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Discussion Starter · #1 ·
I keep on fouling a plug on my clutch side cylinder. I can change the plug, and it runs fine till I stop riding and leave it for a day, then it fouls within 20 mins of riding the next time I go out. My fuel mixture is fine, its only one cylinder and not the other and not both. its a single carb that's tuned stock and is clean and just fine.

When the plug fouls, its a bluish-grey smoke that smells of unburned gas (to be expected) and when its not fouled, hardle any smoke. Top speed when a plug is fouled is about 30mph, and when a plug isn't fouled, its 80 mph. Theres no pickup and hard acceleration when a plug is fouled. Boggy when a plug is fouled. I am running an ngk br9es (recommended by individual dealer, but the shop manual recommends br8es. Ill swich both br9es plugs to br8es and see if they still foul, but its only one plug on one side that keeps on fouling???

The sled has 700 miles on it and its pretty much all original, and compression is 150psi on both sides. I cant see any exhaust leaks anywhere. I don't suspect a poor spark plug wire because when I change the plug, its fine. runs like a top. 1980 Everest 500, bone stock base model. Its the rotax 503. Its the points style ignition (I wish it was cdi). Should I replace an ignition coil??? If I replace one, do I need to replace the other (one would be 35 years old and the other would be brand new if I replaced one coil).

I would greatly appreciate help on this guys, its really bugging me, and I don't want to be paying for a set of plugs every friggin week. I got out yesterday for a ride and once I changed a plug, it ran great all friggin day (at least 4 hours of riding). Then today, after 15-20 mins of riding it fouled up on me and I thought forget about riding today, the snow is too deep and powdery and I don't have the power to get through it, because if I stop, its really hard to get going again and I used my spare set. I love riding and it bugs me to have to quit riding after 20 mins due to a fouled plug when I could have been riding for hours.

I know that a lot of 2 stroke motors have problems with fouling plugs if the motors aren't run hard at times and there aren't good bursts of full throttle and hard acceleration and load, so I put my machine in good high speed runs (approx. 60 mph) and get her to accelerate hard and get her under a good load, but still I keep on fouling the same side plug. Its original everything on that sled and it wasn't run hard in the 565 miles my grandparents put on it before I got at it. Its a hell of a beast when it runs good and I wish I could get it to run properly.
 

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Longest post award.

So your problem is intermittent.

First I would check the plug boots. Are they orig? Possibly a loose one.

If no improvement, I would clean the points with a points file.
 

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Discussion Starter · #4 ·
Spark plug caps are original. All the electrical wiring is original. Coils, stator, everything. They aren't loose I checked that.

If I clean the points with a file, well, first of all I don't know how to do it, and it should have been done by my mechanic when I paid him a good amount of money to get the sled running properly after pretty much 20 years of sitting. I only asked him to make the engine run and go through clutching and basically make the engine run like a top and id do everything else. Do I need to use dielectric grease when I put the wires back on? Is there a normal dielectric grease or a specific cold temp dielectric grease? How much do I file off? What if I file too much, and I have no spark in that cylinder or a very low spark? Would I be better off replacing the wire and/or coil?
 

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Discussion Starter · #5 ·
Nope its premix (which I prefer)
 

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Most likely points. Weak spark won't keep the plug clean and it fouls. Best to replace both pairs of point and the condensor.
 

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Discussion Starter · #7 ·
Woould replacing the coil do the same thing? Otherwise, what is a condenser and where would it be located? And where are the points? I am pretty mechanically inclined, but I have just been replacing plugs till now, and I haven't been reading up about what part is which in a rotax 503, I know simple stuff like a stator, coil, but not specifics like points and condensers.
 
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Earlier today after reading your first post I found rather easily a PDF of the 1980 service manual for free and downloaded it. You should get one and then you can learn about the points and IGN system
 

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Put a br8es in the cly that fouls all the time and see what the results are. Sounds like a little hotter plug is the problem as it is fine until the next cold start, easy to do and not much money.
 

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Discussion Starter · #11 ·
I am going to throw in a brand new set of br8es plugs and see if it helps. The thing is, I have access to my operators and shop manual. my shop manual is a 1983 shop manual and by that year the Everest 500 sleds were running cdi ignition systems. Mine is 1980 and points... I don't want to have to tear into my flywheel and stator, I really don't. I will change both plugs out to br8es (which is what is recommended in the shop and owners manual) but for some reason the guy who fixed it recommended br9es even though I emailed him saying there are br9es plugs in my machine now and the book recommends br8es, which ones should I run? and he just simply said just run br9es without explanation...
 

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Discussion Starter · #12 ·
The thing is, thumbdoctor, when I change the fouled plug, she runs like a top and has no problems. The plug looks wet and brownish, but not like intense carbon build up and black. I could change the plug and run it for days and not have a problem, its just when I park the sled overnight and come back to it and cold start it, after 15 mins of riding it fouls and runs on one cyl and really ****ty and is smoky as hell. This leads me to believe it is my coil.
 

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I am going to throw in a brand new set of br8es plugs and see if it helps. The thing is, I have access to my operators and shop manual. my shop manual is a 1983 shop manual and by that year the Everest 500 sleds were running cdi ignition systems. Mine is 1980 and points... I don't want to have to tear into my flywheel and stator, I really don't. I will change both plugs out to br8es (which is what is recommended in the shop and owners manual) but for some reason the guy who fixed it recommended br9es even though I emailed him saying there are br9es plugs in my machine now and the book recommends br8es, which ones should I run? and he just simply said just run br9es without explanation...
B8ES (non-resistor) is what is recommended for your 1980 with points and IMO works the best in them. BR9ES is what is recommended for CDI (1982 and up).
 

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Discussion Starter · #14 ·
I've heard that iridium spark plugs are really good and don't foul and have like 2-4 year warranties. Im thinking about getting a pair (20$ for a pair of spark plugs, never thought id see the day) and maybe since they are supposed to be so great maybe I wont have a problem as long as I use them. Would this work?
 

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I've heard that iridium spark plugs are really good and don't foul and have like 2-4 year warranties. Im thinking about getting a pair (20$ for a pair of spark plugs, never thought id see the day) and maybe since they are supposed to be so great maybe I wont have a problem as long as I use them. Would this work?
They are a much better plug but they will still fail. I saw some fail for no reason.
 
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