98 AT Running problems

[smithy]

Hi all,

My first post on here, seems to be a great site/forum!

I have a problem with a 98 AT which my father has just recently given me the use of - hopefully you knowledgable souls can help!

The bike has been lying for over a year in my garage, and previous to it being taken off the road, it had a problem which was suspected to be the fuel pump (bike kept dying for no apparent reason and coming to a stop), so my dad bypassed this and run it without the pump for a short time (he said that it ran fine like this).

Anyhow, I have since pulled the bike out, got it running again and MOT'd + Taxed it. However, the bike has a problem. The bike runs ok at first, but after a bit of riding it will start spluttering a bit and then begins to run on 1 cylinder (rearward cylinder is the one that stops firing as pipe is cooler). If you stop the bike for a while, and fire it up again, it runs fine again for a while but then the same fault will re-occur. Looks to be a fuel problem as there is a healthy spark. I also pulled the carbs off it, cleaned out the float bowls and jets, blasted out everything with the compressor - no change.

Ok - so I thought, lets connect the pump back up again and see what happens. Pump back on, fired it up - pump didn't seem to work for the first few mins then started to "buzz". Took it for a decent spin... great, fault didn't re-occur. However, when I got back home, I had the bike on the sidestand running, and noticed that fuel was pissing out of the carb overflow Pump seemed to be making a "ticking" noise about once a second at this point which didn't seem right....

Any ideas? Is the pump just knackered and pushing too much fuel through? Could running without the pump cause the "running on one" fault?

I'd appreciate any help on this, its a great bike and I really want to get this sorted.

Cheers
Paul

[BlindPugh]

Fuel out of the carb overflow is very unlikely to be pump - this is a low pressure pump so the problem is most likely a sticking float in the carb which is allowing the pump to push more fuel into the float chamber faster than the engine can use it. As for the poor running on one cylinder - it could be the float sticking the other way cutting off the supply.
The bike should run with the tank full and the fuel hose connected directly to the tank. This is usually enough for 100miles of running. So if you still have fuel peeing out of the carb it is nothing to do with the pump. The pump does make a ticking noise. It also stops ticking if it is knackered ( the contacts usually get welded shut)

HTH

[smithy]

Sticky float certainly sounds like a good explanation right enough, looks like i'll have to take the carbs off again then. Very strange though, as I checked the floats when I had them off before, even removed the floats and re-fitted, they seemed plenty free to move.

About the ticking, the pump seemed to tick a lot faster at first and then slowed down, though that could be due to it pumping/priming on initial use I suppose...