Steadfast Amal 626 alternative pwk 26 mm carburetors set up

clyffh · Post by **clyffh** » Tue Mar 22, 2016 2:39 pm

I have just fitted a pair of these to my newly restored 1963 CB77. It starts and idles well but I am having trouble getting it to run properly over 3-4000 rpm.

Does anybody have a recommendation regarding the correct jet sizes and needle position for these carbs?

Thanks

Clyff from NZ

G-Man · Post by **G-Man** » Tue Mar 22, 2016 4:50 pm

Read through Vince Lupo's post on Japan meets Britain. He has Amals on his CB77.

G

Nick · Post by **Nick** » Wed Mar 23, 2016 12:29 pm

Drop the needles one notch, that will lean out the mid-range. If it gets better you're going in the right direction. If it runs worse, raise the needles one notch (richer).

If the bike gasps when you open the throttle, it's lean, if it stumbles, it's rich.

Main jets may also be too rich, or too lean.

Air screws one and one-half turns out from full bottom -- that's a starting point, adjust from there for best running at idle, one cylinder at a time! After adjusting both air screws at idle (one cylinder at a time!), start engine on both cylinders and reduce idle rpm to proper level. After idle is set for both cylinders, shut off engine and check that both slides lift off the idle stops simultaneously. Adjust cables as necessary to ensure that slides are lifting at the same time.

G-Man · Post by **G-Man** » Wed Mar 23, 2016 1:24 pm

http://amalcarb.co.uk/downloadfiles/ama ... _guide.pdf

G

Nick wrote:Drop the needles one notch, that will lean out the mid-range. If it gets better you're going in the right direction. If it runs worse, raise the needles one notch (richer).

If the bike gasps when you open the throttle, it's lean, if it stumbles, it's rich.

Main jets may also be too rich, or too lean.

Air screws one and one-half turns out from full bottom -- that's a starting point, adjust from there for best running at idle, one cylinder at a time! After adjusting both air screws at idle (one cylinder at a time!), start engine on both cylinders and reduce idle rpm to proper level. After idle is set for both cylinders, shut off engine and check that both slides lift off the idle stops simultaneously. Adjust cables as necessary to ensure that slides are lifting at the same time.

Vince Lupo · Post by **Vince Lupo** » Fri Mar 25, 2016 3:20 am

Unfortunately I'm not really able to provide specific numbers, as the way my bike is set up is completely different from a stock bike. Having said that, when we first mounted the carbs (prior to all the engine and transmission work), they pretty well worked right out of the box.

In order for us to dial it in (as we didn't have access to a dyno), we had to do plug chops. Lots of plug chops. That way we were able to get a reading of what the plugs looked like at a particular throttle setting. It was very time consuming, and the idea of having to shut the bike down at full throttle was more than a bit nerve wracking, so if you do have access to a dyno, that would be the most direct route. Failing that, I'd suggest buying a couple of boxes of spark plugs and start testing.....

Nick · Post by **Nick** » Sun Mar 27, 2016 1:27 am

Another technique to use when doing plug chops is to put a piece of tape on the throttle body, and put another line on the grip. Then, noting where the carburetor slide is in its travel, mark those points that equate to pilot jet, needle jet, main jet, etc. This makes it easier to hold the throttle steady in those areas.

The factory test riders in Japan use this technique regularly.

But if there's a dyno in your area that would be ideal.

Of course, before doing any of this check the timing with a strobe and set the valve clearance.

Vince Lupo · Post by **Vince Lupo** » Fri Apr 01, 2016 2:26 am

Nick wrote:Another technique to use when doing plug chops is to put a piece of tape on the throttle body, and put another line on the grip. Then, noting where the carburetor slide is in its travel, mark those points that equate to pilot jet, needle jet, main jet, etc. This makes it easier to hold the throttle steady in those areas.

The factory test riders in Japan use this technique regularly.

But if there's a dyno in your area that would be ideal.

Of course, before doing any of this check the timing with a strobe and set the valve clearance.

Yes that's basically how we did it. I think I would have had a hard time figuring out 1/4 throttle, 1/2 throttle etc on the fly, so the tape was a big help.