Topic: 75F' 750 cafe w/ CBR F2 mods

[Shtonecb500]

Just sourced a 91' cbr600 f2 roller for 200 bucks in east lansing. I've decided to draw inspiration from Mike Hodgson's super bike build.

[Shtonecb500]

just trying to figure out the direction of this bike. So, i've always wanted to graph a more modern front end to one of my bikes, Ive purchased modern front ends, hoping to piece together a full one for cheap with no success. This entire roller coming my way for 200 bucks was a blessing. I always liked mag wheels on our bikes too and these six spoke mags I think are the best looking, over any 3 spoke at least. When I saw the red super bike I figured it wasnt really that far off from what I was going for anyway, outside of the motor upgrades.

Right now, Im leaning hard towards a stock sulfur yellow with blue pin strip on the tank, the chin scoop, the rear cowl, and the mags, with a high polished motor all the way down to the cases with a nice polished breadbox.

I ordered the conversion bearings for the front end and Im under the impression I will ned to press out a 750 stem and press it into a cbr lower.
Ill get to test fitting everything in the next week or so.

[Shtonecb500]

Based on some light research on some other forums, the f2 and f3 stems are the same diameter as SOHC and DOHC stems but are shorter?

The f2,f3 stems are welded so we grind it off and press it out, meaning a 750 stem can be pressed in, and solving the problem of mating the f2 front end. The F2 WHEEL is still a mechanical speedo and becomes digital/electric for the f3 version...so that keeps things simple for that. The rear wheel seems to fit a 77-78 swinger but will need some mods, Im not sure until I fit the wheel up to a swing arm but the only mods might be axle spacers, machining off some MM's from the sprocket carrier and whatever comes along with the sprocket adjustments, and modding the rear brake hardware for the CBR caliper. I have another 4-1 exhaust that I feel will hug the frame a little better, hence making the chin scoop an easier fit, it will be hard to compete with the cleanliness of the yoshi exhaust and how it tucks neatly under and runs parallel with lower frame rail, this exhaust system was designed to be a free hanging system as well...so I don't need to bother with support bracket hanging out there distracting from the natural lines of the bike. If anyone has input on this mod please share, All the posts around here seem to be in 2006-2012 range and didnt discuss too much about the stem differences. Unlike GSXR stems....I know they are bolt on for 550s but need stem mods for 750s.

[Shtonecb500]

holy #$%*, I was just quoted 3500-4k to nickel plate a 750 frame, then was told they didn't want to do it.

plain powder coat it is then...

unless, someone knows of a metal finishers in or around metro detroit? Ive only found some industrial placed and that looks to only do commercial stuff.

[Shtonecb500]

Do I use conversion bearings for a cbr f2 to a cb750 when Im pressing out the 750 stem and pressing it into the cbr lower? Or do I press the 750 stem into the cbr lower and install cb750 roller tapered bearings and call it done?

Im having a brain fart.

[Alan F.]

press the 750 stem into the cbr lower and install cb750 roller tapered bearings and call it done

Use bearings that go with the original stem and original frame, that part isn't going to change.

[Shtonecb500]

Here is the donor motor that phils brother hand polished on the stand, usually does one of these a season.  I’ll be doing some more work once it’s taken apart.

Im assuming some people were waiting for me to realize the stem is welded on at the bottom. So what the heck are my options? Could I give the 750 and cbr triple to a machine shop, have them machine the bottom of the weld off, get the stems out and swap it? Can I do that and just weld it back in? I called Cognito and they basically said it costs too much to drum up the triple tree needed for that swap.

[Alan F.]

Just grind the weld off, thread the top nut onto the stem to protect the threads and press it out. If your new lower triple is Iron like the old one, you should be able to weld it. I'm not sure what you'd do if you've got an aluminum tree. Cut a groove and put a snap ring? Heat it up and pound a taper into the bottom?

[Shtonecb500]

Just grind the weld off, thread the top nut onto the stem to protect the threads and press it out. If your new lower triple is Iron like the old one, you should be able to weld it. I'm not sure what you'd do if you've got an aluminum tree. Cut a groove and put a snap ring? Heat it up and pound a taper into the bottom?

You are right, both lowers are the same I put a magnet on both. Im going to grind the welds off and press them out.

[Alan F.]

If the CBR stem is the same, just longer, you can just press it out a little until it matches your 750 stem then tack weld, cut, and weld it up.

Know what I mean? Think it might work?

[Shtonecb500]

If the CBR stem is the same, just longer, you can just press it out a little until it matches your 750 stem then tack weld, cut, and weld it up.

Know what I mean? Think it might work?

The cbr stem is too short, just like with the GSXR swaps, the gsxr stem is long enough for a 550 neck but too short for a 750 neck...thats why we need conversion stems. its the same with this, the 750 stem is longer by 1-1.5 inches. But lowers are are steel, the cbr upper triple is aluminum. Ill get my grinder out tomorrow and practice cut a 750 stem weld off and press it out.  Maybe using the stock cbr triple is the reason why Hodgson's builds changed the way the rear shocks lay down on their swing arms?

