pod filters and carb jetting

[Pat Conlon]

Haha the poor mans option sounds like a bit of me. Where can I get an ignition advancer?

Good question Kev, Ignition advance plates/rotors; they used to be popular, but I have not seen them around much lately.
Vance and Hines along with Factory Pro here in the USA used to carry them, not sure now.
FYI, There are 2 types of FJ ignition advancers, the plate type which the later model FJ's use, and the rotor type which the early FJ's use. Make sure you get the rotor type for your '85.

Happy hunting...

[Rampant_ant]

I dunno David, it gets pretty toasty warm down under...I think his main jets need up sizing.
The Yamaha microfiche shows the euro '85 FJ to have 110 main jets and 40 pilot jets vs. the USA version's larger 112.5 mains and smaller 37.5 pilots (am I reading that right?) if so....

I know we spend very little time WFO on the main jets, and 80% of our time on the needles, but #110 mains are kinda small with pod filters and a 4-1 pipe. (#40 pilots are fine) considering the hot weather.

Fr Paddy

Just found out I have 112.5 main jets. Not sure what pilot yet as I don't have the tools to pull it all apart.

Was wondering if those mains sound right for a standard filter and airbox with the 4-1 exhaust
Cheers

[andyb]

Just found out I have 112.5 main jets. Not sure what pilot yet as I don't have the tools to pull it all apart.

Was wondering if those mains sound right for a standard filter and airbox with the 4-1 exhaust

Ask your plugs what they think! 

[Pat Conlon]

I dunno David, it gets pretty toasty warm down under...I think his main jets need up sizing.
The Yamaha microfiche shows the euro '85 FJ to have 110 main jets and 40 pilot jets vs. the USA version's larger 112.5 mains and smaller 37.5 pilots (am I reading that right?) if so....

I know we spend very little time WFO on the main jets, and 80% of our time on the needles, but #110 mains are kinda small with pod filters and a 4-1 pipe. (#40 pilots are fine) considering the hot weather.

Fr Paddy

Just found out I have 112.5 main jets. Not sure what pilot yet as I don't have the tools to pull it all apart.

Was wondering if those mains sound right for a standard filter and airbox with the 4-1 exhaust
Cheers

As Andy says, "check your plugs".
In doing so you will see that the FJ with the stock jetting runs on the lean side. Yamaha did this for emission reasons, not tuning reasons.
DavidR (who btw is our in house FJ Carb Guru) recommends to raise the needles. That is spot on, and for the sake of this discussion will cover ~80% of your riding conditions.
The other 20% of your riding conditions, again for discussion, can be further divided into 2 areas;
1) Riding on the pilot jets (~10%) and;
2) Riding WFO on the main jets (~10%)

1) Riding on the pilot jets (oem 38.5) happens at low "intake air velocity" speeds with the rpms in the 0-2500 rpm range. At these low speeds, the difference in the air flow with the change from the stock air filters to the Unipods is not that great, no big deal .
IOW: air flow thru the carbs is not much different at low speeds with Unipod vs. stock.
(Side note: In hot weather climates increasing the Pilot jets from oem 38.5 to a 40 or 42.5 results in cooler running motors (richer mixture) when idling around town at low speeds)
 
However...

2) Riding on the main jets happens at ~WFO with higher engine rpms and thus much higher air intake velocity thru the carbs....
This in my opinion: Here's where Uni pod filters really kick ass, they really flow much much more air than the oem filter at high velocities. This additional air thru the Uni pods needs additional fuel, thus (again in my opinion) the need for bigger main jets.

110 and 112.5 main jets are too small for FJ's equipped with a header and Unipod filters... I'm not alone in this opinion.

1) Get your bike toasty warm,
2) Run your bike WFO. Listen for ping.
3) Chop your throttle, turn your bike off, coast to a stop.
4) Remove your tank and pull your plugs and look at the colors. Wear gloves, they're hotter than.....

I'll bet you a jelly donut: If you have 112.5 main jets with Uni's and a header, you will hear ping or as Andy recommends, by looking at your plugs you will see that you need fatter main jets.....Wanna bet? Any takers?

