Author Topic: Thin flange plunger A10 barrels at +60 can they be sleeved?  (Read 1165 times)

Offline nigeldtr

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Hi,

I have +60 pistons in my plunger and have been told that they can't be sleeved and I will need to find a replacement - is this true or can they be rescued?

Thanks

Nigel
1951 Golden Flash (engine now rebuilt) 1953 M21 a pain to start and 1961 GF that is turning into a black hole!

Offline Rocket Racer

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I have seen the results of thin flange barrels run with +100 10.5:1 pistons and they took quite a bit of abuse before the flanges came off!

If the bores are still central and have even meat round them, I'd be thinking about putting some +80 pistons in before I rushed to re sleeve.
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
New Zealand

Online muskrat

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G'day Nigel,
                I sort of agree with RR. +80's at low comp say 7.5:1 or 8:1 should be OK. I just picked up a set of +70's but their 9.5:1.
The other alt is to bore to +100 and turn down the sleeves to suit and go back to std pistons. Small fin barrels would be getting a bit thin on the ground now. I have gone big fin on my '51 A7 and they don't look too bad.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline Rocket Racer

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Muskrat, good point, I am not suggesting you bore out to 10.5:1 compression on + 100 pistons merely that I have seen the results of substantial A10 thin flange abuse in wrecked barrels that did not fail due to the overboring but due to high compression and by the looks of it some sustained hard use! (both sides flanges had broken off *eek*)
So with sensible use and sensible pistons I think OS beyond +60 must be considered, ideally flat tops so the head radius will not foulthe wider pistons.
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
New Zealand

Online muskrat

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Know what you mean RR. I have 3 sets of A7 thin flange barrels only bored to +60 (rocket 3 pistons +20) let go. Don't know weather it was the 13:1 comp or the 8000RPM that did it !!! *eek*
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline A10Boy

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There's an easy fix to stop that which we used to do back in the day when we used to run 14.5:1 compression upto 12,000 rpm on our 150mph C11 and C15s. You go out in the woods on a dark but moonlit night with a good bowsaw, you find a nice oak tree, saw off a lump of oak about a foot long and 6 inches thick, take it home and leave it near a heater for about 3 years. Then, you shape it into a nice wedge, remove the tank from your C11 and bash the oak wedge in between the rocker box and the frame until the frame just starts to bend. Then you get the Hilti gun and fire a few nails through the top tube into the oak and there you go. It'll never come off again. It stops all that annoying agro when you are burning some kid on his R1 off at the lights. The additional weight of the oak helps to keep the front wheel down coming out of fast corners. you dont need any anti - wheelie devices on those babies.
Regards

Andy

1958 Super Rocket
Plus
1974 Kawasaki Z1a
Yam XJR 1300

Online bsa-bill

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Andy, I can't decided whether you've not taken your medication or have taken a double dose, in any case don't ride today
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline trevinoz

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I rode my Flash home one night like that but I had to use an unseasoned piece of wood and didn't have a Hilti gun to hand!

  Trev.