Throttle Response

[miatamarty]

I'm new to the FJ1100 world. I just got an 1984 FJ1100 with 50k miles. It's a barn find that was brought back to life by the guy I bought it from. He's a retired hot rod builder with some decent skills. All new fluids, fork seals, rebuilt brake and clutch hydraulics, new brake pads, new battery and rebuilt carbs. I bought a carb synchronizer from Motion Pro which worked out great. Excellent idle that stays right 1000rpms when warmed up all the way.Snappy throttle response when in neutral, drops right down to idle quickly My problem is really poor throttle response from idle to about 3000rpms requiring lots of throttle. Above that it runs great. I was told that the main jets went up one size from stock. Pilot jets are 37.5 I think. Pilot jet screws are about 2 turns out.  The exhaust is a Vance and Hines 4 into 1. Air box is stock with paper element. Its been a really long time since I've had to work with carbs. Is my problem too lean or too rich right off idle? Are the needles adjustable? Can they be raised to richen midrange or is that even my problem? My other bike is a Buell XB9S with fuel injection so the carbs are a return to ancient history for me.

[Pat Conlon]

Welcome Marty. I had a 1999 10AE for 22 years, what a great Miata. I do miss it.

Yes, you can shim the stock needles. RPM sells 1/2 step washer shims for the stock needles.
http://www.rpmracingca.com/proddetail.asp?prod=Carb%3AMainNeedleShim&cat=24

They also sell the adjustable needles:
http://www.rpmracingca.com/proddetail.asp?prod=Carb%3AMainJetNeedleSet

Does your bike bog? ....or is it just slow to accelerate?

I don't think shimming the needles is your problem.
Jetting won't fix a carb that's misbehaving.

You could have leaking carb diaphragms on the sliders, under acceleration causing the sliders to lag in raising up in the bore.

Do the finger test.
Take the air box off so you can see the carb sliders.
With your index finger, lift up each slider then release.... The sliders should slowly drop down. If the slider (or sliders) drop quickly that indicates a vacuum leak on the diaphragms. Check to make sure all sliders drop at an equal rate. If one drops quicker than the others, that's the carb you want to check.

You could have a clogged pilot jet circuit(s)
 1k to 3k rpm is right where the pilots do their magic. It's not just installing new pilot jets...
It's not the jets themselves but the small passageways that feed the jets.
You may need to ultrasound clean the carbs.

Check your fuel line routing. Make sure it's correct (see link below)

Do us a favor, go to your profile and in your signature line put in that you have a 1984 FJ1100.
That info will appear automatically in all your posts. You won't have to remind us.
That will help us help you.

Cheers

Pat

[miatamarty]

I had to take the carbs off altogether unless there is some magic trick to getting the airbox out with carbs in place. Anyhow the #1 carb had a bad diaphragm. I had a new one that came with the bike. Thanks for the tip, I really appreciate it. Since the carbs are sitting on the bench tomorrow I'll check the circuits behind the pilot jets.

[Pat Conlon]

 

http://www.rpmracingca.com/proddetail.asp?prod=Carb%3ARPMPod&cat=39

Many of us have ditched our oem air boxes and have gone with UniPods.
They sure make carb work easier. The Foam UniPods fit better than the aftermarket individual paper filters which always seems to run afoul of the frame rails on the #1 and #4 carbs.

If you do want to keep your stock air box, cool, no problem.
To help get more room for air box removal and reinstall, you remove the 3 air box mounting bolts then the 2 upper bolts on the subframe, the subframe tail then can drop down giving you clearance to get the box in and out while leaving the carbs installed.

Cheers

[miatamarty]

Just ordered the Unipod filters. That airbox really pissed me off. Thanks again

[Millietant]

Gotta say, the airbox is a non-issue for me. Carbs are so easy to get on and off on a FJ once you slide the airbox back and drop the subframe down so that the undertray sits on a towel on the back wheel.

I honestly can't see a good reason to ditch the airbox.

[86FJNJ]

I am happy I switched to the pod air filters. when doing so shim your slide needles. I would also suggest bumping up the pilot to 40.0 but that's just me and the rest of the guys in this group know a lot more than I do.

[miatamarty]

Going to be a while before I can ride the bike again.I thought the clutch cover gasket was leaking but no. It was a large rubber gasket that seals the the part of the cover that says YAMAHA. Found one in Florida but it's almost 2 weeks out. Disappointing but hey it's a 40 year old bike. Just glad I found one. PO was a little lacking in finesse. I was able to get dowels and the right length bolts plus the rubber grommets that were pretty much petrified. Hope I don't have to change out the needle clips. I'm at 4200 feet elevation with regular runs up to Crater Lake at 7500ft. I'm hoping the elevation will naturally  richen things up.

[RPM - Robert]

We have both the center gasket and the silver cover in stock and would be to you in 2-3 days.

[miatamarty]

Thanks for the heads up but I'm kinda committed to the order in place. I have bookmarked RPM for future orders. You'll be getting more of my toy allowance.