Crm siezed up, Main bearing play?

[jim-cr 250]

Hi all, i have the mk2 crm, amd im just wanting to know how much side and upper play there should be in the conrod? Im sure there quite a loose fit?

Whats happened is the other day i was out on the bike, throttle was wide open in 5th when it suddenely tightened up and siezed, pulled in and let it cool and it turned over fine and had compresion, would even start but not idle, and it was knocking like mad.
So today i have stripped it down, top end is fine, no marks, has not over heated. There is quite a lot of play in the big end, but im not sure what they are like anyway. BUT the thing i have found that the rollor bearings for the balance shaft have all collapsed, this would explain the knocking maybe, but not the seizure?

The thing is the bike would turn over straight away after it siezed, so im not sure weather its just that the balance shaft bearings have give up and exploded, or the big ends are goosed and had locked it up whilst it was hot.
Any help would be great. Thanks you. Jim

[Blau Zedong]

It's not unusual for big ends to have a fair bit of side to side play (and often alot more than the manual suggests) and still be ok. It's up and down play that's the killer. If you can discern any up and down play when the conrod is 90 degrees to the crank pin, it's fucked. Once the play is there the big end gets massive hammer, overheats and then fails.
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[jim-cr 250]

Cheers for that, yeah i did think they were meant to have a bit of side play, but mine does have the up and down play aswell, ahwell never mind, rebuild time it is then. Time to strip it down completly.