Topic: K vs. F for Cafe - Big Differences?

[theoctopus]

I've done what searching I can, and I just can't really seem to find the info I need.  You guys are always so damn helpful, and I really appreciate it.

So I picked up a '76 CB750F to kick off a bike build between my pops and I.  The plan is to do a complete frame-off cafe over the next couple years.

Both of us are pretty mechanic-stupid, so I'm looking to make this as simple as possible.  Part of that is starting with the right bike, so that we don't have to do any unnecessary modifications (chopping the frame, so forth and so on).  We'd really like this one to be a long-term keeper, since it's the first big project we're undertaking together (we haven't always been that close).

What I do know is that there are body and brake differences between the K and F models.  Since both of those components will be replaced (likely a whole new front end will be put on), this does not matter to me that much.  What I'd like to know is if there are big frame differences, or changes between the two that will cause me undue stress.  The F for some reason feels more bulky, whereas the K feels more classic, and with better overall lines.  It seems like most of the cafe builds I'm attracted to are done on K models, and I'd like to know if I can achieve the same things with my Super Sport, or if I should keep this one for fun and pick up another K model.  In looking at body parts, it seems like quite a few are F or K specific, and that makes me wary of kicking off this build with the 750F if it's going to end up being difficult.

I hope I'm clear enough with my questions.  It's been a long night in the lab....  If I need to clarify anything, please let me know.

[campbmic]

I don't know much about the difference I have a 75 550K1 and probably couldn't tell the difference between a K and a F. I do know that the kickstand is in a different location on an F. Ask "Fastbroshi" I believe he has both a K and F model hes working on right now.

[JP]

All that u will be interested in will be no difference between the F and K. You see more K builds that you like simply because there are more of them. But if you like the K tank, put one on your F. Frame setup is nearly identical. You should have no issues at all. Any frame differences are not really differences at all. They are just little things like different foot peg positions and stuff. Nearly anything that works on a K will also bolt right up to an F as well. I recently got my F good enough to ride, not finished yet- but you can find a picture of it in the sohc4 forum if you look for my posts.

[Retro Rocket]

The "F" model frame is longer at the back and has different seat mounting points, different rear guard, disc brake on the rear, different wiring harness, different tank {although they are interchangeable} , different dash, different oil tank, different side covers and mounts, There are plenty of small differences between the 2 so i suppose its up to you to work out what you want to do....

Mick

[JP]

Mick is right, but I deffinetly don't think that ANY of the differences will cause even the slightest bit of hassle since you will not be trying to make it look like a K, but simpy a cafe racer. Also, although I have never measured the two frames side by side, I have owned 7 of these bikes and I do not think that the frame is any longer at all. The F just looks longer due to the plastic rear section that comes on it from the factory. However, even if it is longer, you will probably be makeing a rear section to fit and even if you order a fiberglass seat, nearly all of them come to long in order for you to trim to fit different bikes. Do not stress over these tensy tiny differences. You will not notice any issues at all when doing a cafe build and the SS is a superior platform to start from anyways. That's why its the SS. There were some minor difficulties with the valve stems, but if yours runs good now you will probably never have any problems. All the different subtle changes were to make the 750 a better performing machine- and Honda succeeded. Build your cafe my friend.

[Retro Rocket]

Hi JP, i have a K frame sitting next to an F frame in my garage and the rear rails on the F are about 2 and a half inches longer than the K frame, this will probably not matter as most cafe bikes i have seen have the rear rails modified. Valve stems or guides was a problem in the F2 750's with the black engine, 16.5 750's and counting.....

Mick

[JS550]

I think the hp was up a couple ponies also on the F, compression bumped up a little and the gearing is different. The F also came with a 4 into 1 I thought? Either way its a great bike, K or F! I have a K with an F tank, its not a direct swap, rear mounts a little off due to the tank being longer, but I made it work.
happy building, Jim

[JP]

Thanks Mick, I have never known anyone that had them side by side to do a measurement.  Until now, it was always just hearsay.  Man oh man I've been loving mine.  Finally got it looking pretty sharp and running excellent!  Still a lot to do as far a little things here and there, and as far as I go- it'll probably never be finished.  But now that it is finally up and going it is my hobby once again.  It's been down for so long that it had become more of a burden and now I'm back to having fun.  You know you've found what you like when you keep on going back to the same bike over and over again, but 16.5?!  Well, you've got a few years on me- maybe my count will be up there someday but hopefully I'll keep this one around for a while.

While I have someone's attention, just wanna share in some of what has happened.

My bike is a 78 F model that spent about 20 years under a pine tree in Ohio.  I got it for way too much money $320, and proceeded to restore.  Engine was seized worse than any I have ever seen.  I replaced the guide valves and of course full valve job and resurfaced the head, big bore from cycle exchange, power arc ignition, CR carbs and about a thousand other little things.  Divorce hit and really screwed up everything.  Selling parts for extra cash, buying them again, selling again, blah blah blah.  I finally got it running about 3 weeks ago and MAN WAS IT STRONG!  After around twenty miles, I had oil pump failure and seized the engine that I have been working so hard on.  I literally almost puked.  Got lucky and found a '75 K engine for a good price, snatched it up and threw it in the frame with fingers crossed...........Runs excellent!  Not as strong as the F engine was, but the carbs and ignition make such a HUGE difference.  This thing has no problem hefting the front end up.  I'm loving this, now I just need to get a group of guys together around Atlanta and start a Ton Up club.

Thanks for reading,
JP