Topic: Why did the 77-78 cb750K get shafted?

[KrautKoffin]

Not to rant (because I'm probably misinformed), but it seems like everything I want to upgrade on my bike isn't made or discussed. Example: I'm looking for rear sets for my 77K and was told they arent available as a bolt on. I'm not like some of you with a welder at my disposal, I live in a rad apartment in an overly crowded city on the west coast that doesn't offer garage space. I just keep noticing a lot of parts are only offered for the 'desirable' years, not the later models. /rant.

[goldarrow]

Yup. I know how you feel. Sell the bike and get the early k before you plunge any more money into it

[lucky]

The 1977-78 CB750K model was and is VERY desirable.
It had the most improvements of all of the SOHC CB750 models.
Larger valves.
More cooling fins on the engine and oil filter housing.
Longer swing arm.
Stronger cam chain.
Wider cam chain galley with better oil drains.
Higher 4th and 5th gears.
Larger gas tank.
Improved redesigned clutch.
Thicker engine case in the chain area.


Etc.,.

Adapt.

Adapt the parts by making a bracket.
Do you have a drill?

The 1977-78 frame had a slightly longer swing arm.
Also the frame was a little longer.

[Stev-o]

I like my stock K8.  I would never consider chopping it into a cafe bike, prefer my 550 for that.

[ekpent]

From a parts maker's perspective it probably doesn't make good business sense to make up a lot of specialized parts for a bike that had only a 2 year run.

[Djfob]

To own a 77-78 you must be willing to modify things to fit. The only thing that really gripes me right now is no access to new carb insulator boots. We seem to be a small lost market.

[Stoli]

^ekpent hit the nail on the head when it comes to the reason why the parts are harder to find.

They are out there though. It just takes a little more time and effort to find them or figure out what will fit and what won't. Lots of sellers just throw '69-'76 on their compatibility listing but in may cases that is out of laziness.

As far as a bolt on bracket for rearsets, I think that is a bad idea anyways. The chances it will fit your seat position and leg length are slim. A custom bracket that is welded on is the way to go, but there are alternatives if you don't have the means. For instance, I mounted DCC rearsets on my '78K using a hacksaw, file, drill and bench grinder. For materials, I used a couple of strips of 1/4" steel, the mounting bolt and bracket from the original rear-peg and a $3 spacer + washer I found at my local hardware store. They have almost 2000 miles on them so far and I can stand up and bounce on them (I weight 200 lbs) and they don't flex at all. Here is a pic:



Not the most elegant of mounts I suppose, but functional and cheap and very comfortable for me and my long legs. I'm biased of course but I don't think they detract from the overall appearance of the bike:



There are some more pics of the mock-up on the bottom of page 3 of my project thread here:

http://forums.sohc4.net/index.php?topic=117106.73

[KrautKoffin]

^ekpent hit the nail on the head when it comes to the reason why the parts are harder to find.

They are out there though. It just takes a little more time and effort to find them or figure out what will fit and what won't. Lots of sellers just throw '69-'76 on their compatibility listing but in may cases that is out of laziness.

As far as a bolt on bracket for rearsets, I think that is a bad idea anyways. The chances it will fit your seat position and leg length are slim. A custom bracket that is welded on is the way to go, but there are alternatives if you don't have the means. For instance, I mounted DCC rearsets on my '78K using a hacksaw, file, drill and bench grinder. For materials, I used a couple of strips of 1/4" steel, the mounting bolt and bracket from the original rear-peg and a $3 spacer + washer I found at my local hardware store. They have almost 2000 miles on them so far and I can stand up and bounce on them (I weight 200 lbs) and they don't flex at all. Here is a pic:



Not the most elegant of mounts I suppose, but functional and cheap and very comfortable for me and my long legs. I'm biased of course but I don't think they detract from the overall appearance of the bike:



There are some more pics of the mock-up on the bottom of page 3 of my project thread here:

http://forums.sohc4.net/index.php?topic=117106.73

From a business stand point I definitely understand why there aren't a lot of parts that just bolt on like the earlier years, two years is a short run. 

