Author Topic: CB750 K3F - AKA The Red  (Read 118587 times)

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Offline 70CB750

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Re: CB750 K3F
« Reply #325 on: April 23, 2015, 02:42:34 PM »
The #$%* always flies from the side you are not expecting it. I was not sure about the head, pucks, charging system but I would never imagine I will have to pull the engine because of transmission. It just simply does not shift from 2nd up.

Fork? Who knows.

Offline calj737

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Re: CB750 K3F
« Reply #326 on: April 23, 2015, 04:10:19 PM »
At way to peek up her skirt from underneath? Maybe something visually can be confirmed. Doubtful since the gears are so far back, but who knows-
'74 550 Build http://forums.sohc4.net/index.php?topic=126401.0
'73 500 Build http://forums.sohc4.net/index.php?topic=132935.0

"Of all tyrannies, a tyranny sincerely exercised for the good of it's victim may be the most oppressive. It may be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated, but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience." - C.S. Lewis

Offline edwardmorris

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Re: CB750 K3F
« Reply #327 on: April 23, 2015, 06:39:01 PM »
Bottom end can be taken apart without messing with the top end as long as you don't need to touch the crank. Sorry for your troubles, hopefully it'll get sorted soon.

Offline 70CB750

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Re: CB750 K3F
« Reply #328 on: April 24, 2015, 02:57:18 AM »
Yeah, that's the plan.   Pull the engine, flip it over and open it up.

Offline Roach Carver

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Re: CB750 K3F
« Reply #329 on: April 24, 2015, 04:04:31 AM »
Doesn't shift at all? It's not the shift mechanism under the cover on the left is it?

Offline 70CB750

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Re: CB750 K3F
« Reply #330 on: April 24, 2015, 04:10:30 AM »
With engine off, I can get it to all 5 gears.  It involves some wheel rocking.

But on the road it only has 1 and 2, never goes to 3rd.

Offline Kickstart

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Re: CB750 K3F
« Reply #331 on: April 26, 2015, 07:15:10 PM »
Argh... sorry to hear that Prokop.

Does it make any noise when you try to go into third, like a clunking or clattering noise?

I had to open my engine back up... I threw together this upside down stand, that worked out nicely. 
http://forums.sohc4.net/index.php/topic,107713.msg1642736.html#msg1642736
It made it a easier to flip the engine over (still had my son help), and I was able to access both sides while it was upside down so I didn't have to flip back over to bolt the fasteners on the top half when putting the cases back together.


- Chris
75' CB750F Orange flake (rider)
75' CB750F Blue (Project)
75' CB750F Painted black (Project)
No Reserve Racing #171 AHRMA

Offline 70CB750

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Re: CB750 K3F
« Reply #332 on: April 27, 2015, 02:45:43 AM »
That's a neat idea, Chris, thank you.

No it makes no noise, the lever just stops dead and what it seems little short of actually shifting.

Offline turkey4me

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Re: CB750 K3F
« Reply #333 on: April 27, 2015, 06:26:44 AM »
If you need any parts, I have an F3 bottom end that I'm parting out.  Hopefully you sort out your gearing.

Offline 70CB750

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Re: CB750 K3F
« Reply #334 on: April 27, 2015, 06:37:09 AM »
If you need any parts, I have an F3 bottom end that I'm parting out.  Hopefully you sort out your gearing.

I will take any of these parts:



I still believe it is in the shifting mechanism somewhere.

Thanks!

Offline 70CB750

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Re: CB750 K3F
« Reply #335 on: April 30, 2015, 04:03:11 AM »
I cleaned and polished all the shifting linkage, it made no difference. 

On the positive side, she is charging when she runs.

I will need to pull the engine, there must be something wrong.

Offline MoMo

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Re: CB750 K3F
« Reply #336 on: April 30, 2015, 02:39:58 PM »
^ :(   I have not touched my Red Rider 750 with the F motor because of a shifting problem  in 4th gear >:(  Good luck with it Prokop

Offline 70CB750

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Re: CB750 K3F
« Reply #337 on: May 03, 2015, 08:37:04 AM »
There she is. Double o-rings under neutral switch solved the shifting problems and she shifts like new.

