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An Amal just being an Amal! #366329
04/03/11 2:07 am
04/03/11 2:07 am
Joined: Sep 2006
Posts: 609
Mexico City, Mexico
MexicoMike Offline OP
BritBike Forum member
MexicoMike  Offline OP
BritBike Forum member

Joined: Sep 2006
Posts: 609
Mexico City, Mexico
A few days ago I went up to the bike and, for no particular reason, twisted the throttle to WOT and let it snap shut. The "snap" sounded odd. I then opened the throttle again and noticed considerably less resistance to opening until about 3/4 open.

Yep, left carb slide stuck at about the 3/4 position when closing.

Now this surprised me considerably because I am extremely careful and precise about rebuilding my Amals. I ensure surfaces are true and am very careful of the torque in re-assembling. I had redone the carbs a few months ago and they were perfect. There was no slide sticking on a short ride just a couple of days prior.

But sitting in the garage the slide stuck. I loosened the outer carb-to-manifold screw just enough to barely see it move and the slide snapped back to full closed.

This would indicate that the nut was too tight originally and had warped the body. BUT, per AMAL instructions, I don't tighten those nuts at all - I just turn them down until the mating surfaces just touch - allowing the o-ring to do the job it is there to do.

So I have to admit I'm a bit mystified on this one since there was never any real tightening torque applied that could warp anything. Plus the fact that the carb slide showed no hesitation whatsoever when out riding nor did it stick when just rotating the throttle on the non running engine at any other time up to that day.

Can't really decide if I should do anything or just leave things as they are with that one nut backed off a tiny bit. You can see a slight gap between the carb/manifold surface; It's running just fine...


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Re: An Amal just being an Amal! [Re: MexicoMike] #366357
04/03/11 6:33 am
04/03/11 6:33 am
Joined: Oct 2007
Posts: 1,253
Nanaimo, B.C. Canada
W
Wilfred Online content
BritBike Forum member
Wilfred  Online Content
BritBike Forum member
W

Joined: Oct 2007
Posts: 1,253
Nanaimo, B.C. Canada
Mike. I had my 930 bored and sleeved years ago and was very careful about tightening. Came back to my bike one day when it was parked and someone had been playing with the twistgrip and the throttle was stuck wide open. Got it down and rode home with my hand ready to shut off the ignition but no problem. Took it off and carefully eased off the high spots on the sleeved slide and now it's gone 28,000 miles with no more trouble. I suspect that the vibration might have prevented it from sticking while riding but I wasn't keen to rely on that hence the careful high spot removal. Carb is still great due partly, I'm sure, to the air cleaner and most miles are road.

I sometimes wonder if I shouldn't buy a new one when this one is worn out, have it sleeved before I even put it on the bike and then have an unwarped instrument with a new brass sleeved slide. Might last forever...Cheers, Wilf.

Last edited by Wilfred; 04/03/11 6:34 am.

"It's about the ride..."
Re: An Amal just being an Amal! [Re: MexicoMike] #366394
04/03/11 1:48 pm
04/03/11 1:48 pm
Joined: Sep 2006
Posts: 609
Mexico City, Mexico
MexicoMike Offline OP
BritBike Forum member
MexicoMike  Offline OP
BritBike Forum member

Joined: Sep 2006
Posts: 609
Mexico City, Mexico
When I got the bike, the cabs had been sleeved by the PO but they were a disaster. Bodies/all mating surfaces warped from overtightening, etc. Sticking slides even with springs that had been stretched by the PO to 1/3 more than correct length.

So I carefully went through everything, including adjusting the bodies to true them up with the slides and all pertinent new parts/surfacing/drilling tapping for new body screws (old ones partially stripped).

