Impeller shaft wear, too much?

8 replies to this topic
  • upthemaiden

Posted September 02, 2011 - 07:54 PM


I'm replacing the 2 seals and bearing for the impeller shaft and I wanted to get some opinions on whether or not I should replace the shaft while I have the motor open. I've looked on here and people say to replace them when they wear, but I'm not sure what's considered out of the ordinary. There's definitely a black mark on mine and you can feel a slight indent when you rub your finger over it, but I see pictures of others online that looks similar and people say their bikes were running fine. Who knows though.

Does this look acceptable to you guys, or toss it out and buy a new one??

Thanks! (sorry the picture sucks)

Posted Image

  • grayracer513

Posted September 02, 2011 - 08:08 PM


I would replace it if it's as you describe.

Does the previous link help you?

  • cbrewer450

Posted September 05, 2011 - 07:10 AM


If you've already got it pulled, and you're questioning it, I would replace it. Better than having to pull it a month down the road. I did everything on mine when it went.

  • upthemaiden

Posted September 06, 2011 - 03:52 AM


Thanks, I ended up ordering a new one over the weekend so once a couple parts come in I'll button everything up and hopefully be ready to go.

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  • upthemaiden

Posted September 10, 2011 - 06:19 PM


Does the previous link help you?

Which link are you talking about? The previous thread about the cam timing? Before I got the bike running right I had an unrelated problem with the crankshaft. I'm going to rebuild it with a new crankshaft probably over winter, but in the mean time I picked up a whole used yz426 and I'm gonna swap the motor in to try to get some riding in before the snow gets here. It was in parts when I got it because it needed new seals for the impeller shaft, so I had to put it back together myself.

You sure it's 13 chain pins between the marks on the crankshaft at 12 o'clock and not 12? Again I can't get the timing marks to line up, although they'd be perfect if I only had 12 pins between them. I know before you guys said that maybe my marks were off because the chain was stretched, but for the timing mark to be 1 whole tooth off with only 13 pins between them, that would mean the chain was really(8%) stretched, and I don't think the chain would even have tension on it if it was that stretched. My manual doesn't say anything about it, and I bolted it back together with 13 pins between because I trust you, I just wanted to double check.

  • grayracer513

Posted September 11, 2011 - 11:14 AM


You sure it's 13 chain pins between the marks on the crankshaft at 12 o'clock and not 12?

The 450's were 13, as were most of the 426's, but earlier engines were different. It's best to go by the I & E marks instead (at 9:00 and 3:00). When in doubt, the question is whether on tooth either way makes it line up better or worse.

  • Yama450YFZ

Posted September 11, 2011 - 11:15 AM


Replace it this is the reason your seals went in the first place.

  • upthemaiden

Posted September 11, 2011 - 06:55 PM


It's replaced! I replaced the impeller shaft, the oil seal, new bearing while I was in there. Right now I'm just waiting for the water pump seal to come in the mail, RonAyers is taking their sweet old time getting it here, tracking number says it should be here on Tuesday.

With any luck I'll be out on the road by next weekend.

  • upthemaiden

Posted September 11, 2011 - 07:01 PM


The 450's were 13, as were most of the 426's, but earlier engines were different. It's best to go by the I & E marks instead (at 9:00 and 3:00).

I spent some time finding all the pictures I could on google, and it looks like most of the top ends I could find had 12 pins. Oddly enough I did find one guy who said his engine had 14 pins.

I also came across an old article about sprucing up the engine on the 2001 wr426s. They were all standard things like pulling the exhaust baffle and taking off the airbox cover. One of the things on the list was rotating the exhaust cam clockwise 1 tooth, so that would've even made it 11 pins. Sounds interesting but I'm still gonna stick with the original setup.

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