OMB Petrol Cut Off Valve

Try running it with the breather pipes disconnected from the carbs!!

 

Also, do you have a pic of how you've got it plumbed in?

 

I'll try that tomorrow and get you some pics. The plumbing is 7.6mm to the OMB valve, 7.6mm to the filter, 7.6mm to the Hardi fuel pump,
5.6mm to the t- piece, 5.6mm to the Weber ICTs.

 

I meant the breather plumbing

 

I used all the original plumbing but replaced all the vent connections with new R9 and then connected both sides to a tee then split them via a tee to both air filters .

 

I'm thinking you should only connect to one of the carbs...

 

I agree with your earlier post and it wouldn't create enough vacuum to cause a problem.
Since the problem started after fitting the cut-off, you'd want to take it off? If that cures it you didn't waste your time. If it doesn't you've crossed something off the list and it's coincidence.

 

Yes, I will remove the valve and see how it goes. All I need now is to buy a fuel hose clamp.

 

It's a strange problem. The only thing I can think of is that somehow your fittings have blocked the breather system.