Author Topic: damaged pistons?  (Read 3529 times)

Online groily

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Re: damaged pistons?
« Reply #15 on: 20.05. 2009 20:04 »
Now we're talking. My 2 favourite ashtrays are 1. a Rolls Royce Griffon/Griffin (whatever) out of a late-marque Spitfire, and 2. a 4.2 Jaguar piston. For lighter addicts - pardon the pun - I recommend the pre-war Austin 7: flat top and no wobble. Just have to empty it more often. There's always a rôle for a discarded piston . . . and Snowbeard's would make a nice addition to the life-shortening array round here. Not that there aren't a few waiting for the snip . . . .
Bill

Offline fido

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Re: damaged pistons?
« Reply #16 on: 20.05. 2009 20:21 »
I remember some years ago when the old boy who ran C&D Autos was getting too ill to work he suggested to his wife that she could carry on after he died, just selling pistons and not bothering with the other bike bits. Apparently he had acquired a huge number of pistons and I've often wondered if they still have them, now the sons run the shop.

Offline MikeN

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Re: damaged pistons?
« Reply #17 on: 20.05. 2009 20:50 »
manosound,
  Yes you are correct,the 6" or longer test mandrels are to give an exagerrated error. The piston pin isnt really long enough to detect the error you would be looking for.
   Also,you need a good small end bush already sized for your piston pin before you can start checking with mandrels .
 There is a great old book written by Phil irving  (designer of the vincent twins?) called "tuning for speed" .It tells you how to build an engine properly and check and rectify errors and wear.They often turn up on ebay (but  can be a bit pricey). It was written in the 50's but it is full of good stuff.it explains all of the above
 Also regarding the comment by Fido, the rods supplied to me by SRM dont look to me like they have been bodged up in a shed ,they look like they have been beautifully CNC machined from large lumps of high quality alloy.
  Mike

Offline a10gf

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Re: damaged pistons?
« Reply #18 on: 20.05. 2009 20:53 »
I got an ermail from this company, maybe of interest

http://www.vintagemotorcyclepistons.co.uk

A10 GF '53 My A10 website
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Online BSA_54A10

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Re: damaged pistons?
« Reply #19 on: 21.05. 2009 01:09 »
As stated previously, clean them up , measure them and crack test them.
If they are in good nick then reuse them.
If they are a little worn then you can get away with a set of Total Seal gapless rings.
Critical measurement is the ring gap. If it is too big then they are remelt material.
If they are +20 then they can be machined back to Std so tag them and stick them in the box till you bump into some one with a thirst and a lathe (std +20 & +40 ) are usually machined from the same blank which is why most engines only have 2 over sizes +60 +80 are generally machined from a bigger blank which is why they are not offered very often.
Bike Beesa
Trevor

Offline coater87

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Re: damaged pistons?
« Reply #20 on: 21.05. 2009 04:27 »
I got an ermail from this company, maybe of interest

http://www.vintagemotorcyclepistons.co.uk

 Anyone know why these guys dont offer .10 over pistons?

 Lee
Central Wisconsin in the U.S.

Online BSA_54A10

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Re: damaged pistons?
« Reply #21 on: 21.05. 2009 05:24 »
Well I checked out a couple of different models , just to see what was there.
M20 pistons are GPM and they only have 2 of them in stock
B34 were the same but only 1 in stock.

Best guess they have bought out some ones stock then done some clever HTML work so they look like a massive concern.
There are very few std or first oversize pistons listed for anything and no photos of stock, just 1/3 of the description that you would get if you were browsing an aftermarket piston makers catalogue.

