Crank seal on 22 HP. LA135

I developed a leak on my crankshaft seal the second year of normal use. Pretty easy to replace making a seal setting tool out of a piece of PVC pipe with a coupling. Replaced the seal again in the forth year. Happened to be talking with someone with the same machine and they also have the same leaking problem. Thought mine was unique but now wondering if it's a common problem on the 22hp.

It would be easier to give you an answer if you told us what engine you are talking about. The model number is necessary.