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madkaw

Triple Mikuni Help

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now just be ginger with those idle screws...next thing that happens is guys twist the tips off in the carb bodies and wonder why turning them has no effect on the barrel constantly popping until you really get into it!

They pop out with a screwdriver, but the bummer is you have to pull the carb to get to them!wink.gif

 

You will be turning them in, that's for sure!

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Buy a set of idle screws as wellsad.gif

 

The top one is trashed and will make it hard as hell to get a proper mixture (linearly) as designed.

 

The bottom one...since there's not a sense of scale I can't readily say if that's the proper "point" -- When the break off in the idle mixture port, they are no longer "Pointy" but have a blunted end where the tip of the screw, the 'bluntness" is equivalent to the diameter of the idle port in the carb body... When you see a new one next to the other you can see one is pointy, the other blunted.

 

I guess you could figure the extruded section of the top needle is about where it breaks off. You can see the end sticking into the air side through the idle port.

 

But for every one that is truncated in your set: replace it. "NFG"--it's on the way to breaking off, and with the larger jets you will want all the linear, fine adjustment you can get!

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I should have stated that I already replaced them. When I pulled these out I thought I had found my issue and got on the phone and ordered new ones. The new pilot screws went in with the 60 pilot jets-but still too lean. I have actually found several issues with these seemingly "new carbs", but I think I do have a very nice set.

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Okay, got some 62.5's and some 65's today. Didn't even bother with the 62 at first, just threw in the 65's.

Engine ran a bit better, but still fell on it's face with 2 turns out. Wouldn't idle with just one turn

Now I'm pulling out my hair thinking I still have other problems and I don't have anything else to try.

 

When I received the carbs it had 2 sets of main air jets, 180 and 200's. I have been running with the 180's so I decided I would try the 200's. Wouldn't you know it raised the threshold of the stumble by atleast 1500 rpm, and I can about save it with a little more throttle.

I ran out of time to do more troubleshooting, but the larger main air did help!

 

Thoughts?

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When I read your initial post I would have put money on the pilots being too small

 

I was under the impression the main air jet only had an effect over a very small area at the upper end of the rev range? and going larger leaned out this area?

 

I have PHH44's on a L24, head work, cam, 6 branch and system etc, and my airs are 210, but I do have a stumble just off idle under load, pilots screws out 2 complete turns, 360 + 360, with 57.5 pilot jets......so I've been following your progress with interest

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I concur on the main air jet thinking, but I obviously have a lot to learn.

 

An added note; every once in a while my flakey wideband works and I saw decent AFR's at idle with the 65's, but it still stumbled to death . I need to go back at it with fresh plugs and an open mind. If it wants bigger main air I'll get it.

 

I will eventually get back to Todd on this, but his info usually comes complete with a lecture;)

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140 main should be more than enough. 135-140 was where our Bonneville Engine Ran...but like JM said with higher vacuum comes smaller jet requirements. A 220 might help on the main bleed--that is about as big as I recall seeing them in the past for most street cars.

 

You should only change ONE JET SET at a time. If the 65's didn't change anything, but you didn't go crazy rich on your idle---then they aren't too big. If the bog still happened and didn't get better till you put the Air Bleeds in---raising it 1500 rpms---then that means now you are on the main jet when it's bogging and hitting the throttle gives you an accel shot richening it up.

 

You might be close. A main jet larger might do it but it's late and I may have misread soemthing... But is sounds like the pilots are not causing the issue now your mains are at 3500.

 

Really, you shouldn't be lugging the engine that low anyway...but the test of proper carburetion is to short-shift into fifth and be able to WOT the carb and have it pull (albeit slowly at first till it comes 'on the cam') from 1000 rpms on up. If you can do that without popping, bucking and surging then the jetting and all transitions are correct. This is very similar to the free rev 'gradual acceleration test' you have been doing.

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All I can say is "Control-Shift Arrow Up Up Up Up" Right Key "Control-Shift Arrow Up Up Up" Up Key "Control-Shift Arrow Down Down Down"....

 

That is a LOT cheaper than buying all these jets, and the primary reason I went to EFI!dry.gif

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Thanks for the insight Tony and FI is in the future, but I want to say I've done triples!

 

I'm awaiting a return call from Todd. He left a voice mail suggesting I remove the jet cover and try it again, not sure what that does. Of course I'm on a train and try anything right now- plus my car is still on jacks awaiting my Cibie headlights to arrive and to install.

 

At this point I probably need to drive it to see what it does or does not do.

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Why does everybody think EFI means they can't have triples?

The biggest conversion in Japan now is putting injectors in Triple manifolds, and pulling the venturis out of their carbs.

 

They even make TPS Sdaptors that bolt right onto those Mikuini Bodies (and most other triple bodies)---pick up HP for sure, and ahem...

 

 

 

 

 

 

driveability!dry.gif

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Figured out my issue, but I'm going to make you guys figure it out.

 

Tod really liked my CAI, but it has/had a serious design flaw-that's your clue, along with a pic

D'oh! No hole for the float bowl vent!

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Glad you figured it out. How does it run now that you can take it wide open when you drive it? I had triple Mikuni's on my 3.1L, and it was pure music. My 5.0 that is in there now has a lot more power and has its a great sound, but the I6 with the triples sounded a lot better fo sho.

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I guess I should have posted a pic earlier and you guys would have figured it out for me!

I feel kind of dumb, but live and learn. Atleast it was an easy fix.

 

Still putting it back together so I haven't driven it yet.

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