Subscribe Today

Ski doo one cylinder firing

The name says is all. Got an older sled? Restoring a sled? Discuss your project with other collectors here.

Ski doo one cylinder firing

Postby outback rider » February 9th, 2003, 1:00 pm

I have an 86 377 safari, just for running in the yard. The top end was rebuilt about 6 years ago and I run it each year, but only limited miles. I cleaned the carb and it starts very easily. Changed the voltage regulator this year and lights work great. Changed fuel lines, added fuel filter. Took it out last night and it just wasn't running right, lack of power, blue smoke. Checked it out today, the recoil cylinder is firing great, nice brown burn color on the sparkplug. PTO cylinder is not firing, black wet plug. Clipped plug wire back and still no spark. Checked ohm reading, I get a reading of 15.4 in recoil cylinder, nothing in PTO cylinder. Pulled plugs out, got both to spark in the dark, but recoil cylinder side appears to be weaker than PTO side. Placed spark plug tester lights on both, both light up when engine is running, PTO side appeared a hair weaker. I have not tested compression, do not have the tool. Not sure what to do next. Could it be the coil, or plugs? Please help, kids want to ride, and the dealers look at you as if you have three heads when you look to them. Additionally, I love to fix these things myself if I can. Thanks for your time.


*This Message was edited on 10-Feb-03 03:00 AM by outback rider*
outback rider
 
Posts: 1
Joined: February 9th, 2003, 12:37 pm
Location: new england

Ski doo one cylinder firing

Postby sledwrench » February 9th, 2003, 1:41 pm

You did put new plugs in, correct? Once fouled, always fouled. Don't try and clean them. If you believe you have spark, you can get a cheap compression gauge for less than 20. If thats good, may want to check pto crank seal. I am not sure what you were checking("checked ohm reading on cylinder, got 15.4 and 0") If in doubt of spark, remove plugs, and check for spark, then switch coil primary leads between coils. Try again and see if problem moves. Just because a spark plug fires outside the cylinder, doesn't mean it will fire under compression.
sledwrench
Member
 
Posts: 246
Joined: November 5th, 2002, 12:38 am
Location: Team Cheese

Ski doo one cylinder firing

Postby outback rider » February 10th, 2003, 12:53 pm

Sledwrench, thanks for the reply. I've read your other answers and they seem right on to me. I did not use new spark plugs, what you indicated, once fouled always fouled was something that I did not know. I will get new plugs ASAP. I did get a good compression tester, on cylinder not firing got 131 psi, on cylinder that is firing 135 psi. Compression tested and held for over 5 minutes without loss of pressure. You test the PTO seal with starting fluid, I would guess small squirts around the seal on a cool idle, and if rpms increase, it is sucking air, what exactly does that mean. I pulled the plugs, and checked for spark in the dark. Spark appeared weak, could this be the coil. I followed the test in my multi-tester book for ohm restistance on the coil. The book set the tester at 20k and as I stated, I got a read of 15.4 on the firing cylinder, and no read on the no fire cylinder. I slowly pulled the recoil just to move the flywheel to insure a closed coil circuit, still the same read. The machine has about 2000 miles on it, and the coil is original. Any other thoughts, should I replace the coil for insurance purpose. I checked wiring, all appears to be intact, and without chafing. Thanks again for your help.
outback rider
 
Posts: 1
Joined: February 9th, 2003, 12:37 pm
Location: new england


Ski doo one cylinder firing

Postby sledwrench » February 10th, 2003, 1:38 pm

Outback, spark plugs are cheap. You can clean them all day long, but they are less reliable and more than likely will foul again soon. Seen and towed many people saving a buck on a 5 or 6 dollar plug. Compression sounds great. As far as the seal goes, the crankcase is a vital piece of the combustion puzzle. Its not so much sucking air as its not holding pressure or vacuum. Thats the purpose of these seals. Otherwise they would just put a bearing there. By reading your post, I have to believe that you are checking the coils correctly. Unsure why a coil reading zero would spark. But coils do odd things. Is this a single coil with two wires or two coils? If in doubt, change the coil. But if the signal TO the coil is weak, then we missed a step. Thats why I would try and switch primary wires and see if the problem stays, or goes to the other side. People judge sparks as weak or strong differently. I say white is right, blue will do and red is dead. Good luck. FYI, the pressure held is probably in your gauge, its normal, but has nothing to do with the engine unless you're doing a case pressure check.

*This Message was edited on 11-Feb-03 02:59 PM by sledwrench*
sledwrench
Member
 
Posts: 246
Joined: November 5th, 2002, 12:38 am
Location: Team Cheese

Ski doo one cylinder firing

Postby outback rider » February 15th, 2003, 11:37 am

Sledwrench,
Good news, I changed out the coil and plugs, she's running real sweet now. The cylinder that wasn't firing is now firing. Seems like that cylinder is burning the old oil as after running for 10 minutes the plug was dry, but the top metal electro was blackened, the plug did not appear to be fouled inside, I will keep a sharp eye on it. Great power and engine sound is smooth. The recoil side plug was nice and dry and brown. My guess is that after she is running and real hot, the pto cylinder ought to clean out and the plug burn brown. Any thoughts? Thanks for the input. The kids are glad to have it running, and so is dad.
outback rider
 
Posts: 1
Joined: February 9th, 2003, 12:37 pm
Location: new england

Ski doo one cylinder firing

Postby outback rider » February 16th, 2003, 7:04 am

While reviewing another forum, I found another post that stated that on his sled the pto side spark plug was fouling out. One answer posted was to check the fuel pump membrane for any tears, etc. as the pump may be loosing a bit of gas through the impulse tube, right into the cylinder of the pto, thus causing too rich a mix in that cylinder and then fouling. I am ordering a repair kit for the mikuni pump, which is more than likely original. Any other input appreciated.
outback rider
 
Posts: 1
Joined: February 9th, 2003, 12:37 pm
Location: new england

Ski doo one cylinder firing

Postby sledwrench » February 16th, 2003, 12:14 pm

Glad to see you're riding it. Riding will scrub the crancase of oil residue and burn any oil in the exhaust pipe. It will all equalize soon. As far as the pump kit, was the post talking about the same sled? Some people post guesses. The pulse line is just that, a pulse line. Positive pressure followed by negative pressure. Back and forth pulses that do the pumping action along with some check valves. Posted problems with similar sleds may help find problems before they occur, but just shooting in the dark will only get expensive. Good luck with the sled.
sledwrench
Member
 
Posts: 246
Joined: November 5th, 2002, 12:38 am
Location: Team Cheese

Ski doo one cylinder firing

Postby skidoodler » February 17th, 2003, 1:50 pm

Anyhow,don't worry about the pump leaking into pto side for above reasons,but also because impulse line run off mag side on 377.
caught in a"BLIZZARD"
skidoodler
Member
 
Posts: 15
Joined: January 6th, 2003, 1:00 am
Location: Eastern NewBrunswick


Return to Vintage Sleds Board

Who is online

Users browsing this forum: No registered users and 0 guests

cron