Amal Mk 1 replacing pilot jet

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Corona850

I have recurring idling problems, and have read that is is possible to drill out the pressed-in pilot jet and replace it with a screw in jet (inside the bowl). The carb already has the threads to accept a screw-in jet.

Has anyone done this? Is it a viable option?

I understand that the pressed-in jet came into being to solve erratic idling on Triumph Daytonas, and then became the design standard for four-stroke carbs. Originally, the carb was supposed to have the jet screwed in accessible from the bowl. Will a Norton 850 fucntion OK with the jet location modified?
 
I believe the accepted method is to remove the plug (without damaging the pilot jet) and insure the jet is clear. I believe you can then replace the plugged end with a removable grub screw to facilitate future cleaning.

Being familiar with the pilot jets on the two-stroke Amals I find them to be much more sane.
 
Swooshdave: Thanks. I am familiar with the idea of drilling out at the back of the carb to provide access to the pilot jet. The trouble is, the access is in-board, so with two carbs you'd have to take the carbs off the bike to be able to remove the balnking screw to get access to the pilot jet. I am hoping that the option of adding the pilot jet in the manner of thetwo-stroke design is viable. Then cleaning or clearing the jet can be done by just dropping the float bowls and not requiring removal of the carbs, air cleaner, etc.
 
Corona850 said:
and have read that is is possible to drill out the pressed-in pilot jet and replace it with a screw in jet (inside the bowl).
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Where did you read this from. I believe, in theory, it should work. It may take a little work to get the screw in pilot jet the right size. But they are readily available from the two-stroke folks.

I'm seriously tempted to do this mod, so I'm paying careful attention.
 
In a recent post on Brit Bike forum John Healy recommended not to go to the screw in pilot jet on a 4 stroke, it is too far from the exit point into the venturi and spoils the bike, especially on a Triumph 500 twin. Amal had to come up with the fixed pilot for 4 strokes after releasing the Concentic with 100% screw in pilots and getting a lot of bad feedback. Screw in are still supplied for 2 strokes.

I have no experience of screw in pilots just passing on what JH said.

To clean my pilots I glue a #78 drill into a WD40 can tube and go in from the adjuster side which is facing outwards, seems to work but knowing when you have got to the full depth is difficult the first time, marking the tube at this point makes it easy from then on.
 
swooshdave said:
Corona850 said:
and have read that is is possible to drill out the pressed-in pilot jet and replace it with a screw in jet (inside the bowl).
Click to expand...
Where did you read this from ...
Click to expand...

I read it somewhere online, but I'm damned if I can find it again! The article referred to some old desert-sled tuners (from the McQueen-Ekins days) who did something like this, i.e. eliminate the pilot-jet bushing and replace it with a screw in one.

Actually, when I got my bike (an ebay special) it had carbs like this. I've still got the bodies, with the screw in pilot jets. The carbs had supposedly been re-sleeved. But they were clapped out anyway. Couldn't get the bike to start, idle or run right. So, I bought two new Amals (from Norvil). It was around that time that I read the article, when I was researching options. I wanted to keep the bike more or less stock, so I didn't go with Mikuni.

The Amals I bought from Norvil do not have the stepped spray tube, but they do have the pressed in pilot-jet. My old, clapped-out Amals do have the stepped spray tube, but have screw in pilot jets, similar to the picture in LAB/s post.

So, it seems like there are a lot of ways to run an Amal. For the reasons I said above, I'd like to figure a way to easily access and clean the pilot jet. Mine seem to plug a lot. I drain the carbs and all that, but they still seem to problematic. Maybe it's So. Cal. gas.
 
A lot of folks with Goldwings run Stabil and a bit of Marvel Mystery oil all the time. In my spare Goldwing I run Stabil all the time and I add it for winter in my every day driver as some rainy seasons can keep me off the bike for two or three weeks.
In the future with the crummy gas now it may save you some trouble.
 
kommando said:
In a recent post on Brit Bike forum John Healy recommended not to go to the screw in pilot jet on a 4 stroke, it is too far from the exit point into the venturi and spoils the bike, especially on a Triumph 500 twin. Amal had to come up with the fixed pilot for 4 strokes after releasing the Concentic with 100% screw in pilots and getting a lot of bad feedback. Screw in are still supplied for 2 strokes.

