Odd problem, cant quite fix it (fixed)

took the tank lid/door off, complete disassemble, seemed clear but I have heard a slight hissing sound sometimes after I stopped.
Looked up the filter I have, supposed to be for zero pressure lines i.e. lawnmowers, generators etc.
Field report later

Medina wrote: took the tank lid/door off, complete disassemble, seemed clear but I have heard a slight hissing sound sometimes after I stopped.
Looked up the filter I have, supposed to be for zero pressure lines i.e. lawnmowers, generators etc.
Field report later

It's far better to actually test run the bike with the fuel cap ajar.

If problem doesn't appear with cap ajar, but appears with cap snapped down, then there's no doubt. Then it's time to attempt clearing the vent.

Good Fortune!

Ok, now I'm convinced its the speedometer...everytime I hit about the 100 mile mark on the tank of gas the problem appears...so logically, I'm replacing the speedometer.

Tonight I started to wait for it starting around 93 miles..yup, at 102 cough cough sputter, I was prepared, spare key already in tank popped the lid, no difference, coasted to the side and 3 minutes later,..vroom.
Anyone here old enough to remember the ping pong ball trick? ping pong ball in gas tank floats till its about 1/4 full, gets sucked to the intake and it dies...starts again a little later.
I'm going to gut the fuel line/filter/inline petcock and re-do it all tomorrow.
I've got it down pat now, coast to side of road, four ways on, and act like I'm talking on the phone

where is the vent? looking at the manual, its a hole under the rubber gasket, partially hidden by the large spring? If thats it, I wired it, hit it with 60# of air today.

Yea the vent is in the cap, can disassemble and clean. But sounds like that's OK. Have you checked for spark, when on the side of the road and won't fire?
Otherwise you could take a screwdriver with you and open the bowl drain screws and check for flow.

Medina wrote: ...at 102 cough cough sputter....

If not already done, try switching petcock to reserve position.

Good Fortune!

Motor Head wrote: Yea the vent is in the cap, can disassemble and clean. But sounds like that's OK. Have you checked for spark, when on the side of the road and won't fire?
Otherwise you could take a screwdriver with you and open the bowl drain screws and check for flow.

Have not checked for flow, will do. Haven't checked for spark as I'm assuming (trouble I know) its fuel related. I instantly pulled the enrichment all the out and it fired, engine raced to 6K and died.
Odd..aint it.

Patton, I'm running it in "prime" position, vacuums been plugged, using an inline petcock till winter and redo the carbs- some "pro" shop in Indy worked over twice. But thats exactly how it feels- that not enough gas in tank to reach primary, time to switch to reserve.

good news is last two tanks have averaged right at 40mpg, quite pleased with that. expected 35ish

The stock vacuum petcock on Prime, OK. But this In-Line petcock, what it the internal diameter? Is this a 1/4 turn valve? Can you look and see the D of the valve when switched on? I'd check out going flow, each piece. Use a container and a stop watch. Get some flow checks done.
Just thought that you said the Vacuum Petcock had been gone through. Is it possible that the tubing that is pressed into the valve body is miss installed, the Normal "ON" is in the "PRIME" spot? Or when it re-fires, it doesn't shut down again?
Do you know if the Tank Has been Lined with Chemical for Rust Treatment? Find anything in the filter? Blow through it backwards in to a clear glass bottle or similar.

Patton wrote:

Medina wrote: ...at 102 cough cough sputter....

If not already done, try switching petcock to reserve position.

Good Fortune!

Patten's Other Site :laugh: Just jabbing at ya....

Motor Head wrote: In-Line petcock, what it the internal diameter? Is this a 1/4 turn valve?

Just thought that you said the Vacuum Petcock had been gone through. Is it possible that the tubing that is pressed into the valve body is miss installed, the Normal "ON" is in the "PRIME" spot?

Or when it re-fires, it doesn't shut down again?

Do you know if the Tank Has been Lined with Chemical for Rust Treatment? Find anything in the filter? Blow through it backwards in to a clear glass bottle or similar.

supposed to be 5/16, but will check (making list)

double checked using various websites with photos and the manual, pretty sure its correct

re-fire (referring to side of road using choke) fires, races up then dies.

super clean bike, inside of tank looks like metal, had that filter out, its pristine.
flushed the bowls out, came out clean (allowed bowls to fill and drain a couple of times)
One of the reasons I'm going to toss the new hose out and buy more- a race truck I had many years ago, one of the new summit racing fuel lines partially collapsed inside...its just possible these cheap autozone hoses have a bad spot from production.

The advertised 5/16 petcock was, in fact, 5/16th's...OD..ID was LESS than a 1/4"
By the time I eyeballed the inside you could see the ball or whatever they use to shut off the flow wasn't wide open, end result, about a 1/4" flow rate...
I'm going to convert the factory petcock to manual dammit...

Medina wrote: I'm going to convert the factory petcock to manual dammit...

After staring at it for a while, I figured it out. removed diaphram, plugged those holes that weren't needed, and overnight with full tank "off" didn't leak (left the diaphram cover off) not so much as a damp spot. "prime" is now "on".
Take a hundred mile run soon, weather depending.... and final test.

On my bike, the float valve to the bottom of the tank is about 7". To the top of the tank is about 14".

So the pressure at the needle valve is ...

Pressure at full tank is about .37 psi.
Pressure at empty tank is about .19 psi.

I used .74 as the specific gravity of vehicle gasoline (not raw gasoline).