850 facts needed

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Onder

Onder

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850 1974. Are the specs for the amals based on bean cans or peashooters?
Mine is a Mk2 and I believe it came with peashooters but no way to be sure.
Now it has non crossover pipes with AN straight through (ie loud) silencers
but I have mutes in. With the 750 Norton wanted one size smaller main jet
with mutes.
Since the bike is running well this is the perfect time to go and fiddle with it.
Probably raise the needle one notch and see if I notice an improvement.
Idle hands are the devils playthings. Not to mention the Sin of Too Much Free Time!
 
Mk2 I believe had peashooters, 2A had beancans.

If it is running well, you have the perfect basis to experiment.

ONE CHANGE AT A TIME ONLY!!!!!!

That way, you will know if it helps or hurts.

Without a dyno, you will have to do several tests such as a 1/4 mile blast, highway run, 35-50mph roll-on, 50-70mph roll-on, etc.

Do your baseline runs FIRST!

One needle change might help in one area, but may affect you negatively in another.

Certainly raising the needle will lower your overall fuel mileage...
 
One thing I noticed is that it does seem to run, plug colour wise, a bit lean . Naturally most of my riding isnt at full throttle more in the quarter to
half having geared up recently.
 
Your temping fate if its running good leave it alone if its not broke, but then sometimes we just can't help it lol.

Ashley
 
Well of course lifting the needle and if necessary returning it is cost free and just a lot of fiddling.
 
Onder said:
850 1974. Are the specs for the amals based on bean cans or peashooters?
Click to expand...

The original carb specs (and carb numbers) for Mk2 and Mk2A are different.


Onder said:
Mine is a Mk2 and I believe it came with peashooters but no way to be sure.
Click to expand...

There are certain givaways that can help to identify a Mk2 from a Mk2A even though the original exhaust system and air filter may have been removed long ago. For instance, the 2A battery tray (battery fits across the frame) the battery side cover with Dzus fastener at the lower rear, and oil junction block are unlikely to have been changed. Also 'A' kickstart lever, however, it's common to see those fitted on other models.
A US model is more likely to have been a Mk2.
 
My 850 MK2A with peashooters runs 260 mains which is the same as the MK2 but I still have the plastic airbox, it came with 230's for the black caps but the peashooters had been fitted but did not run well at full throttle until the 260's were fitted. The balance pipe deletion I did later made no difference carb settings.
 
car-bu-re-tor, noun, A device used in internal-combustion engines to produce an explosive mixture of vaporized fuel and air.
Origin: French word meaning "leave it alone"!
lol
 
kommando said:
My 850 MK2A with peashooters runs 260 mains which is the same as the MK2 but I still have the plastic airbox, it came with 230's for the black caps but the peashooters had been fitted but did not run well at full throttle until the 260's were fitted. The balance pipe deletion I did later made no difference carb settings.
Click to expand...

According to Amal, for 1974 there were 3 carb sets for 4 850 configurations and the only difference was the main jet. All used needle position 3, a 106 needle jet, and a 3-1/2 cutaway slide.

73-74 MK1A 230 Main, Marked 31 & 32
73-Early 74 MK2 260 Main, Reverse Cone, Marked 29 & 30
Late 74 MK2 260 Main, Marked 35 & 36
73-74 MK2A 230 Main, Black Caps, Marked 31 & 32

In very late 74, I believe that all 850s were MK 2A including those sold in the US.
 
marshg246 said:
73-74 MK2A 230 Main, Black Caps, Marked 31 & 32
Click to expand...

(932)/33 & /34 for Mk2A according to the Mk2/2A supplement which I think is correct.
/33 & /34 had 220 mains according to the official Amal Norton list.
 
L.A.B. said:
(932)/33 & /34 for Mk2A according to the Mk2/2A supplement which I think is correct.
/33 & /34 had 220 mains according to the official Amal Norton list.
Click to expand...
Interesting, according to Amal, 33 & 34 are for 1975 and had 230 main jets and needle position 2 - I'll check with them to see if they have any updated info. Maybe you could PM those lists to me so I can talk with some authority to Amal. I do think that have a mistake in their list since it doesn't show a MK III and has 33 & 34 as 1975 MK 2A.
 
The old Amal carb 'pack' list for Commando models had a few errors.

According to my factory Amal list sent to me by Burlen, the original (Wolverhampton) factory order date for the /33 & /34 spec. was 10/73 under part numbers 065749 (/34) & 065750 (/33) the part numbers also match the 2/2A supplement for the Mk2A. I will send you a copy of the list.

/33 & /34* are also listed in the Mk3 parts book (and where the main jet size is given as "220").

(Mk3 parts book says "/33 & /24" which I believe to be a typo)

According to the Amal website:

http://amalcarb.co.uk/cf/vehicle/list/?manufacturer=Norton&vehicle=Commando+Mk.+2A

"Norton Commando Mk. 2A 850cc 1974 onwards 932/33, 932/34"

And for Mk3:

http://amalcarb.co.uk/cf/vehicle/list/?manufacturer=Norton&vehicle=Commando+MK+III
"Norton Commando MK III 850cc 1974 onwards 932/42, 932/43"

/42 & /43 are also on my list (order date 5/74) with "200" main jets but I don't remember anyone mention having /42 and /43 carbs on their Mk3?

Do any of our Mk3 owning members have original carbs marked 932/42 or 932/43?


 
Here are the Carburetor Settings from page 5 of the Norton 850 MK 2/2A Riders Manual (p/n 065321). This is the only Norton published documentation that I could find about the carburetor settings for the MK 2/2A's. Andover Norton sells reprints of this Riders Manual however, they say it is for a Mk IA and Mk 2A but this is really for the MK 2/2A.


850 facts needed


Peter Joe
 
Mk2A says 'needle in lower notch', Mk2 says 'middle'.
So if the needle is lower is that not richer than middle
as it drops down into the jet hole more?
Seems like it would be backwards for the application?
 
Could be effect of smaller mains on the 2A, it should only effect 3/4 to full throttle but there could be enough of an overlap that the needle needs raising.
 
Onder said:
Mk2A says 'needle in lower notch', Mk2 says 'middle'.
Click to expand...

Depends how you read it?

Onder said:
So if the needle is lower is that not richer than middle as it drops down into the jet hole more?
Click to expand...

Lowering the needle (by fitting the clip in a higher groove) weakens the mixture. However other sources say needle position '3' (richest) for Mk2 and '2' for Mk2A.
 
I think it is mis-worded.

In my opinion it should read “needle clip in lower notch”

As in, needle raised giving a richer mixture.
 
gtiller said:
I think it is mis-worded.

In my opinion it should read “needle clip in lower notch”

As in, needle raised giving a richer mixture.
Click to expand...


That would be moving the needle in the wrong direction according to Amal's spec. which has the Mk2A needle lower (2) than Mk2 (3). '1' being leanest and '3', richest.

http://amalcarb.co.uk/

Full Set Part Number: ACK138
Description: N/A
Make: Norton
Model: Commando Mk. 2
Engine Size: 850cc
Carb Type: 900 Series MK I
Year: 1974 onwards
Number of Carbs: 2
Needle Position: 3
Internal Bore: 32mm


Full Set Part Number: ACK113
Description: N/A
Make: Norton
Model: Commando Mk. 2A
Engine Size: 850cc
Carb Type: 900 Series MK I
Year: 1974 onwards
Number of Carbs: 2
Needle Position: 2
Internal Bore: 32mm
 
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