CB750 K2- How Delightfully Old School.

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salukispeed
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Re: CB750 K2- Closer, and Farther

Post #76 by salukispeed » Sat Sep 30, 2017 9:41 am

Bend them "slowly" and possibly use a hair drier to heat them up to make them more flexible while you get them in place
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Re: CB750 K2- Closer, and Farther

Post #77 by Track T 2411 » Sat Sep 30, 2017 10:29 am

A little bit of this, and a little bit of that, and soon you'll have another motorcycle! action1 action1 action1
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Lucien Harpress
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Re: CB750 K2- Closer, and Farther

Post #78 by Lucien Harpress » Sat Sep 30, 2017 7:04 pm

You want to know the best part of getting all the wiring back on and connected back up in the bucket?

Wires left over that don't go anywhere.

....

Just thought you might like to know. (I'll grab a wiring diagram and get back with you.)
1969 CT90- Needs rear tube and possibly rings
1976 GL1000 (Yellow)- Carb Shenanigans.
1984 GL1200 Standard- For Sale!
1980 KZ1300- Carb balancing when the weather warms up
1972 CB750 Barn Find- Tires and Head Bearings

All advice I give is only valid until an expert corrects me.

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Lucien Harpress
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Re: CB750 K2- Closer, and Farther

Post #79 by Lucien Harpress » Sat Sep 30, 2017 8:22 pm

So, update. In no particular order....

-Managed to mis-match a wire or two. Apparently colors are hard. (And I have an Art degree, for gosh sakes...)
-Think I shot myself in the foot with the turn buzzer- it didn't come from a 750, so the wire colors are wrong.
-Still have a brown wire coming out of the main harness I can't match up. Stay tuned.
-My battery is pretty much confirmed trashed.

HOWEVER- I ran some jumper cables from my leads to my Jeep's battery, and was able to confirm that the following works:

-Headlight
-Idiot Light(s)
-Right controls
-Turn signals/left controls
-STARTER MOTOR

Once I get a battery that works I'll get some extra plugs and make sure the coils are sparking as well, but so far so good.
1969 CT90- Needs rear tube and possibly rings
1976 GL1000 (Yellow)- Carb Shenanigans.
1984 GL1200 Standard- For Sale!
1980 KZ1300- Carb balancing when the weather warms up
1972 CB750 Barn Find- Tires and Head Bearings

All advice I give is only valid until an expert corrects me.

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Re: CB750 K2- Checklist

Post #80 by Lucien Harpress » Thu Oct 05, 2017 9:05 pm

Got some packages in the mail today. Namely a throttle cable:

20171005_151834.jpg


...and header clamp.

20171005_151856.jpg


So what do I still need before I try to start this puppy? Air filter, oil filter, fluids, and a battery, at minimum.

20171005_153331.jpg


I'm allowing myself to get excited.
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1969 CT90- Needs rear tube and possibly rings
1976 GL1000 (Yellow)- Carb Shenanigans.
1984 GL1200 Standard- For Sale!
1980 KZ1300- Carb balancing when the weather warms up
1972 CB750 Barn Find- Tires and Head Bearings

All advice I give is only valid until an expert corrects me.

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Re: CB750 K2- Checklist

Post #81 by desertrefugee » Thu Oct 05, 2017 9:39 pm

Make sure there's water in the radiator.

. . . Gas, oil, spark.
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Lucien Harpress
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Re: CB750 K2- Checklist

Post #82 by Lucien Harpress » Thu Oct 05, 2017 10:07 pm

desertrefugee wrote:Make sure there's water in the radiator.


:-? ...I mean, I suppose I could wait until it starts raining or something...... :mrgreen:
1969 CT90- Needs rear tube and possibly rings
1976 GL1000 (Yellow)- Carb Shenanigans.
1984 GL1200 Standard- For Sale!
1980 KZ1300- Carb balancing when the weather warms up
1972 CB750 Barn Find- Tires and Head Bearings

All advice I give is only valid until an expert corrects me.

