VMAX SX 700 Backfire and White Smoke

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Straightsixmafia

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Dec 9, 2014
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Pennsylvania
Hey all,
Quick info on me and the sled. I just bought this 1997 Yamaha VMAX SX 700 Triple from a good friend of mine. He has owned it since it was brand new. Sled has 900 miles on it. He said he took the sled in to the local ATV shop for a tune up in 07 and got it back like this. To me, this sounds like it's running lean. I did a basic clean to the carbs and put new gas and plugs in. I just took fuel bowls off and sprayed carb cleaner in some ports. I'm afraid to take the carbs out of adjustment. It starts in 1 or 2 pulls every time. But it backfires and blows white smoke. The exhaust also gets cherry red hot. If I ease into the therottle. She'll run like a raped date. This is my first sled and I'm not to familiar with adjusting carbs. So I would like to find out what you guys think it could be, and then if you guys could tell me how to check and fix it, that would be awesome!

Here is a video of what is looks like.

https://vimeo.com/114079257



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Take the carbs off and clean them using brake cleaner & compressed air. It sounds the pilots are plugged. There are a few write-ups in the TY Tech section on cleaning carbs. "Carb Cleaning 101 with pics" is a good write-up. The button for the Tech section is on the top right of this screen.
 
clean the pilots and all carb passages.Check float levels also.Sounds like you don't have the belt on when you rev the motor.I can hear the primary just slamming shut..you'll end up damaging the primary or create cracks in the sheaves if you let it slam shut like that. Also check the float fuel pins if they are sticking.There are also 3 small screens where fuel comes thru,remove them and see if they are being restricted.
 
also if your exhaust is getting cherry hot,you have some blockage in the the exhaust.You'll end up with a fire if you don't check it.Remove exhaust and see if mice made a nest inside.
 
How to i set these fuel screws? Before taking them out, I turned them in and counted the turns and wrote them down. But I read on another forum that they are set factory at 1.5 turns. And some guy said he does his at 1.75 turns. But these screws were not all set the same amount of turns when I counted them. Also. The right side carb and middle carb were corroded to hell and back!! I actually put the jets in my ultra sonic cleaner and cleaned the passageways. I am close to being done now but may call it a night for now and pick up with it tmrw.


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Also, I found a thread somewhere about the clips on the needle? Someone said their problems and they were similar to mine. Any input on that?


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Set every thing to stock and make sure all passages are clear. Stock sled specs can be found in the tech section.
 
Okay. I will check that out! Sorry if I'm asking dumb questions.. I'm brand new to this whole world! This is the first gas motor I've ever worked on except my chainsaw. I am a diesel tech. But here's the update. She's running and does not backfire and has instant therottle response. However, it still smokes but this time it's more of a blueish tint smoke like its rich. At idle it sounds like it has a performance can tho.. Lol. I'll upload video quick. Then I will check the factory specs. I think I'm gunna order a rebuild kit and just rebuild the whole carb.


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When it was back firing before... Was it warmed up? And it's normal to be smokey until it's brought up to running temp. I would still clean the carb though.
 
I think a rebuild kit for these carbs are a waste of money. Unless you have found something missing or broken in the carbs. Clean them and put them back together. You shouldn't have to mess with the clips.
 
The spark plugs are brand new. If that's what your referring to as plugs. And by non contact thermostat? Would an infrared temp gun work?


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And in that video, it was not warmed up. But no matter how long I let it warm up, it still back fired and smoked like crazy, the smoke actually got worse as it warmed up. Now that I cleaned the carbs and reset adjustments, it response a lot better does not backfire. I don't have snow right now so I can't really ride it to see how it runs now.


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Is there any kind of specific tools or equipment for tarring down carbs and cleaning them? I have no problem getting stuff to make cleaning more effective and easier. I have an ultra sonic cleaner but it's not big enough to put all 3 carbs in. I'm not sure if those would be real effective to let the carbs sit in to clean them. If yas think that would clean them out really well I will buy a bigger ultra sonic washer.


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