Fuel problems

[paul doran]

My Lawson 1100 wont start
its had a new head gasket fitted
shims done and carbs ultrasonically cleaned
I have also overhauled the fuel tap
the engine spins over freely there is fuel in the carbs but plugs are dry after trying to start it
if I put fuel down the plug holes it will fire
any ideas please

[Pigford]

Is the air filter & air box all free from blockages?

Check slides aren't stuck - the throttle plate (opens with twist grip) maybe working OK< but if slides are stuck due to lack of use over winter, not much fuel will be getting thru

[paul doran]

slides operate freely

[Al]

If the inlet cam timing is a little off you can get down to near zero vacuum on the starter.
No problem for slide carbs but CV's.................

If you have some vacuum gauges give them a try and the vac reading is around 22 ish.

If its less or no reading at all and they're morgan sliding tube gauges then turn the gauges upside down!

Wrong is 41 and 67 degrees where you should have 35 and 65 degrees thats approx equivalent to 103 lobe centres. Torque to spare but it wont start!

AL

[steve.w]

squirt some easy start in airbox just to help it drag fuel through or put hands over back of carbs ..

[Rich]

Fuel in float bowls?

[paulmceleney]

Take your spake plugs out and check if you got good compression just place your thumb over the hole and turn the engine over if its not pulling your thumb into the hole you have problems with the engine sorry paul

[PJ]

Sell It me cheap

[kev edwards]

what about float needles sticking, happened on mine, i just rubbed the edges of the needles with a bit of 1000 grade wet and dry just enough to let them move freely.

[paul doran]

compression excellent
I have checked valve timing for the hundred time its spot on
still the bike will not start
the carbs were overhauled so I am at a loss as to the problem

[Robw]

Just on the off chance, have you checked that fuel flows freely through the tap.
Rob

[paul doran]

yes Rob I did

[Z.O.A]

Sounds like the pilot circuit on each carbs is blocked, but that would be very unusual, everything engine wise sounds ok, especially if valve timing checks out. Seems there is just no drawing the fuel up from the float chambers, I would have the carbs off again, I'm not familiar with the 1100 set up, are they CV carbs and vacuum tap?

[z1bman]

have you tried it in the prime position? if you have fuel in the float bowls it is possible a pilot jet is blocked. chances of all four being blocked at the same time very remote? are the inlet rubbers in good condition no leaks at the mounting surface. if you remove the carbs + hold the palm of your hand over the inlet rubbers have you got good suction

[Robw]

Thats really weird, fuel going to carbs and not going to engine. Fuel float level correct in carbs as they have been overhauled.
Rob