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2007 yfz450 Wont Start and backfires

This is a discussion on 2007 yfz450 Wont Start and backfires within the Yamaha YFZ450/450R (2004-Present) forums, part of the Performance /Technical category; Hello i just got a yfz450 guy said he can get it started and was leaking gas out of overflow so i pulled carb and ...


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Old 06-26-2010, 06:26 PM   #1
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Default 2007 yfz450 Wont Start and backfires

Hello i just got a yfz450 guy said he can get it started and was leaking gas out of overflow so i pulled carb and cleaned it float needle was stuck. now i cant get it to start and idle and is backfiring real bad i did have it started for a minute and all it did was backfire. any help would be great

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Old 06-26-2010, 09:36 PM   #2
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did you take the slide out? it can be put in upside down, with the results like your describing.

or maybe you moved the TPS a little on the carb (little black round wire thingy on the left side of the carb)
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Old 06-27-2010, 09:36 AM   #3
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how would u adjust the tps?
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Old 06-27-2010, 10:11 AM   #4
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leveldrummer said it. I had the same exact problem after I was messing with the carb. Turns out the throttle plate, aka slide, can go in two ways. This will cause it not to slide all the way down. It's worth a look. The tps is where the electrical connection goes into the top of the carb, and according to the book you turn it clockwise or counterclockwise to adjust your throttle position....
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Old 06-27-2010, 10:34 AM   #5
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just adjusted tps still no fire gonna pull carb and double check slide will update with what i find thanks everyone for the responses
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Old 06-27-2010, 12:43 PM   #6
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If you ever suspect that the TPS is bad, then just unplug it, the bike will fire and run with out it hooked up. Double check the timing and make sure that all the marks line up right. If you don't know how, get a shop manual from here.
YFZ450 Garage
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Old 06-27-2010, 12:50 PM   #7
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tps is good according to manual checked it and adjusted with a volt meter how could you tell if the throttle slide is in upside down?
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Old 06-27-2010, 03:34 PM   #8
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ok got it fired up ended up being the spark plug had no gap adjusted the gap and fired right up still a little boggy on throttle unplugged tps and tors up in throttle housing seemed to help a little could i run the bike without these?
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Old 06-28-2010, 01:45 PM   #9
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You can run the bike with out the TORS, that's not an issue. But if you unplug or jumper the TPS, you turn the 3d timing map in the CDI into a 2d map. There are those that will argue that it makes a difference. I honestly didn't feel a difference between the three settings.
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Old 06-28-2010, 05:51 PM   #10
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ok took it for a test ride and have to feather throttle a little to get it past a bog coming of idol. other then that it runs fine Would rejetting take care of that or something else?
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Old 06-28-2010, 06:16 PM   #11
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Read this thread
The Bog, the Zip Tie / O-Ring Mod and You
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