1975 Mazda REPU - Build and Repair thread

[chuyler1]

Hi Everyone,

I've been on this site for quite some time. I started out with a 2003 Protege5, then it was a 2006 Mazdaspeed6 (which I still have) and now my latest project is a 1975 Mazda REPU. Updated December 2015 jump to page 3.

I purchased this beauty from Gary in California and had it shipped sight-unseen to New Hampshire. He performed a frame off restoration of the body which included the following:

* NOS fenders, hood, and entire bed
* Chrome plated grill and all other trim pieces
* Custom front coilovers up front and lowered leaf springs in the rear
* Painted calipers and drilled rotors
* NOS 4-port 13B motor of appropriate vintage (0 miles)
* Removed emissions equipment
* Rebuilt 4-speed transmission
* Racing Beat exhaust
* Custom white/orange interior

On the outside, the truck is immaculate. Since I don't have access to an auto body repair shop, its exactly what I was looking for. Anything less than perfect and I would have just been dishing out cash for someone else to do the repair work. I cannot take credit for any of the body work.

Under the hood and under the dash, the truck could definitely use some attention. Especially if it is going to be driven every weekend from Spring to Fall (which is my intention). Since it's arrival last week, I have already started digging in and getting things operational.

Projects completed thus far:
* Replaced Speedometer Cable
* Bled clutch and readjusted pedal travel (Master cylinder may need to be replaced)
* Rebuilt central control unit relay system and turn signal relays
* Repaired horn switch inside steering wheel and replaced broken horns
* Replace clutch master cylinder
* Tune-up (its backfiring and bogging under WOT)
* Install dash speaker and make radio operational
* Make heater operational
* Install 12v acc socket (aka cigarette lighter)
* Install choke cable
* Fix interior lights and dash warning lights
* Fix washer fluid pump, hosing, and switch
* Repair exhaust (I think there is a leak plus the pipe doesn't extend to the back, it's really loud)
* Replace rims with something of appropriate vintage
* Add "Rotary Power" decal to the tailgate

Upcoming projects:
* More Power

 

[daonly1around]

where did you find new old stock parts for this truck.. that is amazing.

 

[chuyler1]

I didn't find them. Gary, the previous owner, sourced them. He sent me photos of the bed getting painted. I don't know where he found it but he must have paid a pretty penny for it. The motor came from a dealership that had them stowed away still in crates. Apparently there are two more 4-port 13Bs that were with this one. Gary is a diehard rotary fanatic. He has another REPU that he's considering selling and mentioned his next project was going to be a R100.

 

[CTt3P5]

Congrats, again! She's a beaut and sure to be a head turner.

 

[magnumP5]

Big time sub; very neat. Let me know if you have any questions about the rotary stuff as it sounds like you may have a couple common problems. A couple comments:

1. You should be able to upgrade to later RX-7 alternators without issue but some wiring changes will need to be made (different pickup points, etc.) Generally, the later the year, the better the alternator output.

2. I'd seriously think about the electric fan. The stock clutch driven fans are very good (when you still have the shroud). For an electric fan you definitely need to upgrade the charging system first. I would also only go the electric fan route with a good control system (i.e. no "on/off" switch or cheap "push-in" type thermosensor). I know this doesn't apply to you but in my RX-7 I'm using an aftermarket ECU (Haltech) with its own sensor, tapped into the water pump housing, to control the fan.

 

[speed3 britz]

Love these Classic REPU's... Looks good!

 

[fishdonotbounce]

Subbing. Beautiful truck.

 

[chuyler1]

Big time sub; very neat. Let me know if you have any questions about the rotary stuff as it sounds like you may have a couple common problems. A couple comments:

1. You should be able to upgrade to later RX-7 alternators without issue but some wiring changes will need to be made (different pickup points, etc.) Generally, the later the year, the better the alternator output.

2. I'd seriously think about the electric fan. The stock clutch driven fans are very good (when you still have the shroud). For an electric fan you definitely need to upgrade the charging system first. I would also only go the electric fan route with a good control system (i.e. no "on/off" switch or cheap "push-in" type thermosensor). I know this doesn't apply to you but in my RX-7 I'm using an aftermarket ECU (Haltech) with its own sensor, tapped into the water pump housing, to control the fan.

The guys over at mazdarepu.com have quite a bit of information. A few have upgraded to RX-7 alternators and that is likely the direction I would go. I would have to remove the external voltage regulator and install a better fuse box. The stock fan works pretty well, but at high RPMs it is very loud...and the rotary is all about those high RPMs! Anyway, I listed the fan after the electrical system upgrade since I wouldn't attempt it until I knew I had the amperage to handle it. I also dropped the stereo below the electrical system since I don't feel the stock charging system could support the transient loads of today's high output amplifiers.

 

[Rockin03mp5]

Totally subn here.

Awesome project.

 

[chuyler1]

Click the links below for details on some repairs I've done thus far, mostly electronics related...

Turn Signals - Click for full write up



Horn upgrade - Click for full write up



AM Radio Repair Part 1

 

[Antoine]

A fascinating Mazda...Thanks for sharing your progress with us...Can't wait for updates...She's a BEAUT! (2thumbs)

 

[bazooka joe]

can't wait to go for a ride!! see you, amanda and the TRUCK next week!

