426 top end, what should I replace on rebuild?

[Guest BrandonV]

I posted this over on the YZ forum, but noone will answer. I think I may have wore out my welcome....... hope you guys dont mind me asking in here.

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My 2000 is getting a 'freshen up': bored jug, 97mm wiseco, 450 cam and anything that should be replaced/checked will be.

I will be replacing all these parts:

Cylinder

Piston (rings, pin, circlip,)

Cam chain

Cam chain tensioner

ex. cam with 450 cam

What else should I replace? How about the cam chain guides?

What do I need to check for excessive wear?

The bottom end was rebuilt back in 01' or 02' and it got new 2nd & 3rd gears, shift fork and 01' clutch update. Is it time to split the cases again?

I seized the motor last weekend and although I'm fairly certain the lower end is okay, I only want to do this once and might as well do it now.

Thx!

[jonova]

Are you going to have your cyclinder replaced or are you getting it re-nikaciled?(sp)

My 01 426 just stopped idling and backfiring so I'm also putting in a big bore piston as well as intake and exhaust hot cams.

I would love to know how your refreshing goes.

[Guest BrandonV]

I'm having the stocker bored and re-nikaciled. I've spoken to Mike at Luke Racing and will go with them for my rebuild. I was also considering the hot cams as well, but I'm already looking at a $600 bill so I decided to go with the 03' 450 cam instead.

I'll be gone for a while, but will definately let you know how it went after getting it done. I expect that sometime around mid-May.

[jonova]

Thats just about what I have into my project. I'm going to start pulling mine apart as soon as I can get it running. I went riding yesterday and my bike started to backfire and won't idle. But when I'm on the gas the bike runs great. Any advise??

[sleeman]

Replace the valve seals as well.

[Guest BrandonV]

Thats just about what I have into my project. I'm going to start pulling mine apart as soon as I can get it running. I went riding yesterday and my bike started to backfire and won't idle. But when I'm on the gas the bike runs great. Any advise??

Either the valves are out of spec or your carb is dirty. Do not run the bike any further until you check the valves, if they're tight and you end up dropping one it can ruin the head. The bare head alone is $650.

Search for 'valve check' or go to motoman393's site for instructions if you are not familiar.

[jonova]

Either the valves are out of spec or your carb is dirty. Do not run the bike any further until you check the valves, if they're tight and you end up dropping one it can ruin the head. The bare head alone is $650.

Search for 'valve check' or go to motoman393's site for instructions if you are not familiar.

I went to start the bike and found that is won't start without the choke. When you turn the choke off the motor dies. I think it is the idle circuit in the carb. I had the valves done 1500 miles ago.