Author Topic: Plain jet B&B questions  (Read 5125 times)

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Offline Ian

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Plain jet B&B questions
« on: 28 May 2011 at 06:16 »
Folks - still trying to get the E28 running properly. I had a go at rebuilding the B&B back to the standard diffuser configuration - made some progress but need to sort out float levels, etc. I have a couple of questions about the diffuser carbies :

1. What did the slides look like ? The slide in mine is a full slide with provision for a small choke on the inlet side with grooves. Is this what the diffuser ones had or were there two separate slides more like veteran carbies ? If anyone has one apart and could put some photos up it would give me something to go on
2. Were the E28s set up with a twist grip ? Mine has one and has a choke/air level on it. Do these carbs need constant adjustment of the air or once started do you just leave the air fully open ?

Offline Clive

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Offline Doug

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Re: Plain jet B&B questions
« Reply #2 on: 30 May 2011 at 01:27 »
Ian,

Yes, the diffuser throttle valve is a near solid lump with a small slide keyed into it for the choke.

The Sport versions of the 350 and 600 EW were fitted with twist grip throttle. So the F28 was advertised with a twist grip throttle and the E28 made do with the lever and the less sporty foot boards. Likewise the H28 600 OHV had the twist grip and the G28 retained the lever control. In neither advertisement is there any mention that a different carburetor is fitted based on the handlebar control.

The E/F28 handbook only mentions and describes adjustment of the plain jet B&B, with the variable jet superseding it in 1929 (though available from B&B before then.) In the 350EW handbook it states the air valve (choke) was only for starting; once the engine is warm the air valve is fully opened and the engine speed controlled solely with the throttle valve.

-Doug

Offline Ian

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Re: Plain jet B&B questions
« Reply #3 on: 30 May 2011 at 01:38 »
Thanks Doug - thats great !!

Offline Ian

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Re: Plain jet B&B questions
« Reply #4 on: 15 Jun 2011 at 23:01 »
Latest update - I got everything working on the carb - runs fine at idle and full throttle but super-lean in between. This is going to be a long process !! Made up a new slide with no cutaway and its way too rich - almost wouldn't run at all.

What I really need to do is get hold of either a good original carby or something like a clip-mount Amal 274 to put on it and make sure the carby is the only problem. The trouble is there is not much space above the carby so need a short one - most Amals would be too tall I think. If anyone has one I could borrow (or buy) to try it out I would be very grateful !

Offline eddie

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Re: Plain jet B&B questions
« Reply #5 on: 18 Jun 2011 at 14:15 »
Hi Ian,
            I have an AMAL 274 clip fitting carb body to fit on a 1" stub. It's brand new old stock - if it's any use to you, send me a PM with your details and I will post it to you.
             Regards,
                            Eddie.