Snowmobile Repair: 1973 yamaha SL282, spark plug gapper, vintage sleds

Question
I have went to get the thing tuned up after it wouldnt start. they fixed a gas leak, rebuilt the carb, and replaced the coil. we got it home, it started fine and then if you sat down to ride it it wouldnt go even when you pushed the gas in as hard as it could go. then you stand up and it slowly takes off and then stalls. i replaced the belt and it still does the same thing. now it wont even start! because of that, it is now stuck in my back yard. please give me instructions on what to do.

thanks for your time,
charles

Answer
Hello Charles,

  First off, I am very sorry I wasn't able to answer your question, Allexperts is experiencing some technical problems, and never forwarded your question to me until now. Unless you are in Alaska, it's probably hot where you are, and the carb will need to be re-jetted for the temperatures. What is happening is, the engine is running too rich and probably overheating, and fouling the spark plug. Your best bet would be to go to a Yamaha dealer and ask for new main and low speed jets that are one size smaller than what is in the carb now. You can even take the carb off by the two bolts that hold it on, and have them install the jets. For now, try turning the two fuel mixture screws on the side of the carb in, clockwise 1/2 turn. Then, install a NGK BR7HIX spark plug, gapped at .020 in. with a spark plug gapper availible at Walmart or any auto parts store. The plug I quoted is somewhat expensive, but worth it, as it won't foul as quickly. If you would rather use a standard plug, it is NGK B7HS. If the sled runs good with a new plug and the mixture screws in a touch, don't worry about the jets. In the summer, it's easy to go through plugs as fast as every 4-6 hours of operation on vintage sleds, but they're fun! Let me know if you have any questions at all, and I will be glad to help. Good luck with the sled! --Arcticatman