Help / advise 2015 WR450F top end rebuild

[oldguy]

I think its time to do a top end, on my 2015 Yamaha WR450F, Ive decided to do it myself, It looks relatively simple enough. I have all the tools needed to do the job, but want to know is it a simple matter of ordering a top end kit or are there things to look out for before ordering anything.
Also does one go with the genuine or GYTR, looking at MotoXparts they have 3 piston Kits JE, Meteor and Wossner from $220 to $248 will still have to chase up a gasket set.
Which would you recommend, would I have to re-shim. do I check before I pull top end down then if need be order the correct shims or do that after the new top is put back together.

Thanks John.....:wait::corn:

[SVboy]

If it were me, I would go OEM, but I would have a shop manual as my first purchase, as it will give you all the clearances/ wear limits to measure, as well as step by step instructions. My two cents.

[rogson]

I have an 05 and an 08 and have replaced pistons/rings in both. The stock pistons (in those years) are cast while many/most of the aftermarket ones are forged, which are supposedly stronger. I've used aftermarket forged pistons with no problems. You will need head and base gaskets - I would go with OEM on both. You should check valve clearances before disassembly and after reassembly. I've found the before and after clearances are the same - so do any shim changes needed from your pre-disassembly check when you reassemble and you should be good to go - but definitely check to confirm.

The cylinder head bolts tightening process in the manual (again for the 05 and 08 years) is a convoluted process involving an initial torqueing to 30Nm, removal and re-lubrication of the threads then a re-torque to 20Nm followed by tightening another 1/2 turn in two steps. I don't recommend doing this unless you are using new bolts - it yields them so they won't tighten to same torque when reused. I have personal experience of the consequences of this - successively blown head gaskets that I only fixed when I used new bolts. However, since then I have successfully reused bolts by just doing the initial torqueing to 30Nm. Personally, I would probably reuse the bolts if I knew it was the first time the head had been off (or you know new bolts were used on the current assembly) - and as I say just do the initial torqueing to 30Nm and leave it there.

[caseye]

Geez OldGuy, that bloody thing goes well enough now! Cept'n of course for the ridiculous amounts of fuel it uses when you're out wiv da boys on a leisueriely South Auckland Thursday Night Ride.
Need any help mate, give us a call, most of the tools torque wrench etc in da garage.