Off-idle stumble & bleed screws

[Waiex191]

Hey all,
I've not been riding or working on the FJ much, as I've been buried in airplane issues etc. Since I got it back together it's had a bad off-idle stumble, and I've had to rev it a bit to get it going. Sort of like a beginner. A couple years ago I was convinced my stock idle jets were getting plugged up, possibly from kreem degradation in my tank. I've replaced the filter, cut the old one up, seemed fine.

I've been on the forum despite my inactivity and bleed screws have come up a few times. I set mine after synching the carbs, mostly my blipping the throttle while parked on the centerstand. But I suspect the engine was not up to temperature.

So I pulled the tank, screwed them all in - 5 turns!  Set them all to 2.5, and it's much better. But not perfect.

Looking for advice. Do I turn them in or out?  How much per iteration?  Do I test by riding, or is there another more efficient method?

Thanks!

[86FJNJ]

Turning the mixture screws clockwise (in) will reduce fuel, turning the screws counter clockwise (out) will add fuel.

Can we assume that at one point in the past the bike was running fine with this same configuration of pilot jets and air intake filter etc? No changes in set up since it was last running well?

Most in this group will suggest a good carb cleaning and they are probably right. I had some issues with a dirty pilot circuit and ended up increasing the size of my pilot jets...bigger hole, less chance to clog. I have also been running Yamalube RingFree + Stabilizer fuel additive in my fuel and that has actually helped a bit and I've been running it in my fuel ever since. Or some people use Seafoam in the fuel which can also help.

If you have a concern over fuel filtration and your FJ has a fuel pump you can run this Golan 10 micron filter between the pump and your carbs. I've got probably 1,500 miles on my Golan filter and not one issue with fuel starvation. I still run the standard yamaha (40 Micron?) fuel filter between the tank and the fuel pump but like having the 10 micron Golan in there as well to keep the carbs clean. The filter is rated at 6 gallons per minute so I would assume it would be ok for a gravity fed FJ but I've not confirmed. Since the gravity fed FJ carbs have two fuel inlets, if you did have fuel starvation issues by running one filter you could run two filters with one filter dedicated to each of the two fuel inlets on the gravity fed FJ carbs, that would certainly eliminate any fuel starvation issues IMO with one filter only servicing two carbs instead of four.

https://www.amazon.com/Yamaha-Yamalube-ACC-RNGFR-PL-12-Ring-Additive/dp/B002GU4SN2/ref=sr_1_5?crid=3MDHKOC2GLCZJ&dib=eyJ2IjoiMSJ9.9MbbKhISmpLz7J71jhJqAHB2Z9O1DjDCnE3n6R3boAAdBurBSZ-6eTZTyhUrzBlrOK2dc_F5LxGJjLHSEfNcdAT-FNDBWgLNRY3fpkFXUbPbjyjNpynagBYawIG3LVGRZw6QzEQWgJBUru4XdhK63Xo-U_Xr4A8cQI_nuw-E6qppQOcNzSMQi2xlRnkcDHtdYEtSFvKuS_qLwCis3WPF8QhZ1pM2gQ9ra2KUqhq5q4P-WpeMEAkV4FdXO4H-L_pm1no_CyMpHiYMdeKZYH2Bag9T4vM4s76GvxfyyVq4Hno.6ySt1bRY3p54N12-YoY71Rbno64oOZFipN2kDh7syXA&dib_tag=se&keywords=yamaha%2Bring%2Bfree%2Bplus%2Bfuel%2Badditive&qid=1761051006&sprefix=yamaha%2Bring%2Bfree%2Bp%2Caps%2C76&sr=8-5&th=1

https://www.amazon.com/Golan-Inc-Super-Filter-70-250G/dp/B00D3R1WOA/ref=sr_1_3?crid=ICZE3UZL4HFX&dib=eyJ2IjoiMSJ9.DoBHOCOFb6G-tWrNM9XNdZZ_XX4gCyz6qlPwMHUVj6y6CauEaRGrGD0Fu7GsNb4DXznSGWE0D4ytJz5gsaI2wcgoWLIn9XvXk8zQDptjtZEmfhw4tE8GoaELm4Xr7T98v9AgD17Xs22IsXydNmMKrOJganGaZlakolZiChzYwNkDZyubxAeTVy8MG8RLgQF0WvLRONdapdlcCwwerx3Qlw.PVhKC8ipxi_GlT6Pj4WT4YQFaBNAKJJF0x9xfRAuv4o&dib_tag=se&keywords=golan+super+mini+fuel+filter&qid=1761051298&sprefix=golan+super+mini+fuel+filter%2Caps%2C59&sr=8-3

[Waiex191]

I've been through the carbs, and except for these bleed screws I've gained a little experience.
https://fjowners.com/index.php?topic=19343.0
I've had the bike since nearly new, all stock jets and airbox. Problem was it sat for 16 years. If I wrote down my bleed screw settings when I took it apart, I've lost that note. I'm pretty sure it's good except for the bleeds.

[86FJNJ]

If the bike sat for 16 years I would suggest sending the carbs to RPM and have them do a full ultrasonic cleaning. That should fix it. If you're bike is all stock then putting the fuel mixture screws at 2.5 to 3 turns out is probably a good starting point and then you can tune from there. But if you're like me you may want to run some Yamalube Ring Free or Seafoam through the fuel and see if it gets any better first.