1998 500 Quadrunner running rough
 

I have a 1998 LTF500F that sat idle for 5 months while I got the time to diagnose an electrical problem. Finally fixed it (the regulator/rectifier failed and shorted), but now the quad runs rough. It won't idle unless it is in full or partial choke and it backfires alot. Also if I punch the throttle it bogs down or even stalls. The only way to get it rev'd up is to coax the throttle.

I figured the gas got old so I drained and replaced the gas. Not much better.

Any ideas on where to start? I suspect the carburator needs work but I don't want to tear it apart without trying something else first.

Thanks

adjust the idle setting maybe? did you check the spark plug lately? otherwise yes, the carb would be the place to look.

For the choke, Its the lever thing on the left handlebar next to the switches right?
Which direction is full choke? Pointed forward, or pointed towards the rider?

Full choke is towards the rider and down. Or if you are looking along the length of the left handle bar (standing on the left side of the quad looking at the end of the handle bar), choke is clockwise.

I have had the quad since new and the choke reliably starts the quad any time the temp is below say 55 degrees then after a minute or two it has always run just fine after I open the choke. When it is warmer I only have to run it on choke for 15 seconds or so.

My gut tells me that a good carb cleaning or overhaul will fix it since it sat idle for 5 or 6 months and the gas could have been a couple of months old to begin with. I don't ride it much, just to plow snow and pull gang mowers to cut grass. The electrical problem cropped up in the spring which means I was at the end of snow plowing season. Sometimes I go through a whole winter on one tank of gas.

Thanks to all for your advice.

My guess is carbs also
 

You might try carb cleaner directly into the intake, but that's just a quick try and see. Pull the carb bowl and clean the jets. Good luck.

any progress?
I'm having some issues with my '98 quadrunner 500.
I bought it as a project so no tellling how long it had been sitting.

I got it to start on choke and it would run on choke. Throttle responce seems ok, but it dies when I take the choke off.

So far I've:
Put a fresh change of oil
Changed the plug
I cleaned the carb best I could: removed jets and soaked for a while. The floats move freely. There is an adjustment screw of some sort on the bottom recessed into a sleave, and its far enough in there that none of my scrw drivers fit. What is that?
Also, the is the throttle adjustment screw the one with the extension? What is a standard adjustment? I have it all the way tight right now.

Any other ideas?

I have other issues, but I'll adress those later. [possible oil leak]

I haven't done much lately (deer season is taking up my spare time). I did change the spark plug and that helped a little. I also put a can of carb cleaner in the gas tank, but only time will tell if that will fix it. If I get time today, I might give the carb a once over, but I am leaving for Montana on Wednesday and will be gone for 10 days so I suspect it will be Thanksgiving before I can do any good. Like I said I really think my problem was due to letting the quad sit for 4-6 months. I think my key is the carb.
Good luck with your project. Let me know how it turns out. I will not be able to check my emails until Nov. 15 so don't think I am ignoring you if you post a reply. I will let you know how mine turns out, but like I said that might be a while.

I am having the same problems as xarcher with the idle i rebuilt the carb 3 times, adjusted the idle Clean gas but the bike will not stay running. Any Suggestions?

Did you buy a carb rebuiuld kit? If not it may be a good idea, to make sure you have all the right stuff. The pilot (idle) jet has a spring on it. Also make sure its adjusted properly. Turn it in all the way until it seat (not hard) and then back it out 2-3/8 turns. That was one of the problems I was having after rebuilding the carb, I also has the idle adjustment way too high

I ended up taking mine to the shop. They replaced the pet cock on the gas tank. It had a leak in it. The shop tech told me it has to be sealed to maintain some sort of vacuum.

Of all the things to make a carb run rough.