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Author Topic: New to building. Like really new. Like moron new.  (Read 7690 times)

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Offline Jeff750

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New to building. Like really new. Like moron new.
« on: June 23, 2013, 06:04:28 PM »
So I buy a 1977 cb750k for $300 Canadian dollars. Hasn't run in 10 years. Has compression. Wiring is toast.

Maybe I should have tried to get it going before ripping out the motor. But any way. Where to start now that I'm in this sport?
Full engine rebuild. Top end? Put the engine back in and hope for the best or see if it leaks?

I'm a little (a lot) nervous about opening up the engine.

There is some corrosion around the intakes. But like I said the pistons do turn.

I don't know. Help me out.
Thanks.
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Offline MoMo

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Re: New to building. Like really new. Like moron new.
« Reply #1 on: June 23, 2013, 06:14:15 PM »
A compression test would have been the first thing to do but now that the motor is out you still can do that, battery ground to the motor and positive to the starter terminal while the compression gauge is in the plug hole. Welcome, and  the manual can be downloaded from this forum.  Have fun with the build...Larry
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Offline knowsnothing

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Re: New to building. Like really new. Like moron new.
« Reply #2 on: June 23, 2013, 06:16:16 PM »
Hey jeff, congrats on the purchase. 

First i would get a manual if you dont have one. 

Second, i would clean everything up (carbs, electrical/wiring), then put the engine back in.  Change the oil and do the 3000 miles tune up and see what you got.  Chances are it will run just fine.  If it does, then its new chain, tires, wheel bearings and anything else that needs to be addressed.

Like you, i was all excited about my first 750 and started ripping into the engine.  The thing is still in pieces....

Small steps first.
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1978 CB750k Green - 811 engine
1978 CB750k Blue - for sale
1974 CB375F Faded Black - had to have that 6th gear
1976 CB400F Red - in many pieces
1973 CB350F TBD - in many pieces

Offline HondaMan

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Re: New to building. Like really new. Like moron new.
« Reply #3 on: June 23, 2013, 08:01:47 PM »
$300!

Wow, a steal! You can get a whole new wiring harness from PartsNmore.com in Canada for $75, or from CB750Supply for about that, American.
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Offline Jeff750

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Re: New to building. Like really new. Like moron new.
« Reply #4 on: June 24, 2013, 07:34:44 AM »
Thanks a lot for the advice fellas, much appreciated! Seriously.

Since that question went ok I'll ask another dumb one.

So I cut off the old rusty spokes, purchased a set off of ebay for a cb750 rear. And got the following result.

spokes too big. So either ebay sent me the wrong size or someone changed the wheel at some point (I guess).

I assume this isn't fixable.... So I either buy smaller spokes or bigger rim. Would you guess I need 1" bigger rim?

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Offline MoMo

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Re: New to building. Like really new. Like moron new.
« Reply #5 on: June 24, 2013, 08:18:21 AM »
Look like spokes for an 18" rear wheel, you have 17...Larry
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Offline Jeff750

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Re: New to building. Like really new. Like moron new.
« Reply #6 on: June 24, 2013, 08:22:39 AM »
Thanks Larry! I'll find me a 18". Hopefully not everything will fight me on this bike.

I want to keep her low. I'm on the shorter side, 5'8". Would 300mm springs be the best way to go or a smaller wheel? Or both?
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Offline MoMo

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Re: New to building. Like really new. Like moron new.
« Reply #7 on: June 24, 2013, 09:19:21 AM »
If  you want the bike lower stick with the stock 17, you can raise the forks up a bit in the triple tree to lower the front...Larry
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Offline iron_worker

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Re: New to building. Like really new. Like moron new.
« Reply #8 on: June 24, 2013, 09:42:05 AM »
I would double, triple, and quadruple check that you have the spoke pattern correct first before finding a new wheel. I thought I had the wrong size spokes for a while too ... but later realized I just didn't have them angled as much as they should which makes them appear too long.

IW
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Offline Jeff750

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Re: New to building. Like really new. Like moron new.
« Reply #9 on: June 26, 2013, 05:25:47 AM »
Thanks again fellas for all the help!

Presently degreasing the engine and going to paint it black.

How about this for a question: I found the following picture on Kijiji, $50 for a '72 CB550 tank..... how much effort would it be to make that fit on my '77 CB750? I really dislike the shape of my present tank.

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Offline knowsnothing

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Re: New to building. Like really new. Like moron new.
« Reply #10 on: June 26, 2013, 06:41:47 AM »
550 tank will take some work and the seat will need some work to make it line up.