Offline seanbarney41

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Re: CB750 K3F
« Reply #338 on: May 03, 2015, 09:15:55 AM »
Glad to hear you figured it out.  Bike looks good...how about some more pics.
If it works good, it looks good...

Offline Stev-o

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Re: CB750 K3F
« Reply #339 on: May 03, 2015, 09:56:52 AM »
Looks great, good to hear shes a shifter.  Nomming you for BOTM....
'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline SOHC4 Cafe Racer Fan

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Re: CB750 K3F
« Reply #340 on: May 03, 2015, 11:39:53 AM »
Seconded.  Please post your acceptance of the nomination in the BOTM Nomination thread: 

http://forums.sohc4.net/index.php/topic,147381.0.html
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 70CB750

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Re: CB750 K3F
« Reply #341 on: May 03, 2015, 01:15:41 PM »

Looks great, good to hear shes a shifter.  Nomming you for BOTM....

I am honored, Stev-o, but Comstars and BOTM?  LOL!

Anyway, accepted. Will have detail pictures and a story in few days.

Offline Stev-o

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Re: CB750 K3F
« Reply #342 on: May 03, 2015, 02:24:13 PM »

Looks great, good to hear shes a shifter.  Nomming you for BOTM....

I am honored, Stev-o, but Comstars and BOTM?  LOL!


Hey, ya never know?!  Black rims have won and Sam hated them!
'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline SOHC4 Cafe Racer Fan

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Re: CB750 K3F
« Reply #343 on: May 03, 2015, 06:33:46 PM »
Not all Comstars are bad.  I confess they've grown on me a little over the years.  Still haven't put any on a bike.
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 Retro Rocket

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Re: CB750 K3F
« Reply #344 on: May 03, 2015, 06:40:07 PM »
Not all Comstars are bad.  I confess they've grown on me a little over the years.  Still haven't put any on a bike.

I like the boomerang comstars we got on the boldor series bikes... ;)
750 K2 1000cc
750 F1 970cc
750 Bitsa 900cc
If You can't fix it with a hammer, You've got an electrical problem.

Offline SOHC4 Cafe Racer Fan

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Re: CB750 K3F
« Reply #345 on: May 03, 2015, 06:41:23 PM »
The reverse Comstars are better than ok.  I like the wheels on this bike.
« Last Edit: May 03, 2015, 07:40:38 PM by CB750 Cafe Racer Fan »
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 Kickstart

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Re: CB750 K3F
« Reply #346 on: May 03, 2015, 07:39:18 PM »
Great news!

Looking great... I like the way the comstars look on your bike.

Just curious... how did the double o-rings on the neutral switch cause the shifting problem... and was the neutral light always on?

- Chris
75' CB750F Orange flake (rider)
75' CB750F Blue (Project)
75' CB750F Painted black (Project)
No Reserve Racing #171 AHRMA

Offline 70CB750

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Re: CB750 K3F
« Reply #347 on: May 04, 2015, 02:55:57 AM »
Great news!

Looking great... I like the way the comstars look on your bike.

Just curious... how did the double o-rings on the neutral switch cause the shifting problem... and was the neutral light always on?

The double O-ring actually allowed me to shift all the way up and down and smoothly.  It tells me the problem is somewhere around the switch seating, but the shifting forks are - as far as I dare to say - okay.

Will try different switch now.

Offline MoMo

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Re: CB750 K3F
« Reply #348 on: May 04, 2015, 05:08:12 AM »
You think the switch was down too far and binding against the drum? Extra O-ring raised it enough to prevent that?  Interesting fix, may try the same on the F engine in my K4...Larry

Offline 70CB750

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Re: CB750 K3F
« Reply #349 on: May 04, 2015, 05:24:52 AM »
You think the switch was down too far and binding against the drum? Extra O-ring raised it enough to prevent that?  Interesting fix, may try the same on the F engine in my K4...Larry

I suspect the shoulder of the switch against the drum groove edges, just dragging little bit. 

But I polished the switch  and gthere was no witness mark on it.