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carb help

Started by Sanders46, April 27, 2012, 09:22:20 AM

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I converted a set of 92 fj carbs over to duel inlet for my 86. Rebuilt them in the process.  I have stock jets with K&N pod filters.  The bike will only seem to run with the choke on and will not idle at all.  Anyone have any ideas??
86 fj x2
80 cb 750f

Pat Conlon

You still have plugged choke/air circuits or pilot jets. A good time to throw away the oem #38.5 pilots and get some new #40 pilots.

BTW, did you also change your float needle seats?
You know that the '92 float needle seats are smaller sized (1.5) for fuel pump applications, and the gravity fed carbs are larger sized (2.3)  Scroll down:

Our resident carb guru DavidR reports that he is running the smaller fuel pump seats on his gravity fed bike and has reported no problems, so I suspect the plugged circuit/pilot jets..
1) Free Owners Manual download:
2) Don't store your FJ with E10 fuel
3) Replace your old stock rubber brake lines.
4) Important items for the '84-87 FJ's:
Safety wire:
Fuel line:


Here's a couple of ideas :-) for you.

The '92 carbs have the smaller float needle jets and may not flow enough fuel since you don't have a fuel pump, but that won't be the case at idle, only at higher rpms.

The K&N pods will reduce the vacuum signal in the carbs, so you're probably very lean.  You probably need to upsize your main jets by a couple of sizes and lift your needles 1mm (0.040") too.  Your pilot jets could easily be plugged and need cleaning too, especially with the (reportedly) crap fuel you guys in the US are getting now.

Wait for one of the true carb guru's to reply.  They'll probably have more or better ideas to offer.



I do have a set of #40 pilots I can put in but I would need to order bigger mains.  Not sure how much bigger to go.
86 fj x2
80 cb 750f


Quote from: Sanders46 on May 02, 2012, 07:00:38 PM
I do have a set of #40 pilots I can put in but I would need to order bigger mains.  Not sure how much bigger to go.

If you still have stock exhaust, I'd leave the mains alone. Big-bores were mostly lean at idle and off-idle, because that's the carb circuits used during the EPA emissions testing for certification, they never even get into the main jets. Put in the 40 pilots and see how she's running.... And, make sure all the jets and carb body passages are clean.
Rich Baker - NRA Life, AZCDL, Trail Riders of S. AZ. , AMA Life, BRC, HEAT Dirt Riders, SAMA....
Tennessee Squire
90 FJ1200, 03 WR450F ;8^P