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Topics - berniej

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Singles / M21 engine - factory records?
« on: 10 August, 2021, 14:56:07 »
When I built my B31/M21 hybrid a few years ago I got a dating certificate through the club which recorded that the original bike was despatched (as a B31) direct from the factory to 'The High Commissioner of Southern Rhodesia' in 1952 which was rather interesting.

However, when I got my hands on it - completely dismantled in several old tea chests, it had a 1949 M21 engine with it.
I don't know if this engine had ever been fitted to the frame before (although M21 engine plates were included so maybe) so I would be interested to see if it's possible to search the factory records for the engine number to get some idea of it's history.

However, I'm not sure what sort of request to make or whether such a search would be possible.

Thanks for any info.


Bantam / Bantam recommendations please
« on: 13 July, 2021, 12:24:27 »
I recently sold a D7 that I bought a while back to carry on the back of my motorhome, the carrier is rated at 130kg max.
It was OK but a bit underpowered and I felt I needed another gear.

So, I bought a B40 SS90 to get some more power and I can just get this to < 130kg if I remove tank and seat every time we travel but it's a bit of a palaver.
It's also a struggle to keep my rear axle weight below the max limit with it on the rack.

So, I'm now thinking of going back to a later model bantam, definitely a 4-speed and preferably something that has more modern looks that the vanilla models.
Any recommendations please for models and or mods that might fit the bill?


The Star and Garter / Lucas magnetos - care in marine applications
« on: 23 January, 2021, 16:54:07 »
I have a few bikes with magnetos and am particularly familiar with the M01 assembly. Up until now though I hadn't encountered the marine variety.

However, I have just acquired three old Stuart Turner twin cylinder marine engines that look as if they may have been dredged up with the Mary Rose.
I am intending to restore each one but it may take a while due to the extent of rust, age and general neglect (and bike projects!).

The justification for this purchase, as presented to Mrs. Jones was that this year I expect the domestic holiday market to boom due to international travel and holiday restrictions so there will be a high demand for inland boating holidays, and therefore engines for the hire fleets. These classic old engines will therefore be a worthwhile investment and are sure to return an early and considerable profit as they will also be in high demand.

The alternative view - that "I saw, I lusted, I bought" is of course something that I will vigorously deny.

Anyway, the point of this post is to share this rather marvellous fragment from the service manual relating to the Lucas SR magnetos that were used.

I thought this rather hopeful as these engines were commonly fitted to boats that would remain in commission all year round and put to sea in all conditions so the idea of returning from a hard day's fishing, mooring up in the harbour and then popping down into the bilge to remove the magneto and take it home to keep it warm is, I suspect, something that was occasionally overlooked!

Those were the days!

Twins / A50CC restoration
« on: 22 December, 2020, 17:17:33 »
I'm about to start on the restoration of a 1965 A50CC that I bought about a year or so ago but have only just got around to examining in detail.

I plan to post regular updates on progress - and also no doubt a lot of questions.... which I'll start with now  :)

I don't have much info on the bike other than it's been brought back from the U.S. largely dismantled.

VIN is A50B8751 and I beleive the engine number is correct.

I'll be rebuilding it as a road bike but I'm still unsure as to whether this was originally built in road or off-road spec.

Some clues are....
The fork top sleeves lack ears which might suggest no headlight - but the BSA parts book shows this part just as 'A50C East Coast'
It has a 5 wire alternator stator and the one coil I've found so far is the 'energy transfer' type rather than in a can.
10:1 pistons fitted and appear original
No headlamp or tail lamp fouind in the boxes of bits
No battery carrier on the LHS
Large rear sprocket - I'll count teeth tomorrow but probably 50
It comes with both high-level and regular pipes and a pair of small silencers
Pretty sure pillion footpegs are present - but will check tomorrow

Looking at the brochures on the club web site I can see that there were different versions for West and East coast and rather intrigued as to what the differences were and how this related to 'road' or 'off-road' trims.

Any thoughts on this or suggestions as to what other clues to look for would be most welcome.


Twins / A50CC Piston Puzzle
« on: 18 December, 2020, 10:42:17 »
I'm just starting to investigate the crates of parts that will hopefully become an A50CC road bike and I'm not sure which pistons are fitted.
I'm pretty sure the part number stamped on the crowns is 68-0506.

Image below is from my parts book, so which pistons do I have please?


Sidecars / Looking for a 2-seater
« on: 20 October, 2020, 19:05:47 »
I'm looking for a sidecar or project that is capable of carrying 2 adults in relative comfort - preferably one of 'the period'.


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?


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