Had a piece of 1.5" chromoly in the back of the shop and it was slow today so I got this done towards the end of the day. I left the ends long and just cut, tacked and fit, and welded it out at the house.





Thinking of putting two chromoly supports coming down rather than cutting and bending a piece of sheet metal. I just think it will be stronger and won't flex. I'll build the supports downwards into the unibody and then bolt a piece of sheet metal to the front (or weld it). I will try to angle it as much as I can (without interfering with the shifter) towards the drivers head.

If nothing comes up I should be able to knock it out tomorrow, then start on wiring everything back up. After that I can get the carb back on and see if she runs.

 

 

I may end up remaking the instrument panel with a slight kickout at the bottom to angle it up. That or bending sides so it can bolts in between the two columns and swivel to tilt.

 

Need some help here guys. Can I use the stock oil pressure sensor for an aftermarket guage? I've got what looks to be aftermarket oil temp and water temp sensors but the stock oil pressure sensor. What can I do?

 

racing beat sells something that mounted between the oil filter and the block. has ports ready to go for your standard autometer type sensors for pressure and temp.

 

Nice, thanks.

Wiring is 90% done. I just have to put power to the instruments and ground them. Everything else is wired up. My main goal was to get the OEM harness out of the driver side footwell and clear of the entire driver side. Goal accomplished as far as I am concerned.

 

Looks like I have an autometer sensor already, wondering if this will work with the RB adapter.



I am going to replace those old oil lines too if the sensor will work.

 

Decided I had better wait before spending more money on new oil cooler lines and the sensor adaptor. Better to get the car running first!

 

Finished terminating the electrical just now and testing/calibrating the O2 sensor. Everything works as far as I can tell without starting the car.

 

Carb is back on, same thing, won't idle. The carb does not have a vacuum leak. What are some other points on the car that can be leaking?

There are no vacuum hoses that go to the carb so I ruled out the brake booster at least.

Could this also be caused by low compression?

Help me Tom Cruise!

AFR gauge says leaning out to free air around idle speeds so no new info there...

 

Where can I get one of these:



Says RB on the header-to-engine flange but the other end doesn't match anything Racing Beat sells... Trying to figure out where I can get a new gasket and I don't even know what brand to try and start at...

That and I have still been trying to locate a vacuum leak. Been over the car for a fourth time now with a can of ether and 2 can of brake clean I still can detect a leak. Maybe it's because I can't even get the damn thing to idle low enough to be able to hear a difference in the rpm. W T F rotary. No damn hissing sounds either. Re-ran compression test, both are 70-80+ and within 20 of each other.

How many places could there be to have a vacuum leak that would affect the carb? The carb and the intake manifold, right? So wtf...

 

Need some help with diagnosing this guys. I am lost at this point. Leans out as it goes down to idle according to the AFR gauge.

 

That is definitely an old RB gasket you should be able to find it under exhaust components..or try mazdatrix theyll have it for sure.

Your pilot jets are too lean that's why its stalling..motor sounds pretty healthy though. That may be too much carb for a 12a..everything I've read about sidedrafts everyone says 44s run way rich on 12as and they're hard to get right. A lot of people just tune um rich and leave it, I would do the same since its a race car.

If you've gone over it 4 times and rebuilt the carb I doubt its a vac leak..only other thing I can think of is where the OMP injectors go..I'm not familiar with 12as but on the 13Bs they go into the centre iron under the intake.

 

The OMP is deleted, running premix, and I sprayed that area thoroughly with brake clean, nothing. I've got the recommended jets from Mikuni in there and it can't be running lean because my plugs are turning black. I think the afr displays lean partly because the exhaust isn't attached all the way so it doesn't have pressure enough at idle to push through to the sensor.

 

Yeah dude **** recommended jets. Put in what you need..but first you said it was lean and now I'm learning that its rich and fouling plugs. Has it flooded at all? What plugs are you running?

 

These:
NGK


I believe it flooded, I took the plugs out and had slight fuel clouds coming out, have changed plugs since then though. If I run it for a bit and take a plug out it's slightly black, I can wipe it clean basically.

The set I took out was very black.

Check it:



Was running with the Mikuni as jetted now, except I have leaned out the main air jets to the recommended jets.

