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ES2 piston weight

Submitted by paul_knapp on Fri, 13/12/2013
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Singles

Can someone tell mewhat theweight should be of an original early to mid1950'sES2 piston, with gudgeon pin? (with or without rings)

Thanks.

Paul

Submitted by steven_lewis on Sat, 14/12/2013

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Hi Paul,

From balancing a few over the years they seem to average out @ 425gms for the complete assy.

Cheers

Steve

Submitted by michael_sullivan on Sun, 15/12/2013

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Will not the weight be relaticve to the bore size? Certainly, the +10, +20, +30, +40 pistons will weigh more that standard. Also, I have seen gudgeon pins with thick walls and some with thin walls.

In a perfect world it would be noce to find an original NOS piston and pin on the back shelf of an old time dealer's shop. But that will probably be asking too much.

Have you talked to Mike Pemberton at Pushrod Singles (01257 471014)? He should have the answer for you.

Mike

Submitted by neil_wyatt on Sun, 15/12/2013

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You might get a NOS piston from Bantam John?

I fitted an AP piston to my poor man's Manx (59 ES2 engine) without thinking about weight. The AP pistons are a tad heavier I have since been told so it's a bit more lumpy than it might have been at higher revs but thanks to very high gearing it's fine up to 65mph.

Submitted by paul_knapp on Mon, 16/12/2013

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Thanks for the replies, I am in OZ and am fitting a +.040"16H new old stock piston (readily available down here) I have cut the skirt and pocketed the crown to clear the flywheels and valves and am now down almostto the weight of the old +.030"16H piston I removed, and which did have a bit of excess vibration above 45MPH. I weighed an old +.020"piston from a friends ES2 and it is 414 gms. The old16HI am replacing is 418gms and the new one I am fitting is still 436 after cutting. I have bored out the rather thick wall pin to 5/8"I.D. so am now up to removing weight around the heavy internal pin bosses and around the inside of skirt. So I am trying to establish an acceptable weight for general riding EG, 35 - 55 MPH which for me to aim at.

Regards,

Paul

Submitted by andy_marks on Mon, 16/12/2013

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Hi Paul. Have you tried working out what the balance factor was with the old piston, and what it will become with the new piston? It's suprisingly straightforward to calculate what you currently have.

I drilled the flywheels on my inter to get a 70% factor and am very happy with the performance of that. Have drilled my ES2 to get a balance factor of 67%, can't comment on the results of that as it's still on its way back together.

Submitted by paul_knapp on Tue, 17/12/2013

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Ok on that Andy, I have done a complete overhaul of the engine with new big end, mains, cam bushes, re-bore etc, and had it running with a local piston fitted that I balanced to the friends used ES2 piston weight. Unfortunately, after giving it .0045"clearance, it kept siezing when working a bit hard up hill. I am now told that that brand of piston were nothing but trouble (DIE-CUT, Y-ALLOY) back in their day, so I decided to ditch it and fit an U.K. madeone. I don't want to dismantle the crank from the cases at this stage to do any balance factor balancing. I have this afternoon, removed excess metal fromaround the pin bosses and within the skirt, and have the all up weight down to 418 grams. A little less than what Steve suggested and a litte more than theused sample I have. I fitted it tonight and will, after I fit new clutch springs, fire it up and take it for a run to see how it is.

The forecast is 38 deg C tomorrow and 40 on Thursday, so I don't recon I'll get much done down in the corrugatediron shedfor a while!

regards,

Paul

edit> I was a bit out !...40 today and tomorrow (thurs) forcast 43 deg C. Makes the mono oil run a bit thin! sad

 


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