SKYDRIFTER350

Hello All, I recently bought an 85 GSL has 12a engine. anyways seems to lack the ZOOM ZOOM I was expecting. not pulling hard through the upper RPM zone, doesn't seem to be sucking fuel through the secondaries..

did a compression check tonight and I think I came up a bit short. i got 95 psi on the bottom front, 85psi on the top front (but seemed to fluctuate) I am going to get a remote starter tomorrow so I can more closely monitor the comp fluctuations between the travel of the rotor.

bottom rear 100 psi and finally 94psi on the top rear. The top front plug hole is the only that seemed to give a fluctuation compression number, but going to do a more detailed check in the am...as well as check the IGN timing.

No zip and horrible fuel milage...like 10.5/gal with normal driving. thats my first two issues...ha ha ha....
thanks in advance for any and all advice.

Sam from Florida

7aull

iTrader: (2)

Hey Welcome Sam-
Will let others comment on compression, other than to say you need a special "rotary-engine" specific compression tester to do that correctly. So a Mazda dealer or a mazda specialty shop will be the way to go. That said there are ways to get a "feel" for compression performance that maybe noted by others.

One thing you should (!) do is swap in a new FUEL FILTER. These need annual change and can be a real source of fuel-flow issues if forgotten. Easy swap and cheep at any Auto parts shop.

Stu Aull
80GS
Alaska

lduley

iTrader: (1)

Those compression #'s aren't that horrible really. I agree on the fuel filter, make sure your getting spark to ALL 4 plugs, if your leading isn't firing because of a bad ignitor, that would make it seem doggish

May need the carb rebuilt also, alot of possibilities

Jeff5808

iTrader: (7)

Make sure the engine is warm when doing a compression test. Also, if using a regular compression tester you will need to take out the schrader valve(the thing that holds the pressure for the gauge), and you will be looking for even rises for all three faces of the rotor. This will tell you if any apex seals are stuck or worn/damaged. You won't be able to get the psi of the rotors without a special rotary compression tester, it's the only way to get compression numbers.
Example, if an apex seal is damaged/stuck you will see 1 high rise followed by two low rises. This is caused by the compressed air traveling between two rotors, the third would be making a seal.
If your side seal is stuck/worn you will see two high rises and one low.
Also, as you may already know, make sure you disable the fuel circuit.

Hope this helps, good luck

SKYDRIFTER350

thanks. I did the compression check in accordance with Racing Beat's web site 'tech tips' section...
I did use a regular compression gauge, as you say not the proper tool for the job...but thats all I have. I will check to see if I am getting good spark on all 4 plugs and also check the IGN timing.
the plugs looked pretty dry... with the brown bag color... and not gooey and wet.
Going to check the fuel flow and pressure next...the car came with a new Holley fuel pump and a fuel pressure regulator....so perhaps there is a fault there?
Thanks...I'lll keep wrenching..
Sam

Jeff5808

iTrader: (7)

Did you remove the schrader valve from the compression tester?

SKYDRIFTER350

I did not. I used tape to hold down the button and tyne gauge went to zero after each compression bump...I did it again, registering the max number without the tape. but my tool is for a regular piston engine..so I am sure I am off by some degree. going to buy new fuel filter and checking the fuel pressure now...

Freeskier7791

I would check and replace the vaccuum lines, stock Niki has vacuum secondaries. What carb does it have?

Jeff5808

iTrader: (7)

As long as you're getting nice even pulses and with your compression numbers your engine should be fine.

j9fd3s

iTrader: (3)

if i had just gotten that car, i would go through it with an eye toward making it better. think of it like a showroom stock race car, and that will give you an idea.
shop manuals are here Foxed.ca - Mazda RX-7 Manuals

1. compression. the number you get is tied to the cranking Rpm. without the cranking Rpm the absolute number is meaningless, however you can still look for even bounces. Mazda's spec, like a piston engine, is xx pressure at y rpm, but also you can't have more than i think 20psi variance between chambers.

2. bring the service up to date. these cars are reliable, so the chances are that things like the fuel filter, and distributor cap/rotor are old. you want to change all the filters/cap/rotor, and inspect the plug wires. spark plugs if it hasn't been done recently, etc. nothing fancy needed here, just buy normal stuff. or well, you want NGK spark plugs, probably wires too.

