Struggling to get to bottom of it....

punchy6538

punchy6538

Punchy
Joined
Jul 17, 2023
Messages
51
Age
64
Location
Lancashire UK
Bike
St1100 1991
Hi all,
I've a problem, it's probably been asked before on here but I'm struggling to get the bike started... I've checked fuel pump (that's ok) fuses(ok) no kinked pipes, filter ok.. spark at plugs(ok) fresh fuel in, new battery .. fuel getting through as plugs wet, bike starts for a couple of seconds then that's it. .. won't start again, back fires... cranks great .. I'm hoping one of you boys could come up with the answer.. many thanks, Dave
 
Could be a lot of things, giving your location I'd suspect some corrosion caused Gremlins...

I'd start with battery terminals and ground wire
red starter solenoid connector
RHS switch-pod, the KILL switch in particular...
the ignition lock switch-plate
the mains connector shells behind the head-stock
the feed connectors at the coils
clutch switch
side stand switch
diode

BTW: condition of the diaphragm in the auto fuel valve?
 
Last edited:
Hi, thanks for the reply.. will go through the list you suggest.. not sure on auto fuel valve ? Didn't take fuel pump out ..
 
Wet plugs.

Is the fuel pump OEM ? I bought one project ST1100 that had an aftermarket pump that was putting out about 20 psi and that flooded the bike. I put in another aftermarket pump rated at 1 to 2 psi and all was well.
 
punchy6538 said:
Hi, thanks for the reply.. will go through the list you suggest.. not sure on auto fuel valve ? Didn't take fuel pump out ..
Click to expand...
When I turn kill switch on and off, it primes the fuel pump...

MotorBikeMike said:
Wet plugs.

Is the fuel pump OEM ? I bought one project ST1100 that had an aftermarket pump that was putting out about 20 psi and that flooded the bike. I put in another aftermarket pump rated at 1 to 2 psi and all was well.
Click to expand...
No, standard fuel pump, OEM.

punchy6538 said:
No, standard fuel pump, OEM.
Click to expand...
I usually start it once a week, as a rule it starts either first or second press of the starter..
 
Uncle Phil said:
Got the choke (fuel enhancer) on?
Also you might bypass the fuel cutoff just for grins (easy to do) to eliminate that from the list.
But it sounds 'electrical' related.
Click to expand...
Hi, makes no difference with choke on.. where is fuel cut off?
 
punchy6538 said:
I'm beginning to think it's electrical related
Click to expand...
That's what it sounds like to me.
The fuel cutoff hands on the right side of the air cleaner.
The fuel line from the tank runs into it then to the filter and to the carbs.
They do go south but still sounds like fuel is not your issue - unless your fuel pump is getting flaky where it pumps and then stops.
 
punchy6538 said:
I'm beginning to think it's electrical related
Click to expand...
Remove all the spark plugs, unplug the fuel pump and check for spark while cranking. Check for fuel in the vaccuum line that goes to the fuel cut valve. Sounds like it's flooded. If you have spark put the plugs back in clean and dry. Try stating it without plugging in the fuel pump . There should be enough fuel in the bowls to run for about a minute.
 
Uncle Phil said:
That's what it sounds like to me.
The fuel cutoff hands on the right side of the air cleaner.
The fuel line from the tank runs into it then to the filter and to the carbs.
They do go south but still sounds like fuel is not your issue - unless your fuel pump is getting flaky where it pumps and then stops.
Click to expand...
Ive bypassed the fuel cut off...
 
Al st1100 said:
Remove all the spark plugs, unplug the fuel pump and check for spark while cranking. Check for fuel in the vaccuum line that goes to the fuel cut valve. Sounds like it's flooded. If you have spark put the plugs back in clean and dry. Try stating it without plugging in the fuel pump . There should be enough fuel in the bowls to run for about a minute.
Click to expand...
I've removed plugs, got spark while cranking, will go over it again tomorrow.. did it today and it back fired a few times.
 
punchy6538 said:
I've removed plugs, got spark while cranking, will go over it again tomorrow.. did it today and it back fired a few times.
Click to expand...

Uncle Phil said:
That's what it sounds like to me.
The fuel cutoff hands on the right side of the air cleaner.
The fuel line from the tank runs into it then to the filter and to the carbs.
They do go south but still sounds like fuel is not your issue - unless your fuel pump is getting flaky where it pumps and then stops.
Click to expand...
 
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