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Messages - JulianS

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481
Twins / Re: Gearbox play
« on: 19 April, 2017, 20:31:47 »
If the small mainshaft pinion has rounded dogs then it is likely to cause the box to jump out of third gear when put under pressure such as a third gear overtake or pulling hard up a slope. Over the years I have changed a number of these. First photo shows one which jumped out.

The small journal of the layshaft is frequently scored in bushed boxes, I think due to dirty oil and its small diameter. Photo 2 shows one fit for scrap only.

New layshafts and bushes seem readily available.

I got fed up with worn bushes many years ago and fitted an STDT box to my A10. The layshaft journal does not seem to wear so badly as the bushed ones. The needle roller layshaft small journal is plain, no oil scroll which is found on bushed boxes. The other end looks the same, except for provision for a circlip between ground portion and speedo gear.

The maincase bush can be replaced with a needle roller without modification, though you would, of course need the hardened thrust washer, and the case would not be machined in the outside to take a core plug - which you wont need with a closed end needle roller.

At the other end you would need to machine the bearing housing to accept the needle roller which has a larger outside diameter than the bush. You sometimes see needle roller inner covers on e bay. You would also need the thrust washer.

You can also machine the sleeve pinion, which is very hard, to accept the RRT2 needle roller bearing but you would need the RRT2 mainshaft because it is stepped due to the inside diameter of the needle roller being a few thou larger than the bush. I had this done on one box but concluded it was not really worth the effort.

I would replace both ball bearings whilst it is dismantled.

I would also check the kickstart stop in the inner cover, these have often fretted in the hole due to the nut coming undone.

482
Singles / Re: C15 rear light
« on: 19 April, 2017, 09:28:51 »
Tail/stop bulbs come in 2 different fixings.

Almost all are offset type and the pins are the same for 6 and 12 volt. Then there is a very rare level pin type but I have not seen one and doubt your bike has one of these.

What type of rear light is it? If Lucas or Lucas type you can look into the bulb fitting and see the paths for the bulb pins. See photo.

The centre contact is spring loaded and you should be able to push it inwards against the spring.

483
Singles / Re: C15 ss Max speed
« on: 18 April, 2017, 16:06:15 »
Mick

Maybe the best way forward is to just enjoy riding your C15 as it is. It is not going to be in anyway competative on our roads today.

There is a lot of pleasure to be had just going for a ride without all the pressure and stress of worrying about how fast it will go.

I think the question of gearing has been done to death in this thread and the similar thread on the old forum.

The only thing left to do if you want to wring maximum speed out of it would be to take the advice given by Arthur 2 months ago which was to put the bike on a dynamometer and see what that tells you about the power output and state of timing,and carburation etc.

484
Twins / Re: A10 Shroud replacement
« on: 18 April, 2017, 15:03:13 »
What is the current setup?

Are you replacing a nacelle assembly?

If forks assembled in the yokes and frame you need to remove the fork legs to fit the new shrouds.

Haynes manual, Pitmans Book of BSA Twin and factory service sheets all explain removal.

485
Twins / Re: Aftermarket oil filter
« on: 18 April, 2017, 14:58:05 »
I have used a return side filter on my swinging arm A10 for over 20 years.

No problems encountered.

The only issue being finding one compact enough and easy to fit. Started with a Rocket 3 type in a long cannister for which I could not find an appropriate space to fit which would allow easy replacement of the element.

Then went to a Norton type which fitted in tool box, it was bulky and relied on jubilee clips to secure the long oil line.

Now on a compact Morgo type.

I would be very reluctant to fit anything in the feed line which might impede the flow of oil into the engine.

486
Singles / Re: C15 lighting switch
« on: 18 April, 2017, 09:27:01 »
These switches are essentially crimped together - the zinc alloy body will probably crack if you attempt to straighten it to dismantle or attempt to recrimp it on reassembly.

If you do attempt it I would suggest do it with switch in a plastic bag to contain the bits which may spring out when you open it up!

You could test its internal continuity, using the bike wiring diagram, before buying a new one.

487
Singles / Re: C15 ss Max speed
« on: 17 April, 2017, 17:06:43 »
I have no doubt that your current overall gearing is much to high for the power of your engine, max speed in top and third being the same means top is just an overdrive.

The manufacturer issued a service sheet which recommended a gearbox sprocket with 16 teeth as giving the best performance and you are using an 18 tooth sprocket .

The service sheet is attached below.

488
The Star and Garter / Re: South Derbyshire Facebook Page
« on: 17 April, 2017, 15:19:52 »
One for the Branch, if set up in its name, I would think?

489
Twins / Re: Oil pump
« on: 17 April, 2017, 14:45:49 »
The zinc bodies distort mainly due to pressure from the three mounting points. The oil chambers, the screw holes and  the spindle housing can get squashed a bit causing tightness. Many pumps work quite happily with this but the possibilty is reduced pressure.

You may be able to see a witness mark where it is tight inside but you need to be careful what you do  incase you cause a lose of pressure.

If the steel end cover is scored you can flatten it by lapping on a surface plate. I advise against lapping the body or cover to the body, or the spindle housing or spindle housing to the body because it will reduce lateral clearance of the gears and may make the pump even tighter.

I have not used an electric drill to "run in" an oil pump.

490
Twins / Re: Oil pump
« on: 17 April, 2017, 13:59:00 »
I presume it is a cast iron pump rather than the zinc alloy one (if its zinc alloy they are often found to be distorted)

There will be some drag when you turn the pump with thumb on worm on the driving spindle caused by the gears and the O ring, but with the spindle housing off it should turn with your thumb.

Sometime loosening the assembly screws allow it to turn freely indicating something is too tight inside.

There may be damage to the housing caused by the chipped teeth or spindle is too tight in the housing, either by diameter or by lack of lateral movement - the thrust washer which fits over the end may be too thick to allow your new spindle to rotate freely. You need a little end float.

491
Singles / Re: B40 new carb and timing necessary?
« on: 16 April, 2017, 22:36:34 »
Has he actually examined your bike?

If not then how does he know you will have those problems?

I would be sceptical.

If it does not run properly after the work you are doing, you can always consider a new carb and electronic ignition, they will not take long to fit.

492
Singles / Re: BSA C15G
« on: 12 April, 2017, 12:02:13 »
375/34 is a unique identification for a carb.

 The 375 was the smallest monobloc and was made with bore from 21/32 to 7/8 bore. So 1 1/16 would not have been a standard size bore for the 375.

1 1/16 bore would have been a 376, the next body size up, and probably a bit to big for a standard C15.

Are your sure of the measurement?

Some C15 scramblers and US spec models had a 1 1/16 bore 376 - one number listed being 376/304.

Below are monobloc dimensions from Amal lists.

493
Singles / Re: BSA C15G
« on: 12 April, 2017, 10:36:33 »
GC14 for the Sportsman is below some of the info may be of use.

494
Singles / Re: BSA C15G
« on: 12 April, 2017, 10:30:22 »
photo below is from the 1967 BSA data book and shows the carb settings for the C15G - the same as for previous season bikes.

The production run was only about 2400 machines and no parts book was issued.

The factory issued an unillustrated parts service bulletin for the Sportsman version, GC14, which was just an update of the previous seasons book. They may have issued a bulletin for the standard model but so far I have not found one.


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