[754]

Using the ring in groove will shorten it.
 If the stem is  going into a steel tree , you can weld it, if it goes in an aluminum tree then weld a washer or hat bushing on, the latter can be done to lengthen it.

[Shtonecb500]

I was able to grind off both welds and was able to press out both stems, removed the race from another triple and measured, I’ll have it welded back up tomorrow. The second from last picture is a 750 lower that I took the race off and the other is the 750 stem in the cbr lower.

[Shtonecb500]

Welded up

Races installed

Need to cut off the fork stops and think up new stops.
Last couple pics are new modified lower and then a stock 750

[Alan F.]

You could just weld on some tabs to the rear of the new lower tree to replicate the stock stops. I've seen this done where the new tabs were drilled and tapped so that screws with checknuts can be added to fine tune stop position with different tanks or clip-ons.

[Shtonecb500]

Got the front end and rear mocked up, everything rolls nicely, clears everything, and will only get better as i go from a 170 tire to a 130/140 tire. Once I get a smaller tire on there Ill start worrying about what I need to machine off of the sprocket carrier, chain alignment, and brake stay on the other side. The super bike build used a rear brake caliper mount from a different bike, Im assuming it was a steel one that could be easily modified for the brake stay.
Im not completely sold on side covers but if I do I will cut off the tabs from a K frame and weld them on...I only like earlier k model side covers. I used a second spanner lock nut thingy that goes under the top triple, it didnt catch any threads but happened to be the perfect size spacer I needed. The top stem nut is a stock honda and I used two stock honda washers to fill the gap on the cbr triple. You could use the cbr nut as well, same with the cbr rear axles. Between your stock 750 rear spacers and the ones that come with your donor cbr you will have what you need to get the rear right.

siting on it rolling it around- feels good.

[Shtonecb500]

I ordered 38mm fork ears and a used front fender from ebay. I chopped the extra stuff off the frame, old seat lock and what not and hit it all smooth with the grinder.

[754]

Dont even think 900 cc , if you are on a budget...

[Shtonecb500]

Dont even think 900 cc , if you are on a budget...

Stock motor rebuild is on the books.
I cut off the end rails, cross member and seat lock/mount, ground off remaining welds smooth. I think i like the seat a little further back than how i have it. Pictures of cowl position before I chopped the rails where it sis right behind the cross member is a nice distance back.

Front CBR fender and 41mm fork ears showed up, time to install those and the headlight bucket....also gonna ditch the chin scoop for now...until i can replicate it and custom fit it.

[Shtonecb500]

Fenders fork ears bucket

[Shtonecb500]

I've been considering using chrome vinyl wrap on this frame instead of nickel plating it, I know it's going to be a lot of work but I'm going to at least give it a shot. It's going to take a lot of finesse but I should be able to cut some corners where you cant really see the frame.

I found sulfur yellow 8oz and 12oz touch up paint and was going to order 5-6 cans of that, not sure what blue Ill use for the stripes. Airtech sells the belly pan I need and it just needs paint and the attachments straps they sell with it.

I have a laser tool at the shop but didn't have any triple A batteries, on Monday Ill put a smaller tire on the rear rim, and figure out the sprocket mods and start the new steering stops...I would like to get all the  fabrication done before I start throwing cheap paint on this things and decided which color scheme I'm going with.

So far:
Yellow: tank, belly pan, rear cowl, head light bucket, fairing, side covers, all with blue pinstripe, triple tree.
I might keep the wheels white with fresh paint....otherwise the wheels get painted yellow too, maybe blue or white rim stripes...not sure.

The blue tank doesnt look bad with the white wheels....

[Alan F.]

I've always liked those wheels. Years ago I had the idea to go with alloys on my K3 but the budget was low and I wound up with 750 NH forks and rear drum wheel, front wheel was CBR600F 1987 running just the left brake. I've got them on a 250NH now, should be finishing that one up soon before I lose shop space.
Your thread reminded me that I've got to make fork stops too, I'm so glad I commented that earlier.

[Shtonecb500]

I've always liked those wheels. Years ago I had the idea to go with alloys on my K3 but the budget was low and I wound up with 750 NH forks and rear drum wheel, front wheel was CBR600F 1987 running just the left brake. I've got them on a 250NH now, should be finishing that one up soon before I lose shop space.
Your thread reminded me that I've got to make fork stops too, I'm so glad I commented that earlier.

Alan, what does "NH" stand for?

you have pictures of that build?

[Alan F.]

Oh it stands for Nighthawk, sorry about that.

Btw I built my 41mm forks with the cheap cartridge emulators from ebay, they're listed for 41mm Harley forks but Showa forks are all the same.

[Shtonecb500]

Oh it stands for Nighthawk, sorry about that.

Btw I built my 41mm forks with the cheap cartridge emulators from ebay, they're listed for 41mm Harley forks but Showa forks are all the same.

Im not too knowledgable on my forks, will have to dig more into it.

Ive been searching for kayaba forks that are used on the House Rockers builds, they use magnesium wheels that look just like these 6 spoke cbr wheels....cant find them though or figure out what wheels they are using.