Rubber Carbies. ?

An odd thing happened the other day.
Odd things are happening a bit lately.??
Went out to the shed to start the bike, as I always do, pryor to a ride, and Ed didn't want to start.
After two or three kicks, if nothing happens I generally tickle again, usually works.
Anyway, nothing. Could smell a hint of petrol, so whipped the plugs out and found one very wet.
Umm, what's going on. Cleaned it up, kicked it over a few times, put it back, kick, kick, kick, nothing.
Noticed that the throttle felt very light. Whipped the filter off, and found that one slide was stuck up.
Now I'm not in the habit of opening the throttle wide open to start the bike but this slide was right up.
Why was it stuck.
Removed the top of the carb, and actually had trouble pushing the slide down.
It was hard to get out, and would not go back in.
Me no understand, everything was good when I put Ed away from the last ride.
I cleaned the slide and the inside of the carb, it was a little better, however I noticed that, the slide
would move more freely if the screws weren't done up tight.
OK so the screws are pulling the carb out of shape.?? Remembering these are on top of the carb.
I fiddled for a while but could not get the slide to drop in nicely.
Alrighty then.... Carb off, well not right off, as I undid the first flange nut, 1/4 of a turn, the slide dropped.
Are you joking. What are these carbs made of, Pot Rubber.
I hadn't touched the mounting bolts or Allen studs for several months, and they are by no means super tight.
In order for the slide to work properly, I had to leave the nut only just tight, not much more than finger tight. Loctited.
Right, are we assuming that the carbs are now wearing more rapidly since they were sleeved.?? Dunno.
They have probably done about 400 miles since sleeveing.
Anyway... Jumped on, first kick, away he went, and away I went for another great ride.
I know it's an old story, but it is so sad that someone couldn't come up with a better metal (at the time), than that which
was used on these carbs, as the carbs themselves aren't that bad.
Hurry up Jim, get those new ones over here.
AC.

Infamous Amal carb body warping from slight overtightening of the 2 mounting points.

grandpaul said:

Infamous Amal carb body warping from slight overtightening of the 2 mounting points.

Click to expand...

Often caused by the wrong size O ring x-section, slightly too fat.

Cash

Unfortunately when sleeving the carbs, the bodies must be bored. This worsens the tendency for the bore to distort when the flange is tightened. The propensity for the slide to stick exacerbated by the fact that sleeved carbs generally have a tighter clearances as well.
When Mike Gaylord was the go-to guy for sleeving, he started the process by straightening the carb flange on a jig that pulled the bore and flange back to right angles before boring. I don't know if Lund or any of the other guys do this.

Yes I know about the situation of over tightening, but these are certainly not tight.
And they had been fine for several months.
Thanks for your thoughts guys, I just thought I'd put it up there for all to read, and
it might help those new to the game understand that the carbs really are, or can be, very sensitive.
AC.

I haven't experienced the issue of tight slides. But then my carbies are probably so worn it doesn't happen. Plan is to get a pair of anodized slides and see if that helps with the idle droop with throttle advancing.

Bike came in yesterday for the winter, it was 52F (11C) but everything was muddy.

Dave
69S

The way I got it was to tighten the carb to manifold lock nuts back and forth until the carb body just stopped being able to be moved relative to the manifold then back off a 1/16 turn, or so, until the carb body would just respond to force and move a tad. The set-up includes a dose of Vasoline, or grease on the "O" ring and corresponding surfaces to add to the seal and to the movement; this has worked for me for decades...

RS

Ron L said:

Unfortunately when sleeving the carbs, the bodies must be bored. This worsens the tendency for the bore to distort when the flange is tightened. The propensity for the slide to stick exacerbated by the fact that sleeved carbs generally have a tighter clearances as well.
When Mike Gaylord was the go-to guy for sleeving, he started the process by straightening the carb flange on a jig that pulled the bore and flange back to right angles before boring. I don't know if Lund or any of the other guys do this.

Click to expand...

Mike did mine in 1998. 30,000 miles later they have never been anything but silky smooth.

I never cared for o rings. I junked mine in favor of a real gasket and just a hind of smear. Now I don't wonder if they are up too tight or the o ring has perished or is leaking.

RoadScholar said:

The way I got it was to tighten the carb to manifold lock nuts back and forth until the carb body just stopped being able to be moved relative to the manifold then back off a 1/16 turn, or so, until the carb body would just respond to force and move a tad. The set-up includes a dose of Vasoline, or grease on the "O" ring and corresponding surfaces to add to the seal and to the movement; this has worked for me for decades...

RS

Click to expand...

I start the bike with the nuts fingertight, spray the joint with carb cleaner while tightening the nuts and when the smoking stops they are tight enough, this is how I was taught.
Almost EVERY Amal I have ever tried is too tight!

Vince

Hi,
I'll second Aceaceca's method of just using a gasket and a little smear of silicon, leave the "O"ring out.

GB

The original Lunds shop would true the flange face in the sleeving process, I would assume the new owner does so as well. "Package deal"