ET: Engine (Twin) Engine Intermittent Cutting Out of One Cylinder

[Rob H]

Following on from the previous thread of the rear carb overflowing out of the bottom have now got the bike back on the road but has a problem of intermittently going onto one cylinder for short periods on time. The problem seems to be the worst when just pottering round on low throttle openings. When steady cruising down the motorway at 60 - 70 does not cut out. Tick over is also fine.

My initial thoughts that this is a fueling issue and maybe one of the carbs (probably the rear) is flooding from time to time and causing an over rich mixture and flooding the cylinder?

Anyone had a similar problem? any advice welcome as it is not a pleasure to ride at the moment

 

[Bill Thomas]

Does it chime back in or do you have to change plugs, What plugs do you use. Cheers Bill.

 

[Rob H]

Does it chime back in or do you have to change plugs, What plugs do you use. Cheers Bill.

It chimes back in after a couple of seconds, sometimes almost immediately. Plugs are Bosch W7CC.

Interesting pulled both plugs, the rear is a nice light brown colour and the front is dark, the opposite of what I expected

 

[Bill Thomas]

Might be worth a try running with both petrol taps open.
What ignition do you use. Cheers Bill.

 

[Rob H]

Ignition is coil, tested flow at the taps, have good flow, use brass stop cocks, no problem at high speed cruising even with one open fills the float chamber in about 2-3 secs

 

[Bill Thomas]

Just thought that if the back float was a bit sticky, A bigger head of petrol might do it.
Some time ago I started opening both taps for starting, I didn't think the back one was filling as it should.
Never did like the way the fuel lines went. Cheers Bill.

 

[Garth Robinson]

Just thought that if the back float was a bit sticky, A bigger head of petrol might do it.
Some time ago I started opening both taps for starting, I didn't think the back one was filling as it should.
Never did like the way the fuel lines went. Cheers Bill.

I had an intermittent misfire on the rear cylinder on my first Vin. that I couldn't track down,changed plugs,cleaned carbs etc.,no luck.I had the mag. checked,still no luck.Eventually I found that the exhaust valve guide had come loose and was moving in the head.It had almost worn the flange off the lower guide.

 

[Rob H]

I had an intermittent misfire on the rear cylinder on my first Vin. that I couldn't track down,changed plugs,cleaned carbs etc.,no luck.I had the mag. checked,still no luck.Eventually I found that the exhaust valve guide had come loose and was moving in the head.It had almost worn the flange off the lower guide.

Hope that is not the case, that is what the bike was off the road in the first place for!!!!!!!!!!!!!
http://www.vincentownersclub.co.uk/...l-in-exhaust-valve-inspection-cap.8270/page-4

 

[Bill Thomas]

It might be a tight valve to guide, Stopping the valve from seating, If so, it may get better after some more miles, Did you fit one with the oil seal, I have never used or seen one. Cheers Bill.

 

[Bill Thomas]

Could be just a tight tappet !!, That would be a nice fix. Cheers Bill.