Author Topic: '76 750F in a K frame? (Read 2448 times)

Inkscars · « **on:** June 15, 2009, 03:31:07 PM »

I've been wanting to get an engine to rebuild and make pretty and stuff, came across a cheapie, but I don't know if a 76 cb750 F engine will mount in my 77 cb 750 K frame.
Anyone?
Thanks.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #1 on:** June 15, 2009, 11:20:29 PM »

No problem. The 77 K engine is derived from the 76 F. Increase in performance over the mid year K. Carbs different but either will work. Good swap.

Inkscars · « **Reply #2 on:** June 16, 2009, 05:17:49 AM »

Awesome, thanks, so I guess that means I can swap guts too?
I'll have to find another bank of carbs, but as I'm more familiar with the pd's, it shouldn't be hard to talk someone into parting with them

Anyone know where to find a reasonable 836 kit?
Saw one on craigslist for 175 a few months ago. Kicking myself.

Burke · « **Reply #3 on:** June 16, 2009, 07:04:12 AM »

What about exhaust fitting? If you swap engines are the exhaust ports different from K to F's?

Inkscars · « **Reply #4 on:** June 16, 2009, 07:11:02 AM »

Well, what I had thought of doing was using the head off of the K engine. I was looking at diagrams and they look the same?

Jerry Rxman Griffin aka MuthaF'er · « **Reply #5 on:** June 16, 2009, 10:26:15 AM »

Quote from: Burke on June 16, 2009, 07:04:12 AM

What about exhaust fitting? If you swap engines are the exhaust ports different from K to F's?

The 77 K engine is, for all intents and purposes, identical to the F. The head is the same. Both are the -392 engine head. Is there a problem with the F head? Valve train in the 77 K (not 78) is the same as the F. I'd have to check the specs on the tranny. May be the only difference.

Think I saw a new 836 on EBay at $250.

mkramer1121 · « **Reply #6 on:** June 16, 2009, 10:29:31 AM »

Quote from: Jerry Rxman Griffin on June 16, 2009, 10:26:15 AM

Quote from: Burke on June 16, 2009, 07:04:12 AM
What about exhaust fitting? If you swap engines are the exhaust ports different from K to F's?

The 77 K engine is, for all intents and purposes, identical to the F. The head is the same. Both are the -392 engine head. Is there a problem with the F head? Valve train in the 77 K (not 78) is the same as the F. I'd have to check the specs on the tranny. May be the only difference.

Think I saw a new 836 on EBay at $250.

Jerry, are you sure about that? I always thought '77 and '78 F used larger valves, while the K's still had smaller ones....The F also used higher domed pistons...

Inkscars · « **Reply #7 on:** June 16, 2009, 10:57:52 AM »

We have 1 day to work this out.
It's only a lower end for sale.

mkramer1121 · « **Reply #8 on:** June 16, 2009, 11:08:19 AM »

Oh, just a lower, then you're fine...use the barrels and head off the K...

Inkscars · « **Reply #9 on:** June 16, 2009, 11:17:08 AM »

Worth 40 bux?

Jerry Rxman Griffin aka MuthaF'er · « **Reply #10 on:** June 16, 2009, 11:28:22 AM »

Yes, totally sure. Lets be sure we are talking about the same bikes.

Yes, the 77 F2 & 78 F3 had different tops ends, jugs up, bigger valves plus more, than all the other 750s. So lets totally leave the 77 & 78 Fs out of the picture to eliminate confusion.

What we were referring to was the 75 F0 (aka K0 Super Sport) & 76 F1 and the 77 K. These are the same engines with same top ends but perhaps/possibly different trannys. I haven't looked that up. Often on this site the guys refer to Fs without distinguishing between 75/76 and 77/78. 2 different beasts.

Inkscars · « **Reply #11 on:** June 16, 2009, 11:30:45 AM »

This is all pretty interesting to me. So, If the transmission were different, what would that mean in the way of a transplant?

Jerry Rxman Griffin aka MuthaF'er · « **Reply #12 on:** June 16, 2009, 11:38:59 AM »

Quote from: Inkscars on June 16, 2009, 10:57:52 AM

We have 1 day to work this out.
It's only a lower end for sale.

How much of a lower end? What is the serial number? Should be CB750E-2515094 and up. Is there an issue with the K lower end that you already have? Guess I don't fully understand why you're wanting to do the engine build especially considering the 76 F engine is identical to the 77 K.

$40 is good even for a few parts. Especially if it's in good shape. Spaes are always good to have around.

Go for it.

