need top end re-build tips

Well I got my piston and rings, my gasket kit, and my manual so I'm ready to go for a re-build on my '00 426. I'm going to start this week or maybe next so I'd appreciate any tips you might have. I've done several 2 strokers but this is my first time on a 4 stroke. Thanks in advance...

Just take your time and observe how everything came off, so you'll know exactly where everything goes when you're reinstalling it. Be careful not to drop the timing chain down into the case, it's a real pain in the butt to get back out. :) This was my first four stroke also, and I found the job to be easier than I thought it would be. Also, make sure you have proper torque wrenches on hand, they should be used to tighten everything to the specs listed in the manual.

Good Luck

Ditto on the torque wrenches. You really need two of them, one for small readings like the cam cap bolts and a bigger one for the head bolts, for example.

I use a big zip tie on the cam chain. Since you’ve probably had to swap some valve shims out by this time I’m guessing you really don’t need any help with the valve train.

Check your ring clearances or gaps as per the manual. I installed one that was a tiny bit too tight the first time I did this and could not get the bike started.

I have done this three times and have decided the easiest way for me is to install the piston into the cylinder and then drop them both onto the motor (which I leave in the chassis). I go ahead and put a circlip on one side of the piston then I partially install the wrist pin from the other side so the little end of the connecting rod will still fit in there. Next I stick it in the barrel from the bottom (it is chamfered on the lower edge) until the wrist pin contacts the cylinder. Then, supporting the piston equally on each side with my fingers on the skirt (this is important or the rings will pop out on one side) I lower it over the cylinder studs and onto the rod.

The other option is to install the piston onto the rod first, then get the barrel over the rings. A little harder since the barrel is also going down the head studs at the same time. I did this once with the motor out and on a bench and it wasn’t too bad. Six of one, half dozen of the other I guess.

I also recommend following the manual’s advice and retorquing (no, that word is not in my spell checker) the head bolts after a few hours of operation.

It can be a bit tricky sometimes getting the front chain guide out of the slot in the cylinder where the cam chain runs, if you pull it up about an inch, then twist it 180 degrees clockwise it will come right out. I think the front guide needs to come out before you can get the head off. I can’t remember if the rear chain guide needs to come out to get the cylinder off the bike. I think it does. If so you need to remove the flywheel to get at the bracket that holds it. When you reinstall this bracket make sure the cam chain is on the crank gear nice and snug and will stay there (I tighten my zip tie up for this). If it skips a tooth down there you will have to remove the flywheel again to fix the problem, which is hard to notice until you try to reinstall the chain (“Gee, I’m almost done! I can ride today! Hey! What the??)

I haven’t done this in a while, but ironically I’m going to be putting a new piston in my bike next weekend too.

That is all I can think of, hope it helps some.

[ January 08, 2002: Message edited by: Hick ]

Mike, Ditto what mike and Hick said. Be careful with the timing chain. If you give it too much slack, it can bind under the gear on the crank and you may have to pull your flywheel to access the mess. I use a rubberband (or a string of them) to hold constant tension on the chain so I don't have to cuss the beast any more than I have in the past. Otherwise it's a fairly easy job. Good luck!!! :D:)

I would just like to add that replacing the timing chain is a good idea while your doing the top end.

The timing chain is the weakest link in the entire engine and only takes 10 minutes to change, and you will probably find that the old chain is very kinky feeling compared to the new one once you get it out and inspect it.

This causes severe wear on the primary drive gear on the crankshaft and is the cause for most of the metal shavings you find inside the magnet of your generator.

The primary drive gear is a small radius so all the wear usually takes place here with the chain making this tight corner.

After one year of riding on a 01 426 my chain was toast and the primary drive gear looked like hell.

Later, Jason

What kind of cost for the timing chain and or drive gear?

The chain is $54 bucks, the crankshaft half is $192.

The gear is made onto the crank so you would be replacing one side of the crank and replacing the lower bearing, not to mention splitting the cases.

A bunch of work and money that can be avoided by simply replacing the chain periodically.

Later, Jason

Have some assembly lube on hand for when you re-install the cams. Don't wanna run em dry. If you take your time and follow the manual, it's a breeze. You may wanna wash your bike with the tank off to get rid of whatever dirt may fall into the motor while it is apart. I took a quick video of the motor before I yanked the cam's and the chain. I didn't need it, but if I did, atleast I would have something to go back to for reference. Good luck, if you have any problems there is plenty of experience on this site to help ya, just ask...


Thanks for the help guys. I have it down ready to start taking off the head now, will probably start this eveing. I've been taking lots of digital pictures as I go so if any of you need a picture of something let me know and I'll send it to you. So far I have about 50 MB worth... I'm also going with the 13.5:1 Wiseco so I'll let you know if it makes any performance difference... I just got back from a dune ride last weekend and I couldn't believe how much sand got into everything. Still was very dirty even after a pressure wash.

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