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[Exile]

If anyone remembers me posting about rejettting my carby and changing my air filter for the sporty S&B conical job, you will maybe remember me complaining that the carby was jumping around and my fix was to make a bracket to hold the thing in a stable position. That worked. Since then though, I haven't been too impressed with the way Thumper has been running and ticking over. I decided to set the tickover today and sort out what appeared to be a rich mixture. The plug being covered in soot, I supposed it was running rich.

I fiddled with air and throttle stop, I sweated with it actually, having no good tickover, spitbacks, cut-outs and no appreciable difference, no matter what I did. In desperation, I thought maybe I should take the carby out and have a look-see.


No need. Look what I found between the carby and the manifold, and don't ask why I didn't spot it when I last had the carby off. Although, that bit of rubber has been standing for 8 years and maybe the unsupported carby ripped it on my road trial, which is why I heard the carby jumping around in the first place. Anyone else ever had this happen?

[Gwilly]

Very common. In fact it will happen to every one if they keep the bike for more than a few years…

There is a mod whereby some use a car radiator hose cut to length, just a bit thicker, more support..

Cheap enough though, just change every 4 years regardless...

[Gwilly]

I know, lets blame the efin efinol…

[PeteF]

They all do that Sir!

[Paul M H]

Mine done the same I replaced it with this one below been on there fivee years no problems yet.-------------
This hose replaces the inlet hose, part 143143, that was fitted on 1997 and later 500cc Bullets. It is less prone to perishing than the original.
PART No. DESCRIPTION PRICE
AM/2622/123 RUBBER MANIFOLD, CARBURETTER TO HEAD £8.50

[Exile]

Ok gentlemen, thanks for letting me know that this is common. I shall sleep easier and will be off to get new parts, one way or the other, on Monday.
I have a bike shop just down the road and failing that, I know our hosts have the part.

It doesn't explain how the engine would appear to be running rich though. I would have thought lean, being that the engine is getting a load of extra air through the break.


Or have I, as usual, totally missed the point..?

[Midge]

I said sometime back about replacing it with an Amal connector which would have also solved the support problem. Oh well,some just have to learn the hard way - http://www.hitchcocksmotorcycles.com/vi ... orumorder=

[PeteF]

You're quite right Exile, it would be running weak with the leak.
Did you perhaps re-jet when the carb was loose, then fit your bracket which closed the leak up?

[Gwilly]

I wonder which came first the bigger jet or the split, You may have sized the jet not realising the extra air being drawn through the split and then temporarily closed the split by fixing a bracket hense too rich.. Be interesting to see what happens when you fit the new hose… i suppose its also possible, just. That I may be overthinking the problem…. ha ha best o luck.

[Gwilly]

Pete i don't believe it, Two great thinkers… I've got to get a life..