Inkscars · « **Reply #13 on:** June 16, 2009, 11:49:50 AM »

cb750e-2525926

It may sound silly, but end of riding season this year I wanna pull out the engine and paint and clean up and i've heard horror stories about blasting them assembled, so I'd rather just get a block and go through it and have new, new, new, new, if I'm gonna paint it and make it nice. I have a puck leaking, and it's just kinda noisey so I figure, what the hell, ride the bike now, start collecting parts and prettying it up, that way I'm not hurting for money and it'll go back together faster.
If I get a donor lower case/engine then I'll be able to ride longer AND be able to working on it at the same time. Cut time down.
Does that sound ridiculous?

Jerry Rxman Griffin aka MuthaF'er · « **Reply #14 on:** June 16, 2009, 11:53:11 AM »

OK, now you forced me to get out the shop manual.

If the trannys were different, which they are NOT, the only difference would have been the gearing. Beginning with the 75 F through the 78 K the gearing changed for quicker acceleration. You can use any tranny but you should swap the entire unit or be very careful about attempting to mix and match gears.

The 77 K & 78 K used a slightly different cam that opens and closes 5 degress later. The 77 K & 78 K has a different output shaft for the chain drive thus different size chain and different gearing as far as sprockets go. The 78 K as opposed to the 77 K, the 75 F and 76 F and all the other earlier engines, had the same size valves but the keeper groove was cut differently for different keepers plus the 78 K had different (stronger) valve springs.

All I can think of for now.

I'm trying to help and not confuse so I was doing my best to keep things simple but you are interested.

Anyway, mix and match 77 K and 76 F is fine for what you're wanting to do.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #15 on:** June 16, 2009, 12:01:01 PM »

Does that sound ridiculous?

Not at all. I have a spare K8 engine that will soon become a 1000 and go into a soft tail chop with a 300 rear tire. I've been doing it the installment method. $500 here $1000 there. I have 3 heads for 2 engines. 1 in the basement with 33.5 Kibblewhire valves and ported by MRieck waiting for the 1000 kit from Big Jay. MRieck has the K8 head for porting building with 34mm Kibblewhite valves for my F. Big Jay has the K8 cylinders installing the 900 kit for my F. And my F is still on the road. Boys gotta have toys!

Spares are good!

Better be careful. This is a true sickness that will overcome and possess you as far as your spare change will allow. I got started due to a leaky puck too. Just couldn't stand it!

Inkscars · « **Reply #16 on:** June 16, 2009, 12:04:10 PM »

Ok, well, With my puck leaking lightly, how often should I be checking my oil? hahaha.
It's only leaking between 1 and 2 and it's not enough to even drip.

mkramer1121 · « **Reply #17 on:** June 16, 2009, 01:39:24 PM »

Quote from: Inkscars on June 16, 2009, 12:04:10 PM

Ok, well, With my puck leaking lightly, how often should I be checking my oil? hahaha.
It's only leaking between 1 and 2 and it's not enough to even drip.

Inks, if you're coming up for mods and rockers, take the spare cases and crank et all that I have in my garage....

Inkscars · « **Reply #18 on:** June 16, 2009, 01:41:20 PM »

Are you #$%*ing serious?

mkramer1121 · « **Reply #19 on:** June 16, 2009, 01:43:07 PM »

If you want 'em, they're taking up space....

Inkscars · « **Reply #20 on:** June 16, 2009, 01:46:37 PM »

Yes. I do want them.

mkramer1121 · « **Reply #21 on:** June 16, 2009, 01:49:49 PM »

Quote from: Inkscars on June 16, 2009, 01:46:37 PM

Yes. I do want them.

You want the F2 rods too?

Inkscars · « **Reply #22 on:** June 16, 2009, 02:04:44 PM »

Quote from: mkramer1121 on June 16, 2009, 01:49:49 PM

You want the F2 rods too?

I don't know what that means.

mkramer1121 · « **Reply #23 on:** June 16, 2009, 02:08:12 PM »

http://forums.sohc4.net/index.php?topic=14934.0

Jerry Rxman Griffin aka MuthaF'er · « **Reply #24 on:** June 16, 2009, 03:09:25 PM »

F2/F3 rods have stronger bolts but that all depends on how many times they have been torqued down too. Bolts stretch/weaken each time they are torqued.

Inkscars · « **Reply #25 on:** June 16, 2009, 03:22:44 PM »

I'm gonna go for it. Wish me luck, I'll have to start an Elsa transplant thread.

mkramer1121 · « **Reply #26 on:** June 16, 2009, 08:23:02 PM »

Quote from: Jerry Rxman Griffin on June 16, 2009, 03:09:25 PM

F2/F3 rods have stronger bolts but that all depends on how many times they have been torqued down too. Bolts stretch/weaken each time they are torqued.

i would recommend getting new bolts and nuts, don't know the history, but they make great candidates for a cheap rod upgrade...

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Author Topic: '76 750F in a K frame? (Read 2448 times)