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Author Topic: 1974 cb750 fun "Spruce Goose" (STEP 2: frame/suspension)  (Read 28366 times)

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Offline mashfu

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1974 cb750 fun "Spruce Goose" (STEP 2: frame/suspension)
« on: November 07, 2015, 12:35:46 PM »
Picked up a 1974 cb750 frame a few weeks ago and its missing just about everything. Let the fun time begin! After looking around and finding  out more about the bike, ive found its a k4 frame with an f0 engine. Once i get the engine back to working condition ill worry about the frame, wiring, and suspension...
« Last Edit: August 07, 2020, 04:44:40 AM by Glenn Stauffer »
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Offline mashfu

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Re: 1974 cb750 fun
« Reply #1 on: November 07, 2015, 12:41:49 PM »
So far ive got the engine unseized, got the case cracked, and finally got the evil kick start pin to get out... Time for some loving over the weekend.
« Last Edit: August 07, 2020, 04:46:01 AM by Glenn Stauffer »
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Offline mashfu

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Re: 1974 cb750 fun
« Reply #2 on: November 07, 2015, 12:42:55 PM »
More
« Last Edit: August 07, 2020, 04:47:29 AM by Glenn Stauffer »
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Offline mashfu

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Re: 1974 cb750 fun
« Reply #3 on: November 07, 2015, 12:52:55 PM »
Bottom half soaking in the hot tub. Was not able to get the shifter screw out for fear of stripping it so i will be leaving them in along with the gears.
« Last Edit: August 07, 2020, 04:48:12 AM by Glenn Stauffer »
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Offline mashfu

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Re: 1974 cb750 fun
« Reply #4 on: November 07, 2015, 04:18:00 PM »
Currently dipping the pistons in chem-dip,  next will probably leave the connecting rods in there as well
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Offline Davez134

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1974 cb750 fun
« Reply #5 on: November 07, 2015, 10:25:47 PM »
Quote from: mashfu on November 07, 2015, 12:35:46 PM
Picked up a 1974 cb750 frame a few weeks ago and its missing just about everything.
Nice project, good start! And it's not missing everything. This was missing everything!



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Offline 70CB750

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Re: 1974 cb750 fun
« Reply #6 on: November 08, 2015, 03:53:36 AM »
Quote from: mashfu on November 07, 2015, 12:52:55 PM
Bottom half soaking in the hot tub. Was not able to get the shifter screw out for fear of stripping it so i will be leaving them in along with the gears.

I would make the effort to get it out too. You dont want to be stuck with shiftin problems when it is all together.
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Offline mashfu

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Re: 1974 cb750 fun
« Reply #7 on: November 08, 2015, 11:59:13 AM »
Quote
Nice project, good start! And it's not missing everything. This was missing everything!

Holy ok ya Dave you win haha. I have a feeling i will attempt something along those lines after i get this baby running!
Quote

I would make the effort to get it out too. You dont want to be stuck with shiftin problems when it is all together.
Alright 750 ill give it another go. Hopefully this time it isn't as stubborn!
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Offline mashfu

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Re: 1974 cb750 fun
« Reply #8 on: November 08, 2015, 12:32:19 PM »
Are these pistons ok to use if i clean them up a bit more or should i get a new set?
« Last Edit: August 07, 2020, 04:49:19 AM by Glenn Stauffer »
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Offline 70CB750

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Re: 1974 cb750 fun
« Reply #9 on: November 09, 2015, 04:29:57 AM »
Quote from: mashfu on November 08, 2015, 12:32:19 PM
Are these pistons ok to use if i clean them up a bit more or should i get a new set?

They are good.
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Prokop
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I love it when parts come together.

Dorothy - my CB750
CB750K3F - The Red
Sidecar


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Offline calj737

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Re: 1974 cb750 fun
« Reply #10 on: November 09, 2015, 04:31:09 AM »
Quote from: 70CB750 on November 09, 2015, 04:29:57 AM
They are good if they measure within spec to the bore. Pictures don't tell the whole tale...
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Offline mashfu

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Re: 1974 cb750 fun
« Reply #11 on: November 09, 2015, 10:10:49 AM »
Will double check sometime this week. Still need to clean out cylinders from all the rust that accumulated from previous owner. Hopefully they stay within spec after that
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Offline edwardmorris

