Spray tube gone AWOL!

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SteveBorland

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I was going through the carbs tonight to try to track down a mysterious problem - bike was running very lean, getting awfully hot and bothered, ran very badly over 3000 or so and would not clear by revving.
I suspected an air leak and checked the manifolds and balance tube, no sign of anything there. Tried lifting the needles, and during a test run, the RH cylinder was now very rich.
Turns out that the RH carb has lost it's spray tube somehow - just clean gone!
Now, assuming that I can ignore the possibility of an evil Tokoloshe (or sprite for non-African readers :)), how the hell can a spray tube come loose? Presumably it's gone through the engine, which now means I have to have a look inside (do a compression check first).

This set of carbs has a rather neat pair of velocity stacks attached, with the gap between the stack and the carb inlet filled with (I think) epoxy, so I would like to keep them. I'll be looking through my stash of carb bodies to see if I have one with a stepped spray tube.

Always something new from this bike!!!
 
SteveBorland said:
I was going through the carbs tonight to try to track down a mysterious problem - bike was running very lean, getting awfully hot and bothered, ran very badly over 3000 or so and would not clear by revving.
I suspected an air leak and checked the manifolds and balance tube, no sign of anything there. Tried lifting the needles, and during a test run, the RH cylinder was now very rich.
Turns out that the RH carb has lost it's spray tube somehow - just clean gone!
Now, assuming that I can ignore the possibility of an evil Tokoloshe (or sprite for non-African readers :)), how the hell can a spray tube come loose? Presumably it's gone through the engine, which now means I have to have a look inside (do a compression check first).

This set of carbs has a rather neat pair of velocity stacks attached, with the gap between the stack and the carb inlet filled with (I think) epoxy, so I would like to keep them. I'll be looking through my stash of carb bodies to see if I have one with a stepped spray tube.

Always something new from this bike!!!
Click to expand...
They are pressed in, but bigger question - how did it get past the needle that was in the needle jet? And, it's way too big to get past an open valve so I would look in the intake. If it were chewed to pieces by the valve the valve should not have survived it!
 
Good point Greg. The bike is up at the summerhouse, so I'll be able to have a look this weekend.
Thinking about it though, I did have the slides out to change the needle position, and also had the carbs off. It's possible that the spray tube simply fell out on the ground.
Hmm.
 
SteveBorland said:
Good point Greg. The bike is up at the summerhouse, so I'll be able to have a look this weekend.
Thinking about it though, I did have the slides out to change the needle position, and also had the carbs off. It's possible that the spray tube simply fell out on the ground.
Hmm.
Click to expand...
Hopefully so and it would make much more sense! The only other way I can see is of the jet holder unscrewed and the needle was then free. But then the bike should not run between 1/4 and 3/4 throttle or if it did it would be running much more terrible than you described. Generally, the spray bar is difficult to get out so the whole thing is WEIRD :)
 
Never a problem with a spray tube pressed in falling out . Problem in my younger poorer days with a fractured slide from wear , going through the engine and spitted out . No damage .
 
Twenty five years ago, I had an exhaust valve seat break up on my ford 302 with 351 big valve heads. The cylinder was totally unharmed and the broken pieces somehow went harmlessly outward with the flow of the exhaust. The only way I knew something was wrong was the weakness of the engine due to the loss of one cylinder's contribution to the output. It was mind boggling to look at the heads when I took them off and the exhaust valve was encrusted in carbon goo, but the piston and cylinder were unmarked. The engine builder rebuilt both my heads, I bolted them on and that engine is still going strong.....
 
I had to make a spray tube..the slash cut one...because the old spray tube would not fit into the premier, it was too small on the O.D.
 
Do you have a history of them running well?

If these carbs have had epoxied on stacks etc, are you sure they’ve not been bored out (which would necessitate removal of the tubes) ?
 
I've had to take the spray tubes out on a few occasions
They don't give up easily in my experience
 
Fast Eddie said:
Do you have a history of them running well?

If these carbs have had epoxied on stacks etc, are you sure they’ve not been bored out (which would necessitate removal of the tubes) ?
Click to expand...
Yes, they have been on the bike since 2017 or so - I fitted them before taking the Norton to the Spa trackdays, where they worked quite well. The rest of the bike was another story though :-)

I don't think that have been bored, the manifold end is 32mm.
Don't think I have a carb body with the 850 spray tube, so I may need to switch to the "normal" type and change the needles to suit.

Alternatively, I do have a pair of Premier carbs under the bench, but they are 30mm, and I was planning on flogging them off to a 750 owner, so I'm a bit reluctant to fit them - I would need to rig up some form of filter as well.
 
The mystery has been (partially) solved!
Looking at the carb in daylight reveals that the spray tube was sitting down around the jet holder.
I heated the carb body with a hot air gun
and carefully tapped it back in place with an alloy drift and a hammer. A bit of loctite and it’s secure.
I think…

While it’s far better than it having gone through the engine (!!), I’m still wondering how it came loose in the first place.

Anyway, it’s sorted for the moment, but I found it has no 4 slides, so I’ll be getting a pair of 3.5s. Probably try the Wassel copies, the genuine Amal ones are rather expensive.

Many thanks to everyone who chimed in, and of course, thinking logically I should have immediately suspected this, but for some reason I thought it was pressed in through the top.
 
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