Stoli, the bike looks awesome. I like your rear sets, I'll definitely look into modifying a set to fit.

[lucky]

To own a 77-78 you must be willing to modify things to fit. The only thing that really gripes me right now is no access to new carb insulator boots. We seem to be a small lost market.

  You can just make your own with turbo silicone hose.
Also the early style boots will work too. They are just a little bit longer.

[lucky]

^ekpent hit the nail on the head when it comes to the reason why the parts are harder to find.



3]http://forums.sohc4.net/index.php?topic=117106.73[/url]

You are showing bolt brackets.
QUOTE"As far as a bolt on bracket for rearsets, I think that is a bad idea anyways"

??

[lucky]

"From a business stand point I definitely understand why there aren't a lot of parts that just bolt on like the earlier years, two years is a short run. "


You need to get better at shopping on the internet.

For instance:
Cycle Exchange Wisconsin.

Also when shopping on the net, type into Google or any search engine what you want and then go to IMAGE results, not web results and you will see many images that are what you may be looking for. If you click on that image it often tells you where the parts came from.

Do not just type in "rear sets" Type in "rear sets 1978 CB750"  Be specific.
Also you can get different results by changing the words around like:
1978 CB750 rear sets. OR.....rear set foot pegs Honda CB750.

[lucky]

Try the rear sets search for the 1976 F1

I believe it is the same frame as the K7 and K8.
http://flatracer.com/#/tarozzi-rearsets-honda/4538992107

[Jerry Rxman Griffin aka MuthaF'er]

The 1977-78 CB750K model was and is VERY desirable.
It had the most improvements of all of the SOHC CB750 models.
Larger valves.
More cooling fins on the engine and oil filter housing.
Longer swing arm.
Stronger cam chain.
Wider cam chain galley with better oil drains.
Higher 4th and 5th gears.
Larger gas tank.
Improved redesigned clutch.
Thicker engine case in the chain area.


Etc.,.

Adapt.

Adapt the parts by making a bracket.
Do you have a drill?

The 1977-78 frame had a slightly longer swing arm.
Also the frame was a little longer.

Lucky, what was larger about the valves? Not on the 77/78 K my friend. The F had larger valves not the K. Different keepers and stronger springs though.

[Wobbly]

There is your bolt-on set for the CB750K7/K8:

http://www.speedpro.de/store/zubehoer/raask-fussrastenanlage/honda/raask-honda-cb750k7.html

[xnoahx]

I also lament the lack of availability of less expensive rear sets that go on without having to fabricate a simple bracket.  That said, you don't need to weld or even have much more than basic hand tools to make a simple plate bracket to hold those universal rear sets like the Dime City Cycles ones.  I've seen a few different examples on here while looking for ideas.

[toytuff]

The 1977-78 CB750K model was and is VERY desirable.
It had the most improvements of all of the SOHC CB750 models.
Larger valves.
More cooling fins on the engine and oil filter housing.
Longer swing arm.
Stronger cam chain.
Wider cam chain galley with better oil drains.
Higher 4th and 5th gears.
Larger gas tank.
Improved redesigned clutch.
Thicker engine case in the chain area.


Etc.,.

Adapt.

Adapt the parts by making a bracket.
Do you have a drill?

The 1977-78 frame had a slightly longer swing arm.
Also the frame was a little longer.

Lucky, what was larger about the valves? Not on the 77/78 K my friend. The F had larger valves not the K. Different keepers and stronger springs though.

I have read that the K models in fact had the F motor.

tt

[Terry in Australia]

As usual, Lucky's research is flawed. The K7/8 engines are the same spec as the F/F1, not the F2/3, which has the bigger valves, slightly lumpier cam, etc. The K7/8 engine is probably the best though, as the F2/3 engines were a little more fragile.

The best thing to do with an "F/F1" or "K7/8" engine, is to install it in an early K bike, and then you've got the best of both worlds, the best engine, in the most popular (and easiest to obtain parts for) chassis. Cheers, Terry.

