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I Have a SOHC CB750 question. The turn single blink speed various with the engine RPMs, is this normal for a 1977 CB750? If this is not normal how do I fix it?

First time posting to the forum. I've been reading the forum for a little less then a year and found lots of great info.

I'm currently putting a 1977 CB750 back together after installing new bearing and bushing and a couple of cafe style mods.

When the 77 is is back on the road I have a 1975 CB 750 waiting in the wings as next winters project. Working on old bikes is almost as fun as riding them.
 

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usually that is a sign that your battery is going to pot.

cb750s (hondas in general actually) do not begin to break even charge until above 2000rpm. Below 2000rpm you battery is draining faster than it is charging (but not fast). Try putting your battery on a trickle charger overnight and then ride the bike around. There should be a little varance in speed but at idle if it is blinking really slowly it may be time for a new battery.

Also put a volt meter on your battery and see whay kind of volts you are pulling throughout the rpm range at some point is should stop increasing as the rpms climb - this is how you know your voltage regulator is working.
 

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Thanks You

Does any one know at about what RPM the voltage should level out and what the voltage should be for a 1977 CB750?

The battery is new, and I suspected that there might be a problem with the voltage regulator but am not yet familiar enough with bikes of this vintage to know what was electrically normal.
 

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you do own a service manual for your bike, right?

I don't know what rpms you should see the regulator kick in. However the regulator is probably not a problem if you are getting positive charging above 2000 rpm.

If the battery is new, it may have only been half charged as some are sold that way from the factory and a night on the trickle charger should clear up the problem.

I find that due to age, and corosion, and a host of other factors you'll only see a charging of around 13v above 200 rpm anyway. You want to help your system go through all the connectors and make sure they are clean and not corroded.

If you want to test the voltage regulator to see if it is working measure the volts and amps going into it and the volts and amps coming out. If you need to adjust it, it should be the cannister type that you pop the top off of and adjust with a screw driver.

If this is all for your blinkers, stop worrying about it and just ride the bike (unless you spot a charging problem). these bikes have mechanical blinkers and eventually they weat out and go bad. You can try doing a search over at www.sohc4.us for an electronic blinker to replace the stock one since this issue was addressed there before and someone listed a part number for an electronic replacement.
 
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