Twin Amal 376 Chopped Monobloc Carburetters connecting fuel line / tube. Norton 650SS

Hi:

I have a 1962 Norton 650ss I am in the process of making roadworthy / reversing a number of bodges made by a previous owner. It is equipped with what I believe are the correct Amal twin monobloc carburetters, (386/289 and 376/288).

My question concerns how to connect the two banjo's at the bottom, that allow fuel to flow from the left hand carb, that has a functioning float chamber, to the right one that does not, (i.e. the "chopped" one). I apologize if this is a stupid question, but it appears to need an unusually thin walled fuel line for a direct connection to work. The reason being that a normal thickness fuel line appears to be too fat, leaving no room between it and the bottom of the right hand carb chopped float chamber. Is there a particular type of (presumably thinner) tube (rated for fuel / ethanol) for the job? Or should the connecting pipe just be routed via a more indirect path. Perhaps in a loop to either front or rear?

Many Thanks,

Kind Regards,

James

Hi James, Regular fuel line will fit. Because there is not much distance between the two banjos, getting the fuel line to fit is fiddely and probably easier if you loosen and rotate one of the banjos and then move it back to face its mate. The old brit bike magazines (Motorcycle Mechanics?) Recommended looping the connecting fuel line rearward and this does make it easier to remove and reapply. However if you loop the fuel line the stock air filter won't fit. DAMHIK. Based on ancient recollection, in the home market few people ran filters. I hope the attached photos are useful.

Hi Bodger:

Thank you for your comments and pictures, very helpful! Your setup is similar to some others I have found. It's just that the 3/8" fuel tubing I have encountered so far seems to be a bit more chunky. I shall do the rounds of a few more parts stores, maybe try 5/16". Have also seem some pictures with some form of clear plastic pipe. Not sure what it is, or what it is made of, maybe it's for a marine application or lawn mower fuel hose? Your comments regarding the stock air filter are very helpful. I was planning to fit one, when / if I can get her running right.

Cheers,

James

Thank you Bodger. Looks like some 5/16" line I found is a tight but workable fit, (much less chunky than the 3/8").

I think my problem is solved.

One step closer to getting her back on the road! :<)

I think the gas line is 1/4, maybe 5/16 but I think 1/4. I think the oil lines are 5/16. The 650SS is a great bike. Not too many in the US. The importer, Berliner, brought in the predecessor, the 650cc Manxman, but I think as soon as Berliner convinced Norton to make the Atlas they stopped importing 650cc bikes. So I think most 650SS were brought in as private imports. The later bikes had points and coils but most bikes have magnetos. Most problems with the bikes now are related to the magneto. If the magneto has never been rebuilt it's nearly impossible for the condenser to be any good. The symptom of a bad condenser is a bike that starts pretty easy but runs like crap once fully warmed up. Then after it cools down the bike runs ok again.

The banjos that connect the two carbs, (at least in my case) measure 3/8", (not including the band at the ends). The carbs were recently purchased brand new from Burlen, so I assume they are correct, that and they are the same size as the old carbs I am replacing. Certainly seems odd that they have that large a bore. I have not yet measured the diameter of the pipe fittings from the petcock to the left carb, but I'm pretty sure it is smaller, like you say 1/4" sounds about right. Thank you, I will bear that in mind. She is indeed equipped with a magneto. First startup since full engine rebuild is rapidly approaching. Do not know if the magneto has ever been rebuilt, I was just chuffed that it actually produces a spark - we shall see!

I used a heat gun to form the fuel line (stock ethanol proof from Burlen) into an arc of about 45 degrees, then rotated the banjos rearward to meet the fuel line arc. In this way, I created clearance for an elongated throttle stop screw that makes carb idle adjustment easier.



Without heat, the fuel line is likely to kink.

Slick

Agree with Bodger ... if the magneto has never been serviced, it is highly unlikely to have a good capacitor. The capacitor is internal to the magneto body, and is not a DIY replacement for the average Nortoneer.

FWIW .... just because the magneto produces a spark when the spark plug is grounded to the head or other grounded part, does not guarantee it will fire a plug under compression.

Keep us posted, we will deal with the magneto should it become necessary.

Slick

Thank you slick! The bike has clearly had a lot done to it before it came to me. Some good, some absolutely abysmal. Hopefully the mag will fall into the former category. The mag appears to be a K2FC, (red label). Do not know if this was standard on the 650SS, although clearly at least some of them were equipped as such, I would certainly want to get it rebuilt, rather than replaced - if necessary. Regardless, you and bodger have given me something important to watch out for. Knowledge gained on this forum has been invaluable!

I have two new Monoblocs on my N15 and they are connected by a rear facing loop.

Britstuff said:

Thank you slick! The bike has clearly had a lot done to it before it came to me. Some good, some absolutely abysmal. Hopefully the mag will fall into the former category. The mag appears to be a K2FC, (red label). Do not know if this was standard on the 650SS, although clearly at least some of them were equipped as such, I would certainly want to get it rebuilt, rather than replaced - if necessary. Regardless, you and bodger have given me something important to watch out for. Knowledge gained on this forum has been invaluable!

Click to expand...

I believe the K2F Competition mag was standard on the 650SS. Hang on to it, there'll worth more than the bike when it was new.