question about 1975 cb750f.

[crk4130]

im having a bit of trouble with my bike. the engine sounds like its running fine but im hardly getting any power to my wheels. let go of my clutch i have to pull back pretty hard on the throttle and my bike moves like a snail... any ideas?

[CB750Winger]

  Could be a lot of things. Sounds like lack of power so you could check condition of points, gap, timing, spark plugs, cam chain tension or maybe carb issues such as a plugged or dirty jet not getting enough gas. Have you also checked the air filter or fuel filters?

[crk4130]

i just bought the bike about 2 weeks ago and it ran fine until yesterday. this is my first bike so i dont know alot about the inner workings of it. i bought i haynes manual so ill check the things you talked about and see if a can figure it out.. also i have velocity stacks on my carbs and i noticed that two of my carbs sputter gas out of the stacks a little bit when i rev the engine. does that mean that they are plugged? thank you for your help its very much appreciated.

[CB750Winger]

If you spudder gas out the intake, sounds like it's flooding which also makes it run bad. There might be crud in the float bowls sticking the floats. Take a small bowl and remove the drain screw in the bottom of each float bowl with the gas valve off. You can turn the valve back on to let more gas run. There may also be a sediment bowl you take off below the fuel valve that has a screen to clean out. Does the gas tank look like it has rust or crud in it? Try 2 or 3 oz of Seafoam in a full tank of gas to help clean things out. If your tank has crud in it, you may want to seal it. Also take the spark plugs out to see if they are gas fouled.

[Re-run]

Hard to say what might be going on.
Since you have a manual, start by going thru standard tune up procedures if it has not been done in a while. A set of points may be burned up or badly pitted or may have lots its gap.

As for the gas, hard to say, that usually only happens if there is too much fuel by quite a lot or there is pressure blowing the fuel back out. Maybe check your valve lash and see if those are correct.
If you check the valves, increase the gap on intake and exhaust by .01. This allows for heat expansion and while the engine may be slightly noisier, there is less wear.

[crk4130]

ill try the things you guys suggested.  thanks a million

[pappy0352]

The floats are known to stick on these bikes. Take a screwdriver and lightly tap on the bowl of each carb. There may also be slack in your throttle cable. If these don't work let me know and I'll be happy to give you some more suggestions.

Pappy