New Amal Carb for 250 Monza

[Jordan]

In what position is the jet needle clip?
Have you tried adjusting the air screw?

Information here: http://www.britcycle.com/help.htm

includes: http://www.britcycle.com/Manuals/amaltune.pdf

[Rick]

Half-
If there's enough fuel flow to keep the bowl full enough to run at high rpm there should be plenty to operate at lower rpm.
With the throttle off, slide down, the mixture has to come from the pilot/idle circuit, so the pilot fuel jet would be a good place to start. Even better, make sure the pilot circuit isn't plugged- just because it's a new carburetor doesn't mean the pilot circuit can't be plugged- you're probably using an old tank with plenty of crud in it.
I don't know much about later Amal carburetors, the GP series was used by Dellorto to design the SSI units, and the pilot mixture outlet(engine side of the slide) is so small that they're almost always plugged.
Rick

[halfpast]

Thanks guys for the suggestions and info. The weekend is upon us and I'll report back with what I end up with.

[ducwiz]

Hi,

the early L-twin 750s were equipped witk AMAl 930 concentrics. Here http://ducatimeccanica.com/750gt_manual/pg-16.htmlhttp://ducatimeccanica.com/750gt_manual/pg-16.html you find theirsetting for reference. A #25 idle jet was standard. From your symptoms, I suggest to make it even larger than 30 (40?) and test again.

This article http://www.jba.bc.ca/Bushmans%20Carb%20Tuning.html may also support your job.

Hans

[halfpast]

Well, I tried various settings on the pilot jet screw as well as the slide setting but nothing seemed to help the idle problem. I even tried the guitar string trick to clean out the pilot hole.

Jordan, it's my understanding that the Cocentric carbs don't have a 'needle clip' but the Monobloc carbs do. I could be wrong - as you guys can probably tell I'm still learning about these Amals...

[Jordan]

Amal Concentric does have a jet needle clip, and various grooves on the jet needle. Details are in the literature that has been mentioned.
However, it's not likely to be the cause of your poor idling performance, as that is more the responsibility of the idle circuit. Are you letting the engine warm up? Idle might not be great until it is.
As it's a new carb, I think clogged passages are unlikely.
Maybe worth checking there are no air leaks. For a quick check to rule that out, just smear some grease around the flange area.

[halfpast]

Thanks for the info Jordan. I'll check for leaks tomorrow.

[halfpast]

Just posting a little update - no leaks were found...I'm out of ideas and (unfortunately) going to resort to finding a local shop to consult with. Hopefully I can find someone to get it sorted.

Thanks again to everyone and their suggestions.