QuestionI bought this 85 ski doo formula mx 500(492 to be exact, i think) from a friend of the family this past summer. it has been sitting in a barn since 1992. the motor and carbs were gummed up and stuck but we finally got it free and actually sputter a little. the compression is good but there was some water in the exhaust. i want to make sure i don't miss anything when going through the sled to get it ready. where should i start and what should i do as far as the tune up? i'm new to snowmobiles and don't want to run into further problems because i didn't check something i should have.
Thanks,
Brad
AnswerHello Brad,
First off, congrats on getting a sled. Nothing, is ever more fun than hearing a sled fire-up, and then getting on for a ride for the first time. I will include an excerpt from my website on this reply, that includes every thing you need to know to get it going. One thing to add, you may want to take the head off, and take a look in there to make sure it's not rusty form the water. If it is just wet, or a little rusty, take a can of WD-40 and a rag, and get everything cleaned up and dry. Now, here is the part of my website: STEP 1. Get the sled clean, this is important, especially when doing repairs. Then, place the sled to an area that is clean, well lit, and practical. If you are going to need special tools or parts, get them ahead of time, so you won't get tied up in the middle of a job.
STEP 2. Take a piece of paper and pencil, and write down all the obvious things the sled needs, this really helps alot, as you will be able to know what you need when you go to your dealer for parts.
STEP 3. Take a rag and clean all of the grease fittings on the machine, there can be anywhere from 3 to as much as 10 or more. After removing any dirt or corrosion form the zerk fittings, pump good quality automotive grease into each fitting, until old grease oozes out of the part. They can be in any location, from on the rear suspension to the speedometer drive unit.
STEP 4. If the gas is old, take a siphon and remove as much as possible, old gas will make the sled run terrible. If the sleds carburetor is equipped with a float bowl, drain them also.
STEP 5. Remove the drive belt. To remove it, place the sled on a stand, so that the track hangs loose. Then, remove the belt shield/cover. Take hold of the belt, and turn it, pulling on it, so that it will try to fall off of the torque converter ( secondary driven clutch) .Inspect it for cracks or loose cords. If you have any doubt, replace it. One thing to keep in mind, always carry a spare belt on you sled, it is very important, incase your current one should fail.
STEP 6. Remove the spark plugs. I don't recommend cleaning spark plugs from a snowmobile, it rarely helps, and generally acts as a band-aid, instead of just replacing them. Alot of times, your sled will not have the correct plugs installed from the previous owner. The best way to make certain you are using the right plugs, is to go to this page and verify the plugs your sled uses. http://www.ngksparkplugs.com/apps/snowmobiles/default.asp?nav=60000&country=US Be sure to gap the plugs with a spark plug gaper, not feeler gauges.
STEP 7. This usually applies to older sleds, but is a good idea for all machines. Checking for carbon build up in the exhaust ports. It's a fairly easy task, it involves removal of the muffler and manifold to access. Once you can reach the ports, use a piece of small hard wood to get the ports clean. Be sure to get all particles of carbon out of the ports after the job is finished.
STEP 8. The Chain case. The Chain case will almost always be located on the right side of the sled, when sitting on it, on a 1985 or newer sled. Other wise it can be located on either side, but is always connected to the driven, secondary clutch, either directly or by a cross-shaft. Siphoning the fluid out of the filler or drain bolt is ideal, but not the only method to do it. If you don't have a siphon, loosen the drain bolt and get as much chain case fluid out. If you do have a siphon, remove all of the fluid through the drain bolt, and then use the siphon to remove any remaining fluid. Now for what to use for re-filling. The ideal fluid to use is your sleds manufacturer's fluid. On older Yamahas, 1968 to 1978, 10w30 motor oil is recommended. On many older vintage sleds, SAE 80w90 multi-purpose gear lube is fine. Having a leaking chain case is almost inevitable on a snowmobile at one time or another. If your sled has a leak, it's best to un-bolt the case cover and replace the internal seal or o-ring(s).
STEP 9. Check your brakes for proper operation, and adjust as necessary.
STEP 10. Mixing the fuel and oil on a vintage sled is critical. Too much oil and you will foul plugs non-stop, accompanied with plenty of smoke. Not enough oil and engine seizes. The ball park for all vintage, pre-mix sleds is 20:1. Using synthetic, or even semi-synthetic oil is ideal, and will cut down on fouled plugs. On oil injected models, be sure to top the tank off, and always, carry a quart of oil on the trail.
STEP 11. The cooling system. There are three methods of cooling snowmobiles that have been used. One is free air, the simplest method, where movement from the sled causes air to pull through large vents in the hood, and over the engine fins. Another is fan cooling, still in use today, but hardly. It works the same as a small engine, with fins mounted to the flywheel, the air generated by the fan is blown over the fins. In some cases the fan is driven by a belt, be sure to check the belt for wear or cracks, if your sled is equipped with one. Last of all is liquid cooling, one rare on sleds, it's pretty much the only cooling method used on sleds today, and works much the same as your vehicles cooling system. If your sled is a free air, use an old paint brush and compressed air to remove any dirt or other particles from the fins. Sleds equipped with liquid cooling should be flushed once a year to remove all containments. Re-fill with a mix of 50/50 distilled water and anti-freeze-coolant.
STEP 12. Inspect your starter rope. If it is frayed, replace it, and be sure to carry a spare with you. For electric start, clean the batter terminals, and refill the battery with water, if needed.
STEP 13. Take a look at the track, if you notice tears, or dry rot, replacing it is going to be a step you will want to take. If it looks ok, check for proper tension, and adjust if necessary.
STEP 14. Hi-Fax or slides. These are on your track frame, and on most snowmobiles, unless you have a bogie wheel system. They are plastic like strips that run along your skid frame on the sled. The tracks metal "clips" rub against them, to provide minimal wear. When the slides wear down, it's time for a replacement. They are generally held on be roll pins or bolts. After removing any retainers, use a block of wood and rubber mallet to drive the slides off. sometimes heating them slightly helps.
STEP 15. Last of all, the most important thing you can do for a sled that has sat around. Removing the carburetor and thoroughly cleaning it. Pay the most attention to the float(s) and inlet needle. Nearly all snowmobiles that have sat for a period of time, will have this one problem in common. The inlet needle will be stuck, either shut or closed, causing two problems, no gas, or flooding. Installing a carburetor repair/rebuild kit is always best.
You can also check out my site: http://www.freewebs.com/thesledzone/index.htm .
Hope you find my info helpful. If there are any specifics at all, or you need any help, let me know! Good luck with the sled! --Arcticatman
