Its not very precise but the easiest way is to pop the valve half way in and "feel" the degree of lateral movement of the valve in the guide. If one or more valve stems and/or guides are more worn (or cracked) then the rest then it should be obvious. Valve guide wear is pretty rare on bike engines so that is all I generally do. This technique clearly does not work if all are equally worn :-)

Keith

krisztian_andre wrote:

lukemillar wrote:I usually measure them but have yet to find one that needs replacing so you should be fine

Can you tell me what type of gauge I could use?

https://www.youtube.com/watch?v=LIL1lV_xtHI