Engine Running Problem


Old 01-05-04, 09:20 AM
jim wheely
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help me please it has just snowed and my sled runs like crap

i have a yamaha 440 circa '79. i do not know to much about snowmobiles or small engines. but here is my problem.
my machine starts easy enough and it idles well, but it does not want to rev up .instead it bogs when i try to give it fuel. if i choke it when i want to take off the rpms do pick up but only enough to take off then i have to open the choke so it doesn't stall. if i am on a packed trail it will pick up speed but never really hit the higher rpms. it back fires and the rpms climd and fall and basically it runs pretty bad. i tried to put a cloth over the air intake but this did not work. i have new plugs and new gas. i do not know where to start . is it a carb problem? the carb has 2 adjustment screws one for the idle so this does not effect its running and 1 other screw on the top of the carb . i have tried to set this screw up and down and fine adjustments and right open and right shut but to no avail! could it be engine problems . someone told me i have to replace my rings. is this true? what are the symptoms of this problem?

any advice would be appreciated.
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Old 01-06-04, 08:10 PM
webrebel's Avatar
Join Date: Jul 2003
Location: Louisville, KY
Posts: 233
I don't know about snowmobiles but I'm an ATV nut! What you describe sounds like trash in the carb main jet. I'd get a can of carb cleaner and CAREFULLY remove the carb from the machine and take the float bowl off and clean rverything in sight. Just pay attention to how you took it apart so you can get it put back together.
Old 01-24-04, 08:04 PM
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Join Date: Oct 2002
Location: Hamilton County, Ohio
Posts: 4,292
If you live anywhere near a Yamaha dealer, get a bottle of their carb cleaner. You may not need to tear down the carb. A ten dollar bottle saved me a $200 carb overhaul on my Honda magna.
Old 01-25-04, 09:43 AM
Join Date: Feb 2003
Posts: 153
Jim, is your carb a Walbro or Tillotsen? Regardless, it sounds like you need a good carb cleaning. Depending on the style of carb you also may need a kit. Your variation in RPM tells us that there is crap in the carb..not uncommon for a machine that has sat any length of time. Let us know.
Old 01-22-05, 06:45 PM
turbo kid
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crap in the carb. my neighbor had that same pronblem. everything you said is the same as it was on his. only difference was that his is a suzuki atv.

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