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Topics - berniej

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Singles / B40 SS90 breather options
« on: 02 June, 2020, 14:54:16 »
So, having finally fixed the dodgy ignition switch I have had my first decent run out today.

Ran fine but noticed a lot of oil had been blown from the top-end breather that has been fitted by a P.O.
This is fitted in one of the exhaust rocker covers and currently has no pipe connected to it, hence the oily cylinder head.

The question is where to route it - or maybe block it up?

I added the primary case breather options as per Rupert R during the rebuild, two holes from primary into crankcase.

So, do I need the top end breather and, if so, would it be best to route it back to the oil tank?


Singles / B40 SS90 - still not right....
« on: 30 May, 2020, 13:18:32 »
Kind of following on from my earlier posts on the subject but as it's over 3 months since I've been able to visit the bike I thought a new post in order.

It's a rebuilt-by-me SS90, starts fine, idles fine, picks up and revs fine in neutral.
Pulling away, it misses badly from about 1/2 throttle in every gear. The problem is only there under load i.e. back on the stand in neutral it revs smoothly.

So far I have:

Converted to 12V and replaced the points with a Boyer KIT00059
Replaced the coil, HT lead, cap and plug
Replaced the original monobloc with a new concentric from Burlen configured by them with 170cc Main Jet, .106" Needle Jet, 19 Pilot Jet and a 3 1/2 Throttle Valve
Checked the valve clearances and valve lifter setup
Checked and rechecked ign timing
Changed the fuel
Checked good flow of fuel into carb
Sacrificed a goat

None of the above has made any difference and I'm now running out of ideas.

Engine was assembled using the RR book, I've stuck with stock valve clearances for now.
I thought that the small end bush showed a very small amount of wear on the gudgeon pin but I haven't replaced it.

Any thoughts on further diagnosis or possible causes please?

Many thanks,

Twins / A50CC rebuild - bush or roller?
« on: 18 May, 2020, 10:59:04 »
I've previosuly restored an A50 and an A65, both in vanilla 'Star' configuration. On both of these I had the T/S bush replaced and the cases line bored.

I'm shortly about to start on a complete restoration of a U.S. A50CC road model in original factory spec with 10.5:1 pistons.

The plan is to rebuild to original spec and for road use.

What are the thoughts about the bush/roller bearing options for this project please - and any other recommendations for an engine that will be more highly stressed than my previous two?


Singles / B40 SS90 rough when warmed up
« on: 19 February, 2020, 12:45:27 »
When I restored my SS90 I started with original points (dist) and carb (Monobloc).
It idled fine but pick up and higher speed running was poor and got worse as the engine warmed up.

First I installed Pazon EE which helped a bit.
Then I switched the carb to a new concentric with spec: 28mm Premier, 170cc Main Jet, .106" Needle Jet, 19 Pilot Jet and a 3 1/2 Throttle Valve as recommended by Burlen. This helped a bit more.

However the problem is still there - idle is fine cold and warm, pick up is fine when cold, rough when warm as is running at 1/2+ throttle.

I've just ordered some new HT lead and a plug cap. Coil will be next if they don't fix it.

Any other suggestions please?


Singles / B40 ignition timing advice please.
« on: 13 January, 2020, 15:06:27 »
I've just fitted the Boyer kit to my SS90 (distributor model).

This appears to have had an overall improvement and greatly reduced some mis-firing and rough running issues - next stop carb setup.

However, Id appreciate thoughts on the timing setup please.

The EE kit provides a max advance of 33.5 degrees at the crank equating to a 9/32 or 7mm BTDC static timing (retarded) - all as per book I believe.

However, my bike was fitted with the 10 degree (camshaft) advance unit as described in service sheet 91 (presumably due to an associated change in cam angles?).
This service sheet also specifies an ignition setting of 5 degrees BTDC fully retarded (presumably at the crank although it doesn't say).

My concern is that if I time as per the BB setup that I will be running over-advanced at typical throttle position and therefore need to retard a little.

What thoughts please?


The Star and Garter / Been there, got the T-shirt....
« on: 09 January, 2020, 12:12:08 »
Just spotted this and ordered a couple....


Singles / B40 SS90 alternative carb options?
« on: 02 January, 2020, 16:28:49 »
I think I'm going to have to try an alternative carb. Since restoration it just ain't been right and I thnk I've exhausted other options.

The bike idles too fast when timed correctly and with the slide bottomed out. It also hunts up down a bit.

It idles nicely and pulls steadily at lowish revs but misses badly on accelerating and running at higher throttle openings. This seems to get worse as the engine warms up.
Adjusting timing has no effect and neither does the needle position. Dropping the air slide makes it worse.

When I bought the bike as a U.S. import project it was crusted in a dry, red, sandy dust and had no air filter fitted. I suspect that the carb has worn through ingestion of dust particles when it was last running.

Rather than trying a replacement slide or like-for-like monobloc I think I'd like to try a more modern carb option.
A Mk1 concentric would probably work well if I can get the model number, needle and jet options right but I suspect there are other contenders too.

Any opinions or experience on this idea please?


