starter bolt headaches
 

after getting the engine running fairly well, I'm now having starter problems. in trying to take the starter off I've rounded off the long bolt in the reverse position. it's stuck in there good after having never being removed in 42 years. now that it's rounded I have no idea how to remove it. grind the head off? there's not a lot of room to work in there. any suggestions? I'm stumped! whoever designed this was not thinking about ease of replacement

This is one of the easiest starters to replace, dude. The problem with yours is likely it was rusted into position, and/or it's the wrong thread pitch and someone forced it into service. There are 2 bolts, one electrical connection to the Bendix (*aka Solenoid), and a ground on the main bolt.

If yours is seized, start with penetrating oil. If you rounded off the bolt head, you need better tools that fit the fasteners, or above (wrong size). At this point, your options are to grind flats onto the rounded portion of the head for a tool that DOES fit, cut a slot for an impact screwdriver, or cut the head clean off and deal with the shank stud which remains. For the record, you need to spray it down with penetrating oil and let it soak in BEFORE you start removing anything.

Give those ideas a shot and report back. You're going to need a new bolt of the proper dimensions and a thread tap to clean out the threads, most likely.

The lonest bolt is the ground and it's a through bolt with a threads and then a nut.

First task, as stated, is to be able to get a tool on the head. Second is to free it up. Hard to tell if it's stuck or the wrong tool was used. A little heat might help.

I've replaced the starter a few times on my '84 years back so Yeah, it's an easy job when the bolts turn, but this has never been touched in 42 years, I used the correct socket (14mm 6 pt) the short bolt came out relatively easily, but the long one won't budge. penetrating oil can't really get to where it's needed. I'm a backyard mechanic with limited tools, I have a propane torch that I'll try. getting my impact wrench in there is impossible, I'd need a right angle head to fit in there, which I don't have. and the bolt head's pretty mangled now, so not sure how I could restore it to functional, I'm thinking of clamping a vise grip on it, or just grinding the head off.

that bolt is not very fun ;(, you might try a really long extension, and put the ratchet in front of the engine?

i think last time i used a box wrench from the top

I got it off, it was easier through the engine compartment, heated the threads, hit it with a hammer, pulled the rear plugs, hammered the 14mm on the bolt, and used a piece of pipe for leverage, mistakenly tightened it a few turns, and it came out

I think Mazda still has new bolts available, check the parts catalogue.

I ended up installing an FC starter when I replaced my FB starter. More were available from better quality rebuilders. The FC starter isn't threaded for the one bolt, so I installed an appropriate size/pitch rivnut to allow me to still use the original spec bolt without the hassle of finding a longer bolt and using a washer and nut.

Make sure you re-install with proper threaded hardware. Mazda will use fine thread into the rear iron and coarse thread into the aluminum transmission casting.

Rivnut installed with a backup washer into FC starter:
https://cimg8.ibsrv.net/gimg/www.rx7...ab82f78d1b.jpg

yeah the FC is a little better, it uses a bolt and a nut. bolt goes in the other direction too (i think)

Akins Rotary has starter bolts. I bought both. The only issue for me was the heads were 17mm and my originals were 14mm.
The 17mm on the short bolt was not a problem.
The long bolt would not seat as it was hung up about 3/16inch. However the bolt is 1/2inch longer than the original. With a spacer, or a stack of washers I could make it work. My original was still in good position so I used it.

Just to add a bit of random info for FC starter installs. There’s a Miata engine accessory bolt, I think it is the power steering mount bolt, it goes through the rear plate, trans, starter and nut with a couple threads exposed. Here’s a high torque banzai racing na starter with the original and the miata bolt side by side.
https://cimg7.ibsrv.net/gimg/www.rx7...2b8201b2b.jpeg