Topic: 1971 CB750 with GSXR Front End

[JohnnyM]

I have convered a 81 GPZ 1100 to GSXR forks, wheels and swing arm.  I wanted a simple look so I used the swing arm and fork from a 88-89 GSXR 750.  Do not use the 1100 GSXR swing arm as it is too long.  1989 is the last year of conventional fork for the GSXR. The upside down fork is way shorter than the 89 fork and the 89 fork is already shorter than the stock 750 fork.  A little shorter is OK as it puts more weight distribution on the front wheel and helps to improve handling.  Too short a fork will give you corning clearence problems.   I had to have a machinest cut and weld in a half inch spacer into the stem as the Kawasaki head is 7.5 inches and the Suzuki head is 7 inches.  Went to the All Balls web site and matched the 89 GSXR fork to the 81 GPZ head with the correct bearings and cups.  The 88-89 GSXR swing arm is the lightest of all the GSXR swingarms.  I had to adjust with spacers but it basically just dropped in.  I then was able to use 1995 GSXR wheels with a 180 rear tire and 2003 brakes.  Transformed the bikes handling by 200%  As I remember, the CB750 swing arm pivot is not too different from the early GSXR swing arms.  The pivot bolt is even the same diameter. 
Hope this helps

[CognitoMoto]

Check out grabcad.com lots of random motorcycle parts in 3D. However, I haven't found much vintage honda stuff.


www.CognitoMoto.com

[Retro Rocket]

I have convered a 81 GPZ 1100 to GSXR forks, wheels and swing arm.  I wanted a simple look so I used the swing arm and fork from a 88-89 GSXR 750.  Do not use the 1100 GSXR swing arm as it is too long.  1989 is the last year of conventional fork for the GSXR. The upside down fork is way shorter than the 89 fork and the 89 fork is already shorter than the stock 750 fork.  A little shorter is OK as it puts more weight distribution on the front wheel and helps to improve handling.  Too short a fork will give you corning clearence problems.   I had to have a machinest cut and weld in a half inch spacer into the stem as the Kawasaki head is 7.5 inches and the Suzuki head is 7 inches.  Went to the All Balls web site and matched the 89 GSXR fork to the 81 GPZ head with the correct bearings and cups.  The 88-89 GSXR swing arm is the lightest of all the GSXR swingarms.  I had to adjust with spacers but it basically just dropped in.  I then was able to use 1995 GSXR wheels with a 180 rear tire and 2003 brakes.  Transformed the bikes handling by 200%  As I remember, the CB750 swing arm pivot is not too different from the early GSXR swing arms.  The pivot bolt is even the same diameter. 
Hope this helps

You should have used the 1989 gsxr 1100 forks, some internals as the 750 but with longer tubes, I have 2 sets...  The early gsxr {19891100J}swingarms bolt straight in, I have one that has the monoshock removed and shortened, its about 40mm longer than stock {around 1 and 1/2 inches longer}, it fits the honda pivot bolt perfectly. The axle from the 1989 gsxr 750 is also the same diameter as the 750/4

[JohnnyM]

Thanks, great info.  The 88-89 GSXR is a great source of parts for all kinds of bikes.  There are a lot more GSXR 750 around than 1100's.  And a lot more of them seemed to have been crashed and thus a great source of parts.  When you use a 17 inch wheel from a 90's GSXR, you can use the speedo drive mated to the 88-89 instrument cluster.  The speedo is mechanical while the tack is electronic.  If you use a Dyna 2000 ignition, you can hook the tack right into that unit.  Everything works well together.
Have fun.
JohnnyM

[GNGSXR]

Received the custom top triple tree from CognitoMoto www.CognitoMoto.com
It is a fantastic piece. I'll mount it and update with pictures in the next couple days.

[GNGSXR]

Started finalizing the pieces I need before creating a custom wiring harness from scratch. Just waiting on a tail light to arrive before I dive into the process of rewiring the bike.
I finally took off the left side cover and look what I discovered.


My 1971 bike sure has a lot of 73 and up stuff on it.

[GNGSXR]

My ambition is starting to surpass the amount of time I actually have to work on this hobby.
While wait for electrical connector kits, wires, and lights for the "71" CB750, I was offered this 1980 cb750 from a friend for $300.



It runs great. All components work and are in good condition. It could use a carb cleaning but other than that it was a steal of a deal. The 1996 Honda CBR F3 I picked up a couple months ago will probably lose it's front end to this 1980 CB750.
I also came across a mint condition CX500 that I may pick up in the next week or so. I promise that I'll at least have one of these projects completed before spring. 

