Topic: bike stops running after it gets hot

[tsliwinski26]

I have a 1975 cb750. Haven't done anything to it yet and was going on a couple of rides to get familiar with the bike. Well after the 4th or 5th ride once the bike gets hot and this happened in a matter of 10 minutes, the bike won't run. I was close to home Thankfully but I had to stay in the throttle just to keep it alive of I let go at all ot would die and when it did it wouldn't start back up till it cooled down. I'm not extremely mechanically inclined on these so any help would be great. If more details are needed let me know

[flybox1]

You really should complete all of the 3000mi periodic maintenance items.
Most ailments are remedied by doing this, first.
In the meantime, you might be getting vapor-locked.  Try (safely) riding with the gas cap slightly undone.

A .pdf of the shop manual can be found and downloaded in the FAQ section under MANUALS.

link...
http://www.honda4fun.com/materiale-documentazione-tecnica/shop-manual

[tsliwinski26]

Thanks I tried the gas cap with no luck I'm going to look into the 3000 mile check up. I started it and let it run for about 10 15 minutes and the exhaust started to pop and then I had to hold the throttle open a bit or it would die on me. And after it died I let it cool for a few minutes tried again and now the battery is dead

[Tews19]

When you state let run for 10-15 min. Do you mean while parked? These are air cooled engines. They are not meant to sit still for long period of times at idle with no cooling.

[flybox1]

Thanks I tried the gas cap with no luck I'm going to look into the 3000 mile check up. I started it and let it run for about 10 15 minutes PUT A BOX FAN ON THE ENGINE TO KEEP IT COOL and the exhaust started to pop and then I had to hold the throttle open a bit or it would die on me. And after it died I let it cool for a few minutes tried again and now the battery is dead  charging systems on these bikes doesnt engage until 3000rpm or more.  so a dead battery after a long idle is no surprise.

[tsliwinski26]

It was parked but it doesn't matter weather it's parked or not if I'm riding it it will do the same thing. When I started it earlier I took it around my neighborhood and died while riding too. I had to hold the throttle open to about 4k just to get it home. I was told it could possibly be the old regulator rectifier is this possible?

[tsliwinski26]

Turns over and over and just won't start until it cools off. When I was riding it I noticed the exhaust starting to pop and like I said had to hold the throttle open but felt like it had no power. I'm not the best at describing this I appreciate your help tho thank you for being patient

[Patrick]

It sounds like it is running until the carb bowls run out of gas. I know, you said it quits after 10-15 minutes, but I'm betting it just seems that long. You might have an obstruction to the screen at the top of your petcock in your gas tank, or possibly old crimped fuel lines. If it cranks when it stops I am betting it is not overheating and seizing, so I would look at fuel flow. I have never know spark to disappear at a consistent point.

Patrick

[Don R]

 I had a 750 that died 2 blocks after going through an underpass every time. not sure why but removing the additional fuel filter cured it. I could blow air into the gas tank through the filter but gas would not flow back out. A plugged exhaust will cause one to die but it usually happens sooner.  Check inside the fuel tank for internal rust too, it can plug the screen on the inside of the tank.

[tsliwinski26]

I don't know what's going on with uploading pictures but it won't let me right now but the coils and points look stock and the points don't look worn out. As for the tank and the filter I'm going to look into it tomorrow.

[Wobbly]

They are not meant to sit still for long period of times at idle with no cooling.

My bike has to endure this every time I synchronize the carbs.

[LesterPiglet]

Probably our climate Wobbly. I've never needed a fan yet.

[70CB750]

Some coils will do this, quit when hot, but hardly both in the same time. 

My$0.02 only of course

[DH]

Some coils will do this, quit when hot, but hardly both in the same time. 

My$0.02 only of course

I agree. And I've never heard of stock coils doing. That's why I would suspect the condensers as possible culprits.

X2 on the condenser(s)