Author Topic: Frame mod cb 750  (Read 35387 times)

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Offline ianmck

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Frame mod cb 750
« on: December 15, 2009, 05:14:29 am »
Can anyone please help, I'm thinking about doing the frame mod on my K4, (to make it possible to do top end engine work without removing the complete motor). Firstly is it a safe and acceptable mod, secondly has anyone got any info, (tech drawings/measurements) or point me in the right direction to find some help to get parts made, and general instructions to complete the mod.
Regards ianmck.
1977 400/4 supersport,  1973 CB750 K4

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Re: Frame mod cb 750
« Reply #1 on: December 15, 2009, 05:17:26 am »
Can anyone please help, I'm thinking about doing the frame mod on my K4, (to make it possible to do top end engine work without removing the complete motor). Firstly is it a safe and acceptable mod, secondly has anyone got any info, (tech drawings/measurements) or point me in the right direction to find some help to get parts made, and general instructions to complete the mod.
Regards ianmck.
Many of us have done this. I used an old APE kit no longer available. One of our members engineered a much better solution and was selling them but I don't know the inventory status.

Search "frame repair kit" "frame modifications" and the like for pictures, and discussion. Others may chime in with the links.
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1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
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Offline ianmck

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Re: Frame mod cb 750
« Reply #2 on: December 16, 2009, 07:44:33 am »
Thanks MCRider, have tried the searches you suggested, only reference I could find was a kit supplied by "GORDON", some years ago, but from what I can see he no longer does them. So if there are any other members with any idea's I would be very grateful.
Regards ianmck.
1977 400/4 supersport,  1973 CB750 K4

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Re: Frame mod cb 750
« Reply #3 on: December 16, 2009, 07:54:01 am »
Thanks MCRider, have tried the searches you suggested, only reference I could find was a kit supplied by "GORDON", some years ago, but from what I can see he no longer does them. So if there are any other members with any idea's I would be very grateful.
Regards ianmck.
Yes it was Gordon's kit.  You can study how he did it.

I'll dig up a picture of my APE kit which is much easier to duplicate, though not as robust as Gordon's. I've run the APE kit since 1980 on a 888cc touring CB750 which was often overloaded and run very hard. I never had a problem and I'm sensitive to wiggle issues.

Big Jay from APE is a sponsor of this site and has said they sold (tens of?) thousands of them back in the day.

Post a want ad in the classifieds here for a Gordon Kit. Someone may have one they haven't used and would sell.
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1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline Yoshi823

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Re: Frame mod cb 750
« Reply #4 on: December 16, 2009, 08:00:56 am »
I did this to my 750F2 frame, and it made things a lot easier to service the top end.



I'll dig out some more piccies when I can find them.


« Last Edit: December 16, 2009, 08:03:18 am by Yoshi823 »
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Re: Frame mod cb 750
« Reply #5 on: December 16, 2009, 08:03:27 am »
Yoshi, your modificatio is way cool! A lot like the CB750A chasis, I'm sure you've been told.

Does it interfere with a stock gas tank? Looks like it might.

had I the wherewithal to make a change like that I'd change the tank too. Very nice work.
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1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline ianmck

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Re: Frame mod cb 750
« Reply #6 on: December 16, 2009, 08:25:23 am »
Yoshi, I like the look of your mod, any details of how you did it,  measurements, what tubes you used, where you welded etc ?
Regards ianmck.
1977 400/4 supersport,  1973 CB750 K4

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Re: Frame mod cb 750
« Reply #7 on: December 16, 2009, 09:22:24 am »
Here's a pic of the APE kit


Ignore the cam cover, the tube replacement kit is above. Essentially you have 2 tubes the same diameter as stock frame rails, and 4 slider bits which are a real tight fit to the replacement tube.

You cut your tubes out just a tad longer than the replacement tubes. The closer to exact the better. But you need to cut far enough forward to get the head off. That's about 2-3 in back from the front downtube. Then slide a slider onto each end of the replacement tube, set the tube into the space you have opened up in your frame rail now, slide the sliders out to cover the stubs of your original frame tubes.

