Topic: 75 CB750F Rebuild gone mutt.. (in for a ride?)

[CBcafeJunkie]

So i Dragged this badley mistreaten bike home from a lake with my now annahilated Tacoma pickup. The next day started tearing into it, as I pulled the exhast off about 2-3 cups of water poured out.....joy   Once i got the head off and was able to gaze into the nearly rust engulfed cylinders I realized this is going to be fun   I got some information from my boss to throw some marvel mystery into the cylinders for a couple days and let it loosen them up. So thats what i did. I then took a cut down 2x4 that fit accross the entire width of the piston and smacked on it with a hammer freeing them from the cylinders....finally. I figure ill just replace the whole top end with another used set. So now i have some cylynders and a head from what i belive to be a 78 but they cam from 2 different people, so im calling this a mutt bike.
If you have any suggestions please share This is my first engine rebuild. im currently getting the frame powdercoated white the forks and swing arm red, painting rims black, and calipers white. looking at rewireing everything into the tail and moving the oil tank too. Think this will take longer than i want it to due to monetary reasons . Oh...Im am currently ridding a 76 cb550k and lovin it  

[CBcafeJunkie]

Heres a link to my projects progress

http://gallery.me.com/ahrenswett/100208

[scottly]

Mutts are welcome here! If you drug a bike out of a lake, then it sounds like you have quite a project on your hands. At least you have a running 550 to keep your pulse going!

[CBcafeJunkie]

No doubt

[Jerry Rxman Griffin aka MuthaF'er]

Greetings.

Another F saved! I'm hoping you are using a 78 750K top end. That will transplant easily. The 78 750F will not without much more effort and all the right parts from the case upward.

[CBcafeJunkie]

Greetings.

Another F saved! I'm hoping you are using a 78 750K top end. That will transplant easily. The 78 750F will not without much more effort and all the right parts from the case upward.

How can I tell if they are k or F? and how do I make sure I do this right? 

[Jerry Rxman Griffin aka MuthaF'er]

The 77/78 750F had a black engine from the factory. BUT, my 75 750F engine was painted black by me so don't just go by the color. If it's still on an engine I think you'll find a "405" on the head on the top fin intake side by #3. If it's off the engine measure the valve heads: 34mm intake with a 31 or 32mm (don't remember which) exhaust is a dead giveaway. All the other heads use 31mm intake and 28mm exhaust. You could use a 77/78 F head but you'd also have to use everything above the top case half. A 78 K head will probably have a "392" in the same spot the 77/78 F has "405".   

[CBcafeJunkie]

The 77/78 750F had a black engine from the factory. BUT, my 75 750F engine was painted black by me so don't just go by the color. If it's still on an engine I think you'll find a "405" on the head on the top fin intake side by #3. If it's off the engine measure the valve heads: 34mm intake with a 31 or 32mm (don't remember which) exhaust is a dead giveaway. All the other heads use 31mm intake and 28mm exhaust. You could use a 77/78 F head but you'd also have to use everything above the top case half. A 78 K head will probably have a "392" in the same spot the 77/78 F has "405".   

So here's what I got. I have a black head reads 410 that I plan on using and a silver head that reads 3926 in the sane place as well as another one that reads 3925 i'm guessing these are different years and the 2 later ones ate k heads. I also have two sets of jugs one black one silver. as for pistons I have a few sets but not sure which to use. also all heads are complete thanks a ton for all the knowledge and help
 

[Jerry Rxman Griffin aka MuthaF'er]

OK then, the 410 (my bad on the 405) is the F2/F3 with the larger valves. It can be used with the 75 F but you must use the matching cylinders AND pistons. The other 2 will work fine with the 75 F and are the better heads of all the years. They are either F0/F1/K7/K8. If your pistons are 392 or 300 they will work with the 392 heads on the 75 F. The 392 head originated with the 75 F.

[CBcafeJunkie]

OK then, the 410 (my bad on the 405) is the F2/F3 with the larger valves. It can be used with the 75 F but you must use the matching cylinders AND pistons. The other 2 will work fine with the 75 F and are the better heads of all the years. They are either F0/F1/K7/K8. If your pistons are 392 or 300 they will work with the 392 heads on the 75 F. The 392 head originated with the 75 F.

So if you had my montage of parts you would use the earlier f parts instead of the f2? what made the 392 head better?