Reciently I was looking for some round wire internal c clips.
Found about 7 different catalogues on line with extensive range but when I tried to do an order, no one actually had any in stock and all bar 1 of them had never stocked plain round wire circlips but the computer geek that did their web page had just coded in the entire catalogue of each of their suppliers so their sites have an impressive 300 pages of stock most of which they did not have and never ever stocked and will never stock.
I think I mentioned this in a previous post.
YOU CAN NOT BELIEVE ANYTHING THAT YOU READ ON THE WEB UNLESS YOU HAVE INDEPENDENTLY VERIFIED IT IS TRUE.
Any supplier that give you a turn around of anything more than 1 day has no stock and is just playing middle man between you and a wholesaler somewhere oft in China,  India, Indonesia or the Phillapines.
Two day for him to get it from them then 2 more to get it to you. 
Bike Beesa
Trevor

Offline fido

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Re: damaged pistons?
« Reply #22 on: 21.05. 2009 08:11 »
manosound,
 
 Also regarding the comment by Fido, the rods supplied to me by SRM dont look to me like they have been bodged up in a shed ,they look like they have been beautifully CNC machined from large lumps of high quality alloy.
  Mike

I don't know how the BSA ones were made but they were certainly not machined from stock material. As you know, a forging would be stronger as the grainflow follows the shape of the object. Having said that, if good original parts are not available, SRM products would be my next best choice.

Offline RichardL

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Re: damaged pistons?
« Reply #23 on: 21.05. 2009 12:10 »
I wonder, for the SRM rods,

...is the billet forged (hot or cold?) to a very high strength rectangular shape, then machined?

...is the rod forged to near its final shape then cleaned up by machining?

...is the final shape after forging so good that it does not need machining other than big end, small end and bolt holes?

One thing I am rather certain of, you can't just go to your local metals yard and buy a block of 6061-T6, machine it yourself, and end up with the same product. Did I mention that these rods do not require small-end bushes?

Richard L.



 
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Offline A10Boy

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Re: damaged pistons?
« Reply #24 on: 21.05. 2009 16:41 »
Just going back to Fido's comments on C&D Autos, I was in there today getting some fork stantions, bushes etc etc, and I asked him about the pistons. Apparently they sold them all years ago and dont have any stock at the moment but can supply some eyetie ones.
Regards

Andy

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Yam XJR 1300

Offline A10Boy

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Re: damaged pistons?
« Reply #25 on: 28.05. 2009 13:27 »
Its seems that Wiseco are making "Rocket" pistons and these are available in the uk via cake street classics. Not sure about other compression ratios - does any one know ?
Regards

Andy

1960 A10 - Black Golden Flash
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1974 Kawasaki Z1a
Yam XJR 1300

Offline beezalex

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Re: damaged pistons?
« Reply #26 on: 28.05. 2009 14:51 »
Richard, here's an excerpt from MAP's catalog (they make SRM's rods):
Quote
M.A.P. Rods are Strong as Steel with LESS Weight. Compare our FEATURES to the Cost! You'll
understand why M.A.P. makes the BEST HI-Performance Products for the Best of British Motorcycles
STANDARD FEATURES:
True FORGING: Made from Specially Selected "Ultra-Strong" 7075 Alloy FORGING
C.N.C. Machined: Exact Specifications EVERY Time.
Light Weight: POWER Increaser with Less Vibrations than steel counterparts
(290 gram Big-End with 390 gram Total Weight (prox. T120) 420gr stock: 550+ Steel)
Machine Polished: Normalize "Stress Risers" for the Ultimate in Strength.
Serrated Big-End CAP: Allows Repeat Concentricity with "Rugged" Reliability. Eliminates Cap Walk

This is confirmed by conversations with the owner who told me that they are machined from billet forged aluminum, so they are apparently machined from big forged chunks. This makes sense since the tooling for forging to finished shape would be too high for such a small-volume part.
Alex

Too many BSA's


Offline RichardL

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Re: damaged pistons?
« Reply #27 on: 28.05. 2009 15:39 »
Alex,

Thanks. I forgot to look for such info on the MAP site (I knew they made the SRM rods, from talking to SRM). This is how I thought it must be, but I got a little confused by Fido's comment, which is not wholly wrong,as they are not simply machined from some random lump of melted down bear cans.

Richard 
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