[JohnnyM]

While the 71 is a more classic look, the 80 can also be turned into a cool bike.  Wonder if you can put the 71 tank on the 80.  As for forks, just measure the head on the 80 and make sure the stem from the CBR is long enough.  I know the 81 CB900F had a 9 1/2" head and it makes it difficult to just bolt on any other fork.  Good luck.
John 

[Retro Rocket]

While the 71 is a more classic look, the 80 can also be turned into a cool bike.  Wonder if you can put the 71 tank on the 80.  As for forks, just measure the head on the 80 and make sure the stem from the CBR is long enough.  I know the 81 CB900F had a 9 1/2" head and it makes it difficult to just bolt on any other fork.  Good luck.
John

All the 750F, 900F bikes from 1979 share the same headstock measurements...

[GNGSXR]

Custom top triple tree and nut from http://cognitomoto.com/. Sorry for the finger smudges.

[GNGSXR]

Not to much to update with. I have been working on a "customers" 954 engine rebuild in my tiny garage. Only enough room for 1 project at a time. All I have had room for on the CB750 build in the garage was for brain storming and test fitting parts. I ordered a seat from Dime City Cycles. http://www.dimecitycycles.com/vintage-cafe-racer-caferacer-chassis-seat-parts-black-dcc-originals-ribbed-leather-wrapped-one-up-racing-seat-dcc-lwrapcafe-r.html

A few pictures of this seat on my CB750 with zero frame modifications as of now. This will give others a good idea on how much work is needed to use this seat.



This is a nice high quality seat, but I have discovered that you can get it for almost $100 cheaper from here. http://www.motolanna.com/ourshop/prod_1910098-Seat-Cafe-Racer-v30.html
The seats are almost identical in every aspect. I hate to take attention away from DCC (I've ordered a few hundred dollars worth of parts from them so far on this build) but very few of us are trying to build a +$10,000 bike so shopping around for the best deal is a necessity. Double check the dimensions for yourself and motolanna also gives you stitch options.
I ended up returning the above seat to DCC. The amount of frame modification I would need to do to make this seat work and look good is a bit to extensive for my skills at this point. I've decided to model my own seat in autodesk inventor and locate someone to build it for me. I am a mechanical engineer during my day job and this gives me a good excuse to brush up on my 3D modeling skills. I'll post pictures and cad files later. The seat will be longer and allow me to only need to chop the back couple inches of the stock frame and install an upswept hoop.

[JohnnyM]

People just don't realize how much work is involved in re-engineering a custom bike.  Most people, if it isn't a simple bolt on operation, are lost or impatient.  If you're doing a custom re-built bike, the beauty is in the details.  Looks like you are doing all the right things.  Keep up the good work.  Might I suggest a set of rear sets from a SF900 Suzuki.  They carry the brake master cylinder and also have rubber padded foot pegs that the GSXR rear sets don't have.  You have to cut off the Honda's rear foot peg tubing and weld on a bracket to attach them but they'll look good on an older bike.
JohnnyM

[GNGSXR]

People just don't realize how much work is involved in re-engineering a custom bike.  Most people, if it isn't a simple bolt on operation, are lost or impatient.  If you're doing a custom re-built bike, the beauty is in the details.  Looks like you are doing all the right things.  Keep up the good work.  Might I suggest a set of rear sets from a SF900 Suzuki.  They carry the brake master cylinder and also have rubber padded foot pegs that the GSXR rear sets don't have.  You have to cut off the Honda's rear foot peg tubing and weld on a bracket to attach them but they'll look good on an older bike.
JohnnyM

I should of double checked the full length measurement of that seat from DCC. I am wanting the rear of the cowl/hoop to be collinear (from a side view) with the end of the swing arm. I may end up with it a little longer which is fine. I just didn't want that short stubby look for this build. I have a couple rearsets to try and use. '06 GSXR, '96 CBR600F3, or I may order a set of tarozzi rearsets and a custom bracket from http://cognitomoto.com/collections/rearsets/products/cb550k-cb750k-rearset-brackets. Ill take a look at your suggestion too. Thanks

[GNGSXR]

A few small updates.