Singles / B40 alternator puzzle
« on: 14 November, 2019, 11:37:44 »
The last item in the snagging list of my B40 SS90 restoration is to fix the charging problem (it doesn't).

I've modified the alternator wiring for 12V as per RR and tried two different regulator/rectifiers. Although I get an AC voltage reading straight off the stator the DC - about 18V at idle - the DC output is low and fluctuating.

I went back to read the RR book and it mentions an 8 thou clearance between rotor and stator. I have about 3mm so wondering if the rotor and stator might be mismatched.

The rotor is 70mm and the only stamp I can see looks like 246592. The stator is stamped 47164A 5 64 which I guess includes the date of manufacture.

So - I think I need to find either a 74mm rotor or another stator - any idea which would be correct please for a '64 SS90 with a B40B engine?

Many thanks,

Singles / B40 SS90 first ride after rebuild
« on: 17 October, 2019, 14:23:40 »
Finally got the V5 from DVLA and took the bike for its first ride out after the rebuild.
It starts easily, idles nicely but is rough and stutters on pickup from about 1/4 throttle.

Feels like it's a carb problem - any thoughts about diagnostics please?


The Star and Garter / Name that pint!
« on: 08 October, 2019, 18:42:43 »
I have just racked 5 gallons of home-brew into a barrel which is now ready to condition in my workshop for a week or two before being offered for consumption during my own October-fest.

It occurred to me that as one of the local breweries (Woodforde's) has recently launched a brew named Try-umph in support (and demand) of the current Rugby World Cup then it is only fair and reasonable to respond with a BSA themed name for my brew which is currently sharing the workshop with a number of BSA bikes and projects in various states of build.

Suggestions for naming the brew are therefore welcomed - all contributors will be welcome to come and share a pint if you're within staggering distance  ;)


The Star and Garter / "Smart" chargers
« on: 15 September, 2019, 08:34:05 »
I have bikes with both 6 and 12V electrics and normally use a 'smart' charger when needed.

However, I've found that these will not charge a fully discharged battery - if the detected battery voltage is below a minimum threshold they will just display an error code.

I accidentally left the pilot/tail lights switched on and my 6V Bantam battery is totally flat and I'm currently (!) unable to charge it.

Does anyone know of a simple, old-fashioned transformer/rectifier type charger that will deliver 6V - or an alternative way to get some charge into my battery (bearing in mind that I'm in a field in Germany for the next week!) - I was wondering if a 5V phone charger might get enough into it for the smart charger to then be happy to take over....


Singles / B40 SS90 - first start uneven idling
« on: 05 September, 2019, 13:33:38 »
Just finished rebuilding my 1964 B40B SS90 and got it running. All seems well except the idle speed seems to vary and is difficult to set.

This engine has the 10 degree advance plate and I've timed it as per the service sheet at 5 degrees BTDC fully retarded (or pretty close).

The carb has been completely dismantled, cleaned throughout and reassembled by me. I've used new fibre washers but kept the jets and needle that were there. They may be original but I can't be sure.

Pretty sure I have no air leaks.

The bike starts OK with the pilot screw 1.5 turns out but idles unevenly and is slow to return to idle after a 'blip' even though the cable is slack. I'm pretty sure the slide is not sticking and is sitting tight on the top of the idle adjuster screw.

Turning the pilot screw in results in a faster idle with it fastest at about 3/4 turn from seated, but still the idle speed varies when left at tickover for no apparent reason.

I'm currently running without an air filter - mainly because I haven't got one yet!

It may also be running a bit hot as the new exhaust is already staw coloured at the head after about 10 mins running on the stand.

Any thoughts on the cause or what to check please?


Singles / B40 SS90 ignition advance
« on: 04 July, 2019, 11:11:18 »
Just finished cleaning and rebuilding the distributor and, as per RR singles book, was checking for the advance stamping on the bobweight platform.

Mine shows 10 degrees although RR states "B44 and B50 12 degrees, all others 15 degrees except energy transfer models which are 5 degrees".

Is 10 degrees correct for the SS90 and what is the static timing setup please?


Singles / B40 clutch cable routing
« on: 04 July, 2019, 08:28:15 »
This may become more obvious when I source a chain guard but - do you route the clutch cable over the upper chain - and guard - and then down and under the casing or between the upper and lower chain with it clipped to the frame or rear chaincase bolt to make sure it doesn't chafe against the lower chain? The latter seems to be the option with fewer bends.


Twins / A50 Cyclone Competition project
« on: 23 June, 2019, 19:59:44 »
I've just collected an A50CC project - U.S. import and all in bits but looking largely complete.

I'm not yet sure if this was a full competition model or the road legal variant. So far all I have to go on is that the rear hub has a notch for a speedo gearbox drive tag (but there's no speedo gearbox with it) and it has an alternator which I think is the 5 wire type.

The pistons are stamped 68 506 and then 30 4/65M
A quick measure of the piston diameter just below the rings with a vernier shows 65.30mm

It will be a while until I get around to the rebuild as I have other bikes on the go but I'm keen to find out what these pistons are - I haven't been able to find any good references using that part number.

Grateful for any info.


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