Amal Carb Issues

Today I changed out the Amal carb gaskets on my 74 commando. When I put everything back together I started it and immediately revved to 3000. I shut it off and ran the throttle through a couple of times and started it again. This time it would not hold an idle and stalled out. I didn't remove the carbs at all, the only thing I did was let them hang in order to change out the gaskets. Has anyone else had a similar problem with their Amals?

Check that you didn't over tighten the bolts you undid - it's very easy to put too much torque on any / all of those bolts warping the mating surfaces and causing 'unmetered' air getting in.

Also, if you left the carbs hanging on the throttle cables make sure you haven't bound one up.

I recently rebuilt the carbs on my 1971 and did a couple of stupid things when putting it all back together, all in the cause of over exuberance!

Have to say though, they run better and I get a kick knowing that I understand how they work.

There are a ton of threads on this board and some excellent Youtube vids on the subject.

Thanks Nellie, I did not have a torque wrench and used my calibrated elbow for reference sometimes I don't know my own strength. Do you know the proper torque on those bolts? When I took the bolts out they were actually pretty loose. I will definitely check a couple of things later when I can get some alone time with my bike...thanks again.

-Joe

Hmmm .... I'm not sure the torque values but wiser minds on the board I'm sure will chime in.

The bolts between the carburetor and the flange aren't too bad but the bolts between the flange and the cylinder head are the problem - if you over tighten them, the flange "cups" for want of a better word, meaning the flange bolt holes are pulled out of true with respect to the plane of the flange surface that mates to the cylinder head with the thick gasket in between. This allows a gap to be created that then allows air to be sucked in weakening your mixture. Easiest way to check is to spray carburetor cleaner or WD40 into that area with your bike running, if the revs drop then you have a leak.

If you do have a leak, then you'll need to correct the flange surface. Take a piece of glass (I ransacked the house and pulled the glass from a picture frame, really PO'd the girlfriend ...) and get some fine sand paper (320 grit) and using a figure of eight motion work the flange surface. You'll quickly see where the high spots are and just keep going until you have a universally bright shiny surface.

When I reinstalled the flange to the cylinder head, I tightened the bolts down just enough to deform the split washers but with enough torque to make sure they were secure. I've kept an eye on them since and all seems well.

It sounds like a bit of a PITA but it's really not - took me about 30 minutes to do both and have them re-installed on the bike.

Good luck!

Nellie, thanks again I loosened up the bolts and re torqued them to about 70 in lbs. after that I kicked it over with no issues and it idled as it should. Thanks for the reply and advise as I am a bit younger than most on the forum and just as inexperienced when it comes to Nortons. Of the 100+ people that looked at this post you are the only one with sound advice I appreciate it!

We just figured it would be a learning experience. Ha, believe that, I would have guessed idle pilot. So much for experience.

Dave
69S

Decemberist said:

Has anyone else had a similar problem with their Amals?

Click to expand...

No.

Never .

:mrgreen: