3 times recently, the following has happened.

Start up and set off in the morning, get between 5-8 miles and the engine cuts out in 5th/6th.
Pull over, get into neutral. Lights are on and strong. Engine starts up nicely with a strong spark, and I continue on to work. In the afternoon, ride back absolutely fine.

My first thoughts are problems with fuel/air supply, but I have checked the following and everything looks fine:
breather hose and connection, fuel line and vacuum tap, air filter and air box. Carb intakes look clean as a whistle.
The only thing is some greasiness around the inner edge of the air box housing.

As a note, I am running 33bhp washers and probably err on the side of under-choking in the morning rather than over-choking.

Any thoughts on the cut-out.

Have you checked the vacuum hose?

uber pikey wrote:Have you checked the vacuum hose?

On the left-hand side of the airbox? If so, yes.

No... on the right hand side of the bike, attached to the fuel tap and the engine....

CMSMJ1 wrote:No... on the right hand side of the bike, attached to the fuel tap and the engine....

Ok, that one!

The end I can see looks fine, fits snugly on the tap. Obviously can't see the other end of it without yanking off the carbs.

well run the motor and you can feel it pulsing as it sucks...if it does not suck

If it does, is it on the right spigot?

Saying that, when this is warm it works OK? just not from cold? 25 quid dyno run would see if your jetting is out due to the 33bhp

Man_Named_Dave wrote:

CMSMJ1 wrote:No... on the right hand side of the bike, attached to the fuel tap and the engine....

Ok, that one!

The end I can see looks fine, fits snugly on the tap. Obviously can't see the other end of it without yanking off the carbs.

The best way to find out if it's faulty is to just replace it.

Rick Oliver sells thick walled tube that won't collapse, doesn't cost much.

I think you can replace it without taking the carbs off, can't quite remember. Anyone?

Cammo wrote:

Man_Named_Dave wrote:

CMSMJ1 wrote:No... on the right hand side of the bike, attached to the fuel tap and the engine....

Ok, that one!

The end I can see looks fine, fits snugly on the tap. Obviously can't see the other end of it without yanking off the carbs.

The best way to find out if it's faulty is to just replace it.

Rick Oliver sells thick walled tube that won't collapse, doesn't cost much.

I think you can replace it without taking the carbs off, can't quite remember. Anyone?

Aye, you can...but small hands and dexterity required. If you are a farmer you have no chance..

CMSMJ1 wrote:well run the motor and you can feel it pulsing as it sucks...if it does not suck
Hard to say on the pulsing; if I'm looking for it, I'd probably convince myself it was there.
If it does, is it on the right spigot?
It's on the spigot as per the Haynes manual: large tube on the appropriate horizontal spigot, and the smaller tube on the other horizontal one. Nothing at all on the vertical spigot.

Saying that, when this is warm it works OK? just not from cold? 25 quid dyno run would see if your jetting is out due to the 33bhp

Didn't happen either morning or evening today. I warmed up for a full 5 minutes with a bit extra choke, kept it in 4th gear and 6-7k revs. I'm still not convinced it's ok, so I'll have a look at the weekend.

As per the jetting, it's set to Cammo's guides and 110s all round. Do you think I may need to adjust the pilot screws?

you can feel the pulsing on the vac tube easy. replace it mate, it is only £7 or something..

they do split with age and also perish and collapse. worth eliminating it from your enquiries