250-500cc Instructions for top end rebuild WR-300

I have rebuilt a few dirt bikes in my day, but I am told that the newer 2010 WR 300 needs a coating on the cylinder walls once it has been honed or bored out. This is a first time I have ever heard of a nickel coating, but as I am a llttle rusty about this, perhaps this is true...

Does anyone know about this?

There should be a web site for the rebuild, I used to have my Suzuki manual, and it gave a complete top end instructions for my RM-125. It was thorough. Does anyone know of the same online manual for the Husky WR-300?

You shouldn't bore or hone a nikasil cylinder. If the bore is damaged you will need to send it to someone who knows how to replate it correctly.

View: https://www.youtube.com/watch?v=vaFp8aYkHNA

If you need to get it recoated these guys are the best!

http://www.mt-llc.com/

Sure you can hone a nicasil cylinder, normally you always do when putting new rings.
But you need diamant hone with fine profile.
And like others, while you hone the diameter of the bore increases.
With nicasil only being a coating, you cant take off much... Also match your piston to bore size...

I've been researching coatings myself recently. After a fall from my trials bike it stuck on full throttle resulting in melt down, despite pulling HT lead off spark plug!! It kept running.

For me the 'rule of thumb' is NOT to hone. You can, if the coating is thick enough. Typically thicknesses will be about 0.002". Some coatings can be applied up to 0.006" thick which would allow honing (with the correct material honing tool) but the thicker the coating the higher the likelyhood of chipping. The best idea, as stated above, is to give the piston you're installing to the plater, he can apply a coating to the bore to match that piston.

Rule of thumb is when putting new rings you need to clean up the bore.
This means honing the bore.
Pistons are in diffrent sizes, dirtbikes mostly have a,b,c pistons.
Most likeley his bore will be fine and he can use the b or c piston, if he has the possibilty he can let his dealer clean up the bore and supply the correct piston.
Replating here cost arround 250€... Costly rebuild then and not neccassry.
Also, if you or your dealer doesn't have the tools to clean up the bore just place the new piston. It won't go bad...
With the vertex pistons the sizes are printend on the piston crown. If you remove the cilinder head you will see this.

Is it possible to find the piston size on a stock piston using a bore scope?

You can try but i have my doubts, carbon build up...
Do not know if standard piston has it marked on top?
Vertex pistons do...
Try the bore scope, if ot doesn't work pull the head. 30min work max...

All the pistons ive used or seen have markings on the top or casting marks either side of the gudgeon pin.

Most likely not since the difference between pistons is .01mm or .00039 thousands, yes that is 39 ten thousandths, not much at all.

There are 3 bore sizes of the OE cylinder for the 300. They are marked on the cylinder with an "A, B or C". It has to do with the finished bore size and the correct piston. Find the marking on your cylinder, normally stamped on the reed area, and order the matching piston, if you are sending out the cylinder to be replated, you have to send a new piston with the cylinder or buy one from them.

I like PowerSeal for this work (Outside of Philadelphia).... http://www.powersealusa.com/

if you need a pic, look at this......http://www.cafehusky.com/attachments/image-jpg.53673/