bottom end limits

Personally, I would not worry about such a small overage in the side to side play. It's the vertical play you really need to worry about.

That said, if the bike is heavily used, replacement of the crank as part of your preventative maintenance program is not a bad idea (check a service manual to see what Honda recommends for your bike). Honda crank assemblies are usually pretty cheap, especially compared to a catostrophic big end failure that takes out your crankcase (don't ask me how I know).

I was reading dirt bike daves reply and was about to reply with-" preventative maintenence by replacing the crank, blown cranks are the worst thing that can happen to a bike - just leave it until it dies" - then I read the part about the cases. Ouch - I didn't know that was possible. That means new bike really ? doesn't it.

UTS

In my experence side to side play is not a problem as long as verticle play is in check. If it were my bike I would finish the top end up and run with the current crank (in fact I would probably not have measured side to side to start with as its not a concern imo). My family (all of us ride) has only had one crank/main bearing failure in all our years of riding (>10). This was a KX100 which was used hard consistently from 1991 to 2000. It gave lots of warning, made all sorts of weird noises as the bearings eventually started to go. Eventually it locked up, but did no damage to anything else. A new crank assymbly and it was good to go again. I did have the crank re-built on my old KX250 which had very high hours and was way above the limit for verticle play.

best of luck and have fun:)

As stated above, the side-to-side play isn't as critical as up-and-down play. That being said, I have had 2 different experiences that I will share. Years ago I was riding in Hollister and was about 3 miles away from my truck. Without any warning, the bike started to vibrate excessively and made noise from the the bottom end. I was towed back to the truck, and on disassembly found the crank bearings were ready to completely come apart. The crank play had been checked recently before the incident and all was good. The 2nd experience was more recently with my 99 cr250. After a routine check of the crank, I found out of limit side-to-side play as stated above, AND also a bit of up-and-down play. I decided to ride one more time anyway. The bike ran well all day without any problems. After tearing the bike down, the bearings were in fact worn out, and had actually spun in the ignition side case, destroying it. To replace the crank, bearings, and seals would only cost around $300 if there is no other damage. Not much considering what it will cost with damage to other parts. I must admit that there was probably play at the crank for some time before I detected it. Honda cranks are relatively cheap, and gives peace of mind. No fun riding wondering whether your bike is going to grenade or not. Good luck.

If the side clearance is a little too big , I wouldnt worry about it. If the clearance is too small however , the rod bearing wont get lubed properly.
If the rod bearing fails , it will normally start to rattle , and seize if run for much longer.
The main bearings will normally also give a bit of warning , engine will start to knock , and maybe vibrations will be felt.
I have only seen gearbox bearing spin in the cases , never a main bearing. Theres is no reason to doubt the condition of the main bearings because of the side play at the rod.