2000 Suzuki Quadmaster 500. Runs for 15 mins, stops - Oil in air filter

[MMC]

I have a Suzuki Quadmaster 500, that I got from a customer.  It has less than 400 miles on it.   I think I put most of the miles on it, so they sold it to me.    I used to drive it a few times a year,  treatinjg the gas or emptying it when I could.

I relocated and wanted to get it running again.   It will start with little trouble, then run for 15-20 minutes, then start to chug a bit, then finally stop.  Sometimes I can start it again, but it doesnt continue to run long after that.

when I first opened the oil filter when I moved, it was drenched in oil and fell apart.   I went and replaced it with a OEM foam filter.     I notice now, when it does stop, there is a small amount of oil on the bottom the air filter box, and it's clean oil.  I had recently changed the oil before I moved.     Each time I clean that up,   I go through the same process.  It will run, and I can drive it for a bit, but then it slows down and stops.  

Any suggestions?  I am not an ATV mechanic by far, but can work on most of the stuff I own.    I did have trouble finding a dealer who would work on it.   One local one, said "We dont' work on stuff that's over 20 years old"   It can't be because of parts,  I just laughed.

[Parham]

Two thoughts...and I'm not familiar with your quad AT ALL.

Check your fuel shutoff (petcock).  If it has the auto shutoff valve with a vacuum connection, start there.  The vacuum line or the diaphragm in the valve could have a leak.

Oil in the air filter housing could also indicate a vacuum issue.

Again, just guessing...I am confident the experts on here will get it sorted out...

[flyinbrian365]

Check the valve lash clearance sounds like they need adjustment. 

[Mech]

As has been suggested, it might be a tight valve causing it to stop after it gets fully warmed up, or it could have fuel in the oil, which would account for the dirty filter and the behavior after it gets warmed up. The fuel could be evaporating out of the oil once it's warm, flooding the engine and dirtying the filter.

[Curmudgeon]

The foam filter falling apart is normal at 20+years.  They come oiled if you get the Suzuki part.   I would add to the other suggestions that you check for blockage in the tank vent/vent line.  

Is the 15 minutes at idle or normal driving?

[MMC]

It seems to be 15-20 minutes, riding or idling.   I replaced the filter, but do see oil in it.  I'll have to locate the tank vent line and check it.

[Curmudgeon]

The tank vent is on fuel cap.

[Mech]

"Is the 15 minutes at idle or normal driving? ".  Good question Curmudgeon..

If it definitely seem like it's more a matter of time rather than load or temperature, then it could be electronic.. If it just takes a bit of time(long enough to clean out the airbox), then starts again for a few more minutes, and it's sort of consistent, that really sounds like electronic. If you have a timing light put it on and watch it when the bike starts to falter.. See if the spark is giving up..

[MMC]

All of these suggestions have been great.  I was thinking there was a vent line elsewhere, but the one on the top is clear.   the air box has one, which is capped, so I guess you'd open it to drain oil if it's necessary at the time.

The 15-20 minutes is pretty consistent.   I could see it being something electronic.    Somewhere I read about checking the stator.     Some of that is beyond my backyard skills.   I'm near Gainesville FL, and the local Suzuki place said that they don't work on anything that old.   It's a 2000.   I haven't find another place to take it to yet.

[Mech]

The way you describe it as chugging to a stop makes me think you should check for fuel in the oil.. when it's cold and before you start it check the level hasn't/isn't going up, and take the oil fill cap off and smell for fuel. That does happen. 

Other than that you should check the state of tune, how the spark plug is, replace it if necessary, adjust the valves, adjust the idle mixture and speed..  That might cure it and is the recommended starting point..

Then, if you bought a cheap timing light it would tell you if the spark was dying out after fifteen minutes if you still had the problem..

Or.. To eliminate the electronic part, any way you could borrow a buddiy's cdi unit, or that would be ok with you trying your's on his bike to see if it changed things.

 

[gimmie11s]

Jetting?