If i were you, I would hold out and wait for another year 750k tank (69-76) or even a 750f tank (75-78).  The k tanks are pretty much a direct swap.  The f tanks will require you to mess with the seat since they are a few inches longer. 
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1978 CB750k Green - 811 engine
1978 CB750k Blue - for sale
1974 CB375F Faded Black - had to have that 6th gear
1976 CB400F Red - in many pieces
1973 CB350F TBD - in many pieces

Offline Jeff750

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Re: New to building. Like really new. Like moron new.
« Reply #11 on: June 26, 2013, 10:08:55 AM »
Thanks for the tip!
I'll do the 750k idea!

Now just to find one.
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Offline knowsnothing

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Re: New to building. Like really new. Like moron new.
« Reply #12 on: June 26, 2013, 11:33:03 AM »
Just an FYI, you will need a petcock too.  The one you have for the k8 tank won't fit.
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1978 CB750k Green - 811 engine
1978 CB750k Blue - for sale
1974 CB375F Faded Black - had to have that 6th gear
1976 CB400F Red - in many pieces
1973 CB350F TBD - in many pieces

Offline jneuf

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Re: New to building. Like really new. Like moron new.
« Reply #13 on: June 26, 2013, 01:08:57 PM »
Call me crazy, but I don't even think that's a cb550 tank. Looks like a 400f tank to me as it's squared off in the back and has the raised ridge running up the centre.
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'75 CB400f

Offline Bankerdanny

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Re: New to building. Like really new. Like moron new.
« Reply #14 on: June 26, 2013, 03:10:17 PM »
I agree, that does look like a 400 tank. The 74-76 550K tanks have are much more oval shaped with a slightly offset exterior filler. The F models and 77-78 K models have a centered filler hidden under a door.
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Current: '76 CB750F. Previous:  '75 CB550F, 2007 Yamaha Vino 125 Scooter, '75 Harley FXE Superglide, '77 GL1000, '77 CB550k, '68 Suzuki K10 80, '68 Yamaha YR2, '69 BMW R69S, '71 Honda SL175, '02 Royal Enfield Bullet 500, '89 Yamaha FJ1200

Offline Jeff750

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Re: New to building. Like really new. Like moron new.
« Reply #15 on: June 28, 2013, 05:48:48 AM »
As I was cleaning the engine I got an urge to see what was under the dynamo cover. Oil, still more oil pours out.

I wanted to see if the pistons would move. Tried turning the AC generator mounting bolt and was happy to hear things moving around in the top end.

It will only turn 1/4 the way around before it starts undoing the bolt (this is normal correct?). If so, I'll just button it up with a new gasket and carry on my way.

Thanks again for all the help fellas. I think I'm about 3 hours in to that whole "10,000 hours to make you an expert" thing.
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Offline mrrch

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Re: New to building. Like really new. Like moron new.
« Reply #16 on: June 28, 2013, 01:54:50 PM »
Don't worry, the oil does circulate through the alternator.
Normal
Your center bolt is too loose, should not come loose when turning over the engine.
Sparkplugs are out when you turn it over?
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my build

1977 CB750K WITH 1976 CB750F ENGINE

Offline Jeff750

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Re: New to building. Like really new. Like moron new.
« Reply #17 on: June 28, 2013, 04:46:43 PM »
Ummm nope... I take it they should be?
 ???

Time for a beer
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Offline UncleD

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Re: New to building. Like really new. Like moron new.
« Reply #18 on: June 28, 2013, 09:07:58 PM »
Welcome to the forum! You'll meet lots of knowledgeable people here that will be happy to help and give advice.
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Offline Jeff750

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Re: New to building. Like really new. Like moron new.
« Reply #19 on: June 30, 2013, 08:14:02 AM »
So what do you do when this happens?
Happy Canada Day!
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Offline Jeff750

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Re: New to building. Like really new. Like moron new.
« Reply #20 on: June 30, 2013, 09:01:51 AM »
One plug came out nicely. The other left half in the hole
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Offline D-Ral

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Re: New to building. Like really new. Like moron new.
« Reply #21 on: June 30, 2013, 09:39:43 AM »
Ooh. Yuck.
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Offline Jeff750

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Re: New to building. Like really new. Like moron new.
« Reply #22 on: June 30, 2013, 09:55:17 AM »
Well that's not encouraging.
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Offline D-Ral

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Re: New to building. Like really new. Like moron new.
« Reply #23 on: June 30, 2013, 11:23:54 AM »
Ha ha. Don't listen to me. Where there's a will there's a way.
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Offline Jeff750

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Re: New to building. Like really new. Like moron new.
« Reply #24 on: June 30, 2013, 12:05:43 PM »
Time to take the jugs off?
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