Author Topic: 1975 CB750F - Project Yellow Jacket (Read 59395 times)

HavocTurbo · « **Reply #100 on:** March 04, 2009, 08:41:37 AM »

Probably will be best to make a stem and a spacer and them have them pressed and welded.

I'm assuming that your bottom tree is aluminum. Have a shop (or go buy some) use T6 aluminum and make your stem with the 750 dimensions, but the GSXR base. Then use an aluminum spacer to fill the diameter gap at the base of the tree.

After everything is pressed on, have the spacer weled to the stem and tree. Then machine for your bearing races.

Takes a few days to get the job done, but it will be rediculously strong, and you can still use tapered bearings with ease.

Reason why I suggest welding, I have had several stems break that were machined to just press in without a spacer.

For what it's worth.

DollarBill · « **Reply #101 on:** March 04, 2009, 08:50:26 AM »

That's good to know Havoc!

I didn't think aluminum was strong enough to use as a stem? I'm pretty certain the stem that is in there now is steel...

HavocTurbo · « **Reply #102 on:** March 04, 2009, 09:46:55 AM »

You "could" use aluminum. It depends on what riding you are going to do.

I would say 356-T6 Aluminum that been treated or whatever should work just fine for street riding.

But you never know.... every batch is different.

DollarBill · « **Reply #103 on:** March 11, 2009, 06:30:57 PM »

Got both my CBR 600 f2 wheels finally. Will have to have bushings made for the rear axle to fit the CBR 600rr swingarm. The front will require either the same or a custom axle turned.

I have some makeshift axles in just for this mockup. The wheels and frame will be powder coated gold as soon as I finish the swingarm mods and make new brackets for rearsets.

volkswagendan · « **Reply #104 on:** March 11, 2009, 07:24:58 PM »

glad u stopped in on my build. it reminded me to check on your progress.
your bike is coming along well. i'm so jealous of those wheels. ...and everything you have done to get them on there!
i cant wait to see this thing on the road.

DollarBill · « **Reply #105 on:** March 23, 2009, 06:22:44 AM »

I want to document the parts I have bought so far just so I don't forget year/make later on....

07 CBR 600rr Swingarm
07 GSXR 600 Forks/Brake calipers
96 CBR 600 F3 Rear Wheel
93 VFR 750 Front Wheel (same as F3)
05 Yamaha R1 Rearsets

Just got a quote to have a new steering stem turned and it was $300! YIKES! Will have to hold off on that for a while or find a cheaper machinist. Hell, with all the spacers I will need turned and the stem I might as well buy a small bench lathe, learn to turn the parts myself, and then sell the lathe when I am done. Okay.....so I probably wouldn't sell the lathe if I learned how to use it. Seriously, you can get a small bench lathe for $500, maybe another couple hundred in parts, cutting/threading bits/materials.

I know...easier said than done. Ughhh....my wife talked me out of selling my 350 twin(couldn't believe it) but now I am thinking about it again. Just so damn impatient with this project. I want to finish before summer but it's not looking like that will happen.

Right now I am looking for a new/undamaged stator cover to replace the dented/gouged one I have. If any of you have a nice spare let me know.

HavocTurbo · « **Reply #106 on:** March 24, 2009, 11:36:30 AM »

Send me specs and material (or ill buy it here) and we can work something out for your stem.

DollarBill · « **Reply #107 on:** March 24, 2009, 12:15:19 PM »

PM sent Havoc...thanks!

babyfood1217 · « **Reply #108 on:** May 13, 2009, 06:23:55 PM »

$bill, you never revealed what you ended up doing to make your swingarm work! reveal! reveal!!!

babyfood1217 · « **Reply #109 on:** May 13, 2009, 07:06:24 PM »

Oh, what was that dollarbill? You say you wouldn't mind taking a measurement of your new wheelbase so we can compare it to the stock cb750 wheelbase you started with?! Awesome!

