Guess that's the difference Ron.I buy quite a bit up there and so I'll ask him about it next couple of weeks or so.As a matter of fact,my MOTOMARINA runs so well with the bigger rear sprocket,that I'm going to ask him if he has one for my other MOTOMARINA ,and I'll get a new chain to match.I put new rings on the Franco-Morini engine on that bike,and honed the cylinder,but not much difference yet in power.It has a very small rear sprocket.I weigh over 230lbs.,so I think the MOTOMARINA will appreciate it.So if I find there's a significant difference in the drive chain,I'll post it for sure.Happy `pedding!