Commando 75 Mk 3 Wont idle

worntorn said:
I'll have to be the odd one out , as usual.
My stock MK3 will run very nicely right from cold startup as long as the chokes are on. It will idle smoothly and pull away easily with chokes on. It will rev high enough to accelerate reasonably thru the gears, maybe to about 3500 rpm in each gear. Above that it sputters because the chokes are on.
A mile or so down the road I pull the chokes off and it runs fine thereafter.
Old original Amals.
Not quite like a new efi engine but not far off.

Glen
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You are not odd. That is my experience with ALL properly tuned Amal carbs, even in Texas which is not often cold. Really, tickling is all we need for 3/4 of the year; enricher slides for cool/cold weather. A GOOD SQUIRT on the ticklers
 
Thx for all the feedback does anyone know if Mk3 carbs are different from standard 850 I am running a 230 main jet and the pilot jet says 17 but I have seen other info that the pilot jet should be 19 I am not running the chokes as I have never needed them in any other 850 maybe I need them in the MK3 I am about to reinstall them Thx Drummer 99 I cant let go of the throttle to make any adjustments even after it has warmed up
 
Drummer99 said:
does anyone know if Mk3 carbs are different from standard 850 I am running a 230 main jet
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Depends on what you mean by "standard 850". The correct Mk3 carbs are 932/33 and 932/34 however 230 main jets would suit the original black cap silencers. If peashooters are fitted then you are likely to need 260 main jets.

Drummer99 said:
pilot jet says 17 but I have seen other info that the pilot jet should be 19
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19 pilot jets would probably be better and that's what Amal fit now so how come yours have 17 pilots. Were these carbs built up by a parts supplier from generic units (932/300 and 932/301)?

According to Amal the 850 Mk3 had 932/43 and 932/44 carbs but that's incorrect.
 
I purchased 3 years ago from reputable supplier they are new but not premier carbs Box says
832/36 pilot RJ17 main 260 put in 230 main jets
 
Drummer99 said:
I purchased 3 years ago from reputable supplier they are new but not premier carbs
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If they have removable pilot jets then they should be Premiers unless you mean a pilot jet in the float bowl (which they wouldn't normally have).

Drummer99 said:
Box says
832/36
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932/35 and /36? would be 850 Mk2 carbs.

Drummer99 said:
pilot RJ17
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If you bought them 3 years ago, that would explain it, but they should be Premiers.

Drummer99 said:
main 260 put in 230 main jets
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Why, unless it has black cap silencers/mufflers?
 
The pilot jet if non-Premier should be pressed in opposite the pilot air screw (seen in the right-hand picture).
Commando 75 Mk 3 Wont idle
 
Drummer99 said:
I purchased 3 years ago from reputable supplier they are new but not premier carbs Box says
832/36 pilot RJ17 main 260 put in 230 main jets
Click to expand...
If the sticker on the box says that, then they are Premier. Across from the pilot air screw will be a brass pilot jet that screws in. AMAL switched all 850 carbs to #19 pilot jets around three years ago, prior to that they were #17. Your carbs are likely slightly older stock, Zinc alloy, and Premier. If they came as a set of two in a box, then the box should also say PACK xxx and since you say /36 then the xxx should be 138.

The will start, run, and idle with #17 pilot jets. The idle is more reliable with #19 and the starting is a little easier.
 
Another item to check if not mentioned yet...the rubber balance tube between the two manifolds....must be secure to both spigots, not leaking air and not blocked. That will affect idle as it's function is to keep some vacuum pulling on the non-intake stroke carb during idling....helps keep the pilot circuit filled with fuel ready for next intake stroke.
 
