I have a 1986 NA 13b that had the bearing weld to the eccentric shaft when it was overheated and I have a 1990 NA with good compression on the rear rotor and nothing on the front one (not sure what the cause is yet). I am wondering what I need to look for when I tear into them to see what parts would be useable, and what is compatible between the 2 motors? I am also wondering if I could pair 1 rotor and housing from 1 engine with 1 good set from the other ( I know they are different compression and weigh a bit different so I wonder if it would throw something off)? This is going in my sandrail and I don't have to worry about any emissions, or anything, I just need it to run as strong as possible to carry me up and down the hills. I have also found a lot of options for rebuild kits and wonder what I would actually need to plan on for this? I have searched some of the threads trying to find what answers I could but just need some help. Thanks

 

You need keep the balancing set together your talking s4 and s5. If you open them both up label everything. Irons and housing will have minimal differences, use the s5 rotating assembly(rotors, shaft,front counterweight, flywheel) grab the best looking housings and iron and clean as much as possible, and measure your specs.