How to Install 1987 Ski Doo Stratos Head Gaskets
In 1987, Ski Doo produced the Stratos snowmobile, powered by Austrian engine maker Rotax. While the Stratos was known to have some odd design features, the two-cylinder, two-stroke 550cc Rotax was a pretty straightforward engine. Installing a new head gasket is a fairly easy task on the Stratos. Removing the head, while much simpler than in four-stroke engines, is a bit more involved, as is preparing the mating surfaces and evenly torquing the head back in place.
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Things You'll Need
- Metric sockets
- Impact driver
- Shop mallet
- Gasket solvent
- Gasket scraper
- Torque wrench
Instructions
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1
For safety, disconnect the battery terminals.
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2
Remove the Stratos engine cowl.
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3
Identify the head and the two spark plug wires, then remove the spark plug wires.
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4
Remove the head bolts. If the head bolts give you any resistance, use an impact driver -- a tool that will deliver a quick burst of torque to bolts, usually breaking the bond loose. Just tap the impact driver on the back a couple times with a shop mallet.
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5
Remove the head. Place it where it won't get dropped or damaged. You don't have to worry about complex valves or timing chains in this engine.
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6
Remove the old gasket. Carefully remove all gasket residue. Use a commercial gasket solvent along with a gasket scraper. Don't dig the edges of the scraper into the machined surface of the head; keep it flush with the head deck. Wipe all the residue away. Do this for both sides of the mated head surfaces.
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7
Place the new gasket over the head bolts, making sure it's oriented in the proper direction and centered to the cylinders. You must use the proper head gasket for this engine. Using the wrong gasket or making your own can change the compression and the behavior of the engine and cause damage.
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8
Place a very small amount of high temp RTV silicon on the base of each head bolt hole on the outside of the head, where the head nuts will be seated. This is an optional step. It can be helpful with stock head-bolts which don't always seal completely, especially on re-torquing.
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9
Tighten each bolt finger tight.
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10
Tighten the bolts further with a torque wrench in a crisscrossing pattern. Tighten one bolt a couple foot-pounds with a torque wrench, then move to the bolt directly across the cylinder from it. Switch to a bolt on the adjacent cylinder and tighten two bolts on that side a couple of foot-pounds. Work your way around the bolts in this pattern, never applying more than a two foot-pound differential in pressure to any adjacent bolts. Continue until each bolt is torqued to 18 foot-pounds.
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11
Replace the spark plug wires, battery terminal and cowl.
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12
Start the motor and let it warm up to its normal operating temperature, then shut it off, letting it cool down completely. After this full heat cycle -- usually overnight -- re-torque the heads to 18 foot-pounds.
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Tips & Warnings
It's especially important with older two-strokes to measure the depth of the head known as the "squish band" to determine whether or not any machine work as been done to that head. If any work has been done, it may alter the specifications of the gasket required for your engine. However, if your engine ran well before, you can replace it with an identical gasket without worry.
References
Resources
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