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Re: CB750 K2- Checklist

Post #83 by JSBail » Fri Oct 06, 2017 4:51 am

Make sure the clutch plates aren't stuck. If you can put it into gear but still be able to push the bike with it in gear and the clutch lever pulled in you should be OK. I had a 73 cb750 that sat for 20+ years and it's clutch plates had gotten stuck together from setting for so long, once the bike was initially up and running it would jump and die the moment I'd try to put it in gear. I didn't have to replace anything but I did have to disassemble the clutch and lube all its plates before reassembling.
Scott

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Lucien Harpress
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Re: CB750 K2- Checklist

Post #84 by Lucien Harpress » Fri Oct 06, 2017 10:31 pm

Clutch plates are DEFINITELY frozen. If I remember correctly, you need a special tool to get the clutch plates out. The good news is that I already had to buy one for my CT90, and I'm fairly certain it's the same size.

Assuming the motor runs, that opens up a whole new set of things to fix to actually get it roadworthy. In no particular order...

-Clutch plates frozen
-ENTIRE front brake (from master cylinder to caliper) needs cleaned or replaced
-Drive chain
-Everything rearwards of the battery needs wired
-Front forks need rebuilt, including seals, fluid, and possibly replacing the downtubes
-Gas tank de-rusted and checked for pinholes (AND new petcock)
-Tires

But, hopefully I can put that off. First thing's first- get running, then move on.
1969 CT90- Needs rear tube and possibly rings
1976 GL1000 (Yellow)- Carb Shenanigans.
1984 GL1200 Standard- For Sale!
1980 KZ1300- Carb balancing when the weather warms up
1972 CB750 Barn Find- Tires and Head Bearings

All advice I give is only valid until an expert corrects me.

JSBail
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Re: CB750 K2- Checklist

Post #85 by JSBail » Sat Oct 07, 2017 7:15 am

Lucien Harpress wrote: First thing's first- get running, then move on.


That's precisely the thought process I have when messing with a bike that hasn't ran in years, I resist buying any parts until I've heard it run first. Yeah you'll need a special socket to get the clutch apart, if the one you purchased for the CT90 doesn't work you can make your own if you have the patience, I'll dig around later on to find mine to see what size socket I used. You may already be aware of all this but I'm letting you know to make sure you know so you don't run into any headaches. To start out with (after you're satisfied with how the engine sounds) make sure you're very patient with that cast aluminum pressure plate on the clutch because it can snap real easy, don't ask me how I know. I loosen the bolts that secure it 1 full turn at a time and install them 1 full turn at a time as well, it's kind of time consuming but I haven't snapped another one since I learned my lesson on the first one I broke. Also there is a concave/convex washer behind it all, make sure you have it facing the right direction when installing or you may not be able to get into 5th gear when done. It sounds crazy I know but there is a member on the 750 site I visit who's 750 had no 5th gear since he bought it, he even split the cases and installed another trans and still no 5th gear. It wasn't until one of the experts on the site questioned him about that washer, it turned out the owner had been reinstalling that washer the same way he had taken it apart assuming it had already been positioned correctly in the first place but it turned out it was the previous owner that had it installed wrong. Once it was determined it was facing the wrong way the owner pulled the clutch apart, installed that washer correctly, got it all back together and viola, his 750 now had 5th gear.
Scott

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Lucien Harpress
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Re: CB750 K2- IT LIVES!!!! ...a bit

Post #86 by Lucien Harpress » Mon Oct 16, 2017 7:36 pm

I finally got my battery in the mail today, so I figured I'd pop it in and see what works. To my surprise, the answer was "quite a bit". Horn, lights, starter motor, blinkers, etc. I popped a spare spark plug on one of the plug wires- no spark.

Just for fun, I pulled the points cover and gave the points a good swipe with some sandpaper. I checked again, and was rewarded with that sweet, sweet little blue blinkey light.

