gs 500 looses power then cuts out after high speeds

[jackinacabin]

Hi ... i am back on a bike after 23 years despite disability , its great but my 1989 gs 500 has a problem . It  bogs down after a mile or so at high speeds , sometimes it stalls ... if i have to coast to a halt it then restarts after a few seconds , backfires and then runs fine again .... if i ride with beans this repeats , if I am moderate all is well ... any ideas

[J_Walker]

Running lean, I've had GS's that would run super lean [pipe would glow faint red 8 inches off the headers lean] during the daytime on the highways it would stall.

Could be starving for fuel too.

[The Buddha]

Tank or carb vent could be blocked, or something not letting it fully flow. The lean condition is also possible lie J_walker said.
Check for a clean airfiter and all fuel passages in the carb and lines.
Cool.
Buddha.

[Kookas]

Yeah, either too much air or not enough fuel!

[mr72]

Yeah, either too much air or not enough fuel!

Which is two ways of saying "not enough fuel".

The amount of air is pretty much going to be constant.

Anyhoo..

sounds like low floats to me but could be any number of things that restrict/limit fuel flow. Might be helpful to post the bike's most recent service/operation history which might have clues to help narrow down what to investigate.

[herennow]

+1 for checking tank vent. Also try to ride it with the petcock on PRI (prime) and see if that helps.

[pliskin]

+2 tank vent. I had this happen on another bike of mine. That bike and a little BB valve in the cap that was sticking. As it sucked gas a vacuum was created in the tank and fuel would not flow. I'd pull over and pop the cap and be back on my way. However, I have never heard of this problem happening on a GS.

You could try going for a very very very careful ride with the cap open and see if it happens. I know this is dangerous (gas splashing out) so as a disclaimer I do not recommend doing this  wink wink.

[marc]

I have a '90 gs500.

These were affected by the fuel starving issue: troubleshoot if you are affected: ride with the petcock on PRI. If it works, then it is your petcock starving fuel. Not sure if there are still available rebuild kits for this item.

Then check the things that could be caused by lack of maintenance:
- Dirty air filter.

Then check the tings that could be caused by age:
- Dity Tank fuel filter
- Ruined float valves
- Carb and tank breather.

Take care if you try to drive with the tank cap off. If you bath your balls in fuel, you'll remember the feeling forever.

[ajensen]

Mine did the same thing until I cleaned the frame petcock and put on a new vacuum line from the intake to the petcock. Make sure you have the gas lines on correctly. I reversed mine and had an unpleasant surprise when I switched from what I thought was regular position to reserve.

[jackinacabin]

Thanks for the replys ... I have tried  running with the tank cap open ... no change ... tried running on prime ... it helped a bit , it does it less but the essential problem remains. I have yet to try a new air filter as the one in it seems pretty good but i will try this . After this i will check all hoses and clean them out and clear out the fuel filter and petcock  then  strip the carbs and see if they are filthy... I hope that will solve it . The bike cost me peanuts and it runs well this problem aside. its done 52 thousand miles  so it could be well worn as uses a  bit of oil  but if i can solve this  fuel starvation issue I will run it as long as it runs ... for 450 pounds its a lot of fun ... its tidy to look at and is the slingshot model with a fairing .

[jackinacabin]

Put some red line gloop in the tank and its a little better , not solved  but improving , may try that again  for another tank and hope to avoid taking stuff apart ....

[alpo]

It sounds like a fuel starvation issue. I'd shine a penlight in the tank at the fuel filter. See if it is covered in gunk and if there is debris in the tank.

[jackinacabin]

I hope it is as simple as the filter , I will have a peak once the fuel is lower ....  Cheers

[jackinacabin]

The old gs is belting along. I put a lot of red line gloop fuel cleaner in the tank and it seems to have sorted the bike out . I have oredered a carb rebuild kit because its an old bike and came to me after sitting for a year and a half and really needs the carbs attended to .. but for now its fine at all speeds though  still has a flat spot low down  which I think may be a jetting issue with the Delkavic exhaust ... very useable , but will need attended to some time.. Thanks for the replies

[jackinacabin]

I spoke to soon , the issue returned nd with good reason . The fuel tank is internally rusty and crusty. The fuel filter is filthy and there is all manner of old tank sealer floating about in the beastly bugger. POR 15 tank sealer has been ordered , its a mess  but saveable , no leaks .---- the joys of a nearly 30 year old bike!!