[wakdady]

what should one be looking for on the plugs? i stuck with the airbox and only got #40's with the headers. but it seems way to rich. you can smell fuel quite readily. if i were to switch to pod filters, which main jets would i need? oh, its a '90

[SlowOldGuy]

For a WOT throttle chop plug check that means cranking the throttle open for a FEW seconds then pulling the clutch, kill the engine, coast ot a stop, pull the plugs and look at them.  Not exactly a convenient thing to do out on the road.

You'll be looking for the plug insulator to be a light tan color.  Not black and not white.  If you think you're too rich at idle, check the mixture screws.  You can usually smell rich at idle.  Once underway, it's hard for you to gauge the mixture.  Ask the person behind you. 

I remember my first day riding behind Carey on his '86.  I thought I was going to pass out any second.  When we got back to camp I lowered his needles a clip and a half.

DavidR.

[andyb]

On a WFO plug chop, I wouldn't want the easily visible part of the insulator to be tan.  Ideally, you'll need to cut it in half and read the ceramic portion down near where it attaches to the metal portion of the plug.  Yeah, it means you're cutting up nearly new plugs, it feels awful.  You can also use a 5-10x magnifying glass to read them.  

 

If it's tan all the way out near the center electrode after a WOT run, you didn't use a new plug, the plug is far too cold, or you're comically rich, as the insulator should be cleaned by the heat of the combustion cycle to prevent fouling.  If the insulator is glassy, it means you're probably using too hot of a plug or you're quite lean.  If you're seeing speckles on the ceramic portion, there's a good chance that you're getting detonation that you're not hearing.

[Dan Filetti]

On a WFO plug chop, I wouldn't want the easily visible part of the insulator to be tan.  Ideally, you'll need to cut it in half and read the ceramic portion down near where it attaches to the metal portion of the plug.  

Wait, you're saying you have to destroy your plugs to read them??!!  A bit like the Heisenberg uncertainty principle -no?

Dan

[weymouth399]

Everything I have been tought about jetting is. Use a old plug, they will color better, and quicker than a new plug will. Thats what's what Yamaha told me back in 1989 when I was at school. What would they know.

Bob W

[Klavdy]

On a WFO plug chop, I wouldn't want the easily visible part of the insulator to be tan.  Ideally, you'll need to cut it in half and read the ceramic portion down near where it attaches to the metal portion of the plug.  

Wait, you're saying you have to destroy your plugs to read them??!!  A bit like the Heisenberg uncertainty principle -no?

Dan

Hmmm.
Perhaps Schrödinger's Cat would serve as a better analogy?

[carsick]

That's what Yamaha told me back in 1989 when I was at school. What would they know?

Bob W

Well, if they knew what they were doing we wouldn't have to rejet, right? Oh wait, we screwed with the bike, never mind.
While we're on this topic, anybody know why my needles have 6 grooves? I've seen 4 and 5 clip grooves, is this some strange brand of jet kit?

[Dan Filetti]

Perhaps Schrödinger's Cat would serve as a better analogy?

You simply can not mitigate for quantum decoherence.  Schrödinger's Cat is a fascicle paradox. 

Dan

[carsick]

On a WFO plug chop, I wouldn't want the easily visible part of the insulator to be tan.  Ideally, you'll need to cut it in half and read the ceramic portion down near where it attaches to the metal portion of the plug.  

Wait, you're saying you have to destroy your plugs to read them??!!  A bit like the Heisenberg uncertainty principle -no?

Dan

Hmmm.
Perhaps Schrödinger's Cat would serve as a better analogy?

So you put in new plugs, run them WFO, shut it down on the interstate, pull the plugs, cut them open, measure their present position but are unable to predict their future velocity, then put them in a box with a cat of indeterminate mortality? Is this a Harley thing or Voodoo? Also starting to sound like some rustic advice from the Haynes manual.

[Dan Filetti]

You simply can not mitigate for quantum decoherence.  Schrödinger's Cat is a fascicle paradox. 

Dan

Correction: that is: *farcical* paradox.

[Klavdy]

Ain't it a bastard the way that Fluffy has set the time allowed for editing.
He's done that on purpose you know, just to be a dick.