My first rebuild was an experience. It was a bitch to start and a bitch to finally get running all the time.

I virtually replaced everything in it assuming it would just be better because it was new.

All included I spent upwards of three grand.

I was really stupid and didn't replace the oil control rings, ironically. Its fine, but I just think that's about all I should have replaced as absolutely nec.

I have this theory now that rotories are very very picky and they actually wear themselves into being reliable. So replacing stuff just because it's "new" is stupid.

But on this rebuild. I went bare bones cause I just don't buy the hype after the last adventure.

All I'm replacing this time is the corner seal springs
the side seal springs, The apex springs and oil control rings and their respective springs.

That's it.

Good Idea Bad Idea.

What do you think?

I've had my S5 block sitting on an engine stand for the last 3 weeks because I'm a little wary of ******* this up. I got everything I need to tear it apart but I keep walking around it, looking at it, thinking about it, and wondering.

I will not repeat my last experience even though I learned a shitload.

I want this one to go smooth.

 

what you need to replace in the motor depends on whats bad in the first place

the motor in the cym fc is all new except for the e shaft and its really really strong....

 

Bearing clearances, rotor stationary gear to side housing clearance, apex seal to rotor groove clearance, apex seal height, apex seal straightness, side seal clearance, corner seal clearance, apex seal spring unsprung height, and eshaft endplay have "limit" specs which you need to measure to determine whether or not to replace them. These specs can be found in the factory service manual or Haynes manual. These manuals will also recommend changing the oil and combustion / coolant, and all other internal O rings.

If you don't want to mess this one up, you could always rebuild it "by the book" like the pros do.

I did that with my latest and it has been a gem. For the record, I did not need to replace side seals & springs, corner seals, rotor or main bearings, but I did use different used housings from a few other engines.

 

Standard:

apex seals
coolant seals, dowel orings, and tension bolt seals
front/rear main seals
eshaft thermal pellet
viton oil orings

everything else can usually be reused. Springs don't wear too much, nor do sideseals or corner seals or the metal oil ring carriers. Apex springs sometimes need to be replaced depending on mileage. BEarings are usually okay to reuse, but should be examined...consensus is that less than 40% copper is okay to reuse, personally I stay within 20% or less.