Picked up a new motor for my first complete top end rebuild

[Scallywag303]

I picked up a motor with a vin for a 75 yesterday, which will go nicely with the titled 75 frame I just got last week(pure chance they match in year). It has a hole in one piston about 1/4" diameter, which is fine I am doing a 700cc setup anyhow, and a scrape on the right case cover.

Haven't ripped it apart yet, but I can see the valves do have an excessive amount of carbon build up on them, and so does the bottom of the valve seat.

Yes I do have a manual, and refer to it constantly.

My questions.

1. Anything in particular I should look for with the hole in the piston? I'll obviously check for metal particles or a slapped or bent valve, new/cleaned filters. Anything else? My guess is it ran to lean and burnt a hole in it.(P.O. had no idea)

2. I am already replacing cam chain guide, and the normal seals, etc..Thinking about getting the Athena kit, I know its been covered but reviews all over the place, any good?

3. Cleaning the carbon deposits...Knotted bench grinder wheel okay for the valves? What should I use on the bottom of the head.

4.I got a couple quotes for the boring as high as $250..... Local Yamaha dealer that builds race bikes says $99, seems reasonable. They build race bikes, should know what they are doing... Is price fair?

Also it has a Pamco and PMA in standby when the time comes. Plan on doing a bare bones cafe, w/counter balance cycles seat.

Picked it up in my subbie

 

[TwoManyXS1Bs]

Wow. Dragging up 40 year old memories. Holed piston(s).

Closely examine conrod small end and wristpin.
The condition that led to the holed piston could have affected the valve seats.
Of course, super-flush the bottom crankcase.
Check rod big end side-side wobble, 2mm max at small end.
Molten piston aluminum can sometimes get into and fuse in the ports.

For decoking the combustion chambers, would usually do that before pulling the valves. We would dunk the head into the solvent tank and use a pneumatic drill with a cone wire brush in the chambers, sometimes leaving an old sparkplug in there to protect the threads, depending on the head.

Other than picking/flushing out all the molten piston spray, follow with a complete overhaul...