How do you check for big end wear?

[ericthered]

Hi all,

I've got the barrel off my SIL GP200 to fit new rings and a new little end while I'm at it, but would like to know the proper way to check for wear on the big end and what the wear limits are.
I presume I use a feeler gauge for this but got no specs to use. The con rod does move freely from side to side a little but does not seem to have any up down play but its very hard to check for up/down and I'd guess it would have to be pretty well knackered to have obvios up/down play.
Is there a trick/rule of thumb type thing by how much you can get the con rod to move that is a good indication if its good or bad??
I did have a light tapping/ticking noise coming from what seemed to be the cyl head area hence stripping it down to fit a new little end and rings at the same time, but the rings are worn in the groves so that could have been the ticking, or it could have been the little end but hard to check up/down movement on that.
If the big end is gone that'll be me knackered for a while, not an easy job I guess!

Best regards,
Eric.

[coaster]

I think you would have felt any big end knock whilst riding, it would have seemed harsh and with plenty of vibration. Your ticking noise could also be piston slap.

[nelson pk]

Ideally get the crank out and hold the crank firmly and see if you get any up and down play in conrod. There will always be side to side play as this is a running tolerance. Also spin the con rod and if the bearing feels extremely "dry" and not smooth then replace.
With big ends I would have thought you would notice vibration through the scoot while riding getting worse and worse. A ticking noise from top end could be hundreds of things! Rattling head cowl, piston slap as mentioned, flywheel slightly catching on cowl etc

[ericthered]

Thanks for that guys.
Cant find any up/down play so just ordered a new piston/rings and I'll see what it sounds like when running, if no tapping all is well.
I've got my fingers crossed.
Best regards,
Eric.