When you say cheap mods, I thought, hmm, these things usually cost a bit, but I thought of one interesting mod.... I wouldn't be surprised if some of you have already tried it, and it's probably old history to you guys, but here it is: Take the head and cylinder off and remove the gasket which seals the cylinder to the case. In order to maintain a good seal, I like to use the anaerobic gasket maker because it's the best quality and won't let you down. It's a little scary of a mod, but I've done it, and for me, the piston did not hit the head. When I did it to the stock head, boy that engine really put out a noticeable increase in power, but once the engine started getting hot, it started to detonate, so I had to back off and let the engine cool down. Later, I took a little die grinder and relieved some of the material where the spark plug threads end (slant head) in the combustion chamber. The threads don't do anything except possibly get really hot because they are sharp, so relieving them is a good thing, but don't do too much, cause you will lose the compression gain you were originally trying to attain. If you don't have high flow intake and exhaust, you may not have to do any relieving in the head. I've only tried this with a slant head model. Oh, another thing about the slant head: I like to orient the head so that the spark plug is on the intake side of the engine. This is because when you relieve those jagged threads it will mainly be on one side. This will guide combustion activity to be offset slightly, favoring the intake side of the piston. I believe this is beneficial because the front side of the piston operates at a higher temperature because it is in close communication with the exhaust, and keeping the intense heat a bit towards the intake side helps even out the piston temps. This is a little risky of a mod: My crankshaft is straight (CR Machine reworked engine), and that actually makes a slight difference in the length of stroke for the engine, and therefore would affect the compression (it lowers it). All the cranks I've seen are bent in the same way; they are essentially bent in a way that actually increases the stroke (and compression) of the engine! I know it seems F'd up, but it's true. When I saw how distorted and misaligned the cranks were, I started tearing down every new engine I get and reworking them. Sorry this is such a long post, but just because I didn't have the piston hitting the head, doesn't mean you won't if you try the mod, because unless the engine is one of my reworks, it probably has a bent/misaligned crankshaft.
Hope you found this information helpful or interesting or both. Thanks