sx700 redhead backfiring/bogging

S

slopok

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Dec 16, 2015
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Michigan
Hello guys! I just bought this Yamaha sx700 for what I thought was a good deal. The guy had it in a heated garage and said that he hasn't ran it in two years. I bought it and thought that I could just bring it home and do a carb cleaning and be done and ready to ride. Well it hasn't been that easy. Since I bought it the sled had aftermarket triple pipes on it and v-force reeds. I swapped those out with stock manifold and stock pipe and can and also stock reeds. I jetted the main jet with the stock jets and cleaned the carbs which the pilots were pretty dirty. I took it for a ride this weekend and it backfires and bogs down pretty bad almost like its starving for gas. I then thought that it was just bad gas in the take so I drained the gas and added fresh gas. That didn't do it either. I have done everything I could think of on this sled and its still running like crap. It idles pretty good and then when you rev it up to take off it would backfire and bog until you work the throttle to get though it. Also I reset the idle screws under the carb to 1.5 turns out. The only thing I haven't touched on the carbs would be the needles on the top. Could that be causing my problems? Oh and I almost forgot, while I was out on the trail it would occasionally run perfect. I would hit the gas and I would have to hold on for dear life. Also I pulled the air box out and was looking around after I got back to the house and noticed that I used half of the bottle of oil which I filled up before I went on a ride. The ride was only about 20miles or so. Could this be why I'm bogging out/backfiring? I was just going to see if anyone out there has any other thoughts.

Thank you!
 
is your throttle cable to tight? TORS kicking in, maybe bypass it. Oil pump set correctly? maybe the oil pump is shot when it does it goes rich. what do the plugs look like? had triple pipes, did you check the pilot jets as well? fuel lines routed correctly, not pinched anywhere? maybe the spark plug cap(s) need replacing. crank seal behind the clutch OK? just throwing things out there.
 
Back firing and bogging sounds like tors easiest way to check is disconnect it and plug it into itself. If the problem continues I would set the carbs back stock needle position to and start from there.
 
I unplugged the tors and plugged the CDI harness side into its self and it still does it. My next question is how do I set the carb needles on these. I opened the top and it looks like a screw with a nut on there and I didn't want to take it out of adjustment as I am unfamiliar with this setup.
 
As im looking at other 97 700sx I am seeing that there is a filter on top of the airbox. Mine does not have an air filter there and my airbox is empty. Could this be my problem all along?
 
Can you tell looking at the head gasket if the rivet is missing. They may have done the head gasket mod as it sounds like the messed around quite a bit with the sled. You may need to swap over to premium.

How do the plugs look and can you check compression?
 
I have been putting in 93 octane fuel just because that's what I run in all my toys. I did pull the plugs while I was on the trails and its a light tan color. I am probably running leaner than I like. I am use to seeing a nice dark brown color in my other machine. I haven't got around to checking the needles yesterday but I will do it when I get home from work and update this. Also when I pulled all the gas out I also removed the fuel filter and inspected it and it looks pretty good so I reinstalled it. I did do a compression test before I did anything and I have 120,121,120 so I haven't melted it down just yet but im trying to prevent that. Thanks guys for the help. Ill keep updating as I work on it.
 
I have a vmax 700sx and I just had thins safe issue, it would bog unless given a lot of throttle right of the bat, which is most likely normal, but would backfire all the time. Yesterday I removed the carbs and gave them a thorough cleaning and the back fire is gone. The pilot on #2 carb was completely plugged up. It's kind of a pain, but pull the carbs and clean them! It's not that difficult and I'm sure your sled could use it!(mine did). Plus it allowed me to deep clean the engine compartment.
 
Sx700bb said:
I have a vmax 700sx and I just had thins safe issue, it would bog unless given a lot of throttle right of the bat, which is most likely normal, but would backfire all the time. Yesterday I removed the carbs and gave them a thorough cleaning and the back fire is gone. The pilot on #2 carb was completely plugged up. It's kind of a pain, but pull the carbs and clean them! It's not that difficult and I'm sure your sled could use it!(mine did). Plus it allowed me to deep clean the engine compartment.
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I pulled the carbs off several times to try to pin point this issue and I've cleaned them twice. I will have to pull them off again today to check what pilots I have in there.
 
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