Runs bad when warm

[a4cruiser]

Hey everybody. I have an issue that I can't figure out. I have a 99 600. It is hard to start. I wil usually kill the battery and have to jump it to start it. It will then run fine, until the engine gets warmed up. Once warmed up, it runs horrible from 1000 rpms to 4000rmps. Most of the time it will die if I let it idel or rev it to 3000 and let it fall back, it will die. Any ideas.

Right now, I am in the process of taking it apart. I removed the spark plugs and they had a little bit of oil on them, but not to bad. I haven't got replaced ment spark pklugs yet. Everybody was closed today. I need to change those anyway. they are a few years old. The air filter looks good, there did seem to be a tiny bit of fuel in the air box that i was able to clean up very quickly. Anything else I should look at while I have this thing apart?

[a4cruiser]

oh. I also just learned that i have been leaving the petcock in the prime position while the engine is off for years and resulting is flooding the carbs. which may explain the difficult time it takes to start the thing

[md86]

If the floats and shutting off fuel , yeah , that'd explain it . However , if the floats ARE working , it's a different issue ...

[a4cruiser]

How would I know if the floats are working?

[md86]

Well , if you're getting gas flowing when you're stopped , or when on prime and the bowls are already full , they ain't . If you wanna be SURE ( possible OCD alert ) , take the carbs off , leave the fuel lines connected (may need longer lines ) , take the float bowls off , LIGHTLY push the floats up , and turn the gas on prime . If you don't get wet , they's ok .

[aaron210]

I had the same problem with mine it would run for about 10-12 miles till it got good and warmed up then when I stoped at a light or stop sign it would die. If I tried to start it back up it would run really bad for about 10 sec. then die again. It sounded like it was only running on 2 cylinders. I found the problem to be my pickup coils were going bad but they only act up when the bike gets warmed up. Check them out!!

[a4cruiser]

I did check the spark plug wires and coils and the number 3 wire had a crack in it where the spark plug is connected. I am not good with carbs. I will replace what I can, and if it keeps running bad, I guess I will take it to a shop and have the carbs looked at and rejetted maybe with an Ivans jet kit. I may also need a valve adjustment.

[a4cruiser]

replaced the plugs and but a new boot on the spack plug wire has cracked. It runs better and I noticed the headlights were brighter... but it still ran bad and died after it warmed up. not as bad as before though. I guess I better just get a new coils and get the carbs looked at.

[KenpachiZaraki]

take off the carbs and clean them, its possible you have some gunk in there keeping your float bowls open, what did your plugs look like? if you were running really rich they should be black and sooty, which means you have too much gas going in which could be a fuel issue. don't spend money on the stealership just yet, maybe theres a way to fix this on your own

[a4cruiser]

the old plugs were black and had oil on em. I guess my next step is to pull the carbs off. I've never messed with carbs except one carb off an old 50cc honda scooter engine. as long I keep everthing in order it should be fine.

[smag35]

This sounds very much like the problem I'm having with my 92 750 I just bought. It will run for a while then shut down. I'm not able to get it restarted right away after stalling. It was just serviced so the plugs were checked, I may tell them to check the pickup coils. Did the new coils fix the problem, aaron220?

[md86]

I HOPE dude ain't buyin new coils just yet . You can check them first and save a TON of money .....
If it runs fine when cold , but not when warm , that usualkly points to a ricvh condition , whether it be via carbs , or weak electrical system . USUALLY carbs . So ......

[scottynoface]

I HOPE dude ain't buyin new coils just yet . You can check them first and save a TON of money .....
If it runs fine when cold , but not when warm , that usualkly points to a ricvh condition , whether it be via carbs , or weak electrical system . USUALLY carbs . So ......

Ditto the carb problem...

[a4cruiser]

Well today I started it up and it ran fine... WTF. Yesterday, I just replaced the spark plugs ran it for a while and then died. Now it seems to be running fine. Rode it around the block a couple of times. No problems. Turned it off, and tried starting it again, it started right up. Let it sit for an hour and tried again and it started right up. Maybe the carbs had gunk in em and running it for a while cleaned it up a bit. I will ride it around a little tomorrow to see if its still good. Hopefully it won't leave me stranded somewhere.

[scottynoface]

Hopefully it won't leave me stranded somewhere.

The hard part about diagnosing a fueling/carb problem is that you have to get it out on the open road under a lot of different fueling circumstances to see how it reacts, which is hard if the bike is running less than reliably.