DollarBill · « **Reply #110 on:** May 13, 2009, 07:30:44 PM »

Well, I am taking my frame and swingarm out to my father-in-laws this weekend to do the final welding.

To make the swingarm work I cut the center stand support in half and put a jack in the frame and expanded the frame enough to fit the swingarm. To finish it out I am going to fabricate some new bosses for the swingarm pivot bolt which is quite a bit larger for the 600rr swinger. Then I will weld a section of round steel inside the split center stand support. For the open part of the center support I will take a larger Diameter steel tube and split it horizontally and weld it over it to cover it up. Then I will weld some steel plate to the center stand to bolt the dogbone to. Since widening the frame will leave space on the engine mounts I will reposition the mounts on the right side of the bike to meet up with the engine. This will offset the engine just a little to the left which may just be enough that I won't need to use an offset sprocket.

One other mod in using the 600rr swingarm is upgrading the shock to the 1000rr because the resevoir on the 600rr sticks out to the side and may scrape one of the side frame rails when compressed. The 1000rr shock resevoir angles straight back and will not interfere with anything.

Of course I wouldn't mind measuring the wheelbase babyfood! The forks are just "sitting" in the frame and the wheel is "loose" in the swingarm but the approximate wheelbase is 60". I think the stock wheelbase on the 750k was 57....couldn't find a measurement for the stock 750F but I know it was only slightly longer than the K. When I first started looking at the 600rr swingarm I think I decided it was going to be about 2 inches longer...3 tops. Compare that to the nimble 600rr's wheelbase of 53.9"...

Did all that make sense? It's kinda hard to explain but I will take photos of the process.

babyfood1217 · « **Reply #111 on:** May 13, 2009, 09:06:41 PM »

naw that's great. Even after reading all the posts in this thread, I still think it's too bad that a swingarm fitment couldn't have happened without the frame slice/dice/reweld. Even with all the crap I put my frames through, I feel nervous about such a mod. Any perceived problems with having the engine line up with its' mounts then? I just imagine the the frame kindof clamshelling open and pushing the mounts super-far apart. Anxious to see some pics!

-Chris

Retro Rocket · « **Reply #112 on:** May 14, 2009, 12:11:52 AM »

I wouldn't cut the frame either, i am using a GSXR 1100 swingarm and i had it modded to fit the bike , not the other way around. Just my opinion.

Mick

babyfood1217 · « **Reply #113 on:** May 14, 2009, 05:42:49 AM »

Yeah but the nice thing about the SwA he's using is that the design eliminates the need for an upper shock mount. The dogbone linkage common on some many of these newer sportbikes mounts underneath and they've engineered the remainder of the suspension system within the space the SwA already takes up. Finding an upper mounting point on these things is a B!%@#!

-C

DollarBill · « **Reply #114 on:** May 14, 2009, 05:56:23 AM »

I worried too about cutting the frame but I talked to a frame builder that does this kind of thing all the time and he assured me it would be okay. He told me the piece that is welded inside the cut center stand tube should only be 3/4 the lenghth to allow flexibility.

I am still able to put the engine mount bolts through without issue so it didn't clam shell that much. I do plan on moving the right side engine mounts in a little so I don't have to use spacers and also so I have enough threads to get the bolts tight.

I thought about modding the swingarm but after talking to a machinist decided against it. This swingarm is hollow and filled with foam. Cutting it down to fit would have required a lot of work by an expert with aluminum which I am not. Like babyfood mentioned about this swingarm which I like is the design. My battery box stays where it is and so does the oil tank.

babyfood1217 · « **Reply #115 on:** May 14, 2009, 06:17:24 AM »

oh damnit Dbill, you just gave me an idea. Crap. So, say a person had this swingarm, didn't want to mod it (structural integrity) and didn't want to chop the frame where you have to either (structural integrity).

