RPM's fall when pressing the rear brake??

[RPM - Robert]

Techron is the additive that Chevron makes, u can get it at chevrons, or any parts store. Sea foam, K100, or star tron are also additives like techron along with probably about 50 others.. The K100 is the one we have been using most recently and have had the best results with. Bikes sat since the RPM fall rally and they started right up with no problems this week.

[red]

Where would I buy said techron? I usually just run Seafoam through my carbs. As for gas, I only run premium, but it is still ethanol fuel.
That said, I was thinking about it last night and today, and i have questions about using an aux tank for the testing. If i hang a tank, and just run hose to the carbs, wouldn't that flood it? Don't i need some sort of impedance, IE, the petcock in line to make sure it isnt flooding from constant fuel? What sort of aux tanks have people used?

Ryan,

Man, don't get too wrapped around the axle on this!  Yes, there IS a connection between the rear brake and the engine ignition, and it is the electrical system.  Before you tear into mechanical stuff that may not be sick, try this process.  Run the bike until warm.  Idle the engine, ignore the brake pedal, and pull on the switch that turns on the brake light.  If the revs drop, then the taillight circuit is pulling too much power.  Simple as that.  You may have installed an LED in the taillight (pulling too much power now), or you may have a corroded bulb socket, or you may have chafed wiring somewhere in the circuit.  Brakes do not affect carbs, or fuel mixtures.  Brake lights can affect the ignition voltage, but only if the electrical system has other problems like too many gadgets, a failing voltage regulator, corrosion at connections, or bad wiring insulation..

How much voltage do you read at the battery?  Are all of the battery connections shiny-clean and tight?

You could install a coil relay, to feed full battery power to the coils, which should fix the problem permanently.  These electrical systems are getting old, and corrosion takes its' toll in passing power along.  Most riders report a noticeable power boost from installing a coil relay.

[T Legg]

I use a small gas tank from my lawnmower when I balance my carbs.I just put a cupful of gas at a time in it.your float valves will keep your carbs from flooding, when your engine is running there is always unrestricted fuel flow from the gas tank.the flooding occurs over extended time if your petcock doesn't shut off the flow when the engine is not running. 

[ryanschoebel]

Okay, so I measured voltage with the rear brake pressed, and not. No voltage change at all. maybe .1 to .2 volts less.  I think I'm going to hold off on the blip test for now, and I'll probably just end up sending the carbs to the guys at RPM. The reason being, I filled up the bike 2 days ago, and and reset the trip. When I looked again today, I have 23 miles on the trip and half a tank of gas. No leaking around the bike, and I haven't checked oil yet. Its always smelled DUMB rich, but I wrote it off. But seeing how much its eating fuel, I'm figuring that this must just be some sort of carb issue. Thoughts?

[Pat Conlon]

Yea, you've got some carb issues for sure....You know the drill.

Get Frank's jetting info he used on Stormy.
IIRC his choice for main jets was larger than customary.

[Sparky84]

Thoughts?

I think you got a Lemon!! 

Look, I'm a nice guy and I'll take it off your hands for you Ryan...

Cheers
Alan

[ryanschoebel]

Thoughts?

I think you got a Lemon!! 

Look, I'm a nice guy and I'll take it off your hands for you Ryan...

Cheers
Alan

I don't even want to see the shipping and customs to ship a whole ass bike down under haha. Pat, I sure do. Ill send Frank a PM

[FJmonkey]

Its always smelled DUMB rich, but I wrote it off. But seeing how much its eating fuel, I'm figuring that this must just be some sort of carb issue. Thoughts?

Hold a flame to the exhaust to see if you can throw flames out...

[Tuned forks]

Its always smelled DUMB rich, but I wrote it off. But seeing how much its eating fuel, I'm figuring that this must just be some sort of carb issue. Thoughts?

Hold a flame to the exhaust to see if you can throw flames out...

And that would be the last we would ever see Ryan.

Joe

[ryanschoebel]

Hold a flame to the exhaust to see if you can throw flames out...

Just dumb enough to qualify for a Darwin Award, just fun enough to try... Not 

[Sparky84]

Hold a flame to the exhaust to see if you can throw flames out...

Just dumb enough to qualify for a Darwin Award, just fun enough to try... Not 

Eyebrows will be the first to go...they are overrated anyway!

[CutterBill]

Okay, so I measured voltage with the rear brake pressed, and not. No voltage change at all. maybe .1 to .2 volts less. 

Correct. That means your voltage regulator is working properly. The VR is dumb; it doesn't know anything except the voltage in the system. And it adjusts the alternator to keep that voltage at one set level. So when you press the brake pedal, and therefore turn on the brake light, there is a slight voltage drop in the system. The VR sees this and tells the alternator to convert more mechanical (rotational) energy into electrical energy. Which drags the engine revs down...

The strange part is that your brake light bulbs are drawing enough current to drag the engine revs down. What do ya got back there... couple of headlight bulbs?   
Bill

[andyoutandabout]

Ryan, my 86 used to pulse at idle when the indicator was on. For me the cure all was the direct relay coil mod, see the files for a great write up by some FJ genius. I did this ages ago getting all the parts from radio shack, but you can probably find it all on Amazon. It was an easy enough job, cheap and saved a bunch of troubleshooting time.