REPLACING PILOT JET and Throttle Slides

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Jan 18, 2006
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I have a relatively new set of 32mm Amal mk1's, 9 months old. I purchased them from England shipped out to Australia. The right hand carby pilot jet does not adjust correctly only 1/2 turn out and then its too much.

How difficult is it to replace this jet. the screws are ok both are identical.
I was thinking of replacing The jet with one from an old carby i have that used to adjust ok.

I have other problems with these carby's slides sticking when the engine warms up after 15 minutes of riding.
 
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Aug 28, 2005
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dg - The pilot jet is not an adjustable item on the MK1's, but I seem to remember there may be a thread somewhere on this forum that expains how to drill them out and possibly fit a screw-in jet? Don't quote me on that one.
Sticking slides - I've had the same thing with my new MK1's too. Make sure the carb-to-manifold bolts are not done up overtight. This distorts the carb body which is made of a special alloy of tin and cheese, apparently.........
 
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CARBY SLIDES

Have you overcome the sticky slide problem just by slackening the mounting bolts off?
I have removed the slides cleaned & replaced them only to have it jam again after 15min ride. I was thinking of replacing them with chromed or brass slides.
 
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Mar 19, 2005
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Had sort of the same adjustment problem with my new carbs a couple years ago and it turned out one of the pilot jet passages wasn't fully drilled out, when the top cover was off and you looked down the bore where the throttle/slide fits, by comparing the two carbs, there was a difference in the hole that you can see that comes from the pilot jet passage below. Tiny hole that feeds the gas into the intake , just behind the slide so the bike gets fed with gas even when the slide is seated and the throttle is closed. The tiny hole wasn't drilled out fully and partially blocked. I got in from above and, cleaned the hole free and after that, the carb/pilot jet was finally able to be adjusted. Sloppy workmanship to say the least. When they drilled the tiny hole, the drill bit never went all the way through and there was a bulge of excess potmetal instead of a hole.

Suggest you make sure the passages are clear before replacing jets and such, use steel guitar string cutoffs from someone that installs new strings on his guitar, (check with some musical friend) and use the assortment of sizes to remove blockages if found, or with luck, compressed air. If the passages are for sure free, and the o rings and pilot adjusting screws are ok....the adjustment should be possible.. :D
 
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Dec 17, 2005
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Hi there!

The slides on my brandnew Mk I Amals was sticking.The solution in my case, was to add a small amount of 2-strokeoil in the gastank.
Guess what...the sticking is 100% gone!! I belive the materials used in the carbbody and slide, relied on the lubrication provided from leadedgas in its time!!
I started of working on the slides, but never got rid of this problem, until... I added some oil in the fuel...!!

Benton
 
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Jan 18, 2006
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sticky slides

Thanks Benton its good to hear that the problem is 100% fixed.
A friend has suggested i try a fuel injector cleaner additive. I haven't done that yet.
When I check out the slides they are a tighter fit front to back. But are able to be moved easily with the fingers. I will check out all the pilot passages as Hewho suggests then try your suggestion.
 
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Aug 28, 2005
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No, my sticky slide problems have never gone away entirely, the manifold bolts are just the first thing to check. It would seem the new MK1's now available have not benefited from quality or material advances. They are as bad as they ever were, it seems.
Make sure you don't have teflon slides in the carbs - these are the worst at sticking as apparently they "swell" in damp conditions (so I was told by British Spares here in NZ).
My solution: Find out where the slides are sticking by looking for the wear marks on the slide. Get a pair of "Mole Grips" or similar and some cloth. Get the slide in the "stuck" position. Put the Mole grips and cloth around the carb body and gently start to squeeze with the grips at 90 degrees to where you think the "binding" is happening. With a bit of practice, you'll be able to squeeze in the right place so that the slide will drop on its spring. Looks like you'll need to be careful that the cold clearance is still OK if its happening when the carb body heats up. You do have the thick insulating washers between manifold and carb?
 
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Just a thought, but are you running with chokes ?

It always seemed to me that the choke assembly dangling there was a source of friction on the inside of the slide, in addition to what goes on with the body. it also has the tendency to push the slide over which I can't think is a good thing.

I had my original carbs sleeved by Martin Bratby and am chuffed to bits. Everything operates as it should.
 
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resleeved carby's

A few years ago I sent my original amal's away to be resleeved in Melbourne. Seemed to be a waste of money ( must have chosen the wrong workshop)
The Throttle slide has a protrusion that supposed to ride in a groove down the carby barrell to keep the slide facing the right direction. After resleeving this never located the groove deep enough causing snaging and twisting of the slide. Also the idle & mixture screws let air in because the alloy was worn where they screwed in. I expected oversize o rings would fix this but always had trouble after that. So i opted for new carby's 9 months ago. and still having problems of a different nature. I guess thats why people change to mikuni's.
I found a German site that have manufactured square slides and body to replace the amal. a float chamber has to be mounted elsewhere on the frame but at 350 euros each they are a tad expensive.
 
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