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Discussion Starter · #1 ·
Alright, so I have been on here for weeks getting advice on what might be causing my 1992 Yamaha Exciter II to Bog. I tried everything: cleaning both clutches and trying all the settings in the secondary clutch, ignition, crank seal test with ether, carbs cleaned and gone through twice, idler wheels checked.....had no luck, the sled would still eventually bog down, usualy after a little bit of riding. So today I was tinkering with the secondary clutch again, trying all the different settings C-1 through B-4 and test driving over and over. The sled was actually running pretty decent today, only bogging down once or twice. One of the times I pulled the secondary off, I noticed gas all over the back of the carbs and it looked like gas was dripping down the fuel line attatched to the MAG side carb. I shut the fuel valve off and inspected further, the gas just seemed to be running down that fuel line. I turned the gas valve back on and started the sled. Gas was pouring down that fuel line attatched to the MAG side carb. I shut her down, shut the gas valve off, proceeded to take off both carbs and loosened up the airbox so I could see the fuel pump. The fuel pump was covered in fuel. I turned the gas valve back on and turned the sled over. I could see gas seeping out of what looked like the top gasket on the fuel pump, dripping down the fuel line and some dripping into the bellypan. Looked like quite a bit of gas was leaking out of the fuel pump. I pulled off the fuel pump and will be ordering a new one. Does this sound like something that would be causing the bogging issues I have been having? I know the fuel pump isn't supposed to leak, but would it cause my sled to bog off and on? On a side note, the jack shaft bearing and housing were just replaced. The jack shaft was flopping around when it went and may have struck the fuel pump causing it to leak....maybe, or maybe the fuel pump just went out, it is an older sled that did sit for a while before I rescued her! What do all you experts think...leaky fuel pump cause bad bogging? Once I get the new pump, I get to try and put it all back together......YES!!! Thanks for any help!
 

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I would think if your fuel pump was leaking that bad, the carbs may run out of fuel and cause more of an "instant shutdown". Possibly produce a bog though if they started to run out then all of a sudden got enough gas.
 

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Don't go and buy a new fuel pump, get a rebuild kit for it. I paid $8 for a rebuild kit for mine.
 

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Discussion Starter · #4 ·
I think the fuel pump would still send enough gas to run, but every so often it would lean out and bog. The bog seemed to increase when the sled warmed......I think?!? I don't know, I guess I will find out. polaris_xc_racing, I bought a used fuel pump from Al's Snowmobile Parts online for $10. We'll see what happens when I put it in.
 

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tjmoening is right happened to me i was leaking where the fuel line went to the carb. it would be tough to start at first and then it would be tought to keep it running to.
 

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i had a problem with one of my sleds doing that as well. it turned out that the diaphram in the fuel pump had started leaking over time. evertime the piston went up in the cylinder, it pulled a vacuum in the crankcase, pulling fuel through the diaphram and vacuum line and right into the crank case. try this: on the old fuel pump, try sucking on the vacuum line. you should not be able to suck air through the pump. if you can, you found your problem.
 

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Discussion Starter · #7 ·
I tried what you said Haggie, I couldn't suck any air through the pump. Gas was leaking out of the top gasket of the fuel pump though, pretty heavily. Maybe not enough gas was making it to one or both of the carbs? The bog seemd to show up when you'd hold the throttle at a constant rpm for a while, like around 5,000 rpms. I could then let off the throttle, come to a stop rev the motor bit to get the idle back up to 1500 and take off, only to quickly bog back down again.
 
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