Possible air leak on 79' CB750K

[boesen34]

Hey all,

So my former problem was temporarily fixed, but has returned once again.

Bike starts up and runs fine, but once it warms up, the idle speed increases from about 1000-1200 rpms to 3500-4000 rpms. I'm thinking it's an air leak of some sort, but I haven't found the time to troubleshoot and investigate the problem since I went back to school.

If anyone has ideas or could tell me what's going on, I would greatly appreciate it. I'm a novice when it comes to working on bikes, but I do have experience successfully rebuilding the carburetor. I'm hoping that I will be able to fix the problem without too much trouble if I'm pointed in the right direction. I just need a place to start.

Thanks,
Grant

[riedling]

actually it could be one of the idle jets being dirty.  Gets warm and the gunk leaves temporarially.  Thats what was causing my 79 750K to run poorly.  a thorough cleaning and my idle now sits around 1500 when warm.

[sgtslag]

Try adding some SeaFoam to a full gas tank.  Follow directions on the can.  It will absorb water, and dissolve varnish, throughout the fuel system.  I add it to the gas tank every month, or so, as a preventative measure.  It will also stabilize gasoline for up to 12 months, so it can be used to store a bike through the winter months.

Add SeaFoam to the crankcase, as well, to dissolve carbon deposits within the engine, and the transmission.  Check the oil color before you add it, check it again, after 10 minutes of riding, being sure to run it through all five gears:  if it has turned black, it has dissolved carbon deposits, varnish, and other crud, which has been captured by the oil filter, and is suspended within the oil -- change both ASAP; if your oil remains the same color, change it when scheduled.  Repeat this treatment every 40,000 miles.  Cheers!

[boesen34]

Thanks guys, I'll try this stuff out.

I appreciate the help!