Need help adjusting carbs

okwebb · May 8, 2021

Norton commando. Bike starts and idles fine. When riding there is a popping and slight hesitation when I accelerate. Less at higher RPMs. I’ve tried everything I know to adjust. Any help will be greatly appreciated. Thanks

Triton Thrasher · May 8, 2021

If the needle jets have not recently been renewed, do so now.

Report back.

okwebb · May 8, 2021

They have been. Got a rebuild kit. Good enough?

Triton Thrasher · May 8, 2021

1 Do you do the adjustments with a fully warm engine?

2 If, when warm, it idles for a few seconds and then you slightly open the throttle, does it hesitate?

Tornado · May 8, 2021

okwebb said:
They have been. Got a rebuild kit. Good enough?

I had bad case of hesitation coming off idle while trying to pull away from stops. Ultimately was worn needle and needle jets.

Also had popping and misfires at 3/4-full throttle position, turn out to be one main jet slowing coming un threaded from carb body.

Triton Thrasher · May 8, 2021

The points have to be clean, gapped and timed.

okwebb · May 8, 2021

Triton Thrasher said:
1 Do you do the adjustments with a fully warm engine?

2 If, when warm, it idles for a few seconds and then you slightly open the throttle, does it hesitate?

Not usually

okwebb · May 8, 2021

okwebb said:
They have been. Got a rebuild kit. Good enough?

I meant are needle jets from rebuild kit reliable?

okwebb · May 9, 2021

Triton Thrasher said:
1 Do you do the adjustments with a fully warm engine?

2 If, when warm, it idles for a few seconds and then you slightly open the throttle, does it hesitate?

Yes

marshg246 · May 9, 2021

okwebb said:
They have been. Got a rebuild kit. Good enough?

Amal rebuild kits do not include needle jets. The do include needles and pilot air screws. The needles they include are not Norton-specific. If you have a 750, you have the right needle, if an 850, probably the wrong needle. However, I doubt that it would cause your issue.

Hesitating off idle generally means that the pilot air screws need to be turned in slightly.

Triton Thrasher · May 10, 2021

marshg246 said:
Amal rebuild kits do not include needle jets.

This one, from Amal does.

Shop our MK I Concentric 600/900 Series 4 Stroke Repair Kit | RKC | AMAL Carburetters

MK I Concentric 600/900 Series 4 Stroke Repair Kit

amalcarb.co.uk

Triton Thrasher · May 10, 2021

okwebb said:
Yes

If you’re saying this happens:

2 If, when warm, it idles for a few seconds and then you slightly open the throttle, does it hesitate?

Study it and see which cylinder is hesitating. As Marsh says, slightly screw in the pilot screw on that side. See if that makes it better or worse.

marshg246 · May 10, 2021

Triton Thrasher said:
This one, from Amal does.

Shop our MK I Concentric 600/900 Series 4 Stroke Repair Kit | RKC | AMAL Carburetters

MK I Concentric 600/900 Series 4 Stroke Repair Kit

amalcarb.co.uk

The kit does not. When you order from that page, you are ordering the kit plus the separately packaged needle, main, and/or pilot jet. Notice that in each jet option drop down, there is a not jet required option. I've sold lots of:

Repair kits (RKC/559) (no float)
Major repair kits (RKC/560) (plastic float)
Major repair kits with StayUp float (RKC/601)
Major repair kits with StayUp float and Norton needle (RKC/602)

All pre-packaged from Amal and not one includes jets. Very often people order needle jets at the same time and once in a while main jets as well.

Of course, if he meant that he bought the package directly from Amal and specified the jets he wanted then he did get jets.

Triton Thrasher · May 10, 2021

A rebuild with the old needle jet wouldn’t be a good rebuild.

Need help adjusting carbs

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