Topic: Purchasing a 1977 Honda CB750 K7

[CB500FK0]

I'm contemplating the purchase of a 1977 Honda CB750 K7. Are there any specific issues I should be aware of with this model? Additionally, I'm curious if Honda issued any bulletins related to this particular model? Thank you!

[BenelliSEI]

No issues, great bikes and generally undervalued. Some minor variances but still lots of parts interchangeably. Rear wheel is 17”, not 18”. Spokes are easy, finding a rim is harder. I’ve laced an 18” to the 17” hub and works well.
     Looks like a set of lowering blocks under that side bag? Put it back up to the correct ride hieght. The seat is unique to the K7. A K8 pan will fit too. Replica pipes are available (if you’re so inclined) and they are a LOT less than HM300 or 341 pipes. The brackets that connect two pipes to the rear foot peg bolt are getting hard to find. Check if the owner kept them! Photo is my stock K7. Lovely ride.

[seanbarney41]

77-78 750's are the culmination of 9 years worth of Honda's continuous improvements.  It seems collectors have not yet come to terms with aesthetic changes and thus values are lower.  If you gotta work on the carbs, they are much more complicated, less dependable, and require more replacement rubber parts than the earlier bikes.  Once sorted they run as well or better.

[denward17]

Does the K7 suffer the same fate as the K8 as far as exhaust valve guides wearing out with 10-15K miles?

[seanbarney41]

Does the K7 suffer the same fate as the K8 as far as exhaust valve guides wearing out with 10-15K miles?

I hink that is only the f models due to bigger intake valves and incorrect valve train geometry

[HondaMan]

Does the K7 suffer the same fate as the K8 as far as exhaust valve guides wearing out with 10-15K miles?

Yes. All of these were built with the cast-iron valve guides from the 750F1 onward.

[rotortiller]

Does the K7 suffer the same fate as the K8 as far as exhaust valve guides wearing out with 10-15K miles?
Yes. All of these were built with the cast-iron valve guides from the 750F1 onward.

Odd, I have 55,000 miles on my CB750-K7 and it still runs like a top burning no oil between oil changes. It's never been apart as far as I can tell, unless Honda had a campaign. I have had it since 15,000 miles. Tuff old tanks they are.

[bryanj]

PD carbs are a pain unless its run very regularly

[denward17]

Does the K7 suffer the same fate as the K8 as far as exhaust valve guides wearing out with 10-15K miles?
Yes. All of these were built with the cast-iron valve guides from the 750F1 onward.

Odd, I have 55,000 miles on my CB750-K7 and it still runs like a top burning no oil between oil changes. It's never been apart as far as I can tell, unless Honda had a campaign. I have had it since 15,000 miles. Tuff old tanks they are.

I can only go by the experience I had on my K8.  With 22k miles, all 4 exhaust valve guides were worn pretty badly, enough you could wiggle the valve and it was measured way outside of serviceable limits.

A leak down and compression test would show you things before purchase.

[bryanj]

I had to do exhaust guides on a f2 at 15000 miles years ago

[MauiK3]

So I guess planning on head work would be wise.

[BenelliSEI]

My K7 has 23000 miles and still runs great.

[PeWe]

Worn guides might be caused by too thin oil used?
Like 10W-40 instead of 20W-50?
Plus running hot make it even worse.

I bought a K6 head on eBay USA that looked like a low miler from a not wrenched engine. No bad threads anywhere and residues from Honda stock sticky head gasket.

The exhaust valves and guides were really bad. 2 inlet guides too.
But inlet valves and seats looked very fresh.

My K6 restored and ported stock head had no guide issues at all after ca 50.000km on my bike. Honda guides.

[seanbarney41]

K7 motor I used to use in a K5 frame had no issues.  No idea how many miles when I put it in there.  I put 30, 000 borderline abusive miles on it until I put a K5 back in my K5...drag racing, street racing, long road trips, whatever cheap oil, every shift at red line, lots of missed shift over-revs, you name it...far as I know the thing is still going...I threw that K7 in another frame and sold it running great.  Same deal with my orange F0....that thing has 40,000 on it now.

It's only the F2/3 that have any problems.  My F3 hung in there until 27,000 and then started laying down a quart of 20w50 in 400 miles screen thicker than my 32-1 KDX on a really steep climb.

[beemerbum]

No issues, great bikes and generally undervalued. Some minor variances but still lots of parts interchangeably. Rear wheel is 17”, not 18”. Spokes are easy, finding a rim is harder. I’ve laced an 18” to the 17” hub and works well.
     Looks like a set of lowering blocks under that side bag? Put it back up to the correct ride hieght. The seat is unique to the K7. A K8 pan will fit too. Replica pipes are available (if you’re so inclined) and they are a LOT less than HM300 or 341 pipes. The brackets that connect two pipes to the rear foot peg bolt are getting hard to find. Check if the owner kept them! Photo is my stock K7. Lovely ride.