I received my rearsets and custom brackets from http://cognitomoto.com/


Typical Acewell 2853 gauge. It really is the best gauge for the money. I searched for a needle style all in one gauge that had all the idiot lights but I couldn't find anything for less than $500. Various GXL wire sizes from wirebarn.com. Electrical upgrades from http://www.oregonmotorcycleparts.com/SOHCfours.html. I plan on ordering the  A couple electrical kits from http://vintageconnections.com/ and another site that has slipped my mind. The second kit contains various weather pack connectors. Starter solenoid from vintagecb750.com. I think the only other piece I am waiting for is a transistorized ignition from hondaman.


Bike loaded up to weld a steering damper mount on the stem and resolve the steering stop issue. I don't own a welder or any basic welding skills at the moment.


The new thicker GSXR forks hit the gas tank on a full left turn. The stock steering stops on the lower triple obviously don't utilize the stock bracket on the CB stem. There are a few different solutions to this such as keeping the stock lower CB stem "bracket" and putting some nuts in the GSXR triple, dent the tank or some other wizard like magic. I noticed though the CB horn bracket keeps the fork a few millimeters from the right side of the gas tank. We just duplicated the horn bracket on the left side of the bike. Surface rust is due to getting caught in some rain/snow. Ill be relocating the horn under the tank and using the old bracket and this new one for mounting.....stuff. I am not sure what stuff yet.


I've experienced "tank slappers" from racing/track days and just normal riding. I'd like to prevent them in the future so I had the stock GSXR damper mounted to the CB stem. Similar to how it mounts on the '07 GSXR that I this front end came off of. Had a piece of metal turned on the lathe and welded it on the stem. The front of it will be trimmed/cut when we figure out a headlight mount.

[Retro Rocket]

The forks hitting the tank has nothing to do with the thicker forks, its due to the smaller triple clamp offset, you've lost an inch compared to stock clamps, i found that out years ago, I just changed the stops on the frame, you get less turning circle though...

[GNGSXR]

The forks hitting the tank has nothing to do with the thicker forks, its due to the smaller triple clamp offset, you've lost an inch compared to stock clamps, i found that out years ago, I just changed the stops on the frame, you get less turning circle though...

You're right. The stock one is offset further forward.

[Retro Rocket]

The forks hitting the tank has nothing to do with the thicker forks, its due to the smaller triple clamp offset, you've lost an inch compared to stock clamps, i found that out years ago, I just changed the stops on the frame, you get less turning circle though...

You're right. The stock one is offset further forward.

Yep, 25mm to be precise, which equals one inch...

[Finnigan]

Tuned in

[GNGSXR]

Seat/cowl and seat pan also showed up.
I drew a seat design in CAD and had Dave make it for me. His ebay store is located here http://stores.ebay.com/hotrodmetal 



I decided to use an upswept rear hoop after I had already sent off my design for the seat. I'll have to cut the rear of the seat to match the hoop I ordered from Dime City Cycles.

[calj737]

That's an awfully beautiful seat! Shame to cut it...

[riverfever]

Nice build. If you ever need a hand, I'm up the mountain in Woodland Park. I am learning with my first project but am eager and would love to learn more.

[Sketchy Bikes]

Received the custom top triple tree from CognitoMoto www.CognitoMoto.com
It is a fantastic piece. I'll mount it and update with pictures in the next couple days.

Are you an HVAC estimator?  I see the marked up piping plans behind the pic…  I'm know colored up plans all to well…  I sell large HVAC equipment and love 750's! 

[GNGSXR]

Nice build. If you ever need a hand, I'm up the mountain in Woodland Park. I am learning with my first project but am eager and would love to learn more.

Awesome! I may take you up on that offer.

[GNGSXR]

Received the custom top triple tree from CognitoMoto www.CognitoMoto.com
It is a fantastic piece. I'll mount it and update with pictures in the next couple days.

Are you an HVAC estimator?  I see the marked up piping plans behind the pic…  I'm know colored up plans all to well…  I sell large HVAC equipment and love 750's!

I'm an MEP engineer

[Sketchy Bikes]

Received the custom top triple tree from CognitoMoto www.CognitoMoto.com
It is a fantastic piece. I'll mount it and update with pictures in the next couple days.

Are you an HVAC estimator?  I see the marked up piping plans behind the pic…  I'm know colored up plans all to well…  I sell large HVAC equipment and love 750's!

I'm an MEP engineer

Cool, I call on a lot of MEP firms in Ohio and PA.  A lot of the engineers I deal with are bike, and gun guys.  I always said if I was selling vintage bikes or guns instead of HVAC controls and equipment work would be much more exciting!!