The slider will be half on the old tube, half on the replacement tube. The sliders came with holes in them. Drill the stubs and the replacement tube and bolt the sliders into place. You're done.

There is no provision for replacing the triangle portion of the original frame which is also removed by you when cutting the tubes.

A machinist would be able to recreate this setup quickly I'd think.

« Last Edit: December 16, 2009, 09:27:12 am by MCRider »
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Re: Frame mod cb 750
« Reply #8 on: December 16, 2009, 09:31:22 am »
While i've never had an nth of troube with this, I've since added some triangulation on my new project:


I'm the first to admit this is not as robust or elegant as the Gordon kit or what Yoshi has done. But it is quick and I think effective.
« Last Edit: December 16, 2009, 09:49:48 am by MCRider »
Ride Safe:
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1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline ianmck

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Re: Frame mod cb 750
« Reply #9 on: December 16, 2009, 10:32:35 am »
MCRider thank you, you are a diamond.
Regards ianmck.
1977 400/4 supersport,  1973 CB750 K4

Offline RRRToolSolutions

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Re: Frame mod cb 750
« Reply #10 on: December 16, 2009, 05:51:33 pm »
Guys, there is a board member who wants to make my kit and have them for sale again. I have one set that I'm going to send him along with the drawings and instructions. He will take these to his machine shop and start pumping them out soon - shortly after the holidays.

You guys start making a list of who wants them -

Best Regards,
Gordon

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Offline Don R

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Re: Frame mod cb 750
« Reply #11 on: December 16, 2009, 06:44:13 pm »


This is the kit on my 70 750. it is only tack welded here. This works but I do like the way Yoshi did his, it looks like a DOHC frame. either way it is nice to be able to pull the head off.
« Last Edit: December 16, 2009, 06:48:37 pm by Don R »
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Offline Yoshi823

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Re: Frame mod cb 750
« Reply #12 on: December 17, 2009, 04:42:14 am »
The tank was a special...


built to the contours of the new frame mods, by the person who made them for the Phil Read Replica and the Honda 750SS...


But the frame did start out as a standard F2 item. I bought some Reynolds 531 tubing and bent them into shape using a hydraulic tube bender whilst at work (electronics engineer by trade!). I then had them welded into place, with the rear of the two main tubes sliding over the existing rails that go from the front to the back of the bike.Because it was small amounts of welding, the heat was localised and so the frame didn't distort. I must admit though that I didn't know if it would work, so I went to the pub and had a few beers before attacking the frame with a hacksaw.This is during the stripdown process...


Bikes...they're in the blood.

Yamaha 2001 R1
Yamaha 1990 FZR1000R EXUP
KTM 2004 450 EXC RFS
Honda 1997 XR400R
Honda 1988 CB125T2

http://www.cb750cafe.com/bikes.php?cat=3&id=67

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Re: Frame mod cb 750
« Reply #13 on: December 17, 2009, 05:54:29 am »
Yoshi: Again, nicely done!
Ride Safe:
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1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
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Offline HedNut

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Re: Frame mod cb 750
« Reply #14 on: December 17, 2009, 06:07:25 am »
Guys, there is a board member who wants to make my kit and have them for sale again. I have one set that I'm going to send him along with the drawings and instructions. He will take these to his machine shop and start pumping them out soon - shortly after the holidays.

You guys start making a list of who wants them -

Best Regards,
Gordon




As Gordon said,  I'll be getting these going after the holidays ASAP.  Let me know who is interested and we can Ressurect and make plenty available, the "GORDON FRAME KIT"...together!

Cheers! And happy holidays!!

Offline oldfett

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Re: Frame mod cb 750
« Reply #15 on: December 17, 2009, 10:25:42 am »

As Gordon said,  I'll be getting these going after the holidays ASAP.  Let me know who is interested and we can Ressurect and make plenty available, the "GORDON FRAME KIT"...together!

Cheers! And happy holidays!!

Let me know when these get under way and I'll take one!

