suzuki gs500 feeling like it's running out of fuel.

[samj6]

Hi Guys,

Need a few ideas for what might be causing the problem.

It started last week the bike felt like it was running low on fuel but as earlier than usual - I switched to reserve and it was still choking and jerking but luckily was next to a petrol station so filled up and was fine.

Few days later happened again with a full tank got recovered home and dismantled fuel lines, carbs and emptied the tank. The drainage hole was blocked so there was a lot of reddish water in the tank - drained as best as I could and refilled with fresh fuel. Cleaned the carbs - red dusty stuff in there, but the fuel lines seemed ok. Only other thing noticed was a breather tube from the top of the engine to the carbs was full of white stuff looked a bit like spit.

Test rode and it was fine. Got to work for the next two days but has happened again last night.

Oil level is fine, spark plugs are fairly new and look fine.

Help would be greatly appreciated!!! Cheers, Sam

[doggone]

Assuming you got rid of the yucky stuff it's possible the tank breather is blocked and creating vacuum.
When it's been running a while try opening the top in a quiet spot, see if you can hear air rush in.

It does sound a bit like an ignition coil on the way out too.
They do sometimes work on and off for a while creating a mysterious misfiring and loss of power.
Just possibly that was the problem all along but cleaning the rusty water out will have pre-empted serious problems later anyway - so job well done.

[Robby]

Rusty gunge means you have water somewhere in the fuel system.

It can get there a couple of ways:
1. Poor seal on the fuel cap. There is an O-ring under the fuel cap, if this is knackered then water will get it. Replace it.
2. Condensation. For this to happen the bike would realistically have needed to stand for several months with the tank almost empty.
3. Sucking in water through the breather hose. Possible if the breather is resting in a puddle, make sure it isn't.

Treating it is quite straightforward - drain what you can, and treat the rest with meths. Meths binds with water, and the resultant mix can be pulled through the fuel system and burned. Halfords sell a treatment for water in the fuel system, but this is just alcohol, so I just use meths. A couple of capfuls in the tank should do the job.

This is one of the few areas where modern, high-alcohol fuels should be useful. Alcohol absorbs water, so a fuel with 5% alcohol mix can cause all kinds of problems, but may fix the problem of water.

[samj6]

Got the bike recovered home again today but it doesn't want to start at all. What would you lot do if you were me? Repeat the process of emptying tank and cleaning carbs?? Any other bits I should check on or clean?

Not sure if it is relevant or just coincidence but every time it has happened has been during or just after overtaking on a dual carriageway so 70ish mph with quite a lot of throttle.

Robby - its definitely not either of the last 2 options but I will have a look at the cap.

[samj6]

Thought I would write a little closer for the problem in case someone else comes searching for answers as there wasn't as many people willing to chip in with their ideas as I was expecting.

Not sure which one was the cause or if it was a bit of everything but these were the things I noticed/fixed/added:

1 - In-line fuel filter
2- Emptied the tank to find a lot of water and grit at the bottom
3 - Tiny holes in the fuel and vacuum hose
4 - Red dust/grit in the carbs
5 - Perished O-rings inside the carb
6 - Fuel cap overflow hole blocked
7 - Rubber cap missing on the hole used for compression testing on right hand carb.

Got there in the end after a couple of recoveries and a good few hours spent in a cold garage.

Cheers, Sam

[P.]

I see _Iain_ sold his bike then