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Messages - Derek996

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1
Singles / Re: C15 Breakdown, Hot Engine
« on: 24 June, 2022, 14:43:52 »
The missing parts are the choke assembly. Not really needed as you can get it started by flooding the carb with the tickler. Once you've had it running for a minute or so it will be warmed up enough to idle.

2
Singles / Re: b31 CYLINDER HEAD
« on: 21 June, 2022, 15:22:12 »
It is both an engine stop AND a decompressor for starting. For starting from cold, tickle the carb 2 or 3 times, push the choke lever forward, if it as one, and retard the magneto a smidgen.Then pull in the valve lifter lever and turn the engine over a couple of time with the kickstart. Release the valve lifter and gently turn the engine until you feel the kickstart come up against compression. Pull in the valve lifter lever again and gently push the kickstart down a few inches. Let go the lever and bring the kickstart up again. Then give it a good kick and if all is well it should start.

4
Singles / Re: 1946 B31 gearbox woes
« on: 07 June, 2022, 13:27:44 »
I was at the Belgian Classic TT races in Gedinne a few years ago and there were a few rigid framed BSA racing, all highly modified. The one in this (not very good) photo clearly has a swinging arm gearbox, presumably using a set of special engine plates have been made to fit it. The bike was listed as a ZB33 but has an alloy top end, girder forks but an 8" front brake.
If you have the resources anything can be done.

5
Twins / Re: Year of release BSA A7 ... ??
« on: 21 May, 2022, 09:51:24 »
EA7-101 onwards is listed as 1956 but for 1957 BSA just says EA7- . So it seems the EA7 covers both 1956 and 1957.

6
Which BSA do you ride? / B32 Competition
« on: 12 May, 2022, 14:00:44 »
I thought I'd show a couple of pictures of my 1948 BSA B32 Competition.
As it was when I bought it last summer and one after a bit of work over the winter. Next winter's job is to change the front rim for a 21" and mudguard and stays to suit (if I can find them).

7
Singles / Re: Rear lamp 1947 B33 Rigid
« on: 10 May, 2022, 19:19:54 »
My 1948 rigid B32 has the later Lucas 525 type that a previous owner has fitted. It would originally have had a round light like the Lucas 477. Although not original I'm happy with the later lamp for it's better light output.

8
Singles / Re: B31 (1954) - how to fit side stand?
« on: 29 April, 2022, 10:21:29 »
I think we've drifted from the original topic here, but this is what I've done to restrict the upward movement of the brake pedal. The bracket doesn't need to be super strong as there's little pressure on it. The bolt allows for any adjustment and the rubber prevents metal to metal contact.
I like that. It's given me ideas about doing something similar for my rigid B32. The pedal is higher than I'd like and stops against the footrest with a clank when I release the brake.

9
Singles / Re: Most suitable petrol for an M21?
« on: 21 April, 2022, 10:08:31 »
None in Scotland

10
Singles / Re: Most suitable petrol for an M21?
« on: 13 April, 2022, 09:55:59 »
Back in the '70s a friend of mine ran a plunger A10 sidecar outfit on paraffin. I kept a squeeze bottle of petrol in the outfit which he would fill the carb with to get it started then turn on the tap for the paraffin in the tank. It seemed to run ok, although perhaps a little hot and with a characteristic smell.

12
Singles / Re: Dynamo brushes E3HM
« on: 28 March, 2022, 10:51:20 »
One can always make the brushes smaller.
Correct. I couldn't find brushes for an E3HM anywhere so filed down E3L brushes to fit. Very easy.

13
Singles / Re: 1946 BSA B31 Running Hot
« on: 17 March, 2022, 15:45:19 »
I have had a few Ducatis over the years, and still have two, all of which have had stainless pipes and they all go brown. I have polished some of them to a mirror finish but they still go gold/bronze quite quickly. Wonder Wheels alloy wheel cleaner removes it but must be kept well away from zinc plated nuts and bolts etc. as it removes the plating and encourages rust.

14
Singles / Re: B25S Should I Go For A Small Capacity Increase
« on: 12 March, 2022, 09:28:33 »
As I see it. The original capacity is 247cc and the compression ratio is 9.5:1. The combustion chamber volume = swept volume (247cc) / compression ratio = 26cc.
A 10% overbore takes the swept volume to 271.7cc , so the new compression ratio is 271.7 / 26 = 10.45:1.
I'm sure someone will correct me if I'm wrong but it can't be far out.
The above formula is not quite right as compression ratio = (combustion chamber vol + swept vol) / combustion chamber vol. This gives a combustion chamber vol of 29 cc.

The difficulty in predicting the CR of the enlarged bore is that the piston shape may have changed and therefore the combustion chamber volume may be different. In fact, it's possible that the new piston shape may have been designed to give the same CR - without specific design info on the new piston, it's difficult to know :o
On reflection I see that you are right. I just did it of the top of my head without fully thinking it out. I also assumed no change to the piston crown which would make a compression change by itself.

15
Singles / Re: B25S Should I Go For A Small Capacity Increase
« on: 11 March, 2022, 19:46:47 »
As I see it. The original capacity is 247cc and the compression ratio is 9.5:1. The combustion chamber volume = swept volume (247cc) / compression ratio = 26cc.
A 10% overbore takes the swept volume to 271.7cc , so the new compression ratio is 271.7 / 26 = 10.45:1.
I'm sure someone will correct me if I'm wrong but it can't be far out.

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