Drummer99 said:
Thx for all the feedback does anyone know if Mk3 carbs are different from standard 850 I am running a 230 main jet and the pilot jet says 17 but I have seen other info that the pilot jet should be 19 I am not running the chokes as I have never needed them in any other 850 maybe I need them in the MK3 I am about to reinstall them Thx Drummer 99 I cant let go of the throttle to make any adjustments even after it has warmed up
Click to expand...
Have you tried screwing the idle adjustment screws upwards about a turn each before starting the engine? That should allow it to continue running if you let go of the twistgrip.
 
Ok guys thx for all your help problem solved It always felt to me like it was sucking air and lo and behold when I lifted the tank off the balancing tube was off on the right side Just goes to show when trouble shooting look for the simplest solution first The
tube that came with the carbs was a lose fit so I replaced it Got it idling pretty well still don't like the idle jet adjustment I will take it out for a run and see how it goes Cheers Drummer 99 If I can figure out how to do it I will post a picture
 
Drummer99 said:
Ok guys thx for all your help problem solved It always felt to me like it was sucking air and lo and behold when I lifted the tank off the balancing tube was off on the right side Just goes to show when trouble shooting look for the simplest solution first The
tube that came with the carbs was a lose fit so I replaced it Got it idling pretty well still don't like the idle jet adjustment I will take it out for a run and see how it goes Cheers Drummer 99 If I can figure out how to do it I will post a picture
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I use contact cement.
 
Drummer99 said:
Ok guys thx for all your help problem solved It always felt to me like it was sucking air and lo and behold when I lifted the tank off the balancing tube was off on the right side Just goes to show when trouble shooting look for the simplest solution first The
tube that came with the carbs was a lose fit so I replaced it Got it idling pretty well still don't like the idle jet adjustment I will take it out for a run and see how it goes Cheers Drummer 99 If I can figure out how to do it I will post a picture
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Do I get a gold star next to my name for poiting you to the balance tube?

P.S. For pic posting, as a VIP member, you should find an "Attach Files" button below, left of the text entry box...use tgat to bring up your file browser locate your image or other file and select it. Then you will see an option to display a thumbnail or full image overlaying the attachment thumbnail, in the comment box. Make your choice then save the comment. Should get image displayed in comment box.
 
Tornado said:
Do I get a gold star next to my name for poiting you to the balance tube?

P.S. For pic posting, as a VIP member, you should find an "Attach Files" button below, left of the text entry box...use tgat to bring up your file browser locate your image or other file and select it. Then you will see an option to display a thumbnail or full image overlaying the attachment thumbnail, in the comment box. Make your choice then save the comment. Should get image displayed in comment box.
Click to expand...
Yes you do as soon as I saw your message I pulled the tank and there it was thanks for the info on posting I will give it a try where are you located I'm in Belleville
 
Drummer99 said:
Yes you do as soon as I saw your message I pulled the tank and there it was thanks for the info on posting I will give it a try where are you located I'm in Belleville
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I'm in Vancouver....bit of a hop-skip-jump away from Belleville, Eh?
 
Tornado said:
Do I get a gold star next to my name for poiting you to the balance tube?

P.S. For pic posting, as a VIP member, you should find an "Attach Files" button below, left of the text entry box...use tgat to bring up your file browser locate your image or other file and select it. Then you will see an option to display a thumbnail or full image overlaying the attachment thumbnail, in the comment box. Make your choice then save the comment. Should get image displayed in comment box.
Click to expand...
⭐💥.
 
Drummer99 said:
Ok guys thx for all your help problem solved It always felt to me like it was sucking air and lo and behold when I lifted the tank off the balancing tube was off on the right side Just goes to show when trouble shooting look for the simplest solution first The
tube that came with the carbs was a lose fit so I replaced it Got it idling pretty well still don't like the idle jet adjustment I will take it out for a run and see how it goes Cheers Drummer 99 If I can figure out how to do it I will post a picture
Click to expand...
Btw, for future reference, should be possible to access the balance tube with tank in place. Ive done it several times for connecting my carb balancing guage (a Morgan Carbtune Pro. https://www.carbtune.com/ )
 
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