Piston identification

Bantam John will know.

Have you measured the O.D. of the piston in question?

If so, what does it measure?

Mike

Ask Anna Dixon.

She has got every piston spares book ever made.

or.........checkout the attachment. It shows 18553 as a model 99 (650) pistonwhatever that means. I would guess a 650 piston that could be used as a 600cc substitute.

You can use a 650 piston in a 99 but not a 99 piston in a 650. There is one exception which I am sure will be pointed out in full detail. 10:2 to 1 is a mite high for use with present day fuels. In my go-faster daysI ran 10:2 to 1 for a while and it needed 5 star 101 octane petrol.

Thanks for the replies;

Neil - who is 'Bantam John'?

Mike - 68mm dia (marked as STD (standard)) so is either 600 or 650

Phil - looks to be listed for both 600 and 650 and is shown as 10.2:1; mine are quite domed so I guess that could be right.

Anna - do you have this part number listed anywhere?

Thanks

Well unfortunately we have no records of this Number, As John rightly pointed out, You Can Use the 650cc Piston in a Model(99) But Not a Model (99) piston in a 650 as the Shirt lengths are very different, and the boss in the pistons are higher up to one another, and early 650s did use a solid type oil ring until April 1961 when the twin flex system came out with BHB Covo , BHB was apart of the British heavy industry Co and made all types of pistons for vehicles and heavy plant machinery, Piston number are usually stamp marked on the top of the piston, the AE at the beginning of the number is for Automotive Engineering. Co that was based in Bradford as a part of David Brown industry's they took over from Hepolite and BHB .Covo and the piston you have is and after market one, Yours Anna J Dixon

Previously colin_ansell wrote:

Thanks for the replies;

Neil - who is 'Bantam John'?

Mike - 68mm dia (marked as STD (standard)) so is either 600 or 650

Phil - looks to be listed for both 600 and 650 and is shown as 10.2:1; mine are quite domed so I guess that could be right.

Anna - do you have this part number listed anywhere?

Thanks

Well unfortunately we have no records of this Number, As John rightly pointed out, You Can Use the 650cc Piston in a Model(99) But Not a Model (99) piston in a 650 as the Shirt lengths are very different, and the boss in the pistons are higher up to one another, and early 650s did use a solid type oil ring until April 1961 when the twin flex system came out with BHB Covo , BHB was apart of the British heavy industry Co and made all types of pistons for vehicles and heavy plant machinery, Piston number are usually stamp marked on the top of the piston, the AE at the beginning of the number is for Automotive Engineering. Co that was based in Bradford as a part of David Brown industry's they took over from Hepolite and BHB .Covo and the piston you have is and after market one, Yours Anna J Dixon

Well after some Research On my computer the Pistons in question are AE I8553 are for a 600cc Model (99) with a (9:1 ) Compression ratio , Hope this now helps Yours Anna J Dixon

Slight Corrections.........you can generally use the early types of 99 pistons in a 650 if you carefully machine away the skirt sides so that it will clear the crankshaft flywheel. You can not always do this with some of the modern replacements as their skirts tend to be reinforced with a horizontal rib.

I could mention piston bosses and compression ratios in this note but will save that for later.

Also....some of the 650 pistons made from 1980 onwards, were actually sold as direct replacements for both 99 and 650 models. The fitting instructions, for use in a 99 engine, informed you that each piston was the near to the equivalent weight of the original piston.

The most obvious difference being the shorter skirt. Did this matter???

Hi Colin re: your question about Bantam John -are you in the UK? Do you ever see/read Old Bike Mart? Do you have internet access? If the answer to any of these questions is 'Yes' then it should be easy to find him. 'Mr. Google' knows everything! He is at just about all the bikeshows in England with avery large stand selling parts like seats, silencers, tinware and numerous bike parts for many marques. He also separately runs a businees called Sheffield British Motorcycles whose speciality is pistons Made in England.

Cheers, Lionel