Fuel Issues

[keig2009]

I am just coming to the end of the resortation of a 1951 Comet which has an interesting history having spent the first 60 plus years in Sweden. The bike has run and been riden for a short while however, it was decided to overhaul the cylinder head, muff and piston to overcome the slight 'blue smoke' issue!! After this work, again, the bike started easliy but stood over the winter waiting for a few bits to be returned from the chromers.

Having fitted these, the tank was drained of old fuel and replaced with new E10 but the bike refused to start. It was noted the HT lead had been in contact with the exhaust pipe nut and was shorting out. The cable was replaced and the bike would start but only run for around 2 seconds. It would then not start until the carb was tickled when it would again run for a very short while.

I assumed this could be a fuel starvation issue but have checked the flow from the tank to the banjo and have and there is no issue. I decided to replace the needle and float in the carb with parts supplied by Burlen. The new needle had two grooves so I decided to set it to the higher setting but the tickler then pushes the float down and the chamber overflows.

The carb has been stripped and cleaned (more thimes than I would like to count!!) and I am sure there are no restrictions in any of the ports (including the very small one in the jet block). The timing has been checked and verified at 4 deg BTC when fully retared and 36 degrees fully advanced. THe magneto was overhauled last year by Peter de Kramer so I am convinced no issues there.

One point to note is that the thread around where the mixing chamber union nut is often quite wet with fuel (despite replacement of the fibre washer 29/050) and fuel is sometimes seen leaking from the nearby vent.

Any thoughts? I was looking forward to enjoying the bike in the good summer weather but am becoming very despondent!! Help please!!

 

[Speedtwin]

Yes the fuel level is to high in the float bowl.
Tickler you will have to shorten the pin so it is not in contact with the float at max height.
The fuel is coming out the over flow.
Things to check.
Have you the slim paper washer bottom of the jet block installed and block tight?
There is a small plug screw on the arm from the float bowl you can remove the screw and fit a bit of clear pipe run this up alongside the float bowl to reveal your fuel level.
Adjust the float as needed might need to file some grooves in pin.
Level should be below the air mixture screw.
Check your carb is level when on centre stand move on stub as needed.
Move float bowl forward or back to suit.
That will start you off.
Al

 

[vibrac]

E10! I suggest you get some Aspen from a lawn mower man and once it all seems to run OK then use E5 as long as its available (5 years?) (until the autumn use Esso Supreeme) keep the Aspen to fill the bottom of your tank(all your tanks?) for the winter

 

[keig2009]

E10! I suggest you get some Aspen from a lawn mower man and once it all seems to run OK then use E5 as long as its available (5 years?) (until the autumn use Esso Supreeme) keep the Aspen to fill the bottom of your tank(all your tanks?) for the winter

Sorry, meant I used E5 not E10. I have used Puteline fuel preserver in the past with good results but decided to empty out the old fuel in the Comet before starting.

 

[Speedtwin]

Free flow fuel in a clean carb/system
Check pilot clean and clear.
Position of carb correct.
Set fuel level at float bowl right.
Set tick over and air screw all good.
Helps with starting and nice clean tick over.
Ride and enjoy