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Re: 1974 cb750 fun
« Reply #12 on: November 09, 2015, 10:22:28 AM »
I'm not sure what you're referring to by "Shifter Screw". If you're referring to the shift drum, then yes, make an effort to get it out and cleaned up along with the rest of the trans. If you're referring to the screw that goes into the shift drum holding the pins and plates together, DO NOT TOUCH IT. Trust me on that one ;)

A heat gun will help immensely with stubborn and rusted parts like steel dowels in aluminum cases etc. When cleaning the piston sleeves, be sure to immediately fog them with some WD-40 or cover with light oil, these will flash rust otherwise. Pistons if cleaned up well and still within specs are ok to reuse. Do you have Hondaman's book? I'd highly recommend grabbing a copy as it goes through all this critical inspection stuff in detail.
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Offline SOHC4 Cafe Racer Fan

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Re: 1974 cb750 fun
« Reply #13 on: November 09, 2015, 11:39:27 AM »
Quote from: mashfu on November 08, 2015, 12:32:19 PM
Are these pistons ok to use if i clean them up a bit more or should i get a new set?

I agree that you should get them measured.  If they are within spec to the bore, then you should also get a new set of rings.
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1975 CB550K1 "Blue" Stockish Restomod (http://forums.sohc4.net/index.php?topic=135005.0)
1975 CB550F1 frame/CB650 engine hybrid "The Hot Mess" (http://forums.sohc4.net/index.php/topic,150220.0.html)
2008 Triumph Thruxton (http://forums.sohc4.net/index.php/topic,190956.0.html)
2014 MV Agusta Brutale Dragster 800
2015 Yamaha FZ-09 (http://forums.sohc4.net/index.php/topic,186861.0.html)

"There are some things nobody needs in this world, and a bright-red, hunch-back, warp-speed 900cc cafe racer is one of them — but I want one anyway, and on some days I actually believe I need one.... Being shot out of a cannon will always be better than being squeezed out of a tube. That is why God made fast motorcycles, Bubba." Hunter S. Thompson, Song of the Sausage Creature, Cycle World, March 1995.  (http://www.latexnet.org/~csmith/sausage.html and https://magazine.cycleworld.com/article/1995/3/1/song-of-the-sausage-creature)

Sold/Emeritus
1973 CB750K2 "Bionic Mongrel" (http://forums.sohc4.net/index.php?topic=132734.0) - Sold
1977 CB750K7 "Nine Lives" Restomod (http://forums.sohc4.net/index.php?topic=50490.0) - Sold
2005 RVT1000RR RC51-SP2 "El Diablo" - Sold
2016+ Triumph Thruxton 1200 R (http://forums.sohc4.net/index.php/topic,170198.0.html) - Sold

Offline mashfu

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Re: 1974 cb750 fun
« Reply #14 on: November 09, 2015, 03:09:49 PM »
Quote from: edwardmorris on November 09, 2015, 10:22:28 AM
If you're referring to the screw that goes into the shift drum holding the pins and plates together, DO NOT TOUCH IT. Trust me on that one ;)


Haha ya i was talking about that screw! Looked at  the shop manual a bit today and realized i did not touch the neutral stopper so that might be the reason it didn't want to come out. Once i get home thats the first thing i am going to do!
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Offline edwardmorris

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Re: 1974 cb750 fun
« Reply #15 on: November 09, 2015, 03:50:27 PM »
Quote from: mashfu on November 09, 2015, 03:09:49 PM
Quote from: edwardmorris on November 09, 2015, 10:22:28 AM
If you're referring to the screw that goes into the shift drum holding the pins and plates together, DO NOT TOUCH IT. Trust me on that one ;)


Haha ya i was talking about that screw! Looked at  the shop manual a bit today and realized i did not touch the neutral stopper so that might be the reason it didn't want to come out. Once i get home thats the first thing i am going to do!
Yes, the drum will slide out once the neutral switch is out. There is a rubber seal holding it snug so it may not be easy. Use tons of PB blaster or some other penetrating lube, then try and press it down from inside the case. All this of course AFTER you remove the small metal plate that is holding it in place with a bolt on the outside of the case.
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Offline mashfu

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Re: 1974 cb750 fun
« Reply #16 on: November 09, 2015, 08:47:01 PM »
And they're outta there! Makes it so much easier to clean... Definitely glad you guys convinced me to take them out!
« Last Edit: August 07, 2020, 04:50:30 AM by Glenn Stauffer »
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Offline edwardmorris

