03 900 low rpm hesitation bog/high rpm loss

sierraclimber · Jan 2, 2011

She's running goofy. Rough idle with a hesitation and bog on the low end. Mid range snappy as usual. Loss of top end rpms by about 1,000. Noticed a slight loss of high rpms the weekend before the low end bog appeared.

Plugs look good. Pulled on the power valve cables and they pull freely and snap back. I watched the servo and it does nothing if I blip the throttle wide open. But, after it comes back down to idle the servo rotates real quick and then goes back. Never watched the servo in action before so not sure how it is supposed to behave?

Threw half a tank of 91 in before I started having problems. Also filled my 2010 at the same time and it runs fine so the gas isn't bad. Could 91 make it run this poorly?

Any suggestions on what to check?

Idcatman1 · Jan 3, 2011

My first thought on the low end rough idle and bog is a plugged pilot jet which would give you a hesitation when you hit the throttle. I think you are on the right track with the power valves for your problem on the top end. When you start the engine watch the servo, throttle up slowly and it should cycle once if things are working correctly. If it cycles three times that usually means something is not right and it will not open the valves when you are running. I would check the cables. Unhook them from the servo and see that the free length is the same. I have two different service manuals with two different figures as to what that length is supposed to be. I will try to look it up and post back. Your half tank of premium should not be causing what you are describing.

sierraclimber · Jan 3, 2011

Thanks a lot for the ideas.

resent: I will check everything later today. Great to have an idea of what the PV servo should be doing. My service manual says the length on the cables for a 900 should be 1.2 inches.

So is a servo "cycle" a quick down and back motion that takes about 1 second?

Idcatman1 · Jan 3, 2011

yes and that sounds right for the length of the cable also.

01polcat · Jan 6, 2011

?

What should the cable length be for my 04

snailbait · Jan 6, 2011

Make sure the spring or spider in the driven clutch is not broken. Have seen that cause similar issues that you describe.
I have an 03 that I just did the cables on...and the dealer told me 1.55..or 1 1/2 inches on the length of the cable. Only been out once, but she ran great.
Good luck,
Steve

fishtank · Jan 9, 2011

I had the same issue with the same sled!! Turned out to be the throttle snow safety switch thingy. (im told not all throttles have them though)

Disconnected the kill switch and the problem went away.

sierraclimber · Jan 9, 2011

Interesting on the cable length. Here is what I have from the service manual.

900 cc range - 29.6 mm (1.17 in.) - 30.6 mm(1.20 in.) - 31.6 mm(1.24 in.)

The 700 however has close to the specs the dealer told you.
700 cc range - 36.15 mm(1.423 in.) - 38.15 mm(1.501 in.)

That is crazy about the throttle safety sensor and the fix is to disconnect the kill switch. I guess if it works don't knock it. My key broke off in the switch so if I disconnect the handle bar kill switch I won't be able turn her off!

Looks like I won't have time to work on her till next week but appreciate the ideas! I'll be looking at all possibilities.

resent:

fishtank · Jan 9, 2011

Heh, im the opposite, my kill switch got snapped off. We replaced it with a self tapping screw but its hard to pull the screw up with gloves on so my key is now my kill switch.

I hope I dont go over the handlebars again and snap it off, could make the next trip interesting!!!

Idcatman3 · Jan 10, 2011

Rather than disconnect the kill switch, you can just clip the middle wire from that plug. That's the safety switch. This way the kill switch will still work normally. We've done this on almost every sled we've ever owned.

sierraclimber said:
Interesting on the cable length. Here is what I have from the service manual.

900 cc range - 29.6 mm (1.17 in.) - 30.6 mm(1.20 in.) - 31.6 mm(1.24 in.)

The 700 however has close to the specs the dealer told you.
700 cc range - 36.15 mm(1.423 in.) - 38.15 mm(1.501 in.)

That is crazy about the throttle safety sensor and the fix is to disconnect the kill switch. I guess if it works don't knock it. My key broke off in the switch so if I disconnect the handle bar kill switch I won't be able turn her off!

Looks like I won't have time to work on her till next week but appreciate the ideas! I'll be looking at all possibilities.resent:

Arctic Thunder · Jan 10, 2011

Have you checked for a broken reed peddle?

Just a thought.

Thunder

fishtank · Jan 15, 2011

Idcatman3 said:
Rather than disconnect the kill switch, you can just clip the middle wire from that plug. That's the safety switch. This way the kill switch will still work normally. We've done this on almost every sled we've ever owned.

Oh nice, might give that a try as well, I just zip tied on a new kill switch though that works better than the self tapping screw that is currently my old kill switch. Do you know how hard it is to pull a tiny screw out with gloves on?

sierraclimber · Feb 25, 2011

I hate when these posts are left unanswered after its fixed. And so, drum roll please...

Replaced the coil and everything's running perfect again. $50 in parts to fix. Was only getting spark intermittently to the clutch side cylinder. Diagnosed by pulling the spark plug wire off that cylinder and not seeing a change to the rough idle, then checking for spark.

Thanks for all the suggestions guys!

resent:

Idcatman1 · Feb 25, 2011

Glad you got it fixed. Buddy of mine had coil troubles just last week too. Seems to be a lot of it going around. I should have mentioned that I have had troubles with the spark plug caps getting worn and loosing good connection. I carry a tube of dielectric grease and put a dab on the top of each plug once in a while.

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03 900 low rpm hesitation bog/high rpm loss

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