From a post previous in the thread to save you the time:
The recommended jets according to Mikuni are:

Main Jet: 200
Main Air Jet: 240
Pilot Jet: 62.5
Pump Nozzle: 0.90

What was inside the Mikuni before I changed the Main Air Jet:

Main Jet: 200
Main Air Jet: 190
Pilot Jet: 62.5
Pump Nozzle: 0.90

What is inside the Mikuni in the video above:

Main Jet: 200
Main Air Jet: 230
Pilot Jet: 62.5
Pump Nozzle: 0.90

According to Wolf Creek Racing, the Main Air Jet shouldn't affect the mixture of the idle, rather mid-high RPM. I leaned it out because the plugs were blackening as you can see above.

I had this carb running at one point. I put the nikki back on because I was having bog issues and got tired of having to drive like I was. Nikki ran for a while, took it off to mod it and learn more about carbs and whatnot (which I did) and now I can't get either to idle but both will run at 1300-1500+.

I figured out my bog issues were a combination of clogged pump nozzles and installing the pump diaphragm backwards.

The story:

I did a rebuild of the Mikuni a while back but didn't use the whole kit and never took out the pump nozzles because I didn't know what they did or how to get to them, I just replaced the main gaskets basically. Re-installed it and it ran fine other than still bogging very badly. When I rebuilt it I put the diaphragm in backwards, I couldn't tell the difference because the nozzles were blogged anyway. I put the nikki back on, then took it off to mod it, figured out what the accel pump and nozzles do in the process. Rebuilt the Mikuni a second time, this time taking it down completely and rebuilding it to what it is now, what I believe to be a 100% working carb.

I am not sure I trust my AFR meter yet as the header is only connected to the exhaust by 1 bolt that is hand tight and there is no gasket there.

Trying to give as much coherent info as I can. I am pretty sure the Mikuni runs rich on the recommended jets anyhow.

 

Found the gasket at mazdatrix, RB didn't have it.

 

Adjust your idle screw in until the engine will run on its own and then look down inside the Venturi. There should be no fuel dripping in. It there is than your float level or fuel pressure is too high. If all that checks out and it's still running rich than put a leaner idle jet/pilot jet. And if it still won't idle throw the POS in the trashcan and get a Weber 48 like I told you. Mikunis are very finicky.

 

I'll buy a 13b before I buy another carb for the 12a.

 

Could this be something to do with the ignition timing?

 

I would do what ultimatejay suggested. Also replace those spark plugs..get a couple sets incase it keeps flooding. Dont buy stock 12a plugs buy NGK BUR7EQ (2) and BUR9EQ (2). Run those til its running good then I would buy some BUR7EQP (2) and BUR9EQP (2). 7s are leading, 9s are trailing. Those are FC/FD spark plugs, more durable than BR8s. P is for platinum.

I doubt its flooding due to ignition timing. But I would make sure its set properly.

 

The black plugs are the old plugs. I have a brand new set in the motor right now.

I say it was flooded, but I am going off info I found here on the forum. I removed the plugs and noticed when I turned it over there were very faint clouds of fuel coming out. VERY faint.

I'll get the suggested plugs for my next set.

Going to break out the timing light and check next. The previous owner had the vacuum advance pots hooked to a T but the other end of the T was left open and not connected to the Nikki. I connected it when I rebuilt the Nikki so maybe that did something? I am running them open air right now like it was originally but blocking off the port on the Mikuni.

 

Oh okay. Well down the line I would buy the ones I suggested. The ones you have are OEM for 12A.

Well fuel clouds coming out of the plug holes would indicate flooding/rich mixture..that's why those plugs are fouled. To be sure it is actually rich or lean make sure the exhaust is installed correctly with no leaks (before the sensor) or the reading will skew.

Yes used the timed vac port on the carb for disty vac advance. You definitely need that functioning.

 

Aight, I will hook back up the vac advance to the carb and check the timing. I can maybe use the old gasket temporarily until the new one gets here to hook the exhaust back up.

 

thats normal, there needs to be fuel in there for the thing to run...

if you're serious about tuning the carb, start with float level, then the idle, then work your way up the RPM until you're @wot.

it will take a while to get it right, but you should be able to get the carb to provide a good mixture at all rpms.

if you're running an MSD i'd recommend tuning with the autolight plugs, they are much cheaper, and work better with the MSD, so you can go through a couple sets and its like $9, instead of $90. they don't work with the stock ignition though, the gap is wrong