So, as I said, I was a bit surprised at this. I think I will pull them again and re check every thing. One possibility is that I did not use any loctite on the the carb-to-manifold nuts and perhaps there was some loosening from vibration though I would think that loosening would not cause any binding. Can't imagine that vibration could tighten the nuts! wink

Re: An Amal just being an Amal! [Re: MexicoMike] #366594
04/04/11 3:49 pm
04/04/11 3:49 pm
Joined: Feb 2004
Posts: 86
the wilderness
old-grizz Offline
BritBike Forum member
old-grizz  Offline
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Joined: Feb 2004
Posts: 86
the wilderness
Mike - there is probably Doctoral Thesis material aplenty here - think of the possibilities: positive earth, Whitworth/BSC fasteners . . . perhaps "Loctite" becomes "Loostite" when applied to British machinery??

Over the years, I have had throttle cables break (no power) and carb slides stick (too much power!!), but always made it home on the Amals. I praise their simplicity. The only lesson I've learned is that old adage of helicopter pilots: if nothing has gone wrong yet, it soon will.

We must love it, or we wouldn't be so addicted to these maddening devices.

--OG

Re: An Amal just being an Amal! [Re: MexicoMike] #366612
04/04/11 5:52 pm
04/04/11 5:52 pm
Joined: Mar 2005
Posts: 10,218
Boston, Massachusetts
J
John Healy Offline
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John Healy  Offline
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J

Joined: Mar 2005
Posts: 10,218
Boston, Massachusetts
I have no clue what the people who sleeve Amals are doing these days, but in the past they had some idea that AMAL didn't know what they were doing when they supplied the body with .0035 plus clearance for the slide. I have seen them with slide clearances near .001".

There is very good reason they used .0035 plus clearance (several deaths where the carburetor was over tightened. One right here in Boston) and the SLOW SPEED JETTING WAS ADJUSTED BASED UPON THIS CLEARANCE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Despite what some think, the guys at IMI AMAL were not stupid. The first Concentrics were supplied with less than .002" and they knew exactly what they were doing when they changed the specification. I imagine that it didn't cross their minds when they originally specified .002" clearance that any one would over tighten the carb enough to bend it. Well as it turns out they do!!!!!!!

For this instrument to work with standard parts, and not distort from a BIT of over tightening, you need the .0035 plus clearance!!!!!!!!!! And yes, there is some air that leaks around the slide BUT THE WEAKER MIXTURE IS COMPENSATED FOR in the manufacture of the related parts. When you tighten the clearance up you increase teh chances the slide will stick and screw up the low speed jetting - making it rich.

When the carburetor manifold flange is bent SO IS THE BODY. You cannot bend the the flange without bending the body! Rubbing the flange on some sand paper does nothing to straighten the body!!! You just have a flat flange and a warped body. Without straightening the body the slide will still be prone to sticking. Sanding out the distortion in the body just PREMATURELY WEARS OUT a perfectly good carburetor.

The bike should never be operated with a slide that sticks!! If the slide does stick one can easily regain control of the motorcycle by pulling in the clutch. Once the bike is back under your control (not accelerating at will) you can search for the kill button or ignition switch.

Last edited by John Healy; 04/04/11 6:04 pm.

Re: An Amal just being an Amal! [Re: MexicoMike] #366627
04/04/11 7:31 pm
04/04/11 7:31 pm
Joined: Sep 2006
Posts: 609
Mexico City, Mexico
MexicoMike Offline OP
BritBike Forum member
MexicoMike  Offline OP
BritBike Forum member

Joined: Sep 2006
Posts: 609
Mexico City, Mexico
Good explanation - I have come to the conclusion that sleeving may CAUSE a serious problem while it fixes a minor annoyance.

When I got the bike and it was clear that the carbs were a mess, the first thing I did was to disassemble and then drop the slides into the bodies. Both sleeved slides would stick without the benefit of the stretched springs to force them closed.

So I worked the bodies in a vice to attempt to "true" the roundness by applying pressure as necessary to restore the bodies to "round." I worked them that way until the slides would drop easily and with no resistance. Then I trued all the mating surfaces.

So again, I'm a bit surprised here because everything was perfectly round/true and suddenly it seems not to be. I'm going to pull the carbs tomorrow and again closely re-examine the bodies with the slides to see if they will drop completely by gravity in each direction.

But as you noted, there is almost no clearance between the sleeved slide and body so any slight change in torque - or even ambient - temp seems as if it can cause the slide to stick.

