Author Topic: Senior project for high school - 78 CB750K (Read 175031 times)

Restoration Fan · « **Reply #1100 on:** June 02, 2015, 04:46:51 PM »

Quote from: madmtnmotors on June 02, 2015, 04:24:56 PM

The 77 is unique and the 78 is unique, but they are interchangeable. The 77 discharges to the rear, and the 78 discharges to the center of bike but they have the same connection. The only ones that seem to be available are the 77 (rear discharge) but they will work on the 78, just need a little longer fuel line, or rotate the fuel valve slightly.

Thanks, Wilbur. I apparently have a 77 but it appears to be made by the POS company.

madmtnmotors · « **Reply #1101 on:** June 02, 2015, 07:28:54 PM »

I used one of the aftermarket fuel valves that mounted a little different than stock. The stock valve uses a "captured" nut with an internal (blind) circlip that holds the nut in place. Tighten the nut and the valve tightens up to the tank. The aftermarket one that I had was manufactured by threading the body of the valve to accept the nut. Tighten the nut and it threads onto the tank as it's threading off of the valve! For that type of valve you would have to hold the valve up to the tank, thread the nut part way on to the tank, and then hold the nut while you turn the valve to tighten! Definitely a P.O.S., but I was able to get mine to work without leaking, once I figured out W.T.F. was happening.

Stoli · « **Reply #1102 on:** June 16, 2015, 09:37:38 AM »

My POS '77 petcock didn't do that until year #2. I just tightened up the rivets with a vice and that fixed it.

madmtnmotors · « **Reply #1103 on:** June 16, 2015, 09:47:23 AM »

Quote from: Stoli on June 16, 2015, 09:37:38 AM

My POS '77 petcock didn't do that until year #2. I just tightened up the rivets with a vise and that fixed it.

Yeah, that's a different seal. The seal you describe is the internal seal, which from what Ron describes is a new part. I was just describing my experience with an aftermarket valve and how it attached a little differently to the tank. The stock valves on the later model (77/78 K/F, and maybe "A") can be rebuilt, but probably only once:

Contrary to popular belief, the later model fuel valves can be rebuilt:

Can anyone tell which one is the new seal?

Leave as much of the nubs as possible:

Voila'! (as opposed to "viola'" which everyone knows is a musical instrument)

Good for another 40 years! Good thing too, since this can only probably be done once, which is okay... because 40 years from now I won't care!

Stoli · « **Reply #1104 on:** June 16, 2015, 09:57:16 AM »

On another one, I drilled holes where the rivet was and sealed it back up with some small screws and nuts. Very Rube G but it still works and doesn't leak..

Restoration Fan · « **Reply #1105 on:** June 16, 2015, 12:24:09 PM »

You guys are much smarter and more handy than I am apparently. I went the "buy an original 78 model petcock that's still functioning properly from Bill Benton and replace the POS Chinese made one" route.

madmtnmotors · « **Reply #1106 on:** June 16, 2015, 12:26:14 PM »

That works too!

dave the welder · « **Reply #1107 on:** June 16, 2015, 05:27:26 PM »

+1 for STOLI did the drill and tap route on my 77 matic.works great

Restoration Fan · « **Reply #1108 on:** August 12, 2015, 04:47:16 AM »

Sorry for reviving this thread but I thought it was an appropriate place to say a HUGE 'Thank you' to every one of you guys who were so adamant that I should take the Motorcycle Safety Foundation course.

I completed the course on Monday and Tuesday and had an absolute blast doing it! Our rider coaches were great people and even though the heat was oppressive on Monday afternoon, the entire class wanted to stay out and keep riding when it was time to come in.

There's no doubt that the course not only made me it possible for me to get my license and be a safer rider, it also taught me some bike handling skills at lower speeds that I had never practiced and am glad to have.

Anyway, thank you to everyone who constantly encourages other members of this board to take the class. Please keep doing so because it may save a life and will definitely make them a safer/better rider.

AintNoEasyWay · « **Reply #1109 on:** August 12, 2015, 05:44:33 AM »

Awesome, Ron! Glad to see you survived the weather.

In addition to the course, here's an excellent video:

evanphi · « **Reply #1110 on:** August 12, 2015, 05:56:24 AM »

Another useful one... Ignore the terrible acting!

callmejarob · « **Reply #1111 on:** August 12, 2015, 11:14:45 AM »

Awesome glad to see you're out there enjoying the bikes!

SOHC4 Cafe Racer Fan · « **Reply #1112 on:** August 12, 2015, 12:43:59 PM »

Quote from: evanphi on August 12, 2015, 05:56:24 AM

Another useful one... Ignore the terrible acting!

Yes, terribly acted, but the Keith Code stuff isn't bad. It's a little preachy, but still valuable.

Restoration Fan · « **Reply #1113 on:** August 26, 2015, 09:47:58 AM »

So I rode Stella to the office yesterday. It's about a 22 mile round trip. Because I didn't want to ride her early in the morning while it's dark (too many crazy drivers in Atlanta rushing to get into the office before traffic starts), I waited until about 7 am to leave the house. LOL, bad mistake...it turned a 20 minute drive into a 50 minute ride because of school buses and traffic.

