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Messages - AWJDThumper

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31
Singles / Re: B40WD gearbox oil level
« on: 19 February, 2018, 13:46:25 »
That's par for the course - hopefully, its not the gearbox sprocket oil seal!

32
Singles / Re: Trials specifications for C15
« on: 19 February, 2018, 13:44:32 »
The attached table gives the overall gear ratios for a standard 1961 C15 (Col 1) and C15T (Col 2) with the gearbox (GS) and rear wheel sprocket (WS) sizes indicated. Column 3 shows the C15T gearbox ratio comparison with standard C15 if the 4th gear ratio is made the same and gives some idea of the differences in ratios provided by the C15T lower gears - obviously, the C15T gearbox offers much higher 1-3 gear ratios. In all cases, the engine sprocket and clutch sprocket are assumed to be same; namely, 23/52T.

For a trials bike, which is intended for both road and off road, it's difficult to get the balance right with the gear ratios. You need to work out what 4th gear ratio you can get away with on the road and then see whether the resulting 1st and 2nd gears are then low enough for off road. As a comparison, the B40WD has similar gear ratios to those shown in Column 3 and can do 50 mph in top but the lower ratios (especially 1st and 2nd gears) are next to useless on the road but not too bad off road. Changing gearbox sprocket would obviously change that balance between the gears.

In terms of the difference between the standard (1961) C15 and C15T, the latter used a different camshaft. It also used an oversized inlet valve. There was also a higher compression piston (10:1) available compared to the standard 8:1 piston.

33
Singles / Re: 1957 B31 Maroon colour scheme
« on: 19 February, 2018, 10:48:47 »
You might even find chrome under the mudguard outer paint layers!

34
Singles / Re: B40WD gearbox oil level
« on: 19 February, 2018, 08:14:42 »
Well done! Have you still got the original gearbox fitted?

35
Singles / Re: 1957 B31 Maroon colour scheme
« on: 19 February, 2018, 08:13:19 »
It sounds custom. Definitely never come across chromed lower sliders before and I'm sure this would definitely not have been something BSA would have offered back in 1957!

36
Singles / Re: B40 Star air filter - what's the best option now
« on: 17 February, 2018, 12:06:08 »
I was wrong about the change in carb size for the B40 - I was looking at incorrect data. They all used a larger carb than the C15. I was convinced that was the reason for the switch from the earlier C15-like use of rubber hose and attached filter to the later metal adaptor and separate filter.

One way of checking whether a B40 originally had an attached filter (which may have become attached) might be to measure the size of the hole in the back panel. If the filter was originally attached, the hole would have been 1 1/5" in diameter. If it was designed for the metal adaptor it would have had a diameter of at least 1 7/8".

37
Twins / Re: Headset bearing adjustment.
« on: 17 February, 2018, 09:37:30 »
Normally, with the front wheel off the ground, you should be able to feel any free play in the head stock bearings - the weight of the front end shouldn't affect this. It's best to start with the bearings slightly loose so that you can feel some initial free play. Then tighten the bearings a small amount at a time until you can just tell that the free play has disappeared.

38
Singles / Re: B40 Star air filter - what's the best option now
« on: 17 February, 2018, 09:08:43 »
The earlier B40's used the same carb size as the C15 and were able to use the same filter arrangement and connecting rubber hose. However, in 1962, they changed to a larger carb and at that point had to change how it connected to the filter - connection by rubber hose was no longer possible. Instead, they used a metal adaptor screwed on to the end of the carb which projected through the rear panel to the separate filter. My B40 is from 1965 and uses this arrangement. If the filter was still attached to the rear panel as per C15, it's difficult to see how the adaptor could be fitted. The parts book from 1965 is simply wrong and shows the much earlier rear panel and filter arrangement pertaining to 1960/1961.

I can't remember where my filter came from when I restored my B40. However, if you are careful, you can detach the filter from a C15/ early B40 rear panel and use that as a separate filter to plug into a suitable adaptor for you carb.


39
Singles / Re: Starfire oil tank filter
« on: 17 February, 2018, 08:48:11 »
The BSC thread on the oil tank has to be a sensible imperial size and 0.864" is not one of them - 7/8" must be correct. It looks as though the thread on the filter will have been formed on a lathe rather than using a die and it's not difficult to cut it to the wrong diameter. Your pair of filters might well have been manufactured by the same person who must have got the dimensions wrong for the thread. It's not the first time this has happened!

40
Singles / Re: B40 Star air filter - what's the best option now
« on: 15 February, 2018, 17:09:49 »
Picture of air filter off my B40 (although it seems to be missing the perforated concave plate). Note that, unlike the arrangement for the C15 in which the filter is attached to the back panel, the filter for the B40 is separate. Instead it plugs into the metal adaptor which screws on to the end of the carb and then projects through the hole in the back panel.

41
The Star and Garter / Re: cotter pin
« on: 15 February, 2018, 12:41:58 »
PS. Like most cotter pins, it will be made of mild steel!

42
The Star and Garter / Re: cotter pin
« on: 15 February, 2018, 12:40:56 »
Burton Bike Bits will be able to provide one by mail order. Ordered some parts the other day from them that arrived less than 24 hours later.

43
Singles / Re: B40 Star air filter - what's the best option now
« on: 15 February, 2018, 11:38:08 »
Is it a used B40 panel + filter rather than a C15 version?

44
Singles / Re: B40 Star air filter - what's the best option now
« on: 14 February, 2018, 19:21:23 »
Essentially, the front circular corrugated gauze filter is pop riveted to the rear concave perforated plate. The corrugations provide separation between the front and rear surfaces. On the filter I've got lying on my bench, there is an even finer sheet of plastic gauze sandwiched between the two metal screens. They have the rubber seal around the outside of the filter.

I assume you are missing the filter housing from the rear panel on the B40 which I believe from memory is simply brazed on to the panel.  Is that correct?

45
Twins / Re: A65 Lightning rocket
« on: 14 February, 2018, 09:02:58 »
Plenty of pictures on the web - a highly tuned version of the Rocket intended for the US market from 1965.


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