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Re: 1974 cb750 fun
« Reply #17 on: November 09, 2015, 09:31:41 PM »
Quote from: mashfu on November 09, 2015, 08:47:01 PM
And they're outta there! Makes it so much easier to clean... Definitely glad you guys convinced me to take them out!
I hope we can convince you to grab a copy of Mark's book. You don't want to be guessing or chancing anything only to have it torn open again later...just my 2c ;)
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Offline mashfu

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Re: 1974 cb750 fun
« Reply #18 on: November 10, 2015, 08:50:43 AM »
That book keeps popping up, it must mean its meant to be!
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Offline Davez134

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Re: 1974 cb750 fun
« Reply #19 on: November 10, 2015, 09:16:28 AM »
Quote from: mashfu on November 10, 2015, 08:50:43 AM
That book keeps popping up, it must mean its meant to be!

It is worth it. It will answer so many questions that you don't even know you have yet. And guarantee you won't overlook something important.
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Offline mashfu

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Re: 1974 cb750 fun
« Reply #20 on: November 14, 2015, 09:41:45 AM »
While waiting for the hondaman bookn i decided to get the stuck rings out of my pistoms... They were really stuck and ended up chipping the sides a bit. Time to measure everything out and clean!
« Last Edit: November 14, 2015, 10:01:40 AM by mashfu »
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Offline mashfu

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Re: 1974 cb750 fun
« Reply #21 on: November 14, 2015, 05:22:49 PM »
Decided to start honing out the cylinders and get out some of the rust that built up when the p/o let the bike sit, when i got to number 3 i started honing and after a bit i noticed the walls have been pitted. From what ive measured i still have a few more hundredths mm to play around with before they go over the 61.1mm diameter tolerance. Hopefully it will smoothen out or else I'm just going to order a used one off ebay.
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Offline mashfu

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Re: 1974 cb750 fun
« Reply #22 on: November 14, 2015, 06:31:20 PM »
Alitrle more to go, and i think I'll be able to live with it
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Offline mashfu

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Re: 1974 cb750 fun
« Reply #23 on: November 15, 2015, 04:13:57 PM »
I was not sure what i wanted to get done today, so i just jumped around all over the place: made a connection for the compressor to spray some denatured alcohol for some cleaning, got some plastigage to check bearing clearance,  and decided might as well take out the valves. Everything was nice and tidey, until the valve came out... The gunk could be a small snack!
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Offline SOHC4 Cafe Racer Fan

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Re: 1974 cb750 fun
« Reply #24 on: November 15, 2015, 04:49:01 PM »
That's some gravy you got on that valve.

Looks like you had enough meat on the bone for your cylinders, though.
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1975 CB550K1 "Blue" Stockish Restomod (http://forums.sohc4.net/index.php?topic=135005.0)
1975 CB550F1 frame/CB650 engine hybrid "The Hot Mess" (http://forums.sohc4.net/index.php/topic,150220.0.html)
2008 Triumph Thruxton (http://forums.sohc4.net/index.php/topic,190956.0.html)
2014 MV Agusta Brutale Dragster 800
2015 Yamaha FZ-09 (http://forums.sohc4.net/index.php/topic,186861.0.html)

"There are some things nobody needs in this world, and a bright-red, hunch-back, warp-speed 900cc cafe racer is one of them — but I want one anyway, and on some days I actually believe I need one.... Being shot out of a cannon will always be better than being squeezed out of a tube. That is why God made fast motorcycles, Bubba." Hunter S. Thompson, Song of the Sausage Creature, Cycle World, March 1995.  (http://www.latexnet.org/~csmith/sausage.html and https://magazine.cycleworld.com/article/1995/3/1/song-of-the-sausage-creature)

Sold/Emeritus
1973 CB750K2 "Bionic Mongrel" (http://forums.sohc4.net/index.php?topic=132734.0) - Sold
1977 CB750K7 "Nine Lives" Restomod (http://forums.sohc4.net/index.php?topic=50490.0) - Sold
2005 RVT1000RR RC51-SP2 "El Diablo" - Sold
2016+ Triumph Thruxton 1200 R (http://forums.sohc4.net/index.php/topic,170198.0.html) - Sold
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