wrong carbs

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bobnorton
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wrong carbs

Post by bobnorton » Tue Mar 31, 2015 9:58 am

A pal has built a special using a 900 Darmah motor and fitted it with a pair of PHF carbs from a Laverda Jota!, These do not have idle speed screws. I don't think he will get this to run sensibly. Any thoughts?.

tobaccoblender
Diana
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Re: wrong carbs

Post by tobaccoblender » Wed Apr 08, 2015 11:19 am

So how come they don't have idle speed screws?
Didn't the Jota need them- or was it set up for racing?
My BSA DBD34 had an Amal GP carb and that had no idle screw- you either had to just keep blipping the throttle or have the slide hanging on the cable, which was no good as the tickover changed if you moved the handlebars left or right....
What diameter are the carbs? I ask because it's possible I'm going to have a brand new pair of PHF 36's that might prove to be surplus to requirments.... :vroom:

wdietz186
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Re: wrong carbs

Post by wdietz186 » Wed Apr 08, 2015 6:06 pm

The Laverda carbs are linked together through top caps which have the idle stop incorporated into the linkage. So no stop screws are used on the bodies. The bosses are cast in the carbs but not drilled/tapped. Looks easy enough to do if desperate.

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Miti
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Re: wrong carbs

Post by Miti » Tue Jun 16, 2015 10:42 am

tobaccoblender wrote:So how come they don't have idle speed screws?
... it's possible I'm going to have a brand new pair of PHF 36's that might prove to be surplus to requirments.... :vroom:
I might be able to find those 36's a new home... ;)
wdietz186 wrote:... The bosses are cast in the carbs but not drilled/tapped. Looks easy enough to do if desperate.
I would suggest it's pretty much essential if the 32's are to be used off the OE linkage.. The only other way to set the slides to provide an idle would be to adjust the cables such that they are "too tight", thus holding the slides open... Not an ideal solution...

Wouldn't be a difficult job, but I would take great care with the drilling - the zinc alloy does not react well to over-enthusiastic use of the right tap in the wrong hole... (DAMHIKT) :oops:

Miti
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Diana
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Re: wrong carbs

Post by tobaccoblender » Tue Jun 16, 2015 9:21 pm

No, having the slides hanging on the cables never works - the tickover goes all over the place if you move the handlebars left or right. :wah"

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