[Jerry Rxman Griffin aka MuthaF'er]

Toytuff is correct. The -392 engine was used in the K7/K8 with a few changes. Even the K8 had a few changes over the K8 K7 (correction). K7 used a different output shaft and cam is timed 5 degrees different then the K8 used the F2/F3 springs and keepers. 

[lucky]

The 1977-78 CB750K model was and is VERY desirable.
It had the most improvements of all of the SOHC CB750 models.
Larger valves.
More cooling fins on the engine and oil filter housing.
Longer swing arm.
Stronger cam chain.
Wider cam chain galley with better oil drains.
Higher 4th and 5th gears.
Larger gas tank.
Improved redesigned clutch.
Thicker engine case in the chain area.


Etc.,.

Adapt.

Adapt the parts by making a bracket.
Do you have a drill?

The 1977-78 frame had a slightly longer swing arm.
Also the frame was a little longer.

Lucky, what was larger about the valves? Not on the 77/78 K my friend. The F had larger valves not the K. Different keepers and stronger springs though.

The valves were new on the 77-78's
Valve springs and retainers(keepers) design were new.
The compression was 9.2:1 just like the F models.
1978 CB750E-3000001 engines onward.

[Retro Rocket]

Same valves as the other 392 engines Lucky, they weren't bigger...

[lucky]

Same valves as the other 392 engines Lucky, they weren't bigger...

The groove in the valve stem had to be different to accommodate the new style keepers.

[Wobbly]

Also the engine modifications are nicely listed here:
http://satanicmechanic.org/enginemods.shtml

[toytuff]

Toytuff is correct. The -392 engine was used in the K7/K8 with a few changes. Even the K8 had a few changes over the K8. K7 used a different output shaft and cam is timed 5 degrees different then the K8 used the F2/F3 springs and keepers.

I looked for the link with the article but could not find it.

Senior moment. Thanks Jerry.

Edit<< I also remember reading that Mother Honda in fact wanted to drop the K model and just produce the F model. Honda did a detailed feedback program from Dealers as well as owners. What they found out was a great demand for the K model. Customers wanted a highway motorcycle that was comfortable for the long haul. This lead to the longer frame, increased rake and tire changes.

This is just from memory as I am still searching for where I read that. I can not verify. 

tt

[toytuff]

Copy/paste.


The K-model is all this plus another 3 percent. It has an edge because it's built and sold as a touring bike, so factors such as ground clearance and weight aren't as significant as they are to a bike with "Super Sport" in its name. Ideally the K model would also have ComStar wheels, dual horns, a rear disc and the F's power, but even without them, it's a fine touring machine tainted only by less than satisfactory suspension compliance. Its 1/4-mile time of 13.33 doesn't seem impressive compared to the F's hot-blooded 12.7, until you realize it's still three tenths quicker than the original CB750, three tenths quicker than the current Yamaha 750, and quicker than the BMW 750. In short it's no slouch, and there's a simple explanation why: the K engine is last year's Super Sport engine with the new accelerator-pump carburetion system.

Because of higher gearing which lets the engine loaf, the K is even smoother than the F2, and therefore a rival to BMW for comfort. Further improvements include new seamless mufflers which look better and quiet the engine's 57.13 horsepowerto 78 dB(A) - a whisper. Redesigned triple-clamp bosses bring the new handlebar closer to the rider, partially to compensate for an inch-longer wheelbase. These changes, along with the new grips and two-stage seat, produce an exceptionally natural feel. It's likely a rider will remain comfortable for a whole tank of gas, which is now five full gallons - enough for 200 miles at a 40 mpg average. Nearly an inch more rear shock travel also contributes to the K's comfort and load-carrying ability. In addition, Honda has fitted the same fat rear weenie that works so well on the heavier GL1000 and Automatic.

http://www.oocities.org/siliconvalley/pines/4352/cycle/test.html

tt

[Stev-o]

Good article, thanks for posting, Toy.