Triple Mikuni thread

[Travel'n Man]

Just remember when buying your jets they come in two different head mm sizes. If you buy anywhere other than Todd - be sure to tell them you want the smaller mm size

Here is what I have collected so far:

Main Jet Pilot Jet Air Jet

140 57.5 200

145 60 195

150 62.5 190

155 65 185

160 180

[240znz]

Hey all,

Excellent thread. Lots of valuable info within.

I'm about to send my 44's to a local carb shop for stripping and rebuilding and while they are a away, I'd like to start thinking removing the shaft throttle system to a cable version.

Has anyone written up or got a few good pictures of this type of conversion.

Also running stock fuel pump, should I install a electric pump at the tank? Cabling easy to run still. I see plenty of engine bays with fuel pressure gauges and O2 sensors in headers. Is there any preference to which header primary the O2 sensor is fitted?

Cheers

James

[Travel'n Man]

Here you go - great improvement as well

http://www.classiczcars.com/forums/carburetors-s30/30584-accelerator-linkage-fix-questions.html

[madkaw]

I would comment that my direct linkage works flawlessly. I couldn't imagine cable being any improvement. It can be done!

[madkaw]

I need some insight here guys. Having an issue with running rich on certain cylinders. Primarily #4 runs rich, but 3 is fine. How does that happen that one half of a carb runs rich. Floats have been checked as well as fuel pressure. Ignition has also been eliminated from the equation. I also did a coolant pressure test for a blown HG. Cylinders read 180-190 on cylinders 4-6

Getting ready to pull carbs off completely to look everywhere.

These carbs have been very consistant as far as pilot adjustments, but now I have to turn #4 way in to keep it from fouling out. I will be blowing out passages to I guess. I have been having the biggest issue with cylinders 4-6.

[240260280z]

Is it possible a different circuit is leaking such as a cold start/choke? I'm not sure about Mikuni's but it can happen to dcoe's.

Also check jet diameters. A poorly drilled made in mainland china jet could be the culprit. '

You can move jet and e-tubes around to see if the problem moves to eliminate items.

Edited July 18, 2014 by Blue

[madkaw]

Thanks-keep any ideas coming.

Chokes-maybe-but I would think it would foul both sides are carb, and I did check them

Jets have all been used before with no issues.

I could swap around e-tubes I guess. Not sure what could go wrong with them.

[Kennymonster]

Any progress Steve? For the first time in 2 years, I had one of the needle valves stick in the seat, due to some microscopic dirt build up.. though like most things I would think that should affect both cylinders per carb. If the e tube swap and making sure all the jets are tight on the block didn't get anywhere, maybe swap plugs between cylinders to see if the problem follows the plug?

Came across this thread while searching, good to see it's still going. Here's my jet logs to further contribute;

L28 stock bottom / N47 maxima head

Schneider regrind on stock cam to 270/280 .460

Pilots 62.5

Main 140

Air 190

Pilots out 1.75 or so each

Warm idle AFR @ 800RPM - 15 - 16

Cruise - 12 ish

WOT - 4th @ 6000RPM - 13.5 - 13.7

Now with a Cartech blow through boosting 9psi

Pilots 62.5

Main 145

Air 180

Warm idle AFR @ 800RPM - 15 - 16

Cruise - 11.5 ish (off boost, light throttle in 5th will induce 1 to 3 psi, which will lean it out to 12 - 13, need this transition)

WOT - 4th @ 6000RPM - 12 ish

Still fiddling and gonna try 150 main this weekend to get my WOT down to 11.5, going to leave everything else the same.

[madkaw]

The short answer -No:(

I messed the carbs all day. After seeing #2 looking fouled I decided I needed to tear them all down and put some compressed air to things. In the process I didn't see anything that I could attribute to any of my problems. There was the slightest bit of sediment in the bottom of the carbs.

I put everything back together and and got it running. It's still not right, but once again I can put my finger on it. When I went to synchronise the carbs #4 was hardly drawing air compared to #3. It was off by quite a bit. The engine didn't idle to terrible, but not like it used to. I finally just said WTF, I'll drive it and see how it feels. Well it still not right, hell it even back fired once getting on it. Seems to be lacking power . The AFR's didn't jive with the known jet settings and they seemed a bit erratic.

I pulled the plugs afterwards and none were fouled and they didn't look too bad .

Not sure what I'm going to do next. I will probably drive it again tomorrow weather permitting. Getting really discouraged and pissed with the whole matter. This seems to be dragging on to the point that i don't remember how I got here. This car used to run fantastic.

Edited July 26, 2014 by madkaw

[Travel'n Man]

Warm idle AFR @ 800RPM - 15 - 16

Cruise - 11.5 ish (off boost, light throttle in 5th will induce 1 to 3 psi, which will lean it out to 12 - 13, need this transition)

WOT - 4th @ 6000RPM - 12 ish

Still fiddling and gonna try 150 main this weekend to get my WOT down to 11.5, going to leave everything else the same.

15-16 is way lean at idle - and IMO 11.5 is too phat - your plugs will be black with soot.

[madkaw]

It seemed that a fatter idle made for easier start ups for me, but if you can get away leaner-go for it. Don't forget Mitchell, he is boosted. Want to keep things on the rich side.

[Kennymonster]

Yup, ideally I'd like to have a leaner cruise to rich tip in, but with forced induction (now running 10psi after yesterday's main jet to 150, air still at 180), partial throttle is the biggest issue for me. Basically have to tune for WOT to be low 11's no matter what, as well as keeping it under 13 during transition period, which has been the trickiest part. Ended up gapping the ngk 7's down to .035 even with MSD to avoid any misfire.

Did some fiddling with pilot screws adjustment on 62.5's, now it's at around 14 on idle, I do have some problems on cold start though.. not sure why as it seems to be getting too much fuel at crank, having to hold the pedal pegged & crank couple times to have it catch. When I was NA it started right up with couple accel pumps, but then again I was running .045 gap on ngk 6's.

Edited July 26, 2014 by Kennymonster