backfiring, lack of power, not firing on all cyl's

M

Mills

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Joined
May 2, 2003
Messages
637
Age
55
Location
Elk Mound, Wisconsin
I have an SXR 600 that runs but lacks power and seems to be running and then not running on all three cylinders intermittently. I has also backfired hard enough several times to blow the tuner off the silencer. It runs good after I have let is sit overnight in a heated garage and I have gone through the carbs thoroughly several times, checked the compression, sprayed carb cleaner all over the motor while it is running to see if have any bad seals that are sucking in air and can't find the problem. I am thinking it is CDI and temperature related. When warm from sitting in heated garage is runs like normal. If it sits outside overnight the problems come back. What are you thoughts?
How do I test the CDI units?
Thanks,
Mills
 

I thought maybie the throttle override system was kicking in when the cable shrinks in the cold.It will cause a backfire sometimes.
 
Blue - I have the TORS overridden because the switch at the carbs is not working. I did not think about the switch at the throttle lever though. Is there a way to override it to test the system or a way to test the switch? I would assume an ohm reading would work correct?
 
If the TORS is overridden at the carb than the sensor at the throttle does nothing. I will say though if I were you Id get your TORS working and hook it back up, because one day when you need it, youll wish it had been hooked up. The tors kicking in shouldnt cause a backfire though, it just bogs.

Have you checked your exhaust/silencer/y pipe? Sounds like you might have a clog, which could cause backfiring and Im not sure what you mean by ("blowing the tuner off the silencer") Do you mean it blew the silencer/muffler off the pipe? That could be a sign of a clog.

It could be electrical, but it sounds to me more like fuel delivery, did you try running it with the choke fully on? Does that make an improvement?
 
I don't think there is a test other than a replacement with a new or a good one.You don't hear them being replaced at all but......I would leave the sled outside with the cdi removed and install it the next day see what happens then.Could be a wire rubbing under the tank or motor or a bad stator.As for the tors it will sound more like a Honda on the rev limiter as that is what is doing holding back the revs by cutting power threw the cdi box.This will leave unburnt gas in the pipes causing a back fire not shure about a bog?
 
When your TORS kicks in it retards timing and cuts back ignition, yes its like a rev limiter and if you try to give it gas it will bog. If your sled backfires there is an issue, my TORS was kicking in all the time two years ago, but never a backfire. Backfiring is usually a sign of fueling/air ratio issue or timing issue that should be fixed.
 
the silencer is brand new. however it sat on my garage floor all summer before I put it on so maybe a little friendly mouse found it and made a home. its happened before so I will check it. Like I said, when it was running I sprayed all over each seal with carb cleaner to find if it was leaking air and got no rpm increase at all. the carbs are cleaner than clean and I have verified that all ports in the carb bodies are clean and flowing air/fuel. The problem comes and goes with temperature so I am leaning more towards an issue with and open circuit when cold and closed when warm. I have had this issue before with an '83 VMAX 570
 
that backfire sounds similar to what i had with my 700SXR that i called 'backfire of death'
not sure still what to do with it,, am checking out this thread for clues too.
 
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