Topic: cb 750 cylinder heads

[750mikeb]

I am starting a rebuild on the top end of my cb750 f I also have a bunch of 73 750 parts The intake ports look different between the 75 f head and the 73 k head anyone better to run?  thanks mike

[754]

Some F,s have bigger valves I think and slightly diff chamber.

As far as I know you can switch head/barrel combos, but head only will only work one way, due to oil drain holes.

[Jerry Rxman Griffin aka MuthaF'er]

Use the 75 750F head and pistons if you have them too. There was a nice jump in HP with the introduction of the 75 F and it's -392 head and 9.2:1 CR pistons. Valves are the same size but notice the K head has a more uneven surface as evidenced by the raised shrouding while the F is more hemispherical.

[750mikeb]

I thought the roof of the port seemed different also I read that they made more power in 75 My problem is the bore is rusty and I have a 73 k cylinder that is nice how are the smaller cycle exchange cams and springs ? Is it a dumb thing to think of milling the f head to gain the comperssion? You guys are awesome  Jerry what muffler are you using on your bike? thanks mikeb

[754]

Sleeve swap..

[Jerry Rxman Griffin aka MuthaF'er]

The 73 K stuff is a direct swap on the 75/76 F. You might want to mill the head just to ensure a good flat fit plus you'll get a little extra compression. It never hurts to put in stronger springs. AND if you want to do the best you can to prevent the dreaded head gasket leak for as long as possible get a set of heavy duty cylinder studs from Big Jay at APE. I'll see if I can post a picture of what my piston looked like after I missed 2nd gear and floated the valve. Left is the original. Right is from the 1080 kit I have (73.75mm).

I'm running a Kerker header/muffler.   

[754]

Nice...very, very..NiCE...

[750mikeb]

Thanks for the advice  Wow that piston looks huge any cooling problems? How does that pull? Looks sweet thanks again  mike

[fastbroshi]

   That's not a piston, that's your morning donut 

[Soos]

I'll see if I can post a picture of what my piston looked like after I missed 2nd gear and floated the valve. Left is the original.

I'm running a Kerker header/muffler.   

UGHH!!!!
That picture makes me shudder.


l8r

[Jerry Rxman Griffin aka MuthaF'er]

Thanks for the advice  Wow that piston looks huge any cooling problems? How does that pull? Looks sweet thanks again  mike

Cooling problems? Not a bit, it's pretty well ventilated  .  Actually I have yet to install the 1080 pistons. I don't think they would be well suited for stop and go. Definitely not a daily rider. My intent is a new fashioned pro street chop with a 300 rear tire soft tail frame. Eventually I hope. Long story short, I haven't found a motorcycle machine shop in all of Colorado. The local guy comes highly recommended but he only seems ineterested in dynoing/building 800hp car engines. 

[754]

Jerry, i have figured out the basic plan to make an outboard support for the 750.. allows sprocket offset to at least 22mm..

[Jerry Rxman Griffin aka MuthaF'er]

Frank,

PM or email the info please and we won't clog up this post. My plans are to have Red at Cycle One (ex of Regina, SK) make a soft tail frame using a jack shaft for the offset. Red is relocating to Oklahoma so they will be MUCH closer.