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1969 B40WD carb questions. #32061
12/18/07 4:40 pm
12/18/07 4:40 pm
Joined: Oct 2006
Posts: 14
East Kent
I
Igotknobblies Offline OP
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Igotknobblies  Offline OP
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I

Joined: Oct 2006
Posts: 14
East Kent
Hi.
According to Rupert, for the year ('69), this bike should have a 398 (butterfly) or Concentric AMAL 926. It actually has a worn out Concentric 626. Probably fitted aftermarket. I rebuilt the engine using
an 8.5:1 piston although have no plans for a different cam, but I may do some work on the inlet port. What are my options? Can I get my AMAL re-bored and new slider? If so, what jetting should I aim for?
Or should I look for a different model and if so which one and what jetting. Compliance with original is not necessary as frame and engine are not matching. I have a lathe so could attempt re-boring the 626 and machining up a new slider although unable to incorporate the choke slide. Would omission of this be a problem if I could put a 'hit and miss' choke between air filter and carb?
I expect I could run the bike with the old carb but as its not standard and possibly fitted with dubious jets and needle and is well worn, I need a datum to start from.
Any help would be gratefully accepted.
Thanks,
IGK

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Re: 1969 B40WD carb questions. #32062
12/18/07 4:52 pm
12/18/07 4:52 pm
Joined: Oct 2006
Posts: 14
East Kent
I
Igotknobblies Offline OP
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Igotknobblies  Offline OP
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Joined: Oct 2006
Posts: 14
East Kent
Just remebered I have a carb from a 1984 Kawasaki KL 250. Would this be a fair match if I could fit it in? YEEEAAARGGGGGHHHHH I hear you all scream!!
IGK

Re: 1969 B40WD carb questions. #32063
12/18/07 6:40 pm
12/18/07 6:40 pm
Joined: Sep 2002
Posts: 7,813
Seattle
Alex Offline

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Alex  Offline

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Joined: Sep 2002
Posts: 7,813
Seattle
Get the 626 resleeved, it will work a treat. My friend Jim's WD runs great with the sleeved 626 (after we cleaned the idle circuit). He doesn't run a choke and it seems to be fine after a couple of minutes warming up. I'll try to figure out what we used for jetting if you decide to go that route.

926? Never heard of such a thing....


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Re: 1969 B40WD carb questions. #32064
12/18/07 6:51 pm
12/18/07 6:51 pm
Joined: Dec 2004
Posts: 9,662
Scotland
kommando Online content
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kommando  Online Content
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Joined: Dec 2004
Posts: 9,662
Scotland
If a 926 existed it would have the same bore size as a 626, the 26 stands for 26mm, if you want a bigger bore you need to move up to a 900 series the smallest of which is 928 at 28mm bore.

Re: 1969 B40WD carb questions. #32065
12/18/07 11:00 pm
12/18/07 11:00 pm
Joined: Oct 2006
Posts: 14
East Kent
I
Igotknobblies Offline OP
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Joined: Oct 2006
Posts: 14
East Kent
Thanks for the prompt reply. Think I'll stick with the 626 as the bike is a bit of a money pit already. Can you advise who can re-sleeve? Can I do it myself or is it a bit too techy? Very interested in your jetting too.........
Cheers,
IGK

Re: 1969 B40WD carb questions. #32066
12/19/07 9:09 am
12/19/07 9:09 am
Joined: May 2004
Posts: 3,892
Sydney Australia
B
BSA_WM20 Offline
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Joined: May 2004
Posts: 3,892
Sydney Australia
Now there is a little trick with the 626's on WD B40's
They were at a slight downdraft so the aluminium spacer has a drain hole in it.
As this hole sucks in air while the bike is running the specified jetting was a little richer than it should have been to compensate for this.
Also the length of the rubber hose fitted to the drain is quite important, from memory it was about 19".

You can resleeve the carb if you have the required skills.
There are 2 ways,
1) machine the carb body & fit a speedy sleeve tube in with a new standard slide
2) machine the slide down & fit a speedy sleeve to the slide then bore the body to suit.
I have seen them done both ways, neither seems to have any advantage over the other


Bike Beesa
Trevor

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