Topic: Rebuilding my confused Honda.

[constant_gardener]

Hi everyone,

I'm new to this forum, and I had this bike for awhile now. Most of us thought it was a K7 when the previous owner was advertising it for sale. It was manufactured in 1977, and I'm pretty sure it's a F2 model.

It has the following frame number:   CB750F1101112 , and engine number: CB750E2612248

Bike has never run right since the day I got it, so a couple of mates and I tore the engine apart, and we're trying our best to get her back running right.

From what I read, the F2 used a domed shaped piston, what I pulled out of this bike looks like a K piston as it's flat, and in a box of parts I have, I think there's a set of F1 pistons (a different shaped dome piston).

I'll upload more pics of the rebuild.

[TwoTired]

Sure looks like a K model to me.  F models have a black motor, a 4 into 1 exhaust, a rear disc, and dual front disc, and a seat cowl out the back.

[flybox1]

Based on your vin, thats a K1 frame.  The engine color is confusing.  VIN says its an F2, but....
Just the F2/F3s had black engines.  All F's had a rear disc brake, not a drum.
Does the engine look like its been blasted/painted? 
It is not uncommon to find transplant engines.  My K8 came with a K1 engine, now it has an F3 

[flybox1]

Might be an engine from transition period between clear F1 engines and black F2s....i dunno 

[Bankerdanny]

But doesn't the F in the VIN indicate an F model or do all 750's have that? The VIN info at the 750 info page doesn't list the prefixes, just the #'s.

[754]

Looks like a lot of 73 or later parts, with tank and fork ears and sidecovers painted to resemble earlier stuff. Fork headlite ears are 73 or later.

[BomberMann650]

I thought the f/k delinieation was made from the first three numbers after the letter.

Cause every 550 had an E in the motor serial

[754]

If it is a f frame, the sidestand should be further back.

[flybox1]

Fits within the K1 frame vin range


Model   Model Year   Production Dates   Frame #                 Engine #
CB750 F0   1975   Jan 1975 – Feb 1975   1000002 to 1015054        2500004 to 25115085
CB750 F1   1976   Mar 1975 – Nov 1976   2000003 to 2022317        2525094 to 2563530
CB750 F2   1977   Nov 1976 – May 1977   2100011   E2600004-
CB750 F3   1978   May 1977 – May 1978   2200001   E3100001


K
Model Number   Model Year   Production Dates   Engine#        Frame#
CB750   1969/70   1969 – 1970                   E1000001        1000001-
CB750 K1   1971   Aug 1970 – Nov 1971                    E1053399        1044806-
CB750 K2   1972   Nov 1971 – Sep 1972                    E2000001         2000001-

[754]

Is that a gas guage on the tank, does not look stock from the side.

[martin99]

There is absolutely nothing 'F' about that bike that I can see. Sure is a nice looking bike though. FO and F1 were bare engines, F2/3 were black. Could well be a transplant but not from an F2/3 unless someone went to the trouble of stripping the engine of its black paint.

I'm pretty sure, though I've not done it myself, that a 'F' motor can be fitted to a 'K' fairly easily but requires an offset final drive front sprocket. Might be worth looking to see if this is the case to help solve the conundrum.

[constant_gardener]

Hi everyone, yes, they have sand blasted/soda blasted the engine. There is a gas tank gauge, I managed to find a guy who makes them in a place in Taiwan.

What I suspect happened was that the bike lived it's life as an F2 until one of the previous owners thought "Hey, wouldnt it be cool to have a K model?" so he bought a K frame, changed the VIN number on the frame and mounted the engine in it, and bought all the bits and bobs to make it look like a K model.

I just took a look at the pistons and it seems they are K model pistons, I was told that the heads on the F2 are different, so I'll measure the valves, the F2 has 31 and 34mm valves.

[700504]

Does the final drive have a single bolt and a big washer, or does it have tabbed lock washer and/or lock ring and an oiler bolt?

[drumstyx]

Doesn't the K tank mount on a wider or narrower frame than the F tank?