Something else might be worth a look, check the breather non-return valve on top of the tank. They can stick. Unscrew it and blow and suck to make sure its opening and closing. Give it a dab of WD40.
This happened to me with the same symptoms.

Hello Big Dave

Did You fix the problem???

I too am in the same situation. I think my the HRC set up is fouling my plugs, therefore I'm reverting back to stock petcock..I just need to find where the vacuum hose connect from the petcock to the cylinder.

Cheers and Good Luck

rvf2010 wrote:Hello Big Dave

Did You fix the problem???

I too am in the same situation. I think my the HRC set up is fouling my plugs, therefore I'm reverting back to stock petcock..I just need to find where the vacuum hose connect from the petcock to the cylinder.

Cheers and Good Luck

The hose connects at cylinder 3 - you can see a little spigot if you take the panels off and get looking. It can be a beeyatch to get the hose on with carbs installed...so you'll be better to whip them off.


The HRC mod for the fuelling is a bad idea for anything other than very well fettled race bikes that don't carry 12litres of fuel around and get parked up with the fuel leaning on the carbs..