CB750 K5 (1975)

[desertrefugee]

Soooo, it’s been a while on this one. Summer got in the way and some health issues have surfaced, but this bike calls for me. I am responding - slowly.

Turns out the carbs leaked like a sieve. That bummed me out a bit because I had them off once before and they looked shipshape. Got them off again and found everything still looked ship shape but two of the four leaked – floatbowls overflowed. I hemmed and hawed over them for a week or so and finally concluded that the needles were not seating properly. Ordered new K&L needles and seats and that solved the problem.

They’re back on the bike and I’m ready to ignite it. Maybe today!

Although it pains me to report that stupidity knows no bounds. (Don’t ask):

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[Lucien Harpress]

Ah, yes. I know that particular type of break VERY well.

[Shadowjack]

I also have a K5, although mine is a stock-appearing "bitsa", and just a runner, not done to show standards. The engine is not original, either.
The "resurrector" had put a 4-into-1 header on it, but I looked for the original exhausts until I found all four pipes. The chrome has speckles, which can't be fixed, but the metal is solid, and the patina of the bike ruled out getting a shiny new set anyway. I was surprised to find the exhaust note went from a howl to a growl, which I like better.
It's my impression that parts support for these is much better than for most other old bikes, due to their impact on the sport, and reputation.

[luludog]

Nice find, and it looks like you’ll get it running soon. Thanks for the updates.
I’ve got a ‘75 also. Got it from a friend who was going to use the engine for a project.
Everything needed work.

http://www.ngwclub.com/forum/viewtopic.php?f=13&t=40426

[flyin900]

I feel for you on that break on the side cover. It can be repaired, as I am sure your aware and then reshot with paint. Lots of work though and it maybe cheaper to buy a replacement cover. I did see the post initially when you first got the bike and your making good progress on the restoration.

On the carbs if you have a Mitey Vac you can attach it to the gas line with the carbs off the bike and upside down and pull a low vacuum on the set. If it holds vacuum your usually good, if not then there are leakers. I normally do it with the float bowls off then you can see with a little soap and water around the float valve.

I also suggest setting up a gas bottle 3 feet above the set and I use alcohol rather than gas to test the set for leaks before installation back on the bike.

You may already know these test methods. I have also found some sets test well and still leak when installed until a couple of good knocks on the float bowls help set the fuel valves properly.

[desertrefugee]

Yeah I am still thoroughly bummed over the side cover. I know better but for some crazy reason I had it on when I was fiddling with the carburetors. Leaned on it in advertently with my arm and that’s what broke the darn thing.

And yes, I was not going to hang those carburetors again without knowing for sure that they were golden. I have an IV bottle and I’m not afraid to use it.

Currently slowly battling some ignition gremlins. I’ve encountered what appears to be a pinched wire on one coil feed wire (blue side) from the points up. 8’ish ohms to ground on that side with points open. At least I heard it cough and sputter trying to fire off and run with two cylinders. Didn’t want to run though. I don’t blame it.

[Lucien Harpress]

Yeah, I was surprised how brittle the sidecovers on mine were. I shattered the same corner, but I was pulling it off and it kinda rotated on the pin holding it in place into the air box. Eventually got a new pattern replacement and a full repaint.