Author Topic: 1975 CB750F - Project Yellow Jacket (Read 59391 times)

DollarBill · « **Reply #75 on:** February 02, 2009, 02:26:18 PM »

Thinking about color schemes....the yellowish/orange will probably end up gold metallic. This design will be on the tank minus the 750f Yellow Jacket which will be on the side covers.

HavocTurbo · « **Reply #76 on:** February 02, 2009, 05:42:59 PM »

Very nice.... I like the multi line stripe.

Should be cool when you get it finished!!

DollarBill · « **Reply #77 on:** February 26, 2009, 07:47:43 AM »

Not a lot of visible progress on the Yellow Jacket but a lot of planning and buying of parts. I have always been very intrigued by mono-shock conversions but never wanted to wrestle with mounting points that would have to be fabricated right where the battery and oil tank are on my 750. Then comes along Honda engineers with the 07 CBR 600rr.... The newer swingarm has the rear shock fully incorporated into the swingarm. There is no upper mount to the frame. You have the pivot and the dogbone on the bottom that can be mounted to the existing center stand mount with some fabrication for mounts. One of the other things I was worried about with conventional monoshock systems was stresses on the frame. Here is some information from the 07 600rr press release about the new swingarm..

Integrated into the CBR’s rigid but lightweight swingarm is essentially the
same Unit Pro-Link rear suspension system pioneered on the race-winning
RC211V MotoGP racer. Its highly advanced design completely isolates the
frame from the shocks and stresses generated by conventional rear suspension
systems, especially under aggressive riding and racing conditions. This system
also eliminates the need for extra frame reinforcement to counter those stresses,
thus allowing the frame to be designed lighter than other more conventional
designs, while freeing up space to permit the lower, mid-chassis positioning of
the fuel tank, thus making another large contribution to mass centralisation and
superior riding control.

This was what inspired me to go ahead and try converting to the 600rr mono-shock. The shock sits much lower in the swingarm which will allow me to leave my stock oil tank where it is and the battery as well. The battery may be a tight fit and I may have to raise the battery tray 1/5 inch for adequate clearance of the swingarm. I also need to figure out the correct geometry for the dogbone mount.

The one thing that may bring this to a screeching halt is the swingarm pivot. The 600rr pivot is about 3/4 of an inch too wide to fit the 750 frame. I am taking the whole thing to a machinist tomorrow to see if it can be shaved down without sacrificing structural integrity. WE SHALL SEE!

As for the wheels... I originally was planning on using Nighthawk wheels but that idea is out the door if this swingarm works. If the swingarm works I will use CBR 600f2 wheels. The 600rr wheels are too wide and the 600f2 wheel can accommodate a 150 tire. I think this is doable with an offset sprocket. Again more research and measuring and fitting to be done....

The front suspension will be upgraded to 07 GSXR Forks.

Here are my new parts...

Wheels will be powdercoated gold.

And here is a rough sketch of what I am thinking...yeah the tires are a bit big and lumpy but hey, I'm just thinking out loud with a pen.

HavocTurbo · « **Reply #78 on:** February 26, 2009, 08:34:36 AM »

I am also going with mono-shock conversion.
Except I'm going to use a dirt swingarm I think. Still not sure though.

Any ideas on the geometry you are going to use for the rear?

DollarBill · « **Reply #79 on:** February 26, 2009, 08:42:23 AM »

Still doing research on the geometry. I'm not sure if mimicking the CBR setup would be adequate or not. Any experts with an opinion on that?

HavocTurbo · « **Reply #80 on:** February 26, 2009, 09:06:26 AM »

Well the CBR set-up is determined for that particular weight.

One thing to think about will be placement. Gas tank, engine tilt, battery and electrics, etc.

One thing I try to do is find the balance point in the frame and go from there. That allows you to formulate your geometry based on that particular bike.

http://www.tonyfoale.com/book.htm

These are great resources!!!

