426 Engine teardown help

5 replies to this topic
  • YZFcrash

Posted April 10, 2002 - 03:44 PM


I have found out that either my 3rd gear is trashed or I have a bent shift fork on my 2000 426. I would also like to put it a hinson clutch, and install a new CB Key. With that said, I found out how much it was going to cost to have it fixed at a dealer (WAY TOO MUCH). I was thinking about fixing it myself. I have done minor things on bikes but nothing serious. I would love to learn how these things work, but am a little apprehensive about ripping in to it. How hard is this repair going to be? I do have a service manual, and a good torque wrench, I also plan on buying all the necessory tools as I need them. Any advice on the subject would be helpful. Thanks John

  • MXOldtimer

Posted April 10, 2002 - 04:49 PM


I'm doing the very same on my 00-426. My tranny was starting to skip under power around 4th so I decided to investagate before things really go bad. I found out I have a bent center shift fork and that the dogs on 3rd & 4th are rounded. You'll need a impact wrench to loosen a few nuts, Ignition,balancer,balancer drive & Primary and the only real tool that you'll need is the ign. puller, but if you ask around you can alway find someone with one and a six pack works wonders. I've opened engines before, but I'm no mechanic, if you have good mechical skills and pay attention you can work through it with the manual. When I open things that are new to me I use my digital camera. I remove something lay it out in order and snap a picture, then I take those parts with a note of what they are and put them in a clear sandwich bag for easier ID later. I also seperate my motors parts such as right& left side case,head and so on, that way you wont be digging through a box of parts not knowing one from the other. My bike ran perfect so I'm not going to do a complete rebuild this time just repairing the bad parts, next time I'll do the whole thing after I get my feet wet this time. I'm finding it really interesting and fun as to the goings on inside these hiper engines. Just be carful there's alot of lil parts but if keep an eye on things, follow the manual
you should be OK. The really neat part is I now can do the wet sump on my 250F myself, once you see whats going on it pretty much explains itself, with the manual of course, and these things have a great manual.

  • tony_t.

Posted April 10, 2002 - 05:18 PM


I had the same problem last year. Make sure you have plenty of work space to lay out all the parts so you can keep them in order. It will help to have an extra hand around when you take the engine out of the frame and when you put it back in. As long as you are in the transmission make sure to replace any parts with wear and not just the damaged ones. Make sure to replace the rings on the piston also. Good Luck

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  • Shawn_Mc

Posted April 12, 2002 - 11:48 AM


And go easy on the silver bullets until you know your way around in there to. :)

  • Rich_in_Orlando

Posted April 13, 2002 - 06:15 PM


I've split the cases on my 400 3 times. Here's a few things I've learned beyond the scope of the owners manual:

Part A- Zen and the Art of Yamaha Maintenance
<ul type="square">[*]Clean the garage (or where ever your work space will be) before you start[*]Locate all of your tools in a convenient location.[*]An impact wrench is essential.[/list]
Part B- Just Do It
<ul type="square">[*]Don't take the engine out of the frame until you have the head, cylinder, right side cover and clutch off. Conversely, put the engine back in the frame before you put all those parts back on. It's much easier to move around the smaller, lighter bottom end by itself than the whole engine. And the frame makes a nice engine holder while you reassemble it. [*]The hardest part is putting the transmission back together, but it's easy. You have to get all the parts together (both shafts, the shift forks, and shift drum) and try to put them back in the left case as one unit. The way my manual shows how to do it doesn't seem to work for me. I do it differently: I turn the left case upside down with the inside facing me. That way, the shafts and gears provide a holder for all the other parts as you stick them into the case. It will take a little bit of playing with the whole thing to get everything lined up but it does work that way. Once you get them in and lined up, the hard part is over.[*]I put all the parts from a commmon area in individual ziplock bags and label them with a sharpie marker.[*]I always clean the carbon off the piston face and cylinder head with some fine steel wool. [*]Use assembly lube generously.[/list]
That's all I can think of, for now.

  • nopremix

Posted April 13, 2002 - 07:17 PM


I have torn down my 400F engine 2x's trying to diagnose a noise.

I would say that EVERYTHING the guys ahead of me suggested to you is exactly on target.

It's a little scarey the first time, but don't worry its not too bad. My additional thoughts would be:

1)Be careful when putting the timing chain guides back in, do it before you put on the cylinder.
2)Make sure you are careful when putting the timing chain on the crank gear not to let it slip down and kink, keep it taught, - I use a piece of wire to feed it up through the cylinder when I put on the cylinder. After I get it up through the cylinder, I let it hang over the side and wrap the wire on something, so the chain does not fall back down.
3)Put the timing chain tensioner only after you put the cams back in and set them properly with the chain. You can reverse the tensioner by holding it and using a small flat blade screwdriver to turn the spring loaded extender back into the mechanism. You have to hold it carefully when you have it retracted and start the two screws. Once you pull out the screw driver, it will shoot out and put tension on the timing chain.

Getting the cams back in and the marks lined up is a little tricky, but be patient and work with it, sometimes it takes a few trys. I usually grab a cam in each hand while trying to line up the marks and the chain at the same time. This method seems to work best for me an gets the job done faster than anything else I have tried. Once I have it all lined up, then I put the caps on and carefully torque the bolts. I can't get a torque wrench on one of the bolts, so I have to guess the best I can at that one.

Be very careful about the washers on the head bolts, not to let one drop, you will not be happy. They have a tendency to stick to the head like an oil drain plug washer does sometimes etc... And once you put a head bolt in, if you have to take it back out for any reason, that is when those darn washers want to stick to the head

Be careful not to over tighten the flywheel nut with an impact wrench or you might strip the threads on the crank. I made that mistake!!!

Good Luck, you can do it!!!

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