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0bigsilver6

Rebuilding 02 426 top end...

6 posts in this topic

Ok, as the title says, I'm in the process of rebuilding my top end on my 02 426. Well changing the piston/rings anyways. Going to leave the valves alone until next winter. I left the engine in the frame while I do it, but I have it all torn down and the cylinder and piston off.

My question is, I'm following the manual and some threads on here, but there's one change I'd like to make to the process of it would be acceptable. What I want to do is install the head onto the cylinder on a bench making it easier to torque those bottom side nuts. Other than it adding more weight when it comes time to slide the cylinder on the piston, which I think I'll just put the piston in the cylinder and then slide the pin through the piston, is there anything wrong with doing it this way? From how it all goes together I don't see where there would be, but please someone enlighten me... Preferably grey! The Yamaha master!

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Well, it sounds like a bad idea.  To begin with, you remember how the front cam chain guide is held in place?  It sits in a pocket in the cylinder, and the head holds it down.  So you'd have the bottom 4" or so of it sticking out the bottom of the cylinder while you try to install it.  Secondly, you aren't supposed to torque the nuts on the head studs before torquing the main four head bolts.  Beyond that, I doubt there's clearance under the frame spine to allow the whole stack to be assembled onto the engine like that, and it's a lot of weight and too many parts to line up while you're trying to get the piston or pin situated.  

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Well, it sounds like a bad idea. To begin with, you remember how the front cam chain guide is held in place? It sits in a pocket in the cylinder, and the head holds it down. So you'd have the bottom 4" or so of it sticking out the bottom of the cylinder while you try to install it. Secondly, you aren't supposed to torque the nuts on the head studs before torquing the main four head bolts. Beyond that, I doubt there's clearance under the frame spine to allow the whole stack to be assembled onto the engine like that, and it's a lot of weight and too many parts to line up while you're trying to get the piston or pin situated.

Alright. I'll do it the right when then! I just need to get some 12mm crows feet to reach those back two nuts for the cylinder head. No big deal.

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SBX1820.jpg

LOL! I'm amazed you're recommending that over crows feet! Can't properly torque the nuts without crows feet, unless the motor is off the bike I guess. Thanks again for the help gray! You are a very helpful person. I think we all really appreciate the help from you, you are so knowledgable! I spent the money and ordered a set of metric crows feet that will be here early next week. Looking forward to getting the bike back together with the new piston and see how she runs/starts with the new auto decompression exhaust cam!

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