Topic: BIke stalls when warm, then won't start WTF?

[750K8 Kev]

I really need some help guys.  I have a 1978 CB750K with pods and mac 4-1. Carbs were just professionally rebuilt, but not synchronized. My bike starts up right away, but after a 10min warm up just stalls out and I can't get it to start.  Could my choke always be on?  It's moving the butterfly valves to full postions, so idk why it would always be on.  I am out of ideas other than taking it to the shop. 

If it's not too much trouble, could someone please post a close up picture of your choke setup for me 77 or 78, the linkage and all that.  I suspect it's mounted backwards or something.

Thanks

[DavePhipps]

Were the carbs jetted for the pods,and does te MAC have a baffle or is it open? Lean conditions get much worse when the bike is warmed up. I would suggest doing at least a bench sync. Since you have pods you can take them off and see if the buttterfly is open when the choke is off.
Please don't hate me for this question, but did you turn the petcock to "on". I did this yesterday 

[750K8 Kev]

Were the carbs jetted for the pods,and does te MAC have a baffle or is it open? Lean conditions get much worse when the bike is warmed up. I would suggest doing at least a bench sync. Since you have pods you can take them off and see if the buttterfly is open when the choke is off.
Please don't hate me for this question, but did you turn the petcock to "on". I did this yesterday 

Ha yeah the petcock is on.  The butterflies move to full closed and open using the choke.  The jets are set for my mods, baffle is in for now.  The shop that cleaned the carbs got them as close as they could without being on the bike, but I can't imagine them being that off.  Maybe a dumb ? but does the choke change anything else on the carbs besides the butterflies?

[Hush]

Have you fitted aftermarket electronic ignition or is it still basic points?

[steam-powered man]

plugged gas cap vent?  try running w/cap open
low on gas?  try reserve
plugged in-tank or in-line filters?
bad coil?  look for spark on all 4 when it dies
good luck!

[DavePhipps]

I'm not that familiar with the late 750 carbs, so that's a question for the 750 owners.
I would still double check the work done by the shop. Float level, air leaks, and such.
I'm just that way though. It why I work on my own bikes.
There are very few things that would make it die though. Saprk, fuel, and air make the bikes run. I would look through those systems. As it stands, I can only give general advice and wish you good luck.

[750K8 Kev]

plugged gas cap vent?  try running w/cap open
low on gas?  try reserve
plugged in-tank or in-line filters?
bad coil?  look for spark on all 4 when it dies
good luck!

That is an excellent point man. I just sealed the tank with the lid on of course, and could have easily clogged the pin hole on the cap.  I'm gonna check

[750K8 Kev]

Have you fitted aftermarket electronic ignition or is it still basic points?

I have a Dyna s

[750K8 Kev]

plugged gas cap vent?  try running w/cap open
low on gas?  try reserve
plugged in-tank or in-line filters?
bad coil?  look for spark on all 4 when it dies
good luck!

That is an excellent point man. I just sealed the tank with the lid on of course, and could have easily clogged the pin hole on the cap.  I'm gonna check

Well it couldn't be that simple I guess, not it.  Thanks good idea though.  I have spark on all for.

[750K8 Kev]

Could it be the alternator?  The battery seems to not hold a charge while running, it's a lot easier to kick start than with the button.  It's new battery and I keep it on a trickle charge.

[steam-powered man]

i bought an el cheapo multimeter from radio shack, less than $10.  with it, you can confirm the performance of your charging system at various RPM's.  bike off you should have 12.5v or so, rising to 13+ when running above 1500.  should max out at 14-15v, but the readings will jump around a bit.

these are all general readings i've seen on various bikes, so you prob will see different values.     

[750K8 Kev]

i bought an el cheapo multimeter from radio shack, less than $10.  with it, you can confirm the performance of your charging system at various RPM's.  bike off you should have 12.5v or so, rising to 13+ when running above 1500.  should max out at 14-15v, but the readings will jump around a bit.

these are all general readings i've seen on various bikes, so you prob will see different values.     

I'll check with a meter, I have one for work, I'm a traffic tech.  Should I just check at the battery?  Problem now is I can't get it running.

[dave500]

try and kick or push start it,if the battery is failing the voltage might drop enough so the electronic ignition cuts out,unlike points these wont work below a certain voltage,say 9 volts,this might occur when you hit the button.