Tune up - read the plugs

[iridewheelies]

Here's a pic of my plugs. 1-2 are white and 3 is dark and tan, 4 is darker too. Why arent my plugs even? 115 mains 40 pilots, stock bleeds around 3 and a quarter out on the screws, 4-1 Vance Hines uni pods needles shimmed with rpm parts. Carbs been gone thru, wanna clean them again. Wanna check the valves, valve cover seeping a bit, but the bolts weren't that tight where it was leaking so I snugged up. I dont have a tool to get the shims out, so will hold on the valves the bike starts first click when cold, will crank for a bit and need some throttle when hot. Idle good, just slow on the blip test and back to idle when clutch pulled. I have a set of gauges.

[iridewheelies]

Idk why its upside down.

[iridewheelies]

Also will be checking float levels, I did them once but wasnt sure how to measure so i didnt really make any adjustments. Bike will run out of gas when going interstate speeds for long times

[krusty]

It may help to know over what time period they became the way they and under what driving conditions. Commuting, touring, boy racing, solo or two up, rev range etc.

[Pat Conlon]

Bike will run out of gas when going interstate speeds for long times

Funny how that happens....

Seriously, you have a '85 with a gravity flow fuel system, do you have your fuel line routed correctly?
Read this: http://www.fjowners.com/index.php?topic=18286.0
Your fuel line should look *exactly* like this picture....not close, but *exactly*

[Sparky84]

Bike will run out of gas when going interstate speeds for long times

Same problem here after about 390k's and it'll do that at least twice before I make a state border..

[ribbert]

Bike will run out of gas when going interstate speeds for long times

Funny how that happens....

Seriously, you have a '85 with a gravity flow fuel system, do you have your fuel line routed correctly?
Read this: http://www.fjowners.com/index.php?topic=18286.0

Pat, I've owned dozens of gravity fed bikes but never an FJ
FJ, I'm curious every time someoone posts this. Can you explain why, if all the lines are below the tank, the exact configuration matters?

[Pat Conlon]

....Can you explain why, if all the lines are below the tank, the exact configuration matters?

Hi Noel, sure....the oem Yamaha fuel lines are relatively thin walled (compared to today's high pressure fuel line)
What happens is when the under tank environment heats up the fuel line gets softer and within some time if the hose is at a wrong angle it will pinch off fuel flow.... if this *exact* routing is not followed.
Yes, This routing is counter intuitive. Looking at it you would think: "This can not be correct", but it is.

*What you don't realize is the 1) downward angle of the petcock outlet and 2) how low the fuel outlet on the petcock sits, once the fuel tank is lowered into position*
If you run the single fuel line over the 2 branch lines, because of the outlet level and angle, you will get a pinch on the single line.

Here are the symptoms of a pinched line:
1) Bike cold starts fine, runs fine until getting warm or hot...then the bike starts stumbling like it's running out of fuel (which it is)
2) Bike cools off, starts fine, runs fine until it gets warm, then symptoms reappear.

[FJmonkey]

Pat posted before I could.

Pat, I've owned dozens of gravity fed bikes but never an FJ
FJ, I'm curious every time some one posts this. Can you explain why, if all the lines are below the tank, the exact configuration matters?

On my 86' the fuel line has little room under the tank once the tank is seated. If the line is not OEM routed, or altered as some have successfully posted; the line can get pinched from the tank pressing down on it, or kinked. Either way the 10mm line is restricted. The amount of restriction, the amount of fuel in the tank, and throttle position  determine when starvation occurs.

To be more specific to answering your question, the part of the line from the petcock to the loop around carb 3 tends to get routed over the split line dropping between carbs 2 and 3. This is not intuitive when you have to lift the tank to make the connection to the petcock. Routing it under is OEM. Routing over can cause the pinch. 