DollarBill · « **Reply #81 on:** February 26, 2009, 09:23:09 AM »

Ooo...this does look like good info. Thanks!

rachet · « **Reply #82 on:** February 26, 2009, 09:44:13 AM »

I don't think I've officially subscribed to this thread yet. Good Read and creative build.

Rach~

fastbroshi · « **Reply #83 on:** February 27, 2009, 05:34:40 AM »

Oh hell yeah, keep it up Bill, very cool. I have to say setting up a frame for a mono intimidates the hell outta me, don't know anything about it. Maybe I'll have to read up on that link posted there.

DollarBill · « **Reply #84 on:** February 27, 2009, 06:55:26 PM »

Took the swingarm and frame to a machinist today and he thought it would be easier to stretch the frame rather than mess with the swingarm. He didn't like the idea of the swingarm being hollow and cutting it down and patching it. He explained how these frames are meant to flex and that if we cut the bottom bar where the center stand is that we could probably pull it apart enough for the swingarm to fit and then make spacers for the engine mounts that get spread out a little bit. The other thing that surprised me was the GSXR 600 forks are the same length as my 750f forks. I spent a good bit of time today at a Honda dealership studying the 600rr swingarms and how they mount to the bikes. The salesman must have thought I was crazy crawling around on the floor looking under the bikes.

Here's the first mockup with the forks and the swingarm in place. The frame stretched about an inch at the pivot.

So, I reconnected with an old friend on Facebook and she was telling me one of our old friends owns a motorcycle shop now that builds custom bikes and frames. This news couldn't have come at a better time. I'm going to give him a call and haul this over and let him have a look at the frame.

I have to say the stretched tank really helps balance that whopper of a swingarm. I'm stoked about the possibilites....

dieselndixie · « **Reply #85 on:** March 01, 2009, 08:56:03 PM »

sweet, I'm in austin and watching this build for my 75 cb750f. are you cutting any tabs or rear peg brackets off of your frame?

keep up the info on the swingarm. are the fronts mounting up ok?

HavocTurbo · « **Reply #86 on:** March 01, 2009, 08:58:46 PM »

OOOFFF!!!

Where are you going to put the battery? Lot's of rear suspension in there.

DollarBill · « **Reply #87 on:** March 01, 2009, 09:07:56 PM »

There is a lot of suspension back there but nothing attaches in the area of the battery. I will need to move the battery box up about half an inch so it doesn't hit the shock from what I can tell so far. The battery box has some room to move up. What I like about this swingarm is the way they engineered the shock. What you see in the photo is everything.

The only issue I see right away is the shock resevoir. It might contact the frame so after a quick search I found that the shock for the 1000rr points straight back instead of to the side. Insert 1000rr shock and that problem is solved. If you look you can see the dogbone hanging down. That is the only other thing that needs to be mounted and it will mount to where the center stand is. I'll have to make some brackets for it but that's not hard.

dieselndixie, I did cut the rear triangle's off where the passenger pegs mount.

DollarBill · « **Reply #88 on:** March 01, 2009, 09:12:55 PM »

dieselindixie, the GSXR forks are not a bolt on item. The stem is the same length as the 750 but it is wider. I will either have the CB750 stem welded in to the GSXR triple or I will have a new stem turned and pressed in the GSXR triple. It won't be easy and it will cost a little bit of cash. The end result will be GSXR forks with a CB750 stem and able to use stock CB750 bearings or newer tapered bearings.

Regardless....somehow I am going to make this all work. Period.

HavocTurbo · « **Reply #89 on:** March 01, 2009, 09:16:20 PM »

What year gsxr?? You cannot weld steel to aluminum.... might need a custom press in stem. Been there done that. Lots of time needed.

Do you have any other shots of the arm? I'd be interested to see them.

Looks good so far.

DollarBill · « **Reply #90 on:** March 01, 2009, 09:29:11 PM »

Doh! You're right about the GSXR stem. It will have to be a press job. They are 07 600 forks... I'll try to get some more photos of the swingarm tomorrow.

Right now for me the frame is the biggest issue. Spreading that sucker 1" seems like a lot....but maybe not.