The point of that is that the trip TO the office, I rarely got the bike above 2500 rpm's. The ride home however was glorious. Sunny day with temperature in the mid-70's and low humidity.

I charged my battery the night before and it was reading 13.1. When I pulled back into my garage last night, it measured at 11.77. Because of the morning stop & go traffic, I'm not sure whether this is due to a faulty regulator and/or rectifier or if the traffic was draining the battery.

Tonight, I plan to take the bike out and ride it with a lot of > 3500 riding for about 20 miles again and once again measure the voltage to see if the battery is getting re-charged.

We decided not to use a combination regulator/rectifier before because most people appear to mount theirs beneath the battery box. Well, on a 78, there is a breather/air recirculator down there so there is no room to mount it easily.

My question is this: surely someone has a 77 or 78 with a breather and also uses the combination regulator/rectifier. If so, how did you mount it?

I don't know for sure that mine is a problem yet but I'd like to know how to mount one in the event that I need to replace mine.

SOHC4 Cafe Racer Fan · « **Reply #1114 on:** August 26, 2015, 10:22:37 AM »

Mine is mounted with the other electronics under the left side cover. It gets sufficient air flow.

Restoration Fan · « **Reply #1115 on:** August 26, 2015, 11:04:10 AM »

Quote from: CB750 Cafe Racer Fan on August 26, 2015, 10:22:37 AM

Mine is mounted with the other electronics under the left side cover. It gets sufficient air flow.

So did you just drill a hole and screw it into the cover? Or do you mean it's connected to the battery box there on the left side near the solenoid?

Davez134 · « **Reply #1116 on:** August 26, 2015, 11:56:06 AM »

Quote from: CB750 Cafe Racer Fan on August 26, 2015, 10:22:37 AM

Mine is mounted with the other electronics under the left side cover. It gets sufficient air flow.

I did the same. Mounted to the battery box to left of solenoid. I'll try and find a picture. Made a aluminum bracket to make it easier/clean. As stated, gets plenty of airflow. I'm sorry that I do not know if there is room here, as I have a 72, never seen a 77 or 78 electronics panel.

Edit: found pic.

madmtnmotors · « **Reply #1117 on:** August 26, 2015, 01:42:17 PM »

I mounted mine (also a K8) to the bracket that used to hold the stock regulator. I bent the tabs to align with the new unit, but the next one I will probably use an aluminum plate to mount the reg/rect combo and drill holes in that plate to use the stock regulator mount. The aluminum plate will likely help cool the combo unit by serving as a heat sink too.

SOHC4 Cafe Racer Fan · « **Reply #1118 on:** August 26, 2015, 02:15:43 PM »

It's mounted where the original was.

evanphi · « **Reply #1119 on:** August 26, 2015, 03:20:36 PM »

Mine is mounted where the original is, just with some alu brackets.

Quote from: evanphi on October 09, 2014, 05:53:42 PM

Made some brackets for my reg/rec... no more zip ties!

Stev-o · « **Reply #1120 on:** August 26, 2015, 03:44:34 PM »

Ok, enough about mounting.

How 'bout keeping your R's above 5000! [that's where life begins!]

Restoration Fan · « **Reply #1121 on:** August 26, 2015, 04:27:41 PM »

LOL, very true. I just got back from a 10 mile ride and I stayed up there most of the time. Inconclusive results on the voltage but it was at 12.8 when I left and it was at 12.75 when I got home. I'm planning to ride it into the office again tomorrow and I'll see how it looks after the 20 mile ride.

Oh, and Wilbur, thank you very much for the call last night. I took all 4 pipes off and put them back on, making sure they were on properly and torqued down properly. Now she literally has that sewing machine sound and it makes a huge difference on the performance.

madmtnmotors · « **Reply #1122 on:** August 26, 2015, 05:53:21 PM »

Happy to help. Making them run good is very rewarding indeed.

Stev-o · « **Reply #1123 on:** August 26, 2015, 06:52:37 PM »

Ron - very simple task to check your charging system: start the bike and let it idle.
Check voltage. Then hold a fast idle at 3000 & 4000, voltage should rise if system is charging. I bet you knew this, though.

Restoration Fan · « **Reply #1124 on:** August 27, 2015, 06:45:42 AM »

Stev-o,
Actually I did not know that so thank you. I rode it to my office this morning and she performed wonderfully.

The only thing I'm still not sure about with her (besides the charging) is the clutch adjustment. I've adjusted it about 4 or 5 times now, trying to get it just right. Coming out of neutral down into first, it still makes a bit of a clunking noise as it goes into the gear. It seems to shift smoothly into all other gears up and down the tree without clunking but that noise going into first just kind of makes me cringe. Am I just worrying too much or should I keep adjusting until I get rid of that noise?

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Author Topic: Senior project for high school - 78 CB750K (Read 175031 times)