Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board Mikuni back to Amal for my A65?

Yes, I failed to mention that. I did use compressed air to blow out the Berryman's (after rinsing in water). I did not use compressed air after spraying with the carb cleaner, but I will this time.

It seems I will want to blow into the air mixture screw hole (as opposed to the fuel pickup hole), so as not to just blow the sh*t back into the pilot jet. I may want to first poke out the pilot jet again.

Went back at the carbs today - WD-40, compressed air, then carb cleaner, compressed air. Covered holes as required.

I think the carbs are good to go now; carb cleaner squirts freely out all the right orifices, blew them out one more time. I'm at least confident enough to put them back together and do a test run.

I might mention that these carbs were not grungy. I took them off a running bike and drained them before putting them on the shelf. They were disassembled, of course, for the trip to Lund's, then bagged, boxed, and stored for the duration.

Question, is it kosher to smear a little grease on the float bowl gaskets? I don't usually put anything on them, but this time I'm reusing gaskets. They're essentially brand new, but they've been removed and reinstalled a couple of times now.

Great news Mark!

I never fit anything to mine. Just dont over tighten them, if they dont tighten sufficiently, consider a new gasket.

I always put the barest smear of grease on these gaskets.
Put a dab of grease on both sides, wipe most of it off with your finger.
Belt and braces I guess--- but i have not had a leak at this point since Adam was a lad.
HTh

With carbs back together and mounted, I started the engine tonight. Same problem, still won't idle. Requires tickling the carbs to restart, every time.

I'm reasonably sure the idle circuits are clear now, so I have a new theory, and that would be that the floats are set too low. The bike actually idles for three or four seconds after letting go of the throttle before it slows down and dies, as if it were running out of fuel. Can low floats produce this symptom?

I've never paid much attention to float level, and I've forgotten the specification. I've also never had to move a float needle seat, and I'm worried about damaging the seat. I'm also wondering how one goes about moving the seat without moving it too far.

(Side note: I've concluded that using stop nuts on the mounting studs is positively masochistic, since you can only get an open-end wrench on them, and only turn them one flat at a time. I went through my parts cache and dug out original nuts, and cleaned the studs to the point where I can spin the nuts on with my fingers.)

If you get a spare float bowl plug you can make a tool with a fitting on the bottom and a piece of clear tubing. Then you can check the actual fuel level. There are many here who could say where that should be.

Check the float bowl mating surfaces are flat, they get bowed easily, this creates an air leak and prevents the uptake of the pilot fuel which has to pass through the gasket/ joint. This gets worse as the fuel level drops.

Mark, you never mentioned what speed you were setting the idle to. Hopefully, not a barely tick-over but 900-1000 RPM.
Will it continue to idle with the choke full or partially on?
The float lever can be changed by using a flat nose punch and tapping the seat up or down in the bowl.
The gasket has to have a good seal around the diagonally drilled hole in the bowl which feeds fuel to the idle circuit as Gavin mentioned.

The float bowl and carburetor mating surfaces appear to be clean and in very good condition, and the gaskets are new, except for the few times I've removed the float bowls as part of this exercise. On this last assembly, the gaskets received a very thin smear of grease.

DM, I had the idle speed set abnormally high in an effort to keep the engine running. No chokes, and the holes for the choke cables are plugged with screws. After last night's session, I thought about trying to flood the carbs while it was running, but this is rather difficult to do, especially on both carbs at the same time, before the engine dies. I may still try that before taking them apart again.

I didn't initially check float levels because these carbs worked ok on the T140 I took them from, except for the fact that the slides and upper tubes were worn, which was subsequently addressed by Lund's Machine. I may have changed shut-off needles, changing from plastic to Viton-tipped metal. Anyway, I'll check them out. I just remembered, I have the factory documentation that came with the NEW carbs for the T140, and another pamphlet on tuning AMAL Concentrics.

I was under the impression that you have to heat the float bowl before trying to move the shut-off needle seat. Not true?

You’re in a bad way if the float seat moves without warming up the bowl. I find the new bowls are virtually impossible to move the seat.

Does it idle when the engine is warm? I would check that before pulling the carbs again.
Heating the bowl makes moving the seat easier. The punch should be the largest that will fit with a smooth flat face.

Or, you just slap the heated float bowl gasket face down hard on a flat steel surface, like a drill press table. Wear gloves of course, and do it a few times until the seat moves out a little. Check your float level quickly while it is still hot and tap the seat back in if needed to fine tune the level. I've done it that way for years.

No, won't idle when warm. I ran it long enough under throttle to get it warm, even took it for a short ride.

I'm thinking of just dropping the float bowls off this time without dismounting the carbs.

Would you recommend a torch or an oven to heat the bowls? If I use an oven, to what temperature should I set it?

