Most motorcycle problems are caused by the nut that connects the handlebars to the saddle.

[SOLVED] No fuel through carb

RossObey01
RossObey01
Scratcher!
Scratcher!

Posts : 25

Solved [SOLVED] No fuel through carb

Post by RossObey01 on Fri 17 Aug 2018, 6:47 am

Morning all,

Some help diagnosing a carb issue if you don't mind.

So the bike is only running on one cylinder. Good spark on both, have swapped plugs and coils between good and bad cylinder but still no change to running. Continuity between CDI and coils as it should be and coils test within spec.

With both plugs out and engine turning over you can see fuel vapour coming from the good cylinder only. Plug on the bad cylinder is dry.

Carbs have been apart for new o rings and seals, all jets look clear, pilot screws are at 1.5 out. Sliders and needle have been swapped between carbs and the problem doesn't follow.

Fuel in both bowls and float valve working as it sould on bad cylinder.

Valve clearances done last week so potentially upset something there but I've since rechecked clearances and timing and both still good.

Next step is compression test and swap carbs for known good items.

Any suggestions please feel free!!


Last edited by RossObey01 on Mon 03 Sep 2018, 6:51 am; edited 1 time in total
RossObey01
RossObey01
Scratcher!
Scratcher!

Posts : 25

Solved Re: [SOLVED] No fuel through carb

Post by RossObey01 on Fri 17 Aug 2018, 1:06 pm

Last check before compression was to see just how much fuel was in the float bowls. I knew from cracking the drain screw that I had fuel in there and when it emptied I could turn the petcock back on and more fuel flowed. So with that and knowing I had fitted new float valves, I guessed the float bowl was filling.

Attached a peice of clear tube to each drain and opened the screw, the level inside the bowl is then shown by the the level in the tube.

As you can see the good cylinder has a full bowl, whereas the bad cylinder has only a small amount in the bottom. Obviously not enough to get picked up, but enough to fool me into thinking it was full.

With that, I can only assume the new valve is no good or it's sticking on the seat.

A known good set of carbs fitted confirms it was the carbs at fault.
Good cylinder:
[SOLVED] No fuel through carb 20180811

Bad cylinder:
[SOLVED] No fuel through carb 20180810
Beresford
Beresford
the 900
the 900

Posts : 1684
Location : not that far from Kirkistown

Solved Re: [SOLVED] No fuel through carb

Post by Beresford on Fri 17 Aug 2018, 2:20 pm

@RossObey01 wrote:Attached a piece of clear tube to each drain and opened the screw, the level inside the bowl is then shown by the the level in the tube.
Canny Smile

Sponsored content

Solved Re: [SOLVED] No fuel through carb

Post by Sponsored content


    Current date/time is Sat 20 Jul 2019, 10:15 am