Advice on Amal settings for ‘74 850 please

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kn0ck4times

kn0ck4times

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Finally got around to pulling down my 850 amals to see how the previous owner had set them up. The carbs only have a couple hundred miles on them and look very clean but were installed in 2014ish I believe. The bike has ham can and unbalanced peashooters. Here’s what I found:
Amal 932
R300, L301
220 Main jet
106 Needle
.017 pilot jet
3 slide
Middle needle ring
Straight spray tube
Any help would be appreciated being Ive never set up a carb before. Normally I just change all fuel and electronic changes from my phone.
 
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My 850 has 3.5 slides I have seen as high as 260 main jets in 850's If you PM Greg Marsh he can tell you factory specs from the carb number
 
baz said:
What are you trying to achieve?
Click to expand...
Just looking for appropriate starting point. I’ve only put 30 miles on the bike since I bought it. Was able to ride it but throttle was always hesitant to accelerate and slow for idle to come down. Throttle cables were free and slides were balanced well.
 
220 Main jet is dangerously low in an 850 with peashooters, Maylar's 260 is the same as my 74 with peashooters.

R300, L301 are generic Amals, your pilots should be 19's if premier, stepped spray tube with matching needle, slide 3.5.
 
Here are a few pics of parts in case I’m identifying something wrong. Like I said don’t really know carbs. Also what does brass screw on side of carb do?
 

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kn0ck4times said:
Finally got around to pulling down my 850 amals to see how the previous owner had set them up. The carbs only have a couple hundred miles on them and look very clean but were installed in 2014ish I believe. The bike has ham can and unbalanced peashooters. Here’s what I found:
Amal 932
R300, L301
220 Main jet
106 Needle
.016 fixed pilot( I guess)
3 slide
Middle needle ring
Straight spray tube
Any help would be appreciated being Ive never set up a carb before. Normally I just change all fuel and electronic changes from my phone.
Click to expand...
300/301 are generic carbs not meant for 850 Commandos. Would work fine for 750 Combat. You can get them to work on an 850, but not quite as well as those meant for them.

You should have Norton-specific spray bar, Norton-specific needle. 106 Needle Jet. 3-1/2 Slide. Probably a 260 Main Jet.

From what you said, this is probably the correct set: https://www.gregmarsh.com/MC/Norton/AmalDetail.aspx?key=9
 
kn0ck4times said:
Also what does brass screw on side of carb do?
Click to expand...
The brass screw is the Premier pilot jet.

The 622/104 124 2-ID ring needles and 622/074 flat top spray tubes will work but aren't the original specification 928/104 4-ID needles and 928/107 stepped spray tubes.

932/300 and /301 work fine on my 850 Mk3 Commando with 2-ID needles, flat top spray tubes and 3.0 slides.
 
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marshg246 said:
300/301 are generic carbs not meant for 850 Commandos. Would work fine for 750 Combat. You can get them to work on an 850, but not quite as well as those meant for them.

You should have Norton-specific spray bar, Norton-specific needle. 106 Needle Jet. 3-1/2 Slide. Probably a 260 Main Jet.

From what you said, this is probably the correct set: https://www.gregmarsh.com/MC/Norton/AmalDetail.aspx?key=9
Click to expand...
What size pilot jet should I have? Apparently that was the brass screw previously asked about. Do not see any markings or numbers on it.
L.A.B. said:
The brass screw is the Premier pilot jet.

The 622/104 124 2-ID ring needles and 622/074 flat top spray tubes will work but aren't the original specification 928/104 4-ID needles and 928/107 stepped spray tubes.
Click to expand...
any way to identify the pilot jet? Can the spray tubes be changed out?
 

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So if I try to fix these carbs this is how I would proceed??
Main 220 >>>>>>>>Main 260
Needle 106 >>>>>>>Needle 106
Pilot 17 >>>>>>>>>>Pilot???
Slide 3 >>>>>>>>>>>Slide 3 1/2
Spray tube straight >>Spray tube Norton
>>>928/104 ring needle
 
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kn0ck4times said:
Main 220 >>>>>>>>Main 260
Click to expand...

It probably needs to increase to (about) 260 (for peashooters).

kn0ck4times said:
Needle 106 >>>>>>>Needle 106
Click to expand...

(Needle jet) Ok,

kn0ck4times said:
Pilot 17 >>>>>>>>>>Pilot???
Click to expand...

Possibly 19 (3-ring), however, some 850s seem to run ok on 17s which were the original 850 932 specification Premier pilot jets.


kn0ck4times said:
Slide 3 >>>>>>>>>>>Slide 3 1/2
Spray tube straight >>Spray tube Norton
Click to expand...

And 928/104 4-ID ring needles if changing to stepped spray tubes, however, I have found the generic 300/301 settings (2-ID needles, flat topped-spray tubes and 3.0 slides) to work perfectly well and only the main jets (generic 220s) need to be enlarged.
 
L.A.B. said:
It probably needs to increase to (about) 260 (for peashooters).



Ok,



Possibly 19 (3-ring), however, some 850s seem to run ok on 17s which were the original 850 932 specification Premier pilot jets.




And 928/104 4-ID ring needles if changing to stepped spray tubes, however, I have found the generic 300/301 settings (2-ID needles, flat topped-spray tubes and 3.0 slides) to work perfectly well and only the main jets (generic 220s) need to be enlarged.
Click to expand...
So in your opinion Les would you just start with the main jets at 260 and leave everything else as is and give it a try or completely overhaul?? Starts getting expensive when eventually I will probably put a mikuni on it.
 
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kn0ck4times said:
So in your opinion Les would you just start with the main jets at 260 and leave everything else as is and give it a try or completely overhaul??
Starts getting expensive when eventually I will probably put a making on it.
Click to expand...

Personally (as other members may have different opinions) I suggest you try changing just the main jets (to 260?) and see how it goes.

Maybe also change the pilots to 19s if the pilot screws need to be set less than 1 turn out.

 
If I'm understanding the comments, they are the wrong carbs for the 850. Why not just buy a pair of the proper (might as well get Premiers) carbs?
 
Ok I’m going to try 260 main and 19 pilot , 2-ID needles, flat topped-spray tubes and 3.0 slides first and see what happens. Just wanting to get these acceptable for now. Will probably put a mikuni on when the budget allows.
 
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MexicoMike said:
If I'm understanding the comments, they are the wrong carbs for the 850. Why not just buy a pair of the proper (might as well get Premiers) carbs?
Click to expand...
He already has Premier carbs, so definitely worth trying to sort them out !
 
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