Offline paddy paul

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Re: Frame mod cb 750
« Reply #16 on: December 17, 2009, 02:26:02 pm »
Put me down for 1, any idea what kind of price we will be looking at?  Thanks

Offline HedNut

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Re: Frame mod cb 750
« Reply #17 on: December 18, 2009, 05:11:17 am »
I'm not exactly sure about the price yet...once I recieve it I will be getting quotes from 7-8 different machinists/shops I deal with to get the best price (they all do excellent quality work for the company)  My intention is not to make any money, just cover my costs of hardware, running around and just really get the kit back out there!  The more I order at one time...the cheaper I'll be able to get them done.

Cheers Guys!  Keep the names coming!  I'll start a list...and you'll be the first to know when I do!

Offline bucky katt

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Re: Frame mod cb 750
« Reply #18 on: December 18, 2009, 01:07:21 pm »
heres one installed
Of all God's creatures there is only one that cannot be made the slave of the lash. That one is the cat. If man could be crossed with the cat it would improve man, but it would deteriorate the cat.
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Offline ianmck

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Re: Frame mod cb 750
« Reply #19 on: December 20, 2009, 11:47:28 am »
I know it's on here somewhere, but can't find it, and can't remember, (I think it's an age thing), can someone remind me what the nuts and threaded bits are for on "gordons" frame mod kit ?
Regards ianmck, (I think).
1977 400/4 supersport,  1973 CB750 K4

Offline wannabridin

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Re: Frame mod cb 750
« Reply #20 on: January 07, 2010, 03:39:12 pm »
hednut,

i'm down for one, so put me on the list.  what are the updates?  do you know when they'll be available and for how much?  let me know when you can, as i'm sure plenty of people would be down for purchasing one if they knew about it a little more!  hopefully under $200?
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Offline RRRToolSolutions

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Re: Frame mod cb 750
« Reply #21 on: January 07, 2010, 06:14:51 pm »
Ian, I wanted to keep everything hidden up under the factory/stock tank. That meant being able to mount the ignition switch in the stock location. If you simply welded those 1/2 joints solid to the front, then you would not have room for the valve cover and cylinder head to come off. The solution I found was to weld-in a blind solid insert with internal threads. Then you can remove the 1/2 joint completely and have unrestricted access to the top-end. Some folks thought that threaded rod and locknut was for adjustment - not at all. It allows removal of the entire joint itself. It is also 180,000 PSI machine threaded steel (not some cheap ready-rod, grade 3 crap). Once you remove the center section, you simply thread each 1/2 joint into the front and use the supplied locknut to make it ridgid (rears are welded-in). As others have said - this kit keeps the frame ridgid by using heavy-duty parts and keeping the triangulation in-tact. I assure you that you won't be able to see under a stock tank - even if you get on your knees - it's hidden.

Here is the bike I built this frame kit for. A stock looking sleeper was my goal, but I had to have access without anyone seeing my work. Underneath is a screaming 836cc with ported heads, titanium valvetrain, Mega cam, heavy studs - upper and lower, and Carrilo rods to hold her together.

I hope this clears it up -

Regards,
Gordon







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Offline bucky katt

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Re: Frame mod cb 750
« Reply #22 on: January 07, 2010, 06:28:26 pm »
man o man that bike does sound good too.
Of all God's creatures there is only one that cannot be made the slave of the lash. That one is the cat. If man could be crossed with the cat it would improve man, but it would deteriorate the cat.
Mark Twain - Notebook, 1894

Offline RRRToolSolutions

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Re: Frame mod cb 750
« Reply #23 on: January 07, 2010, 07:28:36 pm »
It has absolutely nothing to do with the frame kit, but here it is making a racket at 11,000 rpm.

Gordon

http://www.vholdr.com/node/49293

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Offline wannabridin

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Re: Frame mod cb 750
« Reply #24 on: January 07, 2010, 07:37:18 pm »
It has absolutely nothing to do with the frame kit, but here it is making a racket at 11,000 rpm.

Gordon

http://www.vholdr.com/node/49293



i've seen that vid before, but it never gets old!!  damn nice bike you have there my man!!  i wish i had the money to make mine scream like that...  hopefully i can get well build 836 put together this year
1976 CB750K, currently under construction:
http://forums.sohc4.net/index.php?topic=64468.0

-And if you don't do it this year, you'll be one year older when you do...

 

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