B40 star best set up for wrong carburetor

AWJDThumper · 02 Jun, 2018, 18:29

I think the needle you've got is the correct one - the other one seems to have been specifically used on a Trident (with a 626 carb).

hoogerbooger · 03 Jun, 2018, 15:59

Mulling over Julian's comment I think I'll put the old needle and needle jet back in as at least I knew I could get it running on that before, even if it didn't run that well.

If I get it running and MOT'd then I think I'll buy a new Concentric 626. and use the set up for the 1967 Australian WD B40 below ......but I guess with a 140 main jet as I'll be using the gauze air filter rather than the paper one that used. Does sound the appropriate adjustment for the air filter ?

( anyone ever seen half depth 5/16 CEI/BSC nyloc nuts ? as the ones I sourced for the carb studs are 11mm deep which is just too deep to squeeze into the gap with a spring washer between tickler & carb flange.........I guess I have to try filing them down)

Phil C · 03 Jun, 2018, 17:17

Hello Hoogerbooger, AWJDT says below that it would be interesting to see how your carb compares with mine. I'm afraid I can't help at this stage, but thought I'd just send this post so you don't think I'm ignoring your issue. As you know, I have a 1965 B40F. It has a 626 carb, but I don't know the settings because I've not needed to take it apart after all yet (it started first kick the other day so I'm not inclined to tempt fate at the moment!) I did at one stage a while ago think I would take it apart but the problem was elsewhere (as I recall, me not knowing which way on the choke lever was open and which way was closed, until I took the air filter off and peeped in the carb intake!) I'm interested to read in this topic that some B40s had concentric carbs from new - I thought they were all monoblocs. I expect I'll have mine apart sooner or later, and will be on this forum asking lots of dumb questions. Phil.

AWJDThumper · 03 Jun, 2018, 17:32

Quote from: hoogerbooger on 03 Jun, 2018, 15:59
Mulling over Julian's comment I think I'll put the old needle and needle jet back in as at least I knew I could get it running on that before, even if it didn't run that well.

If I get it running and MOT'd then I think I'll buy a new Concentric 626. and use the set up for the 1967 Australian WD B40 below ......but I guess with a 140 main jet as I'll be using the gauze air filter rather than the paper one that used. Does sound the appropriate adjustment for the air filter ?

( anyone ever seen half depth 5/16 CEI/BSC nyloc nuts ? as the ones I sourced for the carb studs are 11mm deep which is just too deep to squeeze into the gap with a spring washer between tickler & carb flange.........I guess I have to try filing them down)

As said before, the small differences in settings discussed previously won't affect the basic running of the engine - at worse it will be down on power and may not pick up smoothly from idling. However, if the throttle slide and bore are badly worn then the engine may run very badly. In this case, tinkering with needles and jets probably won't make any difference. So it's best to start with the condition of the slide and bore. If the slide is a very loose fit then it can be replaced but, if the bore is worn, a new carb is probably required.

hoogerbooger · 03 Jun, 2018, 21:26

The slide and bore seem pretty good.

I take it from what Julian says that if I want to use the new needle & needle jet I have, then I can't use the old shorter jet holder.

So I'll have to purchase the new jet holder.

That correct

JulianS · 03 Jun, 2018, 22:29

Attached is a service sheet which explains.

hoogerbooger · 05 Jun, 2018, 20:48

( complete matching set of jet, jet holder & needle jet fitted)

Does the throttle spring push directly down onto the butterfly clip?

( previously it was pushing onto metal cover that went over the old round clip(which is broken).....but looking at it and where the cable has to snag, I don't think I can use the plate it with a butterfly clip)

hoogerbooger · 06 Jun, 2018, 00:38

Just searched Amal website for the code on my carb (627/428)

and it comes up with one bike model.....a 1974 Bultaco Sherpa 350...... which on checking is a 2 stroke !! oh dear !!

Amal site says these were originally made under licence in Spain. Spec there doesn't mention the spray tube. So seems a little odd to have Norton spray tube.

Amal site says 2 stroke & 4 stroke carbs are inompatible.

anyone know what else (apart from the spray tube) differ .... that isn't cheageable ?

AWJDThumper · 06 Jun, 2018, 07:50

They differ in the spray tube and pilot jet configuration. I'm sure it will run with a 2-stroke carb but not as well as with a 4-stroke carb.

JulianS · 06 Jun, 2018, 09:35

2 stroke concenric have a pilot jet which screws in (but not the bushed one), so did some early 4 stroke versions.

Later 4 stroke versions had a bushed non removable pilot jet and did not use a screw in one (new premier concentric now has a revised pilot setup).

Beig the Spanish made item will also explain the lack of O ring, had one like it some years back.

You can find it in the Amal link posted earlier.

To get the best from your bike I think you need to change that carb.

hoogerbooger · 06 Jun, 2018, 10:49

Thanks both.

I was keeping my my fingers crossed it'll do to get it on the road. So that panic over.

Anyone got an answer to my previous post. Does the throttle spring push down directly onto the butterfly needle clip ?

(can't see any other parts on the Amal guidance, but my previous round needle clip had a cover plate which doesn't look like it'll work with the new shaped clip)

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B40 star best set up for wrong carburetor