Wierd symptom at high speed

[f3tz3r]

I have a few questions that i have accumulated since riding. And a weird experience that happened yesterday.

Is it a bad to fill the tank as full as it will go, literally dripping the gas in there until it is about to run over?

In my brake light cover, i see 2 bulbs, but until the brake is actually pressed, only 1 light stays on, is this normal?

Now for the unusual actions the bike decided to do.

On my way home (45min drive, mostly straight 65mph roads) i filled the tank to the brim as usual, then started heading up a hill. The roads on the hill are separated so that traffic going down the mountain cant see traffic going up the mountain. So i usually speed during this area. Yesterday i got it to 120 going up the hill when it started sputtering like it was running out of gas. The sputtering continued until my speed reached around 70-80, then it was fine.

I checked the petcock to be sure it was in the "on" position. I then got the bike to 120 immediately after the hill on a straight away to see if i could make it sputter again, but it didn't.

Any help with these matters will be appreciated.

[cintidude04]

1. its not bad just try to keep it off your paint.
2. What is the bike?
3. Not sure on that one

[Kreylyn]

What air filter do you have?

Krey

[f3tz3r]

04 GSX750F 13,000 miles, recent oil change and oil filter.

What air filter do you have?

Krey

Where should i look?

Mechanically illiterate.

[cintidude04]

In the airbox (which hopefully it has) behind the carbs.

[f3tz3r]

Ok, so i guess that i cannot see what type it is until the fairings are off, so i will be posting here later. once i figure it out.

[05RedKat600]

Take off fairings, remove gas tank. Air filter is under the rear of the gas tank.

[Kreylyn]

Ok, so i guess that i cannot see what type it is until the fairings are off, so i will be posting here later. once i figure it out.

You don't have to remove the fairings. Pull off the tank, remove the tank bracket. Pull the airfilter out.

It should be white ( or slightly tan if it's dirty). Any other color is going to probably be an issue.

Krey

[f3tz3r]

Go ahead and crucify me for asking this, but the tank has to be empty before removing it right?

[JayBell]

check the petcock vac line, from the back of the petcock to carb 4(farthest right) for holes, and the petcock diaphragm for holes.

also, next time it happens, switch the petcock valve to PRIME to see if it goes away... if so, its a vac line/petcock issue.

[Kreylyn]

Go ahead and crucify me for asking this, but the tank has to be empty before removing it right?

It does not, but the less gas the lighter the tank will be...

The petcock should not flow fuel unless the bike is running when in the on or reserve position. Prime will flow at all times, but it should never be left in prime.

Remove the seat, remove the 2 bolts to the tank under it, remove the 2 bolts for the side fairings on the tank bracket, lift the tank, remove the lines on the petcock. You should be able to lift the tank up at this point. There will be a couple of other lines not plugged into anything, and the wires for the fuel sensor. They are bullet connectors, so just disconect them near the battery. Pull the tank all the way off. Remove the 2 (think it's just 2 on a post, 4 on a pre kat) bolts holding the tank bracket down.

Phillips head screwdrive to remove the 4 screws holding the air filter in. Pull it out and inspect.

Krey

[05RedKat600]

You don't have to remove the fairings. Pull off the tank, remove the tank bracket. Pull the airfilter out.

It should be white ( or slightly tan if it's dirty). Any other color is going to probably be an issue.

Krey

Now this is good to know. I've always removed the two side fairings to take the tank off, but usually because I need access to the carbs too, so they had to go.

[f3tz3r]

Just to clerify, i dont have to clamp the hoses coming from the tank and going to the petcock.

just for knowledge if so, what keeps the fuel from free flowing?

[Kreylyn]

Just to clerify, i dont have to clamp the hoses coming from the tank and going to the petcock.

just for knowledge if so, what keeps the fuel from free flowing?

The petcock on a katana is operated by a vacuum diaphram.

Inside is a spring pushing a plunger closed at all times. When you start the bike, vaccum is routed from carb #4 to the petcock. That vacuum pulls the plunger open because it's attatched to a diaphram. As long as the vacuum is there, and the diaphram does not have a hole to cause vacuum to leak... it will hold open the plunger and fuel flows freely.

Prime setting pushes a spring to manually hold open the plugner inside, allowing fuel to flow without a vacuum.

No vacuum, and not on prime... the spring keeps presure on the plunger, which keeps the fuel from flowing out.

Krey

[f3tz3r]

Trying to upload pics, but i have it open and i'm looking at it, the only markings on it are black "A4O7" on the top.

Other than that its just a white air filter.