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1983 Yamaha 440 Question

5K views 12 replies 5 participants last post by  Yamaha_440 
#1 ·
Hello there,
so I have an old 1983 Yamaha 440ss that I have a few questions about. So I got this sled as a gift a few years back without knowing much about how engines work, when I got it the sled ran just fine and I enjoyed taking it for rides through the trails near my house, the problem came around the start of last winter, when I took it for a test ride , it was losing a lot of power and blowing a ton of white smoke from the exhaust. I took it home and pulled out the plugs and they were wet and fouled pretty bad. I left it sit for the rest of the season and am now getting back to it because I want it to run right for next winter, I was thinking about removing the carburetor first and cleaning it. Like I said I don't have much knowledge about engines so i'm completely open to suggestions.

Thanks for reading and sorry if I posted this in the wrong place, First post in this forum :l
 
#2 ·
Welcome to the forum!

First thing to look at is always the carburetor. If it sat with any kind of fuel in it, it will probably be clogged with gum and deposits. My Exciter's carb is particularly picky, and needs a cleaning every year, or it clogs. I neglected a couple times, and was met with the engine dying at clutch engagement due to a clogged main jet, and a clogged pilot jet that didn't let the motor run without choke under 3,000 rpm. Both of those instances occurred after 50-100 miles of riding.

Second, I would look towards the ignition system. If it doesn't have a bright blue spark, then it needs to be looked at. I had an Exciter that had a bad coil that gave me white spark, and it would run on one cylinder and smoke like crazy. Mice and critters can also chew wiring, leading to intermittent shorts and other problems after storage. Make sure they didn't make nests in the airbox or exhaust either.

Third, and last, is compression. With a tester at wide open throttle, you should see at least 110 psi, and preferably 120 psi per cylinder with no more than 5% variance.

And with that, you have the 3 things that an engine needs to run: Air/fuel mix, spark, and compression.
 
#3 ·
Thanks for the welcome!
Finally got the carb off (had to deal with a pesky wasp nest under the hood :p) One of my buddies says it might be piston rings from how I described it, anyways I didnt get to dissembling the carb yet, Ill check that spark and post an update tomarrow hopefully.
 
#12 ·
And check the black hose that goes to the crankcase for leaks. That's the impulse line. Pressure/vacuum from the crankcase causes the diaphragm inside the pump to move, and that's what pumps the fuel. If the line is cracked and leaking, the pulse will be less effective.
 
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