Only 1 cylinder firing

Ryanbgb22

New member
Joined
Dec 6, 2008
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37
Age
36
Location
Lancaster
Ok, I've already went pretty far into this thing, but this is how it goes:

For the past 2 seasons, I've had a bit of a high rpm misfire issue (usually around 7,000 rpm) after the sled warms up, I've been chasing this problem since then and never found an issue.

This season, I took the sled out of storage and it was running terrible, wouldnt idle and lacked power until about 3,000 rpm - then it would run great.....So, I took the carb off, cleaned the jets and found 1 plugged pilot jet, cleared that out. While I was at this point I figured I would pull the wiring harness out from under the engine to check for rub through (the portion that runs up to the gauges on the hood). I pulled it out (was a huge PITA to get it out), and found that while most of the plastic/rubber coating was worn, there was no rub through on the actual wiring insulation. I rewrapped everything and rerouted it around the engine. I then got the sled together and it was still having trouble idling...I raised the idle a bit, and it seemed perfect. Had throttle response and kept itself running well on the trailer.

That brings me to today. I took the sled out, started going through a field and it felt like it was lacking power (like running a cylinder down), a few seconds later it had barely enough power to pull its self. While it was running, I was able to pull both the pto and center plug caps off and nothing changed, but when I would pull the mag off, it would die immediately. It's only running on the mag cylinder.

I already ohm'd out the stator, the plug with 2 wires had ~210 between then, and each of the wires on the 3 wire plug had about .5ohms between then, I believe this is in spec. I also swapped the coils around, and nothing changed, still only running on the mag cyl. While I had the coils off I sanded down the bolt connections and tighened up the electrical connections; this did not help.

I do not know what to do next. Likely a cdi issue? Is there any way of checking the CDI? Possible wiring issue that resulted from pulling the harness out from under the engine?
 

bluewho said:
Do a compreshion check and if it runs better when you flip the choke pull the carbs again.

Compression is good, all around 125 on my gauge that seems to read a little low. What I'm experiencing now is not a fuel issue I don't think. It seems to idle ok, but I will begin removing 1 plug wire at a time....I will start with the pto, pull off the plug wire, nothing changes, put it back on. I will then pull the center, nothing changes put it back on. I pull the mag and it dies immediately. It is only running on the mag cylinder right now.
 
while sitting on the sled, on the left side, the vented peice of plastic above the footwell, remove the screws and check the wiring right by the cdi box, alot of times the 98-99 srx like to rub thru there also, it helps to unbolt the box and inspect.

Another place is right up top by the steering stem.
 
mrviper700 said:
while sitting on the sled, on the left side, the vented peice of plastic above the footwell, remove the screws and check the wiring right by the cdi box, alot of times the 98-99 srx like to rub thru there also, it helps to unbolt the box and inspect.

Another place is right up top by the steering stem.

Thanks. I will check the cdi area tonight. I already had the bar pad off and checked in there, it all looks good. Is there any way to check the cdi its self?
 
Check for rust on magnetic pick up coil and fly wheel magnets if found use sand paper light grit and remove rust then coat with a fine oil like fogging oil or household 3in1 wipe off excess and reassemble
 
I should probably emphasize that it was firing on all 3 last week when I took it out, it just did not want to idle, and felt sluggish off the line (this is when I took the carb off and found a plugged pilot jet). While I had the carb off I put a good deal of abuse on the wiring harness getting it out from under the engine, but it overall looked ok. So what I'm saying is I'm pretty sure I was not having this issue before I pulled the carb off and pulled out the harness. Perhaps I disturbed / agitated a weak spot in the harness that I'm not finding which is causing this current issue.

Either that, or my stator (which ohm'd out fine cold), or my cdi is on its way out....Or something else that I'm overlooking. I'm really lost here.
 
Well last night I looked into this again. I first checked for spark on each cylinder, the mag had good spark, and the other 2 cylinders had none. I then started pulling apart every electircal connection I could find on the sled, all under the hood, handle bars, cdi, etc and cleaned them out with carb cleaner and a small screwdriver. None of the connections looked bad, most looked perfect, and a few had very light corrosion. I plugged them all back in and checked for spark, each cylinder now has very strong spark. I have no idea what caused the spark to come back, as all the connections I looked at looked ok.

It seems to be running well on the trailer now, I have to get it back together and try it out. I'm somewhat concerned still, I'm worried that the problem will come back since I don't feel I found what was really causing it.
 


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