[iridewheelies]

It may help to know over what time period they became the way they and under what driving conditions. Commuting, touring, boy racing, solo or two up, rev range etc.
[/quote

I mainly use the bike to commute and cruise around, I dont put it under high load very often, and when i do, the bike flies. I have upgraded my line to 5/16 I think? Ik its larger inside, high pressure fuel line. Routed correctly under the t, but I have the twist fully around the top of the carb, theres a little bracket to hold the hose there. The bike runs great at any rpm. I wanna get the plugs tan, And I want my rpm to go down to idle faster. Blip test shows very slow on back down to idle. Carbs out of sync? I replaced manifold o rings, sprayed carb cleaner everywhere while bike running, no idle change. Bike idles real low when hot, will start there

[iridewheelies]

The bike has always ran like this. Bought it at auction and got her going myself

[racerrad8]

A couple of things...

1) You cannot really diagnose the carb jetting by the photos. The lighting is not enough and you can't really see the spark plug that needs to be examined.
2) Those spark plugs have never been properly torqued when installed. The "crush" washer to ensure sealing of the combustion pressures and making sure there is a proper ground path has never been crushed.
3) Fuel line routing is important as already mentioned.
4) The petcock diaphragm could have a hole in it and not able to keep the proper fuel flow.
5) The fuel cap vent could be causing a vacuum in the tank and should be checked.
6) You need to ensure the valve are adjust to specifications before tuning on the carbs.
7) Once the valves are properly adjusted the carb sync is the next step.
8 ) What is a stock bleed? There were several different sizes of "stock"
9) What bike are you working with, 1100/1200?
10) If 1100, flat or curved slides?
11) Stock or aftermarket ignition system and coils?
12) Has the ignition timing been altered?

And finally, you mention you want to clean the carbs again. You cannot tune a set of carbs that are dirty and have altered fuel passages. The base of the carburetion needs to be solid before any tuning can occur.

Randy - RPM

[ribbert]

....Can you explain why, if all the lines are below the tank, the exact configuration matters?

Thanks Pat and Mark, if it's a pinching issue, that makes sense.

Noel

[iridewheelies]

A couple of things...

1) You cannot really diagnose the carb jetting by the photos. The lighting is not enough and you can't really see the spark plug that needs to be examined.
2) Those spark plugs have never been properly torqued when installed. The "crush" washer to ensure sealing of the combustion pressures and making sure there is a proper ground path has never been crushed.
3) Fuel line routing is important as already mentioned.
4) The petcock diaphragm could have a hole in it and not able to keep the proper fuel flow.
5) The fuel cap vent could be causing a vacuum in the tank and should be checked.
6) You need to ensure the valve are adjust to specifications before tuning on the carbs.
7) Once the valves are properly adjusted the carb sync is the next step.
8 ) What is a stock bleed? There were several different sizes of "stock"
9) What bike are you working with, 1100/1200?
10) If 1100, flat or curved slides?
11) Stock or aftermarket ignition system and coils?
12) Has the ignition timing been altered?

And finally, you mention you want to clean the carbs again. You cannot tune a set of carbs that are dirty and have altered fuel passages. The base of the carburetion needs to be solid before any tuning can occur.

Randy - RPM

Thank you Randy with the great advice. I thought the plugs seemed loose...I haven't been under the tank since the bike sat all winter, so I must have been running it like that for a few thousand miles. Wow.
Valves are coming soon waiting for the tool to come in. (Even though I dont need the tool to check clearances)
The bike is an 1100. Stock ignition and coils. No advance that I know of.
Pretty sure they're curved slides. 155 air bleed. I have an aftermarket gravity petcock with a fuel bowl, so flow age is not a problem I should get plenty of fuel.

[racerrad8]

I have an aftermarket gravity petcock with a fuel bowl, so flow age is not a problem I should get plenty of fuel.

Are you sure about the petcock?

I see the fuel line diameter is reduced from 3/8 to 5/16 at the tee. The stock line is 10mm and larger in diameter than the 3/8 that is installed.

Secondly,  are the orifices in the petcock big enough to flow enough fuel.  If they are not at least .375", then I'm not sure if it does flow enough.  

I'm also wondering about restrictions of the gravity feed system by having to fill the bowl and then flow to the carbies.

Do you have some photos of it?

Randy - RPM