Aaron's Vintage Snowmobile Site: Technical Stuff

Aaron's Vintage Snowmobile Site

Technical Stuff

If you have any neat ideas, questions or common problems on old sleds and how to fix them, send me an e-mail and I'll post it here.


Fixing "Engine Squeak" or "Spit Back" on Rotax Singles.

From Carman Jordan

First... Are you running the air silencer or not? If not then it could be spit back..Spit back is when the top of the piston on the compression stroke causes a noise (comes back through the carburator) It could also be the carburator is loose on the manifold so you'd have to tighten it. Or, an air leak into the metering system, remedy, make sure all channel plugs, plug screw and lead plugs are tightly sealed.


Old Chrome Rides Again

From Me!

I've done some experimenting with chrome and if it's tarnished, rusty or just DULL, the best remedy is some FINE or MEDIUM steel wool. No coarse, please. That will kill the chrome for good! For a beautiful shine, finish the chrome off with a green scrubby pad and some turtle wax. If the chrome is badly rusted, put some paint thinner on it, and then use the steel wool while the chrome/rust is still wet.


Seat Reupholstering

From me!

Don't buy a new seat if your old seat is torn and worn... just re cover it! Stores like Canadian Tire and Dennis Kirk Off Road sell seat fabric kits, and it is really easy. For a truly professional job, make sure all edges of fabric are UNDER the seat and stapled in, where it can't be seen.


Common Rotax Problems- Single Cylinder Engines

After rebuilding a few Rotax singles I've figured out some of the common problems...

Piston moves a little but gets stuck- The has probably been overheated. But a cylinder hone, hone that baby out. You might need new piston rings, too because they have most likely been bent up.

Whatever you do... DON'T FORCE THE PISTON unless you want to buy a new one!

Piston has to be forced to go all the way or makes a crunching sound- since the Rotax single is so simple, the muffler just connects right to the cylinder. These enables our little furry friends to enter the cylinder and make happy homes in there for the summer. Remove the head (where the spark plug goes) and let them free. Hopefully you will know to check this BEFORE you start up your machine because it REALLY fouls up the spark plug and that must be kinda painful for the mice/rats/rabbits (HA!) that may have crawled up in there...

Engine Backfires constantly- Check the fuel/air adjustment screw on the carb, check your spark plug and check the fuel mix ratio you're using (For Rotax singles it's 32:1 to 40:1)

Engine Seizes Up (Or... I can't even pull the %@$! starter cord!)- Remove the head (where the spark plug screws into) and spray in some (Ok, a generous amount) WD-40, Liquid Wrench or similar penetrating oil (I use gun oil). Let it sit for about an hour. That should do the trick. This is quite frequent on the Rotax Singles, because water can get into the cylinder really easily if you live in a humid are OR there are any holes in the muffler. Nothing serious.

Engine Seizes Up- Part II- So... you forgot to put oil in it, huh? What? You overheated the thing? SHAME SHAME SHAME. Go stand in the corner. OR... load that sucker up with about a liter of Penetrating oil. If that doesn't work, I'm afraid your piston is melted to the cylinder. Have fun!

I don't know how to hook up a kill switch/turn the engine off!- If you can find a key switch from an older Ski-Doo (New ones aren't available) just plug it into the round, black plastic plug. If you don't want to bother with that, just hook up a push button to the two wries that go to the black plastic plug and mount it somewhere. Then, you just press the button and the engine turns off! If you're still too lazy/cheap to do that, just turn on the choke and the engine will shut off. This won't cause any damage to the snowmobile. It just doesn't look as cool as pressing a button or turning a key!!!

I want my Rotax to go FASTER!!!!- Heh heh heh heh... don't we all? Here are some tips:

Get Splitfire Spark Plugs

Remove the muffler BUT BE SURE TO PUT A DEFLECTOR OR A LAWN MOWER MUFFLER IN ITS' PLACE because your engine will double as a flame thrower. And it's really loud, too. Yipee!

Get a performance clutch. Comet (tm) sells great centrifugal clutches. My '72 T'NT has one.

Get a Serpentine belt. These get better grip on the clutch AND last longer AND cost about $150.


Traction Time!

Track Studs/Cleats are kind of expensive but I guarantee you won't get stuck again, and you will have REALLY fast take offs. They are carbide spikes and plastic "fins" that mount in the track. You COULD make your own but it's not highly recommended at all.

Carbide or tempered bolts with very large washers would work quite well but don't do it if you are worried about screwing up your track!


Preventing Engine fires!

I figured this could be convenient. Fires are not fun.

Be a good samaritan and always put your gas cap back on. If you don't, the gas could slosh out when you hit a bump or take a sharp turn (or flip over) and spill on the hot engine. That would make one smokin' sled. Also, don't use a rag in place or your gas cap if you lose it, it will absorb the gas fumes and culd ignite.

Keep your fuel lines away from the muffler... Particularily useful on the old Ski-Doos. I came VERY close to having an engine fire this way while riding a '73 Olympique 335- the muffler had melted through the gas line and I smelled gas, so I shut off the engine and noticed the line was leaking everywhere. I decided I should get a tow back before I exploded.

Keep the engine compartment clean and free of grease and oil. Grease and oil and dry grass (Which can fill up your engine comparment on a Free Air) all catch on fire quite easily.

If you paint your muffler, use exaust manifold or stove (high heat) paint. Other paints could flake, bubble and/or catch on fire.

Don't ride if there are ANY fuel leaks because your sled could explode in a ball of fire.

I think that picture is graphic enough.

If there are any bare wires, cover them up with electrical tape. Remember... if two wires of the opposite polarity hit each other, they will spark. And if a postive wire touches the frame, engine or anything else that's metal, it could spark. A spark could ignite the always present gas fumes under the hood. Also, a short could screw up the magneto pretty badly.


If you have anything else to add, just send it to me through e-mail by clicking here!

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