I have no experience of screw in pilots just passing on what JH said.
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I wonder if the 500s don't have enough suction compared to a 750 or 850. When Amal moved to the fixed pilot it was a long time before the big bore bikes came out.

Amal Mk 1 replacing pilot jet

If you look here the gas goes into the same place as the screwed in pilot jet. It's just a matter of where the gas gets restricted. Theoretically...
 
Hi Gang:
My 68 commando has a screwed in pilot in the bottom.It works fine.I run in line filters on all my bikes and stock them for anyone I sleeve carbs for if they need them.I usually use a .016" drill epoxied into a tube you get with wd 40 can to check for clearing before I send them out. They seem to get calcified from sitting in the passage.I know amal claims putting the mixture closer to the air flow works better,but I have taken out the pilots for customers and moved to a fixed screw in jet. They seem ok on commandos.
Bruce
 
Bruce: - Thanks for the response. That's the answer I was hoping for. What is the best way to remove the pressed in pilot jet? Drill it out (what size drill works)? Or could I tap into it and yank it out? How is it best done without buggering up the carb body?

I have been using Stabil and copious amounts of carb-cleaning fuel additive (STP and the like), but I am not convinced that it's any good. I have resisted in-line filters because I didn't like the look of them, but I am sucumbing to practicality over aesthetics. I noticed some specks of crud when I drained the carbs yesterday. They were very, very small, but it doesn't take much to block a 0.016" orifice. What filters do you use/sell? I generally like K&N filters for oil, air, etc. but their m/c fuel filter looks a bit mickey-mouse to me.
 
You need not remove it. Just drill it out with a .032 drill bit. Than use the old set up location works good on BSA's and Norton's. You sometimes have to do this if the bushing gets damaged by a hack. .016 drill bits once a yer work wonders.
 
bchessell said:
Hi Gang:
My 68 commando has a screwed in pilot in the bottom.It works fine.I run in line filters on all my bikes and stock them for anyone I sleeve carbs for if they need them.I usually use a .016" drill epoxied into a tube you get with wd 40 can to check for clearing before I send them out. They seem to get calcified from sitting in the passage.I know amal claims putting the mixture closer to the air flow works better,but I have taken out the pilots for customers and moved to a fixed screw in jet. They seem ok on commandos.
Bruce
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What size pilots do you use? What size carbs? 930s? 932s?
 
Hi:
Norbsa is right.It was norbsa who originally told me about mounting the drill in the tube. If you want to and you have the carbs off you can drill the plug out of the opposite side with a #21 drill,used to tap 10-32, and either drill like greg said or tap out the pilot jet altogether .I use a 1/8 drill to rmove it.After tapping use an air mixture screw or height adj screw shortened to 1/4" to blank it off. You can leave the o ring on to seal.That way you know it is clear. I think it is a #25 pilot on the 750.There is also a #30,but you will have to check.I am away from the shop right now so I don't have that info.I can check when I get back tomorrow and repost.
It seems the problem of the pilot jet put so far away caused a drop in the venturi,so they moved it closer. My 68 originally had it screwed in and it has always worked fine.They show up at my door in both forms.
Bruce
 
I would agree with Bruce - It is essential to have in line fuel filters fitted to your bike.
All of the carb experts that I have corresponded with over the years say that if you are riding a classic bike you should :-

1. Ensure that the petrol tank is either free from rust and other debris or cleaned and sealed with a tank sealant.
2. Ensure that the petrol tap filters are intact and working.
3. Fit in line fuel filters in addition to the petcock filters.
4. If you lay the bike up for any length of time you should drain the carbs of fuel - for overwintering some people even advocate draining the carbs and removing them from the bike and dry storing them.

Regardless of what modifications you make to the Amal MK1 if you don't at least fit in line fuel filters to your bike you will always have problems. I routinely fit either paper element or plastic screen fuel filters to all of my classic bikes and since I have been using them I have had no problems with pilot jet blockages. There are a variety of filters available so you should be able to find one that looks right for your bike.

Regards

Andy KG
 
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