[Mac350]

confession time. I was going by the look of the carb compared to pictures I found online as I couldn't see any number on it. It looks nothing like this BS26

or any picture I can find of a BS26 but looks exactly like this and every picture of the BS29


I just measured the carb and its 26mm  Then i took a magnifying glass to it and found faintly pin punched numbers and sure enough its the BS26  Sorry about that. I should have learnt to cross check assumptions with measurements by now.

According to the retired model catalogue the pilot and main jets 15 and 110 I have are standard. I just need to get it back together and take out the air filter from the box temporarily and see what its like. If its just a bit lean then I guess I just want to get a decent cone filter and tweak it from there as required. Are K&N cones really worth £50?? Its on a 45mm outer diameter of the carb and I can get either 43mm or 46mm inner diameter cones any idea if i should go small or larger and pinch down? Really can't afford to order 2. If they are good I'm willing to pay that to match the more free flowing exhaust. I would certainly like to remove the airfilter boxes and battery box so do want a cone

For info the inlet on the head is 28mm.

[Mac350]

The BS26 is the correct carb for the later model AVL 350 and people started switching to the BS29 carb from the UCE 350 because it was around half the price of a BS26 carb in India. When I had a BS29 carb on my AVL350 (the motorcycle was sold to me like that), it ran fine on flat roads, but while travelling up hill, the engine would bog down immediately and would be struggling even in second gear (5 speed) while a stock 350 IB would chug along effortlessly in 3rd gear. I had not port matched the cylinder head to the BS29 carb. The inlet port on an AVL 350 from memory was around 27 mm. What I found was that the BS29 was good for highway cruising 80 - 90kph, but lost out on the low end torque, the BS26 was the best all round carb and the IB VM24 (modified flange) had better low end response all the way up to 70-75 kph.
 
 The 350 AVL came with a crankshaft that weighed 8kg (factory lightweight crankshaft) which allowed the engine to accelerate faster, but the engine will not be happy being used at low rpms in a higher gear. So if one wanted to lug the engine around, the heavier crankshaft would be a better choice but will have a slower acceleration.
 
 Also check that there is a sufficient spark at the spark plug, the CDI unit setup had the benefit of being able to be started without a battery, but had a lower spark output, so if the spark plug gap is too big, under load the engine will loose power.
 
 The BS29 carb is one of the more common carbs available in India, since it was used by multiple motorcycle manufacturers and while they looked similar externally, but they were different internally.

Great info thanks. You're not the first person on this thread to say 26mm is a good match. I'll keep trying to get this BS26 to work then. I don't think I'd want to live with struggling up hills in 2nd gear. Presumably having a 26mm carb on a 28mm port isn't an issue like it would be the other way around.

Now I'm realising there are 2 types of BS26 and I've got the one that shares most parts with the BS29 (according to the retired model catalogue) I realise I might be better off buying a BS29 from india for £55 delivered instead of paying £15 for a float bowl O ring that it looks like it could do with and I'd get a diaphragm that isnt available separately here, a float needle, all the other matching o rings, spare float...

[Adrian II]

Thanks Richard,

I was actually going to ask you what the correct carb settings should be.

Also check that there is a sufficient spark at the spark plug, the CDI unit setup had the benefit of being able to be started without a battery, but had a lower spark output, so if the spark plug gap is too big, under load the engine will loose power.

That sounds about right, the spark plug gap on a battery and coil ignition bike would normally be 0.025", but for magneto use the same plug would be gapped down a bit to 0.018" - 0.020" Can't do it on Iridium plugs, though!

*************************

A 28mm port down to a 26mm carb should be no problem, if you WERE obsessed about it (nervous twitch!) you could make a carb spacer from 8mm Tufnol with a slightly tapered big hole in the middle which would smooth the flow nicely. Should be room to squeeze one in, especially if the airbox is going to be removed. This was for a 500 head but it gives you an idea.



There are loads of generic el-cheapo Chinese-made cone filters which will do the job, just make sure you pick one which is NOT for a pit bike as these can be a bit bunged-up in the middle, free-flowing is what you want. 46mm will squash down onto a 45mm outer stub happily enough with a good slimline jubilee-oid clip.

But if those Devon lanes are not too dusty, how about one of these instead of a cone?



A.

[tooseevee]

Right, here is Ric's guide to tuning the BS CV29 carb. Bear in mind this the for the 500 engine, not your 350, but the same principles apply, so it can probably be scaled down, though jets are cheap enough for you to experiment with the 500 settings

      I can't Quote Rick in this response because  your quoted part doesn't show up when I quote you, but I remember all this from when I was tuning my BS 29 BEFORE I had the Ace headwork done & changed to a Mikuni TM 32. A lot was discussed about AVLs & CV & flat slide carbs back between 1999 & 2020. Not so much now.

     What I took (& take) issue with Ric on is:

      Mixture screw turned out 4 turns &

       Raise the needle to it's highest position (needle in bottom notch).

       It just seems to me that his Pilot Jet must have been way wrong for his engine to run right with those settings.

