I have a Magnum 91RFS that I put in a 4* 60 for my second plane. I bought an APC 14x6 prop to put on it. My problem is that when I get the backplate for the spinner, the prop, the prop washer, and the nut on, then the backup nut that came with the engine will not fit. There are not enough threads left for it. Any suggestions?

matt

I've had the same problem with my Magnum 70. I just put on a standard prop washer and nut. I would check it often though. I think that they do make special back plates that are thinner for just this problem, although I have not seem any in the hobby shops.

Just use the one nut. Tighten it well, and check it ocassionally.

Dr.1

That is the way I set this thing up. I just put on the one nut and was going to try it that way and then I got to reading on here and saw that four strokes through the prop more often. That got me a little spooked. I didn't want to hurt anyone so I thought I would ask. The other thread said that as ling as you don't run your four stroke too lean you shouldn't have a problem so I will just go with that.

Thanks
matt

Another possibility is to use an aluminum spinner that has the bolt in the center of the spinner (Great Planes and others also). Trim/cut the adapter and/or bolt as needed to fit. The adapter for the spinner will act as the stop nut for the regular nut. I use this setup on my Saito 72 and 82.

Go to Lowes and buy an aircraft nut, the ones with the nylon lock ring in the last few threads. I have had success with those.