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Condenser?

Anastosopolos

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1972 cb750.....my bike will run for a few miles then start cutting out like it is starving for fuel and die. After I let it sit for 10 or so minutes, I can restart the bike and drive it another mile or so before it happens again. The fuel is getting to the carbs and the battery has plenty of juice. I am thinking it is the bike maybe overheating and needs the condenser replaced. Any ideas???
 
Could also be the coils. As coils go bad they start to fail when they warm up, then work again after they cool down.
 
Could be either the coils or the condensors. I always replace the condensors when replacing the points anyway so the coil normally is the oldest part of the ignition system. Condensor a lot of times wont cool down as fast as you are stating simply because they are directly in contact with the hot motor where the coils will cool more quickly because they are farther away from the heat.
 
Ive kinda had this problem lately. But i have new coils on it. Did you ever figure out the problem. Mine starts up and runs ok and then after about a 20 minute ride once its gets really warm, the bike started running very bad. Almost like it was running on only a few cylinders. then after a few days it started up good and ran normal. Weather has been in the 80s here lately so that why i was thinking overheating.
 
You shouldn't be overheating in the 80s. More like 95+.

Regardless, I use smallblock Chevy condensers like used in the '60s and crimp a longer wire on them to mount them up at coils under tank and run the wires into the side cover, that way they never get hot. Cheap part too. On a 550 but same exact setup.

If they run ethanol in your fuel there, it could be as simple as troubles with that. Water builds up until it gets sucked into carbs and then it runs good again until it builds up again. Motorcycles have fits with ethanol as they vent to the open air, it sucks the moisture right into the fuel. If you let bike sit to ride every 2-3 weeks even more likely.
 
I've only recently come into ownership of a 1981 CB 750, but currently ride a 92 Nighthawk 750 - some people have mentioned that on that bike, when the fuel cap doesn't vent properly, there is a significant decrease in the fuel delivery to the carburetor...not sure if yours has a venting cap, or has a separate air tube to vent the tank.
 
If you don't vent properly you'll have trouble with any carbed system on the planet. Later EPA evap regulations simply complicate that.
 
Which wire do you attach the the condensor wire to?

You shouldn't be overheating in the 80s. More like 95+.

Regardless, I use smallblock Chevy condensers like used in the '60s and crimp a longer wire on them to mount them up at coils under tank and run the wires into the side cover, that way they never get hot. Cheap part too. On a 550 but same exact setup.

If they run ethanol in your fuel there, it could be as simple as troubles with that. Water builds up until it gets sucked into carbs and then it runs good again until it builds up again. Motorcycles have fits with ethanol as they vent to the open air, it sucks the moisture right into the fuel. If you let bike sit to ride every 2-3 weeks even more likely.

Which wire do you attach the the condensor wire to?
 
I've found that using Chevy V* condensers and mounting them up by the coils rather than down on the beaker plate works very well. Not only are they a better condenser that last a lot longer, they're way cheaper...

Tony
 
Never had an issue with condensors in the 750 as long as I used oem. Honestly with the availability of the aftermarket bolt in electronic ignitions there isnt a reason to even be using points. Set it and forget it, the 750 was picky about having the ignition set DEAD on or performance will suffer, Honda stated servicing points every 3000 miles! but you will notice running issues sooner then that many times. Go electronic set it and ride on no worries.
 
X2, that dwell is super b-tchy. I notice the change pretty quick on my 550 as well.

Nothing beats a good electronic ignition. The idle difference is pretty marked.
 
That is a lot of the problem...people dont check the dwell. The put the points in set the point gap and thats it.....check the dwell!!!
 
You so got that right, you can set the gap 10 times as perfectly as you can and all 10 times the dwell will be all over the map, people just don't get that.
 
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