 

[chuyler1]

Just finished my first tank of gas. 223 miles. 14.5 mpg. Not too shabby considering I was driving at 70+ on the highway and did a lot of idling in the driveway, and made a few trips to home depot. I think I should be able to easily hit R&T's estimated 16.5 mpg if I drove 55 or under.

Speaking of which, I picked up the 1974 issue of R&T that covered the REPU as well as small station wagons including the RX-4 wagon. The letters at the beginning were hilarioius. Most of them complained about the national speed limit and how cops in some states chose to ignore it. The advertisements were like reading mini articles. Each one had at least a paragraph or two of text describing what it would be like to own the advertised car. What your neighbors would say. The enjoyment you would get. The custom options you could pick to personalize your model. These days you're lucky if you get more than just a photo and the manufacturer.


Oh, and try doing this in your RX-7 or RX-8 I'm reorganizing the garage and grabbed some Husky metal cabinets from Home Depot. They were a little pricey but come with a lifetime warranty. The big cabinet fit perfectly in the bed with less than an inch to spare.

 

[chuyler1]

I pulled apart the entire dash today. Working on the following...

• Dash lights
• Fluttering speedometer
• Radio
• Dimmer
• Heater
• Cigarette Lighter

So far I have diagnosed the dash lights. There were a multitude of issues. First, the dimmer needs to be connected but the harness is missing. I hotwired it to continue. Second, LED bulbs were installed and some were backwards and wouldn't light up. One was out completely. The rest weren't very bright. Third, a section of the board was missing the contacts and a wire had been used to complete the circuit...but the wire was loose. So after digging through all that I finally got some lights! I replaced all the LED bulbs with standard bulbs and now I'm going to double check all the gauges before reinstalling it.

 

[fishdonotbounce]

Great progress. I bet it's very gratifying to get some of the basic things sorted. Keep up the good work

 

[chuyler1]

Update after a weekend of tinkering...

I used my multimeter to catalog and label all the loose wires and harnesses inside the dash. I still don't know what all of them are supposed to do, but I at least know which wires are powered from the ignition fuse, heater fuse, and light fuse.

* Dash lights. The gauge cluster works now, as does the light inside the radio. I bypassed the dimmer to ensure I had full power for the lights. I replaced all the LED bulbs with 4.9w bulbs. I am missing two light sockets and the corresponding harness to light up the heater controls. I'll have to see what I can find at the parts store for replacements.

* Fluttering Speedometer I think is resolved. I found a few posts online that suggested to grease the cable before installing it. I didn't know that, so I pulled it out and gave it a generous dose of lube. It's been raining for 2 days so I haven't tested to see whether it worked.

* Radio is fried. I installed a new speaker and got the backlight to work. I also got the power light to turn on and could hear a small amount of static from the speaker, but I think the amplifier circuit might be dead. Maybe I'll tinker with it some more later, in the mean time I ordered a RetroSound Model One

* Heater is working again, sort of. I now understand how it is "supposed" to work but I'm missing some parts. First, I am missing intermediate vents that connect the blower to the defrost vents. No defroster until those our sourced. Second, I am missing the wiring harness to connect the fan switch to the fan motor. Third, the fan switch wiring needs repair. Basically the fan switch takes +12v input and will send +12v output to one of 3 leads in the harness. The connector that goes to the fan motor was supposed to have some resistors in it (no idea what size) so that each lead would run the fan at a different speed. Between the missing resistors and faulty wiring it took a while to get this far. The good news is, I can use the interior light dimmer switch to control the fan speed! Yep, it plugged right in and gave me continuous variability of the fan speed! Woot! That'll do for now.

* A generic cigarette lighter from the parts store popped right in to the factory location and I hooked it up to one of the empty harnesses under the dash. That's good to go now too!


Of course, with all my poking around I discovered a few more things that are now on my TODO list...

* There is a parking brake light. The socket and harness are missing but I did find a loose cable dangling from the parking brake. That should be an easy fix.

* The ammeter on the dash is definitely not working and there is also a "GEN" warning light in the gauge cluster that is supposed to do something.

* There is a low coolant warning light and I know that isn't connected because the sensor isn't plugged in on the radiator. Not sure if I'll bother with that one.

 

[bazooka joe]

nice work chris! you guys still coming sat?

 

[chuyler1]

I'm planning on it. I hope the weather holds out. Not sure I want to drive that distance in the rain with this truck.

 

[chuyler1]

I don't have any additional pictures but I stopped by Wankel Works yesterday and Lui and Raul replaced one of my exhaust gaskets that was leaking. It quieted things down a notch, but I think I still need another muffler or resonator. I may leave it with them for a few days to see what they can fab up for me.


I was bored at work again and did some more wheel shopping. I came across "Speedline Corse" brand of wheels that specializes in rally wheels. The ones below are obviously 6-lug but their website, and just about every site that sells them does not list the offset. They might look pretty sweet on the REPU if the lug pattern and offset is correct.

I still think classic 8 or 10 hole alloys are the safest route, but I'm just poking around with ideas. All I know is that I do not want the tires to stick out beyond the fenders, and that really limits selection.

 

[chuyler1]

Tonight's update:

The good: another antenna cable fell from the dash. Turns out I had the dead OEM cable connected to the radio that must be clipped deep in the dash. When I connected the new one I found the AM radio started working! Yay! I'll have something to listen to on the cape run, even if it ends up being talk radio.

The bad: the wheels have locks...and I couldn't find the key in the truck. Ugh.