Slightly off tangent, a few years ago a fellow Beesa owner with a lathe re sleeved his Concentric carbs, closing the slide fit down to 0.0015" from the stock AMAL 0.0035+", result, bike wouldnt start, he borrowed a pair of old carbs from me, bike started fine with worn out slidesand bodies.
I have never needed to mess with float levels in 50 years of playing around with AMAL carbs, be extra sure you need to play with the float level before making any movements..

Interesting. FWIW, at the time of the rebuild, John Healy warned me about the clearance issue. Lund's assured me that they work to the .0035+ spec, but I did not measure afterward, ignoring another bit of John's advice: "Trust but verify."


Will do.

Although I had never before adjusted float levels, apparently I had measured them, because I found this gauge that I had made and almost forgot I had.

Both floats were set high, like right up to the top of the bowl. This is not what I expected to find, for what appears to be a fuel starvation problem, so this might not be the source of my problem, but I decided to set them according to the published spec, .080" from the top of the bowl.

The seats move amazingly easily once you heat the bowls. In fact it's about impossible not to move the seat too far up, but then you can flip the bowl over and tap the seat back down, where you can see what's going on. Pictured is the 1/8" diameter punch I made to move the seat up, and a bigger punch to tap the seat back down.

No test run yet, maybe tomorrow.

Not sure where it was but some one had made a screw tool for setting the float heights
Simply an old banjo bolt drilled & tapped lengthwise then threaded with a fine thread so you can push it a specific amount up without over shooting

I've never needed to adjust the float height on any of the AMAL's I've used over the years, however if you feel its needed there is some good advise on the AMAL website Here and also on the classic British Spares site Here.

The adjustment of fuel height is made by gently bending the tang on the float.

Both of these websites suggest attaching a plastic tube to the bottom of the float bowl and then measuring the fuel height against the top of the float bowl.and then a you need to make a spigot to attach to the bottom of the float bowl, so a bit of fiddling and improvisation is needed.

An alternative method is to mark the correct float height inside the bowl and check the float height against this, which is probably an easier method.

Since it looks doubtful that the float levels are my problem, I decided to take another look at the needles and needle jets.
The needle jet I'm using now is the one in the holder, short .106. (The longer jet is displayed for comparison.) The needle I'm using is the one with the clip on it. It has two rings, and as you can see, it is longer than the other (3-ring) needle shown. Spray tube has flat top.

The needle jet on the left is either Monoblock (most likely) or Mk2 Concentric, both I beleive are longer than the Mk1. The 2 stroke and 4 stroke mk1 Concentric jets are similar on first apperance. there are other subtle differences when you compare them hand in hand.

the 3 ringed needle is a 900 series 2 stroke needle.

you will likely find the stright portion of the needle is a similar length, the pointed portion is more severe on the 2t needle. giving a richer condition sooner in the 1/2-3/4 throttle position.

you might also find this of interest:Tuning the Mk1 concentric by amalcarb.co.uk

Allan, I should have asked my question more directly. The question is, does it look like what I'm using (the needle jet that's in the holder and the needle with the clip on it) is correct, that is, compatible? Perhaps it's not possible to tell from the photo; you said the differences between the 2 stroke and 4 stroke jets are "subtle". These needle jets came with the carbs from a 1976 T140; is that a help? In regard to the needles, am I good with 2 rings, or are there different needs with two rings? Does "2t" mean two rings? If I can't identify what I have, I'll just order up jets and needles and be done with it.

In the meantime, I'll peruse that article, thanks,

Here's an interesting statement in the "tuning AMAL MK1 carburetors" article:

"If your float chamber is fitted with a brass needle valve you may find the valve sealing under its own weight before the float has risen far enough to press it shut. Symptoms of this problem can be that the carburetter takes a long time to tickle, hesitates on pickup, and does not idle reliably. A Viton-tipped aluminium needle valve is now available that overcomes this problem. It is being fitted as standard equipment to all new Mark 1 Concentric carburetters."

Hmm, I have Viton-tipped BRASS shut-off needles. I also have a number of plastic shut-off needles on hand; perhaps I should try those.

Alan, it looks like the article answers my questions. 2 rings does it for the needles. I'm off to the garage to check the jet holders and measure the needle jets.

This all leads to my suggestion of checking the fuel level in carbs

I'll look into doing that this weekend. I have to wait for the aluminum shut-off needles that I ordered tonight anyway.

I also received another tip tonight, from Mark Appleby at British Cycle Supply: The only thing holding the float pivot in its groove is the float bowl gasket. It's a common remedy to make a small punch in the bowl casting next to the groove, which keeps the pivot from lifting out of the groove, and also keeps the pivot from rotating.

BTW, I've verified that my needle jets and needles are the correct ones, and the needle jets are in new condition (although this is tangential to the idling problem).