Amal question

Having a bit of a frustrating day out in the garage, one of those nothing was really wrong with the bike until I started tinkering with it. Bike has been running really well all summer, except for pretty rich so thought I would drop the needles one notch and see what happens.

Got the right side done no problem, but when I went to put the left slide back in it was tight and catching. After monkeying around for quite some time just pulled both carbs and now have them on the bench. Both slides will drop freely into the right body, but neither will even go flush with the top of the left let alone right to the bottom. Have had no issues with the slides sticking/catching until now (was even out for a ride this morning no problem), it is like the left body somehow just tightened up. I have read lots of posts where the slides wear and become loose in the body, but has anyone had this problem? Any ideas on what to try?

Thanks
Trevor

Sounds like it got over tightens and flexed the bore. You might try identifying the tight spot and try to polish it out with semicrome.

I semi local motorcycle shop has a reamer just to clean up such occurrences.

On an unrelated note, check to see it the needles are still straight.

Trevor
Did you tighten the flange nuts by chance (Carb to Manifold)?
Thomas
CNN

As noted, it is typical of overtightened fasteners to warp the throttle bores. Virtually any fastener on the carb/manifold seems to be able to do that. I had major problems with mine when I first got the bike and it would come and go - based on heat, I'm sure. Somedays it was OK, other days it was terrible. Much of the time, a mechanic's solution to a leak is to tighten something which is usually counter-productive unless the fastener truly did "unscrew." Of course, that's quite common on a Norton - that's why safety wire and loctite exists. In my experience most leaks between surfaces are caused by poor mating surfaces, not by insufficiently tight fasteners.

To cure the problem I disassembled the carbs completely and trued all pertinent mating surfaces, including the manifolds, with 240 wet or dry sandpaper on a 1/4" glass surface. Virtually every surface was warped. After that was done I tried the slides in the bores. One was free but the other was sticking. I determined where the "out of roundness" was in the carb body and put the body in a padded vise and just slowly tightened the vise a bit, trying to eliminate the oval-ness. I pulled the body and rechecked the slide movement. I did this until the slide would drop freely in the bore. Then I tossed the bodies in boiling water, took them out (gloves!) and tried the slides again. Again, one was very slightly sticking. I repeated the vise thing until the slides dropped freely whether the carbs were cold or hot.

Then I reassembled everything, being very careful about tightening torque. Not in the sense of using a torque wrench but just being sure the fittings were "snug." I realize that's just a feel thing but I don't know how else to describe it. You certainly don't want to crank down on any of the related fasteners. Slide action of the carbs have been buttery smooth ever since.

Saw an article recently on this forum, I think, that was about a tool to make the carb cylinders round. Then, and only then, was one worried about how flat the flanges are.

Yes, I should have mentioned that after the truing of the bores I rechecked the trueness of the mating surfaces. I agree, it would be better to adjust the bores first and THEN true the mating surfaces. If you do it the way I did it, you might have to re surface some mating parts after the bore work. I didn't - they were still true. But doing it bores first eliminates a step. So do it that way.

Thanks for the quick replies. I took the manifold off the head to allow enough room to move the carb to get the top off, maybe over tighten the manifold when putting back on (could this still affect the slide?) I did true all the mating surfaces this winter when rebuilding the carbs, but looks like I might be doing that again... Will start with Pete V's. suggestion and go from there. I think maybe I'll stick with the "if its not broke don't fix it" from now on.

Thanks again,
Trevor

Reaming or polishing will work but IMO, it's not the correct solution. No extra metal is magically added to the carburetor in use so the problem is warpage and the warpage should be corrected. The warped bore is no longer round, it is somewhat oval-shaped. The slide is too tight on part of its circumference, but is too loose 90 degrees from that point. If you ream/polish, you are removing metal from the tight part of the oval but you are not addressing the excessive clearance present in the wide part of the oval.

Hi Mike,

Thanks for your advice. I did spend a couple of hours last night with the body in a clamp and got the slide moving freely again, and everything back together. Still can't believe tightening the manifold to the head could warp the body (seems too far away) but guess it can, won't do that again.

Hopefully everything works as well as it did before I started fixing.

Thanks again
Trevor