Got a big bore... need tips installing


3 replies to this topic
  • GixRider

Posted June 21, 2005 - 07:50 PM

#1

I purchased a 444cc kit for my 2000 yz 426. I've got most of the crap taken off the bike in prep for removing the engine. When I got to the swing arm bolt, I realized it might be easier to just change the cylinder/piston while its still in the frame. Is this possible? Any other tips on DIY rebuild?

BTW, I got the kit from Lukesracing.com. Very nice people to deal with and it was in the mail the same day I ordered it. :) :)

  • Hick

Posted June 21, 2005 - 10:02 PM

#2

Sure, you can do this w/ the motor still in the frame.

IMO you need 2 good torque wrenches, one larger one for the various 35 lb-ft + ratings, and a smaller one for stuff like cam cap bolts (10 NM I think?), for example.

You can reuse the rubber valve cover gasket many times, it is pretty sturdy, but you could still tear it if you aren't careful.

I like to use a telescoping magnet to fish the cam chain out in case I drop it (better to just wire it up and keep it there), and to lift the valve buckets out in case I'm changing shims. Once you have the head off keep it upright or the buckets and shims may fall off, you don't want to get these parts mixed up. In fact, while you have the head off it is a good idea to write down the shim sizes and their location. Then you can check clearances during reassembly and know what shim sizes you will be needing, if any, for the next valve adjustment (may not apply depending on hours on valvetrain).

If you do drop the cam chain it may drop off the bottom crank tooth, in which case you will need to remove the flywheel/mag to get it straightened out before it will fit over the cams.

I forget exactly, but I believe the front cam chain guide needs to come out before the jug will come off (or is it the head that won't come off until this is out of there?), it just slides into a notch, but the rear cam chain guide is bolted on. You may need to remove the rear guide to remove the cylinder, in which case you need a flywheel puller regardless, as the bolts that secure it are behind the mag.

You should probably be using anti-seize on the longer cylinder/head bolts.

And you will need a quality snap-ring plier for the wrist pin (stuff a rag in the crankcase to prevent an errant snap ring from falling into your bottom end).

Be aware there are a few dowels between cases, jug, and possibly the head (I forget), keep an eye out for these and don't lose them. The larger (like 15mm, in front of the cyl.) water jacket dowel from cases to jug has an o-ring, don't lose it (duh).

There are also dowels that locate the cam caps to the head (and make up the cam oil passages), don't drop those (duh II).

Read the manual, be methodical.

That is all I can think of right now, hope this helps.

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  • grayracer513

Posted June 22, 2005 - 07:57 AM

#3

I forget exactly, but I believe the front cam chain guide needs to come out before the jug will come off (or is it the head that won't come off until this is out of there?), it just slides into a notch, but the rear cam chain guide is bolted on. You may need to remove the rear guide to remove the cylinder, in which case you need a flywheel puller regardless, as the bolts that secure it are behind the mag.

The front chain guide cannot be removed with the head in place, but needs to be removed to get the head off. Obviously not engineered by a mechanic, but not that bad. Raise the head a bit and slip a piece of 1x2 or 2x2 wood under it to support it. Then, using needle nose pliers pop the front chain guide up, rotate it 90 degrees,and pull it up and out of the way. Replace it the same way in reverse. You will want the flywheel off for this job, since once either guide is out of place, the cam chain can and will drop a link off the bottom of the crank sprocket, as Hick said. You were going to put a new cam chain in with the rest of it, anyway, right? A flywheel puller is only about $15 or less, and you will wonder why you never bought one before (the one for the YZF fits nearly everything else, too, BTW)

You will also want to carefully note how the front guide sits in place, both at the bottom, and more particularly the top anchor points, because it can be knocked out of position while mounting the head, and you may not find out about it until you try to install the chain, at which point removing the head again to correct it will annoy you. (DO NOT ask me how I know this! :D ) The rear guide can be removed or installed with the head on by working from the bottom, behind the stator.

On the subject of runaway parts, bear in mind that the head bolts have thick washers under them (all four) which are capable of rolling an impressive distance, blend in with a wide variety of surfaces, and automatically seek out the least accessible spot in the shop to roll under. :) (don't ask about that either)

Read the manual, be methodical.

That is all I can think of right now, hope this helps.

Like the rest of it, excellent advice. :)

  • Ga426owner

Posted June 22, 2005 - 09:57 AM

#4

I purchased a 444cc kit for my 2000 yz 426. I've got most of the crap taken off the bike in prep for removing the engine. When I got to the swing arm bolt, I realized it might be easier to just change the cylinder/piston while its still in the frame. Is this possible? Any other tips on DIY rebuild?

BTW, I got the kit from Lukesracing.com. Very nice people to deal with and it was in the mail the same day I ordered it. :) :D


LukesRacing is a bunch of nice knowledgeable guys.....I have bought from them - very very competive prices :)





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