My friend has a 87 EX500, that just recently began running like crap. The other day he ran it down pretty low on gas and had to switch to reserve, well after he filled it up he forgot to switch it back to the regular feed. Then shortly after that he was out riding the bike and once it warmed up it began to run like ****, it would miss/bogg under 4500rpms and wouldn't idle it would just stall out. It seems like its running rich as you can smell the unburnt fuel, whats weird about the issue is it only happens when it warms up. Any ideas?

 

Dirty dirty carbs..... Clean those out, and should be good to go.

btw, welcome to the forums....

 

We cleaned the carbs out today and it looks like thats not the issue. I'm beginning to believe we have no spark as i can grab hold of the exhaust runner and have no heat at all and there is raw fuel in the exhaust.

 

Just do a simple spark test. take off the plug wires, Put a paper clip in the boot, and get the end of the paper clip close to any part of the engine. (don't allow it to touch the engine) Crank over the engine and see if you're getting spark.

BTW: if the engine still runs, which cylinder is not firing? You also could have a timing problem.

I almost forgot. Running really low on gas, then switching to reserve doesn't have anything to do with your problem. The gas is still comming out of the same tank, (there IS NOT a seperate tank) switching to reserve just lets gas flow out from the lower part of the gas tank. you could always run the engine on reserve, it makes no difference.

 

When i check for spark i just remove the plug from the engine and leave the cap on... press the side of it (nut part) against the engine n watch for spark (be prepared for a lil zap) ...

check that.. get new plugs (its like 5 bucks so its a safe bet anyways)

unscrew the capsfrom teh ignition coil (the sparkplug end) clean out the plastic caps snip a bout a quarter inch off of the wire and rescrew into fresh wire... if your ambitious check the resistances on the coils...(i think its between 450 and 490 Ohms offhand)

check all electrical connections for corrosion and clean them up ( including to your IC box ... just for a piece of mind)

check for air leaks (whether it be in the boots from the A box to the carbs or carbs to engine) and check all air and fuel hoses for leaks as well.

Check your tank for rust, if you have an inline fuel filter check for blockage/ air bubbles restricting flow, check all fuel lines for kinks...

Well back to work for me... let us kno if anything helps if not i'll continue my list...

oh yeah... did u check your compressions?

 

I have a similar problem with my '91 EX500.

Under WOT, the motor bogs and sputters, and can barely reach 5k rpm, and only goes higher if there is no load.

Before this current tank of gas it ran great.

 

Sideways, welcome the forums.

Maybe water in the gas? Bad batch of gas? Try some water remover/ cleaner and see if she clears up.

 

Thanks for the welcome :-)
I'm hoping its just the gas, but methinks its not... 92 octane from a newly built gas station by Purdue. I plan on siphoning out the gas and putting in some fresh 93 or 94.

Otherwise I'll be checkin the carbs, and plugs.

 

Sounds like you have it under control. If the new gas does not fix her, then carbs/ plugs....

You said by Purdue? My wife is from Lafayette.