        And for Mac350: If I haven't mentioned this before remember it's called the UCAL BS-29.
https://www.google.com/search?client=firefox-b-1-d&sca_esv=2ca6f23d8cc3e1e1&sca_upv=1&q=ucal+bs29&udm=2&fbs=AEQNm0AVbySjNxIXoj6bNaq7uSpw-2eW7KIQ8H4T_tEPJYsPzOi5GKsV0RKGmy84LfyUxrl-4_0AusV0IdjeUAdX2KBg7BmnGLOak5d-z-_u-BD5mN13FgBnNWDvju7R9DTlWNidOrJflM1JuVtiWYZDkHFOJzhjFWWukocdFSx3yN5TzfLggWRnI4Aa-8EhEIZUfHR_WMFwmbeNhwTWDi8XltL7qhh3uw&sa=X&ved=2ahUKEwjKk9SfnouIAxVXAHkGHduaKmsQtKgLegQIGRAB&biw=808&bih=387&dpr=2.07

 

[Adrian II]

I dimly seem to recall that both the UCAL and Mikarb versions of the 29mm CV carb were used at various times, not sure if there were any major differences. The 500 AVL Classic was launched somewhat later than the Electra-X, different carb suppliers used at different times?

I could be way off about this, of course!

A.

[richard211]

I dimly seem to recall that both the UCAL and Mikarb versions of the 29mm CV carb were used at various times, not sure if there were any major differences. The 500 AVL Classic was launched somewhat later than the Electra-X, different carb suppliers used at different times?

I could be way off about this, of course!

A.

 Earlier Mikuni and UCAL were a joint venture and later on split up, resulting in UCAL having to take off the Mikuni branding off their products and rebranding the carbs as UCAL.

[Paul W]

I fitted a similar air filter to the one linked to. It fits over the short bellmouth on my WASSELL. It seems to filter well enough and certainly isn’t restricting to the airflow.

https://www.ebay.co.uk/itm/276354704021

[Adrian II]

I had something similar on the 350 briefly, made by Ram-Air. It's a bit scorched on the inside after a couple of back-fires!

A.

[Paul W]

Mine was fitted possibly five years ago.

[Adrian II]

Hmm, it's all gone quiet again. 

You still there, Mac350?

A.

[Mac350]

Hmm, it's all gone quiet again. 

You still there, Mac350?

A.

Hi yes still here, had a manic week ripping out an old shed and fence and building a new larger fence with gates with now a 3x3m marquee safely behind it to use as a bike garage, just finished. Until today I just had a small back yard space I couldn't even turn the bike without dragging the back wheel around but was a bit of a nightmare to reverse out of too and no covered area to work on it. Now I have a 6m x 3.5m fenced in space with a 2.3m high fence and 3x3m of it is a covered enclosed area. Its a bit leaky in places but it only cost £20 used so I can splurge on some gaffer tape. Will add an LED strip and a radiant heater. Now I can wheel the bike in and out easily it will be much nicer to jump on for a quick ride.

Next stage though will have the marquee become an outdoor wood workshop while I turn the back extension into a proper workshop, its about 20sqm so not far off a double garage. Bit of a job though, strip the flat roof off and replace probably all the wood, the wood windows are shot and I'll replace the floor with concrete so i'll be stripping it back to just the walls. Just the weather stopping me again now, the marquee will help a lot for that though and safe enough to leave some tools in. Bike is chained up out the front under a cover for now. Will be great to purpose make this workshop, I can make sure I've got a 16amp supply direct from the consumer unit so I can weld at the same time someone else puts the kettle on and with a concrete floor I'll apply some sort of industrial garage coating. I'll need to get a bike lift that can rotate and move around with the bike on it ideally

The extension was going to be left how it was as a bedroom with en suite (though it needed a full refurb anyway), in case needed for a granny flat but this old bike needs it so it sort of will be doing what we thought it would

[Adrian II]

That's a lot to take on!

A.

[Mac350]

i'm like a coiled spring at this point, been putting it off for years but now the plan has solidified thanks to having this bike I'm just cracking on and getting it done. At least doing it myself I don't have delays waiting for people. Neighbours can't believe how fast the fence went up after seeing the dilapidated one for years.

Relaxing with some video on youtube I watched a this one on the new classic chrome, looks very similar to the machismo https://youtu.be/ygTrZIuEZvc?t=1229 fair play to enfield for managing to get around the emission issue while still keeping a fairly unique appeal. I was wondering what the point was of an enfield with a modern engine that takes care of itself and starts on the button but he seems to be enjoying it just the same despite not having to get oily fingers. Funny though when he says its got hardly any technology and is pleased about it. Buts its got fuel injection, ABS and a headlight that runs off a battery for gawds sake   

[Mac350]

Actually its hard to find bike videos that aren't people advertising new bikes, true on other topics as well, youtube has become a continuous advert. Are there any particularly good channels about older Enfield's that aren't just shilling stuff?

[allanfox]

This guy isn't far from me in Suffolk, musings about his stable of Enfields, mostly a good watch with a cuppa!

https://www.youtube.com/@Volcanicbrown1878