Thanks...it'll be an adventure for sure. And it is looking more and more like my other bike will be the sacrificial lamb to get this thing done before summer gets here. Hate to do it but I'm too impatient to make this a two year project.

Retro Rocket · « **Reply #91 on:** March 02, 2009, 04:33:21 AM »

I don't know if this will help but i used a gsxr 1100 K front end on my project 750/4 and the Honda stem pressed straight into the Suzuki clamps, it was a perfect fit.

Mick

andy750 · « **Reply #92 on:** March 02, 2009, 04:42:20 AM »

Keep going Dollar Bill - I cant wait to see this put together.

Retro - do you have a pic of your bike?

cheers
Andy

DollarBill · « **Reply #93 on:** March 02, 2009, 06:26:32 AM »

Hey retro... How much did you have to grind to get the stem out of the sohc lower clamp. I grinded about a quarter inch off the bottom of mine yeserday with no luck. Just eyeballing it though I don't think it will fit. The 07 GSXR stem is a good bit wider at the bottom. Probably going to have to have a new stem turned.

DollarBill · « **Reply #94 on:** March 02, 2009, 06:29:34 AM »

Here's the thing that was really bugging me about prying the frame to fit the swingarm. The engine would have to be offset. Talking to another cycle buddy he didn't think offsetting the engine was as big a deal as I do. Any thoughts on that?

HavocTurbo · « **Reply #95 on:** March 02, 2009, 10:07:02 AM »

Depends on how far off you are regarding the offset. Usually with offset front and rear sprockets you can get away with it.

You could always machine the swingarm.... I do that on occasion.

DollarBill · « **Reply #96 on:** March 02, 2009, 11:19:41 AM »

If I leave the engine in the center and use spacers then the drive sprocket will be even further inset from the rear sprocket. I can only remove material from the brake side because of where the chain guide lines up along the shock housing on the drive side. See attached image for reference. The swingarm is hollow aluminum filled with expanding foam so if you go more than a 1/4 inch in you will compromise that. Could it be patched/welded and still retain its structural integrity??? Havoc??

There may be a happy medium in removing a 1/4 inch from one side and offsetting the engine to the left so the sprockets line up easier.

Still going to be big challenge to make this work. If I do get it to work though it will kick ass and I think it will be worth it. I hope.

Retro Rocket · « **Reply #97 on:** March 03, 2009, 03:21:05 AM »

Quote

do you have a pic of your bike?

Mine is still being built.

I had the stem "pressed" out and it pressed straight into the GSXR clamps.

dieselndixie · « **Reply #98 on:** March 03, 2009, 07:56:10 PM »

can you list ( in a private message if this is considered a hijack) exactly what parts you got from the gsxr, and what year and everything it was?

i am so close to doing this, i just need some specifics.

DollarBill · « **Reply #99 on:** March 04, 2009, 04:27:05 AM »

Quote from: dieselndixie on March 03, 2009, 07:56:10 PM

can you list ( in a private message if this is considered a hijack) exactly what parts you got from the gsxr, and what year and everything it was?

i am so close to doing this, i just need some specifics.

No problem. The forks are 2007 GSXR 600 forks that came with only the lower triple clamp and both brake calipers. I still need to purchase the upper clamp. Retrorocket stated that his old cb750 stem pressed right into his GSXR 1100k but I don't that will work here. The diameter of the bottom end of the gixxer stem looks to be greater than the CB750. I think I will have to get a new stem turned to match the bottom of the gixxer clamp and have the rest mimic the 750. I think the research has been done before by someone else and you can't get bearings to fit the gixxer stem and the neck of the cb750. I haven't even figured out the front wheel yet. I could go with a gixxer wheel and it would be a no brainer but I am thick headed and want to use the CBR 600 f2 wheels so there will be more figuring out of axles, spacers, etc....AND more money... Hope that helps.

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Author Topic: 1975 CB750F - Project Yellow Jacket (Read 59391 times)

dieselndixie

dieselndixie