Re: An Amal just being an Amal! [Re: MexicoMike] #366707
04/05/11 6:35 am
04/05/11 6:35 am
Joined: Mar 2008
Posts: 338
Lower Rhine Area, Germany
Towner Offline
BritBike Forum member
Towner  Offline
BritBike Forum member

Joined: Mar 2008
Posts: 338
Lower Rhine Area, Germany
Hi,

I am not sure about the benefits of resleeving. If you add the costs of the work and new jets and needles, it is not cheap and new Amals are not very expensive. So I would buy new ones. But as long as the slides do not stick and idle can be adjusted there is no need to think about it.

Ralf


Triumph Bonneville 650 T120RV 1972
Norton Commando 850 MKII 1973
Re: An Amal just being an Amal! [Re: MexicoMike] #366825
04/05/11 9:54 pm
04/05/11 9:54 pm
Joined: Sep 2006
Posts: 609
Mexico City, Mexico
MexicoMike Offline OP
BritBike Forum member
MexicoMike  Offline OP
BritBike Forum member

Joined: Sep 2006
Posts: 609
Mexico City, Mexico
I pulled both carbs today. Both (sleeved) slides were quite sticky in the bores. I could not get a sliver of an .001 feeler gauge between the slide/bore in either of them.

So I worked on them both for several hours with wet/dry paper wrapped around a piece of hose so that it was a snug fit and worked it up/down/rotating - sort of like valve grinding. I started with 240 paper and ended up with 1500. The bare slides in both carbs will now fall open/closed by inverting the body. I then reattached the manifolds to the carbs, checking the slides again after tightening the nuts. I did the same with the float bowls.

So now I am comfortable that the carbs are as good as I can make them and there is actually some clearance between the slide/bores.

Re: An Amal just being an Amal! [Re: MexicoMike] #366835
04/05/11 10:47 pm
04/05/11 10:47 pm
Joined: Feb 2004
Posts: 86
the wilderness
old-grizz Offline
BritBike Forum member
old-grizz  Offline
BritBike Forum member

Joined: Feb 2004
Posts: 86
the wilderness
Try THAT hose and abrasive repair on the roadside with the electronic fuel injection unit on your 2010 Yamasaki Red Wing. The new zoot is nice, and pretty reliable, but when the electrons quit workin', there ain't a lot you can do. I still enjoy the venerable troubleshooting mantra - fuel, air, spark . . . it should run. Everything else is just "details and tuning".

Glad you got 'em fixed, Mike. Time now for a road trip to some languid sea-side resort with muchisimas cervesas. Bebes una para mi.

-O.G. . . . sitting in the snow in the frozen north, still. Basta, already. It's springtime. Somewhere . . .

Re: An Amal just being an Amal! [Re: MexicoMike] #367035
04/07/11 8:17 am
04/07/11 8:17 am
Joined: Apr 2002
Posts: 710
Out There!
N
Nick Offline
BritBike Forum member
Nick  Offline
BritBike Forum member
N

Joined: Apr 2002
Posts: 710
Out There!
Entered my not-a-Norton Brit-bike in an indoor car show. The room was air-conditioned and when I took the bike out to ride it home, one of my sleeved Amals was stuck. As soon as it warmed up, though, no more problems, and none since.

The pot metal must be very heat sensitive.



When people who should have known better cautioned me about the dangers of motorcycle racing, I always told them that a fear of death is nothing more than a fear of life in disguise.
Re: An Amal just being an Amal! [Re: Nick] #367047
04/07/11 1:00 pm
04/07/11 1:00 pm
Joined: Sep 2006
Posts: 609
Mexico City, Mexico
MexicoMike Offline OP
BritBike Forum member
MexicoMike  Offline OP
BritBike Forum member

Joined: Sep 2006
Posts: 609
Mexico City, Mexico
"The pot metal must be very heat sensitive."

But less so than aluminum - I suspect, as John pointed out, there was insufficient clearance provided by whoever sleeved them.


Moderated by  Dave Comeau 

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