Using the OE SwA, take measurements and dimensions, notating everthing (maybe using using a CAD type program in the end), perhaps one could make a one off, brand new SwA, likely from steel, that would mimic all measurements and dim's correctly, save for the SwA pivot, which could be sized to fit into the unmolested frame.

$:-\$

DollarBill · « **Reply #116 on:** May 14, 2009, 10:19:45 AM »

Sounds like you have a new project babyfood! Go for it!

babyfood1217 · « **Reply #117 on:** May 14, 2009, 10:28:29 AM »

Whatever! I can't even get my current project rolling (kicks self) - I'm just fascinated with the notion of this newer SwA with lower mounts only. I'll watch your build instead!

J.Webster Designs · « **Reply #118 on:** May 14, 2009, 02:10:52 PM »

have you made sure that the motor still fits? i mean if you are spreading the mounting points apart, theoretically the motor could shift side to side since there will now be a gap there that was not there before.

DollarBill · « **Reply #119 on:** May 14, 2009, 03:33:37 PM »

Yes it still fits. I will be moving the engine mounts on the frame in a little bit to make up for the gap. I thought about using spacers but would rather move the mounts so the bolts have plenty of length.

HavocTurbo · « **Reply #120 on:** May 17, 2009, 10:45:25 PM »

I

NEED

PICS!!!!!

DollarBill · « **Reply #121 on:** May 18, 2009, 06:49:08 AM »

GREAT TO SEE YOU STILL WITH US HT!

Okay, so the frame stretch took almost all day. Wait...I take that back. Cutting and welding in new bosses and making them straight took all day. Son of a biscuit that was hard. I bought this nice new heavy duty carbide drill bit that would have made the job a lot easier had I not forgotten it at home. My in-laws live waaaaaaaay out in the country so it's not like you can just run up to Home Depot real quick. We made do with some old drill bits, grinder, and a torch.

For the frame stretch we cut out the middle section of the center stand leaving about an inch and a half of the original tubing on either side. We then cut a section to fit and welded short pieces of solid steel bar inside that protrudes into the original tubing. This would be a lot easier to explain had I not forgotten my camera too. All the pics I have were taken after it was done and when I got home. DARNIT!

To remove the old bosses I ground the welds all the way down to try and punch them out. On the back side there was more metal to grind and to get them free we had to use the torch. We had the perfect size tubing to match the 600rr swingarm pivot bolt to make new bosses so we cut sections to the width we needed and welded steel plating on the insides so the swingarm bushing would have a nice flat surface to mate up to. The right side required a little larger plate because the torch opened up that side a little more than I wanted. It's not the prettiest thing you've seen but I think it will suffice.

Next, we welded brackets onto the new section of tubing (center stand) for the dogbone to attach to. I haven't drilled any holes yet because I want to get a wheel mounted to make sure I get the hole in the right place.

I need to clean up the welds around the opening of the bosses a little more and I am still thinking I may need to brace the newly welded sections of that center stand. My father-in-law thinks it will be plenty strong but I'm still not convinced. Thoughts on that???

The photo below is from MCRider's build. He had his bosses redone by a professional and they look beautiful. He's got a great build thread if you haven't checked it out: http://forums.sohc4.net/index.php?topic=36459.msg524136#msg524136
I added this just to show the distinct difference between an amateur's work and a pros.... I still think mine will work fine.

HavocTurbo · « **Reply #122 on:** May 18, 2009, 10:12:34 PM »

Lookin good man. You have to start somewhere.

I would double check for movement of the dogbones and then brace from there.

martino1972 · « **Reply #123 on:** May 18, 2009, 10:16:16 PM »

closely following this........doing the same thing soon with my cb750...

DollarBill · « **Reply #124 on:** May 30, 2009, 08:42:24 AM »

So I have 07 GSXR front brakes and am wondering if my CB750 master cylinder will work with them? The resevoir looks similar in size but what else plays into it? I don't know squat about this subject...

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Author Topic: 1975 CB750F - Project Yellow Jacket (Read 59395 times)