09-11-2012, 07:00 PM #1
1100 STX having intermittent miss, help please.
1999 1100 STX, runs great for about 15-20 minutes then starts to misfire so bad I top out at around 5400 rpm and can go no faster. The carbs are brand new, checked reed valves, checked compression its 130 across the board, No exhaust leaks I can see, what else to check? Disconnecting the air temperature and water temp sensors do nothing.
09-11-2012, 09:20 PM #2
09-11-2012, 09:59 PM #3
Tough one, but here's some things to try. You're sure its a misfire and not a fuel delivery issue- pops and misses, doesn't act like it's starving for fuel right. Possibly heat is breaking down something electrical. Get a manual and check stator /pick up coil readings, if you can , do it when the motor is warm and acting up. Seen a few pick up coils fail as they warm up. Again while acting up, open up electrical box and see if coils or CDI box are unusually warm to the touch. CDI boxes rarely fail, but if you can find one to switch it will help to eliminate this as you problem. Look over the electrical box for anything suspicious. Try new plugs. What happens if you open the choke when its acting up? just some things to try....good luck...
09-12-2012, 09:43 AM #4
All good ideas. It doesn't seem like a fuel issue/air issue. From my past experience I'll say it "seems" electric in nature. Its so on and off. Either it'll go 7100 rpms or it'll stop at 5400, no inbetween, no backfiring, no hesitation at low speed, no trouble starting. I did trim the plug wires. I did open the elec. box and look, no water, lots of corrosion though. I am borrowing a CDI and igniter from a friend later this week, we'll see what happens. The owner swapped the carbs for brand new ones in hopes of fixing last week, but no change. I'm sure that wasn't cheap. I've had issues with sator coils on a kawaski one time before too, hard to know for sure without just swapping.
I had a Seadoo once that would top out at 4000 or so, tried everything I could think of, finally swapped out the MPEM and problem solved.
09-12-2012, 10:09 AM #5
lots of corrosion though, thats your hint, no corrosion tolerated, must be cleaned and corrected, otherwise your chassing your tale when testing.
09-12-2012, 11:19 AM #6
Heavy corrosion in the box tells me that there was moisture in there at one point in time.
09-13-2012, 08:16 PM #7
Okay, removed the e-box and all its contents, cleaned it out real good, checked all the connectors, made sure the grounds were good, replaced the Voltage reg. as it looked a bit suspect, and put it all back in. It made not difference at all.
Any chance it could come from the on/off switch or the start/stop switch... just considering all options here.
09-13-2012, 08:38 PM #8
when it starts cutting up if you let it sit for a while does the same thing start all over again ?
09-13-2012, 08:41 PM #9
Yes, it has to sit a pretty good while, at least an hour. Then the process starts over, run 15-20mins fine, they act up.
09-13-2012, 08:47 PM #10
chk to see if stator cover, cdi or coils are overheated when it happens, have a manual ?
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