Starting problem revisited

[crickleymal]

So the starting problem reoccurred today. I've had the valve clearances done and new carb inlet rubbers fitted. The symptoms are, it will start fine out of the garage in the morning. Then on subsequent starts it will fire and idle then over the next 20 seconds the revs will fall away and even blipping the throttle won't save it. It then takes up to half an hour to get restarted. Oddly enough when I try to restart it I have most success with no choke but blipping the throttle.

My car mechanic suggested water in the float bowls but I drained them this morning and they're ok. I took out a spark plug and it was dry.

Help please!

[Gnasher]

Sounds like carb icing to me.


Check the heater system these are the small black pipes running between the carb bodies, the most common issue is the little metal elbows that the pipe fits onto these are on the carb body.  The problem here is not maintaining the anti freeze to the correct mixture and/or owners/previous owners using cheap or no anti freeze which causes corrosion is the system, which over time starts to be suspended in the coolant and the elbows being small and at almost a right angles block.


Remember it's doesn't have to be freezing to get icing just cold and very damp just like what we've had of late.
       

[darrsi]

Are your tank breather pipes hanging down properly and not kinked at all?

[crickleymal]

Sounds like carb icing to me.


Check the heater system these are the small black pipes running between the carb bodies, the most common issue is the little metal elbows that the pipe fits onto these are on the carb body.  The problem here is not maintaining the anti freeze to the correct mixture and/or owners/previous owners using cheap or no anti freeze which causes corrosion is the system, which over time starts to be suspended in the coolant and the elbows being small and at almost a right angles block.


Remember it's doesn't have to be freezing to get icing just cold and very damp just like what we've had of late.
     

Carb icing after having sat all day at above freezing then ices up in two seconds of running? I could understand that if it happened whilst riding but not at start up. It also happened yesterday. Started bike to check oil level. Stopped bike and left it for about 10 minutes whilst I got kitted up. Went to start it and it fired up then ran for 20 seconds and died. I drained the carbs, no water there. Pulled no. one plug, no sign of dampness or petrol smell and a good spark. Whilst I was testing for a spark the engine started running happily on 3 cylinders. So plug back in and off we go.

Drained the fuel tank today just in case. No water there either. Tanks breathers ok and even if they weren't I tried undoing the petrol cap but that made no difference.

[celticdog]

Oddly enough when I try to restart it I have most success with no choke but blipping the throttle.

Have a look at the choke cable, it might need adjusting/replacing.

[crickleymal]

Ok I'll check it. It does appear to work although if the engine's been started it just seems to act as a fast idle.

[darrsi]

I'm clutching at straws a bit here but it happened to my bike so worth eliminating it anyway.
A few years back i had a carb problem and when the mechanic put them back on the bike the second carb rubber had folded in on itself causing a small air leak, so whenever i tried overtaking or just using more throttle the bike would just bog down.
Took the bike back a few times but they couldn't find the problem    so i ended up taking it to PDQ and he came into the waiting room with my carbs in his hand showing me what the issue was.
Because it was the second one in there was no way you could see it whilst fitted on the bike.
Worth a check, you never know!

[crickleymal]

I'll have a look but as this is a new set of rubbers and the old ones did just the same.......

[crickleymal]

Took it to work yesterday and it was fine. Although I did use the choke both times I started it. Maybe the carb and tank drain has done the trick.... There that's put the mockers on it.