It this normal? Carb question

[VaughanCustoms]

Just curious to know on these main jets are just sqrew on until tight or if they are all supposed to be turned the same? Does this look normal this is before I cleaned them? anything look like it needs replacement?

[fj1289]

Yes - just to snug. The slots will probably all end up oriented differently.

Also, everyone I'm aware of jets all 4 cylinders the same. It is common on some other bikes to jet the inside cylinders one jet richer (for additional cooling I assume). Not sure why not done on FJ?  Not needed?

[Pat Conlon]

At speed, with lots of air blowing thru the cylinders, no need for different needle settings or different pilots or main jets.
At idle, low speeds, on hot summer days in the desert, I like to run my inboard cylinders (#2,#3) 1/4 turn richer on the idle mixture screws...but that's just me.

I recall our Spanish FJ brother Alf, gave me the idea.

Cheers.

[movenon]

At speed, with lots of air blowing thru the cylinders, no need for different needle settings or different pilots or main jets.
At idle, low speeds, on hot summer days in the desert, I like to run my inboard cylinders (#2,#3) 1/4 turn richer on the idle mixture screws...but that's just me.

I recall our Spanish FJ brother Alf, gave me the idea.

Cheers.

I do the same. Can't say it helps or doesn't, just makes sense to me. And seems to do no harm. I am thinking that when the carbs are manufactured they set the fuel air screws out all to the same setting so there must be a fair amount of latitude in the adjustment.
On mine when I crank down (lean out) the screws I get down to around 1/4 turn to zero then I can tell its stalling.
When I turn them out (enriching) at around 3 1/2 - 4 turns I can tell by the blip test that It is running rich.
I ended up at 2 1/4, 2 1/2, 2 1/2, & 2 1/4. and to tell you the truth that last quarter of a turn on any of them I couldn't tell much of a difference. It seems to run pretty good now. Having no other FJ's around to really compare it to, it's the best I can do.

On the jets, mine are down to what I call "snug tight". Be care full of over tightening them. They make special jet wrenches that are nice to own. Some (me included) dress down a screw driver so the blade fits nice, full and square in the slot. As noted the slots are not indexed, where they stop is where they will be....

George

[ribbert]

At speed, with lots of air blowing thru the cylinders, no need for different needle settings or different pilots or main jets.
At idle, low speeds, on hot summer days in the desert, I like to run my inboard cylinders (#2,#3) 1/4 turn richer on the idle mixture screws...but that's just me.

I recall our Spanish FJ brother Alf, gave me the idea.

Cheers.

Pat,
I have taken two sets of FJ barrels to the machine shop in the last couple of years. Both showed signs of more wear on the outer cylinders. This machine shop only bores and grinds motorbikes engines, nothing else, and has been doing so since the 60's. He told me this is not unusual on FJ's, the middle cylinders run cooler because the ducting provides much better air flow to the heads than the outer ones in the air stream. Our bikes spend very little time idling and are best tuned for riding.
If he's right, and that's a lot of experience to argue with, the middle cylinders are always going to run relatively cooler whatever the temperature.

Noel

[Pat Conlon]

That's interesting Noel. Counterintuitive but interesting. Thanks.

[movenon]

That is interesting. Hard to argue with facts. I will have to reevaluate my fuel air screw adjustment drill. Thanks Noel. Facts and numbers are nice.
George

[VaughanCustoms]

So you guys would recommend when I get the carbs back on to start it up and play with the idle and the mixture sqrews? I will get my huge box fan on the big to get it air so she doesnt get to hot.

[movenon]

So you guys would recommend when I get the carbs back on to start it up and play with the idle and the mixture screws? I will get my huge box fan on the big to get it air so she doesn't get to hot.

No not exactly:

Box fan is good 
Set your fuel air screws to factory spec's (did you clean and rebuild ?)
Warm the engine up
Set your idle at 1150- 1200 RPM
Sync your carbs

Then you can adjust the fuel air screws. Or leave the screws at factory setting. Turn the screws out for more fuel and turn in for less fuel. The screws control fuel not air. Suggest you read about "blip" testing.
Personally I think the screws have a lot of latitude and understand that the factory set the adjustments so you can operate in a range of elevations.
George

[Dan Filetti]

Martin-

Take a look here:  

http://www.fjowners.com/index.php?topic=655.0
and here:
http://www.fjowners.com/index.php?topic=46.0


David R. has done an very good job with documenting instructions.  If you read through the entire thing including where he discusses the blip test, after syncing, to adjust the idle mixture screws, you'll have a pretty compressive means of servicing your carbs.  I would, as a rough starting place, set each idle mixture screw at three turns out from lightly seated, and adjust from there, based on the results of the throttle blip test.

Dan

 

[VaughanCustoms]

Ok thanks guys, yeah I have cleaned them and waiting on some parts from RPM so I can put the carbs back together. I have a Vance and Hines exhaust, rejet and k&n are you still supposed to put back to factory and adjust from there or leave it where it is as it was tuned before the clean and adjust from there?

[RichBaker]

Ok thanks guys, yeah I have cleaned them and waiting on some parts from RPM so I can put the carbs back together. I have a Vance and Hines exhaust, rejet and k&n are you still supposed to put back to factory and adjust from there or leave it where it is as it was tuned before the clean and adjust from there?

The bolded.....

[fintip]

Yup, what Rich Baker said.

Has anyone else noticed that David R doesn't seem to post anymore? Do you think he actually followed up on his threat to Noel?

[rktmanfj]

Yup, what Rich Baker said.

Has anyone else noticed that David R doesn't seem to post anymore? Do you think he actually followed up on his threat to Noel?

Yes.

[ribbert]

Yup, what Rich Baker said.

Has anyone else noticed that David R doesn't seem to post anymore? Do you think he actually followed up on his threat to Noel?

Yes.

If you re read his last post you will see he dumped on many people and had a dissatisfaction with the forum in general. My disagreement with him may have set him off but his comments show it had been brewing for a while.

"Do you think he actually followed up on his threat to Noel?"  Kyle, perhaps you should read it again too if this is you take on it.