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800 pipe on, now back fires!

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Old 04-10-2007, 10:14 PM
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Default 800 pipe on, now back fires!

I got my pipe on and now it backfires through the exhaust while "punching" the throttle from an idle. I believe this is a rich condition, but what has me confused is, when I slightly pull out on the choke, the engine rpm's speed up slightly, which makes me think of a lean condition. Engine is totally stock, except a K&N, and this 800 pipe! I let it get totllay warmed up too. Does this carb have the needle setup that I can drop one clip? Any other thoughts? Am I rich or lean?
 
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Old 04-10-2007, 10:21 PM
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Default 800 pipe on, now back fires!

Mine used to backfire after I let up on the throttle. Replaced the header exhaust doghnut. My 700 carb has an adjustable needle.
 
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Old 04-10-2007, 10:22 PM
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Default 800 pipe on, now back fires!

Backfiring is usually a lean condition and you are flowing more with the 800 pipe. You might need to raise the needle (lower the clip) and maybe a bigger main jet.
 
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Old 04-10-2007, 11:19 PM
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Default 800 pipe on, now back fires!

OK, Thanks, I figured a backfire was from unburned fuel allowed to enter the exhaust. I will not argue though, I am the one asking the questions![img]i/expressions/face-icon-small-smile.gif[/img]

Ok, now for the 800 conversion update! I test fitted this pipe for clearance, but not for a total install. The tailpipe is about 1 1/2" lower than the stock pipe location. I forced it up, but the whole pipe is on a bind now. I will try to bend it up slightly to relieve some of the pressure! This is already ceramic coated, so I will have to be careful during the mod process. I didn't think there would be any difference in the location of the can, I have checked the part numbers and a stock MV pipe is the same part number as a stock Sportsman 700 pipe. So this 800 pipe should be able to mount up to a 700 and my MV. We all know the 700 and 800 chassis is the same. For some reason, it doesn't fit ok. Who knows? Anyway, I'll get it to work! I now need to do the shifter mod, that I was warned about. The shifter rod rubs the heat shield. I noticed the front shifter arm is bent in, I wonder why I couldn't just bend the front arm of the shifter out, instead of bending the rod. I would then flip the front eye bolt, so the extra threads are on the inside. Should work! I'll tinker with it tomorrow!
 
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Old 04-11-2007, 12:03 AM
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Default 800 pipe on, now back fires!

My friend did the smae mod to his 700. He had to go up to a 160 main adn did the shifter flip mod. Other than that it runs good and everything bolted right up.
 
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Old 04-11-2007, 12:13 AM
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Default 800 pipe on, now back fires!

Thanks, I appreciate it. Looks like the stock size main is 157.5!
 
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Old 04-11-2007, 12:14 AM
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Default 800 pipe on, now back fires!

Anyone know what the exhaust temp should be. I could easily check the temp with my laser, if I knew what normal was!
 
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Old 04-11-2007, 12:16 AM
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Default 800 pipe on, now back fires!

Yep thats it. I dont think it would hurt to go to a 162.5 but he went up 1 size and it runs good. His never backfired. It just went flat in the top end.
 
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Old 04-11-2007, 01:15 AM
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Default 800 pipe on, now back fires!

Temp is a good question and will be different at idle and under load while riding. Best way to see how you're jetted is to read the plug(s). Install new plugs, ride it for a while and look at the color. Should be grayish-tan and dry. Black is too rich and white with powdery coating is too lean.
 
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Old 04-11-2007, 03:52 AM
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Default 800 pipe on, now back fires!

If your pipe glows red it's too hot [img]i/expressions/face-icon-small-smile.gif[/img]
 


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