Spray tubes and needles

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maylar

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I have 2 pair of Amal concentrics available:

932 R300 (right side) with flat top spray tubes
932 35 & 36 with cutaway spray tubes.

I know the cutaway types use long needles, but should the flat top spray tubes be used with the short needles or can they use either? And would one or the other be more suitable for a 74 850 with standard airbox and peashooters?

Both sets are in very good condition and I have a selection of needles to choose from.

Thanks
 

L.A.B.

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maylar said:
I know the cutaway types use long needles, but should the flat top spray tubes be used with the short needles or can they use either?

Generally needles with the 2 ID markings (2 rings above the grooves) would be used with flat topped spray tubes.


The 932 35 & 36 were the carb types with cutaway spray tubes used on the 850 MKIII models which had the plastic airbox and black cap/bean can silencers.

However as soon as you change any of the jets, needle or throttle slide number etc. then they effectively cease to be type "35" or "36", as the code numbers refer to the original build specification of the carbs, and the spray tubes should also be removeable, so the 932 300 carb bodies (300 is just a generic 932 body number) are identical (apart from being machined as either left or right handed units) to the 932 35 & 36, but with different jetting/spray tube/cutaway installed in them.

maylar said:
And would one or the other be more suitable for a 74 850 with standard airbox and peashooters?

Presumably you mean standard '74 MkII (metal) airbox, rather than '74 MkIIA standard (plastic) airbox? So with a standard metal airbox and peashooters you would probably be better off trying the flat top spray tubes with 2 ID needles, in my opinion.
 

maylar

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Thanks LAB. I'm currently using the flat top spray tubes with long needles and the clip in the middle. Low throttle and upper end are good but there seems to be a flat spot in the midrange. I think I'll drop some short 2-ID needles in them and see if it gets better.
 

L.A.B.

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This is how my 850 MkIII (big valve head) carbs are set up for peashooters and custom filters.

Main jets = 220
Needles 2-ID (2nd. groove)
Needle jets .106
3 slide cutaways
Flat top spray tubes.
Float heights set .040" from gasket face.
 

maylar

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220's seem small for an 850. I've had 260's since the bike was new.

I experimented with carbs about 30 years ago. Put 34 mm Mikuni's on it and sold the Amals to a local guy. I couldn't dial the Miks in right (inexperience on my part) and bought a new set of Amals from my Norton dealer. Those are the 932 R300's that I still have, resleeved 10 years ago.

The workshop manual says needle clip in the top groove for an 850 (manual is from 73?) with 3-1/2 slides and 260 mains. I'm thinking that's the setup I should be using.
 
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