I know this a common post, drive chain rubbing frame just need some ideas to try...

It wasn't an issue when I first built the bike. I recently had to remove the engine to fix a problem. But since I put the engine back on the frame this has been a constant issue with the drive chain rubbing the frame, especially when the master link passes by it. One tip I heard was to use a spacer on the rear wheel to help it clear. Just wanted to see if I could get some other ideas to try if the spacer doesn't work. It's on a cruiser frame. Any help is appreciated.

The first thing you need to check is to make sure that your back hub adapter is properly mounted if it is a rag joint there's not much you can do but if it's a clamp on you can move it back and forth in and out just a little bit.

This is a problem that I had to address. So what I did is I spread the back triangle and it helps. But be careful not to do it too much because you'll compromise the area that you have for the rim to fit.

What I did is I took a piece of all thread and put two nuts on the inside of the dropouts and then one on outside of either side and crank it out. You probably have to go further than what you want to stretch because the frame is going to come back a little bit and only do a little bit at a time or you will very quickly run out of room for your rim.

When you're done check the alignment of your dropouts where your back wheel bolts on make sure those are straight because if they're not it's going to pull back in when you tighten down on it

I also added two bolts to the inside of the axle rod so is to help keep it spread out.

It is possible to spreed your dropouts some. You can also use 2 adjustable wrenches to twist and bend your tensioner to better align the chain.