Help on a 99' Yamaha sx vmax 700 - HCS Snowmobile Forums

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Old 11-07-2007, 06:33 PM   #1 (permalink)
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Hey i have a 99 yamaha sx vmax 700 and when i start it up it idles around a grand and when i give it gas its very groggy then around 3 grand it sounds fine. And also it back fires. I tried new gas i cleaned the carbs and checked my reads. Any help let me know thanks.
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Old 11-07-2007, 09:50 PM   #2 (permalink)
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Sounds like it is running rich when idling and at low RPM(below 3K RPM). I'm not familiar with the carbs on the Vmax 700's. Does it have a fuel screw anywhere on the side of the carb? If so, I would try turning that in, to lean out the idle mixture. See if that changes your idle speed any too, because your idle speed is too low right now I think. I'm guessing it should be around 1500 RPM.
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Old 11-08-2007, 02:53 PM   #3 (permalink)
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If it doesnt go past 4000 rpmTry to bypass the TORS sensor. Its the switch on the top of the carbs follow it back unplug it and plug the end to the machine to itself and then give it gas and see what happens.
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Old 11-11-2007, 09:53 AM   #4 (permalink)
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Hey thanks a lot. and any idea why it would be back firing? The carbs and everything were cleaned new gas put in.
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Old 11-12-2007, 10:19 PM   #5 (permalink)
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check the pilot jets and passage ways real good. make sure the floats are are set correctly and the throttles all move at the same time. The tors system is easily bypassed, see owners manuel. Use new plugs to start with.specs and info is at Tottallyamaha .com
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Old 11-12-2007, 10:50 PM   #6 (permalink)
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Yeah thanks that made a huge diffrence. but now my sled runs better on half choke then it does no choke at all like at half throttle it has a quicker throttle respose. And this is after my sled being run for 20 minutes.
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Old 11-13-2007, 10:16 AM   #7 (permalink)
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Make sure the choke cable is operating freely & is adjusted correctly. Don't assume it is. Check plunger operation & lube it.
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Old 11-13-2007, 10:40 AM   #8 (permalink)
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Quote:
Make sure the choke cable is operating freely & is adjusted correctly. Don't assume it is. Check plunger operation & lube it.[/b]
If it runs better at 3,000 RPM, then at idle and it's backfiring I think you have some dirty, or partially plugged pilot jets. My old 97' 700SX had to have the carbs cleaned and adjusted every year! Look on the belt guard and see what the air mixture screw is supposed to be set at. When you have the carbs off, take that screw out, use carb cleaner and blow it out with compressed air. But, make sure when you remove the mixture screw, you get all the little pieces out with it. It should have the screw, a spring, a flat washer, and a little rubber seal also. Then after you clean it real good, install the mixture screw and turn it all the way in until it bottoms out very lightly. Don't crank it tight, just til it hits bottom. Then put a mark on it where the screw head is pointing and turn it out the specified amount it says on the belt guard. Somewhere between 1 1/2- 2 1/2 turns I imagine. Take the main jet, and the pilot jet out and try and look thru them into a light. You should be able to see clearly thru them. Carb cleaner and compressed air to clean them out as well. Pilot jet is what runs the engine at idle, and a little over idle. Then the mains take over after that. So, it sounds like you have pilot jet problems. Good luck!
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