I have had this one on my wish list for some time. Havent ordered it, but it has good reviews from other RX8 owners. The advantageof the S2 starter is the cranking RPM, which most of the non-OEM ones also have.
I bought this one 9 months ago for $130. Unfortunately it's currently listed for $174, but I'd say it's still worth it. Hugely improved starting for me. Old starter would crank for 2-3 seconds and with the upgrade it's less than a second. I'm actually shocked how quickly it fires up.
random shot in the dark here, try and get one of those remote start switches (some parts stores loan them out, some don't) and try that while its 'hot'.
if you still get the issue, its probably mechanical or heat soak related to the starter itself. the last is less likely due to replacement, but it does narrow things down.
if you hook one side to the main starter power feed cable since its new, it would completely eliminate the whole of the harness as being an issue if it still slow cranks.
however, if it fires right up using this method while hot, it is 100% electrical someplace. possibly just connections someplace, possibly the ignition switch.
for there to be enough drag on the pistons or other things in the rotating assembly sort of implies that either it got overheated to the point of damage (which would mean the block is toast) or ran dry of oil and fubared the bearings in the rotating assembly enough to cause issues, but not enough to seize it. cylinders tend to get bigger/more open with age and wear, not expand, unless they overheat several times with no coolant.
have you tried starting it with the transmission in neutral and your foot on the brake?
when was the last time the gear oil and/or atf in the tranny and diff(s) were replaced? oil change in the engine itself? tried dumping a quart of marvels mystery oil in after draining a bit to put it to full when you add it?
i'm also wondering if the heat off the engine is causing the vacuum lines to expand or even the metal around the intake seals, leading to leaks that interfere with starting.
try that starter switch test first though, if you can, it'll rule out a lot of issues. and also, disconnect the trigger wire from the starter to eliminate the main harness 100%.
check the starter relay on the passenger fender skirt wall just under the crease. its blue. and the main power relay. had a kia that wouldn't start for squat. replaced the main relay, fired right up. these can test alright or seem fine, but still not provide what you need. if you've just flat bypassed these relays with jumper wires, you can ignore this.
if those test alright (or it still didn't work with a bypass), you start looking at the various cutoff switches (e.g.; clutch interlock switches, etc). since these trucks don't really do much if the clutch switch (or the interlock switch on the dash, when present) fails and doesn't send the signal out right.
you might also try to get an external starter button (hooks between the battery side and the ignition stud on the starter solenoid, to trigger it). making sure, obviously, to keep the wires to the switch out of the way. if this method fails with the button properly hooked up, (and the clutch/interlock switches are good) then you're left with starter wiring/connections, battery or starter. since there's not much else to the system with this test.
if the button tester works, your starter is probably fine, and its not getting what it needs (be it the main harness, the main starter power wire, or something from the ignition itself).
another free test, pull the column apart and do an ohms test on the ignition switch, these are a known fail point at this age. they're also not usually that expensive, and easily swap out without replacing the key/cylinder. its a single screw and a plug into the harness.
cheers.
It is an air freshener. It goes on a vent vane.
https://www.amazon.com/BMW-83-12-2-285-673-Starter-Kit-Interior/dp/B00SYS46HI
I just looked at you video again and it's actually a factory original Mitsubishi motor. It might be worth rebuilding.
Maybe just get this guy and then keep the old one as a spare and rebuild it at your leisure. It'd be a shame to sacrifice it for a $50 core charge.
If you just want to throw in some brushes, i put these in my 4.7 starter: https://www.amazon.com/gp/product/B0012P7KV4/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
I also cleaned it out and put a little bit of high temp grease in the gear reduction. A dab will do ya, a glob will screw ya type of situation.
One positive route is; alternator, to start battery, to relay type isolator, to house battery. With this you would use the existing lift cable to go from the start battery to the isolator to the house battery. (The isolator could be at the other end of this cable. Start battery to isolator to house battery.) You would use the existing alternator wiring to the start battery. Or in time, up grade to heavier cable. It can get more complicated, but start out easy. :) Like this; https://www.amazon.com/Cole-Hersee-24213-Continuous-Solenoid/dp/B005K2429I/ref=pd_sim_263_5?_encoding=UTF8&pd_rd_i=B005K2429I&pd_rd_r=RW4JF7HV19CDCYN5YK2Q&pd_rd_w=hscr4&pd_rd_wg=VMhZf&psc=1&refRID=RW4JF7HV19CDCYN5YK2Q There are isolators that work differently than simple relay. They could be alternator to isolator, isolator #1 to house battery, isolator #2 to start battery. they are expensive.
I would absolutley reccomend getting 1 gauge welding wire from the alternator to the house battery. The wire will stand up to the vibration and you want as little voltage drop as possible over that long run. Use a 150amp fuse on either side of it. I us this it's overkill perhaps but better over than under I say
Maybe this will clarify: https://www.amazon.com/Cole-Hersee-24059-BP-Insulated-Continuous/dp/B0064MX7US/ref=pd_sbs_263_3?ie=UTF8&dpID=41jsjsit2KL&dpSrc=sims&preST=_AC_UL160_SR160%2C160_&psc=1&refRID=MH7BMKXWB4AYVXXH118B
Is the solenoid I plan on using
I had the same problem with my 1991 cb750. I bought one of these http://www.amazon.com/gp/product/B000UK08MU?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00 and rebuilt it, as one of the reviews said, it came backwards and I had to solder the contacts in different locations, however if you have a friend who is mechanically inclined, if you know what you're doing it takes 30 minutes. If you don't it takes 4 hours. Mechanic tried to charge me 360 bucks for the rebuild + the part.
A good test is try and start it by rolling down hill and dropping into gear, if it works that means your alternator is working but the starting motor isn't.
Nippondenso starters, in particular. This is a known problem. You can buy the contacts online for a few dollars and rebuild the solenoid.