really not interested. Convincing them to make these pistons was not an easy task, but Jim persevered until they gave in.

Interesting factoid - JE and Wiseco are both owned by the same company, Race Winning Brands.

Ken

Here's the graphite piston coating on Yves 920 after approx 100 miles.



Here's the first Wiseco lightweight Norton pistons (mid 1980s). Molly coated.