3. give the belts and hoses a good once over. the OEM hoses can last for 25 years, so it is possible you might have some on the car still. the aftermarket hoses last about 25 months, so if you replace a hose, OE Mazda is the way to go, they are about the same money too.

4. once its tuned up, i check for spark, and then check the timing. for a 12A i'll set it to stock +1-2 degrees.

5. set the idle mixture. warm it up and set it until it runs the best, and then maybe 1/8th turn leaner.

j9fd3s

iTrader: (3)

after this it should be running ok, so then its time to look at the rest of the car.

1. raise it in the air and check the front wheel bearings for play. its pretty much a certainty that the bearings did not get cleaned and re-greased at 30,000miles like they should have. if play isn't too bad, and they are quiet, i would just clean and re pack them with a good synthetic grease. when you put it together you need to recheck the freeplay after a drive or two.

2. i'm assuming that the brakes got looked at, and worn pads got replaced. i like to grease the slide pins, and if it has drums in the rear its a good idea to adjust them.

3. i also assume you're going to look for worn/loose suspension parts, and replace as needed. i would then follow this up with an alignment, i would run minimal toe in, and as much negative camber and positive caster as the stock bits let you have (its not much), this will sharpen up the car a bit.

4. tire condition matters, as does inflation pressure. make sure the inflation pressures are even, and start with what Mazda recommends

5. i will check the clutch and brake pedal freeplay and adjust as needed. the steering box too if needed.

6. clean the car! its got 30 years of crud all over everything. i pull the seats and get the wet/dry vac and really clean everything. i wouldn't clean the rear carpet like this though, its made from dust, so if it isn't treated gently it will turn back into dust.

7. enjoy!

SKYDRIFTER350

thanks every everybody...

the car seemed to have a sorta-kinda restoration about 3-5 years ago...paint, engine overhaul (i was told 15,000 mi ago) , interior, rims and tires.

needs a clutch bearing I do know that...and radiator cause the one in there now drips a bit...but the water loss is very small as I have checked it many times and don't see a drop in the level..but I plan o changing that soon...car came with new Mazda radiator hoses, so I'll put them on with the new RAD.

anyways, I rigged up the fuel pressure regulator that came with the car (Holley Blue, w/ pressure regulator, that has a gauge)...and it reads about 2.5 psi.....with engine running...no pressure with just the key...

I wanted to check the pressure before I took things apart by the pump...I can't even crawl under there to change the fuel filter...lol this thing is low. wheres my jack?

I guess I can check the timing today, so I'll do that..

I lent my floor jack to a buddy and still waiting on it back...lol...I was using another craftsman crapper I have to mess with the Mazda...and today I went to use it again knowing I was going to have to do something to it (add oil; overhaul??? who knows?) to make to work....but it had a puddle of fluid underneath it and I'm not a jack mechanic....so it's out by the curb....

tomorrow is another day.
Thanks...
Sam

SKYDRIFTER350

j9fd3s,
actually the car came with several bits that You mentioned.
F. brake pads
RAD hoses
F. wheel bearings
Holley Blue fuel pump
K&N air filter
and some other bits
I plan to install all of it...however, I am in the process of building 2 other motors (motorcycle) and one of them needs it's bike built!!...lol...so, I got a few different projects going on...

oh, I have the original aluminum louvers... metal and glass sunroofs as well.
thanks,
Sam

SKYDRIFTER350

FreeSkier7791,

I'm pretty sure it is the factory set-up...if that is a NIKKI from what I am learning...then that is what I have.

4 barrel
big blue Mazda air cleaner on top...
a bunch of small assemblies attached to it.
hoses going all over.

Freeskier7791

That would be it, Definitely check those hoses for cracks and anything disconnected

Jeff5808

iTrader: (7)

Find a vacuum hose diagram, it will be your friend. And if it has any check valves and they are old, I'd replace those as well. Dale Clark on here sells some good viton ones, well worth it.

SKYDRIFTER350

Yea..the previous owner removed like 1/2 of the 'RATS NEST'....so, I am sure there is a Vacuum hose messed up somewheres....perhaps a cracked, missing or disconnected hose. MY inspection and search continues....

PETIT RACING says to bring the car, and they will have it buzzing within a few hours (claims around $250, if no expensive parts are required)....they are in Palm Beach....about an hours' drive for me...So, not super convenient but what is???. I am trying to get all I can buttoned up Myself, then perhaps take to to them???

