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Crankshaft Replacement

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It is with deep, deep, deep regret I ask this question. I just assisted my friend and fellow YZ426 owner in twisting off the threaded end of his bike's crankshaft as we tried to reinstall a new 12oz flywheel weight (his first attempt resulted in scraping noises coming from the flywheel cover area). Since he did not use a torque wrench the first time, we thought we would remove and reinstall it using a torque wrench to tighten it to spec. Well, for some reason the torque wrence did not click upon reaching the set threshold (35 feet/pounds) and to our dismay we twisted off the end of the crankshaft. So....does anyone have a guess at how much it will cost to replace the crankshaft (parts & labor)? I suspect it is quite a difficult task and will be expensive.

Tazeman

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If you have any mechanical ability you'd save big, BIG $$$ if you did it yourself but you really have to pay attention to what you're doing. I've split 4 2-stroke cases in my garage with the help of a good manual and some bike magazine articles (there's a good one in Feb 2K Dirt Rider) that show some good work arounds for special tooling. Bagging and labeling everything is a must. However, if you'd rather take it in I'd suggest tearing the eng down to the point of case splitting to save on labor costs (I would guess $150-$200 just for that). Good luck.

Phil

'00 YZ426

[This message has been edited by YZFWrench (edited 04-29-2000).]

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I am Tazeman's friend. It wasn't his fault ... it was the torque wrench. Anyway for anyone who is interested & this unfortunately happens to the parts were $420 and the labor to have the Yamaha shop do the repair was $315.

Originally posted by Tazeman:

It is with deep, deep, deep regret I ask this question. I just assisted my friend and fellow YZ426 owner in twisting off the threaded end of his bike's crankshaft as we tried to reinstall a new 12oz flywheel weight (his first attempt resulted in scraping noises coming from the flywheel cover area). Since he did not use a torque wrench the first time, we thought we would remove and reinstall it using a torque wrench to tighten it to spec. Well, for some reason the torque wrence did not click upon reaching the set threshold (35 feet/pounds) and to our dismay we twisted off the end of the crankshaft. So....does anyone have a guess at how much it will cost to replace the crankshaft (parts & labor)? I suspect it is quite a difficult task and will be expensive.

Tazeman

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Does this mean you have already had the repairs done?

In the WR section, we went round and round on torque wrenches. I was a nuke machinist mate in the navy where we used torque wrenches everyday. The best wrench is the dial indicator, which is also the priciest. The next best, BELIEVE IT OR NOT, is the cheesy looking one with the needle pointer! The worst and least accurate and MOST LIKELY to go out of calibration is the ratchet type which you used. Contrary to what some may think, you CANNOT calibrate a torque wrench. What they do is put 20%, 40%, 60%, 80% of rated capacity on the torque wrench to check accuracy. You may get the torque wrench back saying for 6o ft-lbs, use the 30 ft-lb setting.

Also you want to use 1/3 - 2/3 capacity of the torque wrench for the application. What I mean by this is if you want to torque to 60 ft-lbs, use a torque wrench where 60 ft-lbs is in the 1/3 to 2/3 range of the wrench. Don't use a 100# torque wrench to torque to 100 ft-lbs. Use a 150# torque wrench, etc.

I am sorry this is too late for you. Unfortunately you'll have to chalk this up to a crappy and expensive lesson in life. I have made many errors and bad judgements in life to cost me tens of thousands of dollars. You know what, I am STILL learning!

Kevin

------------------

99 WR, all YZ mods, de-octopused, OEM YZ tank and seat, jetting by Clark.

AMA, NETRA

Moab bound for 2000, HOORAY!! Gonna be kicking some Moab Ass (Mule or Donkey?)!

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Yes ... the repairs are complete & the bike runs like a dream now. I had to tone the bike down a bit because I primarily trail ride & the bike was geared too tall for trails ... especially tight Georgia trails. Stalls were frequent too. So I added the flywheel weight (after much repair) and reduced the size of the front sprocket.

Thanks for the advice on the torque wrench.

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