Time for an experiment.

I grabbed a bit of starter fluid, took apart the airbox, shot some into the carbs, and hit the starter button again- and that thing, however briefly, ran under its' own power for the first time in probably decades.

Time for another experiment.

I have a aux. fuel bottle "IV" tank. The only problem is that this model of CB750 has two fuel inlets, one for carbs 1 and 2, the other for 3 and 4. Well, I don't have a splitter (yet), so I did the best I could to at least fill up all 4 carb bowls by swapping the line back and forth. After I was happy I hit the starter again, and managed to get a decent 1-2 minutes of continuous runtime. dancr dancr dancr

After my happy dance was done I figured I was only hitting on 3 cylinders, but that's 3 more than I was expecting. One I get a more solid fuel delivery setup I can troubleshoot, but hearing that puppy roar to life was like music to my ears.

Watch this space! I'll be to sure to have updates, and maybe a video or two.....
1969 CT90- Needs rear tube and possibly rings
1976 GL1000 (Yellow)- Carb Shenanigans.
1984 GL1200 Standard- For Sale!
1980 KZ1300- Carb balancing when the weather warms up
1972 CB750 Barn Find- Tires and Head Bearings

All advice I give is only valid until an expert corrects me.

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Re: CB750 K2- IT LIVES!!!! ...a bit

Post #87 by Easter » Mon Oct 16, 2017 8:10 pm

Congratulations. Just remember to go easy with the starter fluid. I still use it but I set a CB900 on fire a while back.
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Re: CB750 K2- IT LIVES!!!! ...a bit

Post #88 by desertrefugee » Mon Oct 16, 2017 8:25 pm

...and I severely wounded a GS1000 several decades ago. I've never used ether-based starting fluids since.
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Lucien Harpress
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Re: CB750 K2- IT LIVES!!!! ...a bit

Post #89 by Lucien Harpress » Tue Oct 17, 2017 8:22 pm

So, I managed to rig up a fuel delivery system better than what I had, and was able to do a bit more futzing around with this bike. The bad news? Part of the reason I have a dead(ish) cylinder is that I've got some kind of stuck/high float on carb 4. Thankfully these carbs come with an overflow. Unfortunately I don't have a tube linked to it yet, so it was just dumping gas right on the engine block. :shock: Got that shut down REAL quick.

On the upside though, I've got spark, I've got compression, and once the bowls drained down a bit I got, well, THIS.

https://youtu.be/2cBX8Uvvgf8

Not bad for something that's been sitting in a collapsed barn for 20 years.
1969 CT90- Needs rear tube and possibly rings
1976 GL1000 (Yellow)- Carb Shenanigans.
1984 GL1200 Standard- For Sale!
1980 KZ1300- Carb balancing when the weather warms up
1972 CB750 Barn Find- Tires and Head Bearings

All advice I give is only valid until an expert corrects me.

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Lucien Harpress
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Re: CB750 K2- IT LIVES!!!! (Now with 100% more video)

Post #90 by Lucien Harpress » Wed Oct 18, 2017 6:30 pm

Figured out why my number 4 carb was flooding. Someone had stomped on the float tab, smashing into the full "open" position. Five minutes later had it bent back to the correct angle. The best part? The combination of the carb location and the simple spring clip holding the bowl on meant I could fix the problem right on the bike!

The (sad) verdict?

Doing next to nothing, this hunk of barn find probably runs better than most of the stuff I own. :lol:

Next up? Find me a drive chain and see if I can bust the clutch plates loose without tearing more apart.
1969 CT90- Needs rear tube and possibly rings
1976 GL1000 (Yellow)- Carb Shenanigans.
1984 GL1200 Standard- For Sale!
1980 KZ1300- Carb balancing when the weather warms up
1972 CB750 Barn Find- Tires and Head Bearings

All advice I give is only valid until an expert corrects me.


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