Thanks...I have ben reading other threads on NIKKI carbs on this FORUM...very informative...lol,.,,,I have to read them a few times to really familiarize myself....and all I really know are MOTO carbs....all of my AUTO's have been FI since I was 18...lol...(my first Mustang 5.0, 1986)....

SKYDRIFTER350

don't know if I posted it here.....Fuel Pressure after the fuel filter replacement was
about 2.5 PSI.

Pressure Seems pretty low....IS that enough for proper operation? Also, is the Holley Blue fuel pump (that came with car) a proper replacement? I know the Holley unit is a bit of a crapper pump...but it is what I have! lol... pump manual says to mount pump vertically....the factory location is horizontal? I have seen (on RX7 Club) a holley pump mounted in the stock location (horizontally). is this ok? any problems anyone has come across mounting the HOLLEY pump in this manner?

Thanks.

t_g_farrell

iTrader: (1)

Petit is a good place. I'd take that estimate with a grain of salt because your car
will probably have parts needed to make it right.

Pressure at 2.5 is spot on as long as the flow is good too. Some fuel pumps
must be mounted verticle or they won't prime or will burnout. Depends on the
pump. Contact Holley for advice if no one here knows. I have a carter and use
a holley 1-4 psi regulator. It has to be mouted verticle and is.

SKYDRIFTER350

[QUOTE=t_g_farrell;12084744]Petit is a good plaof salt because your car
will probably have parts needed to make it right.
ce. I'd take that estimate with a grain

Yea..I know....I had a feeling that number was a bit optimistic.... who knows...perhaps I can track down my problem myself?

Thank You for all the help

SKYDRIFTER350

ok....got the car in the garage today...been swamped with other life. well...
I have good fuel pressure 2.5psi
good fuel flow.
good compression
got a/c cold
got cooling system sorted (for the time being)...needle stays in middle of gauge.
Car not running on the SECONDARIES...and plugs looks lean ..(no zing-zing)...so trying to track down a vacuum leak or broken hose...
bad fuel economy ...
gonna get dirty today..lol...and hot.

SKYDRIFTER350

Hi again...seems the vacuum assembly works...I took it apart and put a hose on there and made vacuum and the lever moved... the passageway (inside the carb body) was full of gook...put carb cleaner and cleaned what I could, with the carb on the car....put air to it and air seems to flow through the secondary bore. assembled it and still NO secondary action with car running.

I have taken some pictures of the lines and where they go...can anybody advise the arrangement of the vacuum hoses? some are this way and some are that...lol...whomever disabled the 'rats nest' I am afraid did not do it correctly...

I'll just start with the driver side...

looking from the driver side...there seem to be 5 outlets in line with a 6th outlet above (that line of outlets) that last one seems to go to a 'PCV valve' by the oil filler pipe and on other side of that valve nothing ....oh, and the 'oil breather', on that pipe, is capped with a bolt.
this is the one side of the carb

.

Freeskier7791

http://maz_tutorials.ten15.net/Tutorial_1.pdf

That should be a big help

SKYDRIFTER350

Thanks Andrew.

I have seen that before... many nights ago (perhaps after a few)....but I couldn't find it again..lol...
Thank You for bringing it back to me.
Cheers!

SKYDRIFTER350

Hi All, tried to get all the supplies to upgrade/lose the Rat's Nest...came up a bit short at PEP BOYS....the employee there, well let's say, he will not be working for Hendrick Motorsports anytime soon...lol....well last night...I monkeyed with, what I thought was the firewall side of the secondary linkage.....from the driver side I loosened a nut before a spring, lessening the tension on that spring, allowing the secondaries to open (not sure if opening all the way) but opening. Am I messing with the accelerator pump tension spring?...not the secondary tension spring? Car is Burning some more rubber than it was before!!!! I am off to get the required remaining parts to rig the vacuum as per the MazSpeed tutorial..... the car already has the big caps that MazSpeed say are hard to find, so thats good!!!
Hopefully today we can get it pretty close to correct.....
my goal is to get the car as good as I can....then take it to PETTIT RACING to get a final tune and set the oil metering pump correct (rod moves...but just seems sloppy).... and all that Jazz....

Thanks Everybody!