I must have put it back together wrong....

[dmartins]

I am not sure if 5 minutes is enough to create a vacuum in the tank, but could it be the vent in the tank lid is blocked? Will it run ok with the tank lid open?

[adidasguy]

Probably running off the gas in the carbs. 5 minutes is sort of the limit for running that way, and considering a little fuel might be dripping in.

I'd suggest you look for your fuel line pinched or did you put a fuel filter in? (Take out the filter)
Something is making fuel flow very slow. Over night, the carb bowls fill up again and give another 5 minutes.

I'm sure you tried the usual of PRIME, RES fuel cap open and making sure there is gas in the tank.

Those fuel lines around that air box are prone to getting pinched or bending too sharp and pinching off the fuel.

[Bluesmudge]

Thats what it seems like, so I guess I'll take the tank off again and make sure there are no kinks or anything, but I was very careful last time. I need to come up with a better temporary tank so I can test everything without the tank blocking view of it all.

[adidasguy]

Thats what it seems like, so I guess I'll take the tank off again and make sure there are no kinks or anything, but I was very careful last time. I need to come up with a better temporary tank so I can test everything without the tank blocking view of it all.

Got one here in the Cave. Works great. Just don't have it higher than your regular tank or gravity puts too much force on the fuel and the floats can't close (hence gas comes out of the carb intakes)

Its by MotionPro. You see the white tank here - hanging a couple feet too high.

[Bluesmudge]

Okay, maybe I'm on to something.
I don't think the problem was ever fuel. My problem is nearly identical to what this guy is describing:

http://www.apriliaforum.com/forums/showthread.php?235576-No-spark-for-a-few-minutes-after-stalling-06-SR50

Twice now I've waited for the bike to die after it idles for 5-10 minutes and then pulled the plugs and checked for a spark. Both times, no  spark. Seems like an electrical problem, which makes sense because when it first happened the bike turned off like the kill switch was hit, not like it was running out of fuel.

I'm not very good with electrical stuff, I'm more mechanically minded. So if you have any suggestions, please keep in mind that I probably don't know any of the electrical terms or what everything does.

[gsJack]

Was thinking yesterday you had an ignition problem.  I've never had a problem with the pickups or modules on bikes but I had a 75 Mustang V-8 that did the same thing.  The Mustang would die after a few minutes running and wouldn't restart for 5-10 minutes but then would restart and run all day including starting and stopping after that, was a bad module.

There's some simple resistance tests in the manuals you can check your pickup with but the easiest way to check the module (ignitor) that I can think of is to replace it with another known good one and see if that fixes it.  Maybe you can find one in a cave somewhere?

[adidasguy]

If it just dies with no spark, check 2 things:

1. At the battery, monitor the voltage. What is it at starting and at the time it does? What happens when you rev it? Could be defective regulator. After dieing, can  you still crank it? Are lights on?
2. I'd try swapping the ignition unit. Possible it heats up and dies. I have extras you can try. If battery and voltage OK then possibly ignition unit. You can try unplugging it and plugging back in if dirty contact. Also check plug for the ignition timing pickup. Its under the seat back of the battery next to the neutral switch.
3. Just thought of another: defective side stand switch and neutral switch or the dual diode (or connection - connectors under seat back of battery box). This circuit will kill the bike. Lights will work. But bike otherwise is dead AND the starter will not work. Same effect as the kill switch.

[adidasguy]

Maybe you can find one in a cave somewhere?

Cave has spares of everything he needs.

[Bluesmudge]

After it dies I can still crank it and lights are on. Clutch and side stand switches are working as they should.

Sounds like it is the ignition unit. I'm not even sure what that is. Sounds like I need to become a caveman.

[adidasguy]

Let me know when you want to come by for some parts. Borrow them and if they work, pay later. If not the fix, return them later.
Sounds heat related so unit would have to run 10 minutes to heat up and flake out.
You can borrow ignition, regulator and whatever else anyone thinks might be a possible cause.
To save the battery, I would change everything first. If it runs fine, then put back original parts one at a time until you get it to die again.

[The Buddha]

As it warms for 5 mins it dies right ... more than likely the crank trigger, not the ignitor.
Cool.
Buddha.

[Bluesmudge]

After some more research, it looks like the buddha is probably correct. The crank trigger (aka pickups, aka signal generator) sounds like the culprit.

Here is a really good thread on the subject:
http://gstwins.com/gsboard/index.php?topic=46028.0


So if adidasguy has the part I'll meet up with him and hopefully have this all sorted out!

[adidasguy]

When its an electrical problem and heat related, it could be nearly any component.
Any electronic circuit can be subject to an open circuit or short as things heat up and expand.
If heat, the problem spot can be found by cooling it.
If the pickup, have the cover off. When it warms up and dies, cool it down. use some freeze spray or a can of air held upside down and freeze that thing. See if things work. You can do the same with the ignition unit and regulator. Do it one at a time to see which is subject to heat failure.
It could be a break in a wire or poor connector that opens up when heated.

When you visit the cave, take one of everything just to cover all bases.

[Funderb]

when it heats up and dies, do a resistance check on your coils. Sometimes you can cook them, they are right over the top of the engine.


just a thought. could be 100% wrong.

[crzydood17]

open the drains on the bottom of your carbs with the petcock in prime... if gas keeps flowing out constantly then keep looking elsewhere... if gas doesn't keep flowing then you found you have localized the issue...

[Bluesmudge]

looks like someone only read to the bottom of the first page... 

[crzydood17]

Ah damn, I need to read more...

[adidasguy]

He visited the Bike Cave tonight. Took home a regulator, ignition unit, 2 coils, timing pickup and 24"x32" color wiring diagram.
Out of all that, the bike should be running soon. There's not much else electrical that can make the bike die but still turn over with the starter.(Which rules out side stand, clutch, neutral and associated relay and dual diode.)

The Bike Cave likes visitors! 

[Bluesmudge]

For those of you following along at home:

Tried the ignition unit: still wouldn't turn on
Voltage Regulator: nothing
Signal Generator: BINGO

The let the bike idle for 25 minutes without incident. Then tore into the engine to check the torque on the cylinder head bolts from the rebuild and fix a minor oil leak from the valve cover.

Then I put it back together and let it idle for 20 more minutes. Looks like its good to go. I'm about to go on a test ride to be sure.

Thank-you everyone for your suggestions and a HUGE thank-you to adidasguy for the assistance with parts and everything else.

[Bluesmudge]

I'm wondering, was the signal generator going kaput just a coincidence or is there any possible connection to having just done an engine rebuild? It just seems weird that it happened only 100 miles after the rebuild. Maybe I should put an extra signal generator in my tool kit if I go on a trip.