To lap or not?
 

Im gonna open up the motor for the 4th time because of bad port work and this time I think the new "used" irons will get lapped. What do you all think? Who does this kind of work?

How do I measure wear on the irons?

http://www.rebuildingrotaryengines.c...ousings_Plates video

also see the rebuild procedure in the manual. you need to use a dial indicator

Get yourself a machined straight edge and go through the process described in the FSM to measure, some people will tell you not to lap them, some people with a lot of experience will tell you not to lap them, other will parrot those remarks as well and even others will tell you to lap them or always lap them. I lap those that are needed and don't lap those that are not. I'm not sure I trust anyone who says you never should or you always should.

~S~

I'm skeptical of lapping only because I think the OEM nitriding process is superior

I would rather go used (JDM or other low mileage part) than lapped

Thanks...thats what I was thinking. I have the FSM and will measure my other housing very soon. Incase I need to lap them.....Who can do this process?

Keep in mind that if you do choose to lap them they need to be done properly by someone who has done them before and knows what to look for. I can't tell you how many plates I've seen lapped that were just ruined because XYZ grinding services says they can do the job but the person who took the plates to them didn't give them the proper info. The video Arghx posted covers it pretty well, plates need to keep their parallelism as well as the bore needs to be kept perpendicular. It's always good to have the place you have do them go over their equipment before running your plates to be extra sure everything is as it should be. If they call you up and say there is still wear marks showing along the sides that is fine, better to have step wear that is in spec than o-ring grooves that aren't. Though If your slick enough you can machine the grooves back in spec and re-nitride the plate.

Arghx, I can agree with you somewhat but over the years I have engines with as many miles on them as the ones coming in for rebuilds with no issue. Also I'm skeptical of buying used rotary engine parts. Basically if I don't know you well I wont buy your stuff.

~S~

My understanding on how to get a finish possibly better than brand new OEM Mazda

#1 Mazda dropped the advertised nitride depth from 85 onwards from ~0.4mm to ~0.1mm from ?1985? onwards. So choose early plates for starters.

My understanding would be to find EXCELLENT condition used plates with less than 1thou stepped wear on the combustion side end due to corner/side seal wear. Send these to a professional workshop that does high precision lapping involving another part which has guaranteed parallelism. I've priced this at close to $500AUD from a rotary expert.

You will come back with very close to factory width parts that have not been ground at all, and still have guaranteed parallelism and flatness.