My K7. Bought used several years ago. When bought it had a rear wheel from an automatic. I found a front alloy on Ebay to match. Benelli is right about the seat. Again Ebay provided a K8 seat which was like new. As to exhaust, Be advised that the stock '77-'78 exhaust is  heavy . Ugly too IMHO. The entire Delkevic system weighs less that one of the original pipes. My old pipes are hanging in my shop with brackets and all. PM me if you want to install the ugly old things. In all, I like the ride of my K7 better than my K1 or K2. The seat is a great improvement. 34K miles with no oil burning. Guides would seem ok.

[BenelliSEI]

No issues, great bikes and generally undervalued. Some minor variances but still lots of parts interchangeably. Rear wheel is 17”, not 18”. Spokes are easy, finding a rim is harder. I’ve laced an 18” to the 17” hub and works well.
     Looks like a set of lowering blocks under that side bag? Put it back up to the correct ride hieght. The seat is unique to the K7. A K8 pan will fit too. Replica pipes are available (if you’re so inclined) and they are a LOT less than HM300 or 341 pipes. The brackets that connect two pipes to the rear foot peg bolt are getting hard to find. Check if the owner kept them! Photo is my stock K7. Lovely ride.

My K7. Bought used several years ago. When bought it had a rear wheel from an automatic. I found a front alloy on Ebay to match. Benelli is right about the seat. Again Ebay provided a K8 seat which was like new. As to exhaust, Be advised that the stock '77-'78 exhaust is  heavy . Ugly too IMHO. The entire Delkevic system weighs less that one of the original pipes. My old pipes are hanging in my shop with brackets and all. PM me if you want to install the ugly old things. In all, I like the ride of my K7 better than my K1 or K2. The seat is a great improvement.

Good to hear someone also appreciates these last SOHC models. The K8 does have a lovely seat, more sculpted for the forward position. The K7 is a more traditional “log”. The K7/8’s also have a slightly larger tank. The pipes are VERY heavy, but I think they suit the bike. Lots of “bling”. K7 is easily spotted. It has a white outside trim strip on the tank. The K8’s are all gold.

[BenelliSEI]

K8 seat is more of a “saddle”.

[Johnie]

Here's my K7 from back in the day. Got it new from my dealer. It was a great bike never had any issues. Sold it to a friend in 1983 and bought it back in 1999. Rebuilt the carb that year and I swear it never ran that good when it was new. I think you're going to like it.

[beemerbum]

Dare I say it? The '77 in many ways is a superior motorcycle to the previous SOHC 750's

[BenelliSEI]

No argument from me, toss up between it and my K1……

[beemerbum]

If you add this part to your K7, all your missing hair will grow back, your beer gut will disappear and Taylor Swift will be calling you asking for a ride on your now much faster K7.

[Rosinante]

That looks like a COOL bike. 

In my view, trying to put a big fat tall tire on that 17" wheel is bad in every way.  Performance and aesthetics.  My humble opinion.

[BenelliSEI]

That looks like a COOL bike. 

In my view, trying to put a big fat tall tire on that 17" wheel is bad in every way.  Performance and aesthetics.  My humble opinion.

Good catch. The rim is probably too narrow for that tire too.

[beemerbum]

Who put a tall fat tire on the 17 inch wheel? I like the look of the 17 inch rear with a stock dimension tire. Along with the 630 chain, I think the back end of the '77 and '78 looks, for lack of a better word, "tough". I  recall somewhere Hondaman saying something along the lines of the combination being better for touring as more capable of carrying more load. The back tire on my K7 in the photo is a Shinko 130/90-17

[HondaMan]

I  recall somewhere Hondaman saying something along the lines of the combination being better for touring as more capable of carrying more load.

Right you are: the wider, fatter rear tire of the K7/8 bikes solved the problem that so many earlier bikes resolved by swapping the rear to 5.00x16 wheel/tire size to carry their big loads. When the speed limit was 55 MPH this was OK as it raised the engine speed about 800 RPM over the stock setup (to about 4700 RPM or so at 60 MPH) and made acceleration a little quicker in the K0-K6. The F0 and all later ones had a lower primary drive ratio, which puts the RPM a little higher (and more power on tap).
Today, with the higher speed limits back again, the 130/70 on the smaller wheel is a good bet, I would think. I even wonder if a 140/70 would fit? This would drop the RPM a little bit at today's 70-80 MPH interstate speeds. On my own K2 I use a 19T countersprocket (for 1-up touring) to do that same thing, but it does make 5th gear into a sort of overdrive, not useful below 60 MPH.