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  1. #1

    Default CB750 electronics question

    I have the coils on my 76 cb750 mounted under the seat, meaning I have plug wires much longer than stock, and am also using the stock coils. I believe the extra resistance from the longer wires are causing my bike to not run as well as it should. Am I thinking correctly about this? I would like to use some hotter coils, and was thinking of switching to a Pamco igniton system at the same time. Am I on the right track with this, or really off base?

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    Quote Originally Posted by PerniciousLies View Post
    I have the coils on my 76 cb750 mounted under the seat, meaning I have plug wires much longer than stock, and am also using the stock coils. I believe the extra resistance from the longer wires are causing my bike to not run as well as it should. Am I thinking correctly about this? I would like to use some hotter coils, and was thinking of switching to a Pamco igniton system at the same time. Am I on the right track with this, or really off base?
    A friend also has the coils mounted under the seat on his CB 750, and loomed the wires up between the two center carbs, and over the top of the valve cover. He used the same exact wires as I did on my CB 750, only his are at least 4-5 times longer than mine. His bike runs perfectly. We both use the later (twin cam) CB 750 coils, and stock point type ignition. His bike has run perfectly for several years. I'm guessing your issues are elsewhere....

  3. #3

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    Ok, thank you. That helps!

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    I have a Dyna ignition and coils, and the coils are mounted under the seat. Plug wires are ran between the carbs and through the holes in the jugs, then up to the plugs. And, my plug wires are nothing more than those universal ones you get out of the back of Autozone. I have no trouble with it at all.

    As far as ignitions go, Pamcos are ok and work, but if you get a Dyna ignition the warranty is outstanding on it. I would highly suggest Dyna ignition and coils. You are better off going to a 3 ohm coil with the electronic ignition, and if you don't want to drop the coin on the dyna coils look for some coils from an early 80s DOHC cb750. they are 3 ohm and will work just fine.

    When you say your bike isnt running right, what is it doing?

  5. #5

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    It's not so much that it isn't running right I guess, but it just doesn't seem to be as smooth as it could be. I have pods and 4-4 short open pipes, so tuning is going to be difficult to start with. I've had trouble getting the jetting right, and even tried paying a shop to do it, but I'm not convinced thats right, either lol. Just a better intake setup and some baffles in the exhaust might make things a lot easier on myself.

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    Before you buy new coils figure out if it's the coils or the jetting.cause if it's the jetting no matter how much you spend on coils and wires the bike will still run like shit

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    Ive tuned these bikes with the same set up, not a big deal. In my experience, most shops aren't good with these old bikes and you will do better on your own. Not a big deal.

    You're problem more than likely isn't just jetting. You may have done these things already, but here is my process for setting them up.

    Before anything, make sure of these things: carbs are synced, valves are set, and timing is correct. Once those are done, you can dial it in.

    If its running rough, like the motor is not running even, i would bet the main problem is the carbs not being properly synced.

    Need any advice on any of it let me know.

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    A few easy things to check as mentioned above are ignition timing and carb sync. A proper vacuum sync does wonders. It's also a good idea to check the resistance on your plug caps. They should measure 5000 ohms. If they measure much higher than that, replacement is in order.

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