CBX750 Project - CBX820RR

[Kristian750]

Hello,

My Name is Kristian from the UK. I picked up a CBX750 back in October 2020 and now have a full on project on my hands! Plan is to build a 80's "GP Bike" with some modern touches...

Anyway, enough with the writing. Here are some pictures...



So far the current spec list is:

CBX750F 1984 Frame
2007 CBR600RR Rear Swing Arm
Ohlins TTX Rear Damper
2012 CBR1000RR Front Showa Forks
2013 Enkei CBR Wheels
1982 CBX550 Fuel tank
Renthal Clip-ons

I have an RC42 Engine to drop into once built with some 70.5mm CP Pistons and will use the RC17 Cylinder head. Got lots of engine work to get done over the next few months and hopefully will have a running bike by the end of the year...

 

[cbxjon3]

Looks great so far. Would you like to sell your old stock fuel tank? cbxjon,,Georgetown, usa

 

[Kristian750]

Possibly, I am located in the UK though so shipping will be expensive.

 

[Kristian750]

So after a little work trip away, I’ve finally had some movement on this. The engine is now currently being built and some very SHINEY bits have been delivered after what seemed like an eternity of waiting…

 

[big086]

how much work was involved in the front and rear swaps?

 

[Kristian750]

A considerable amount in all honesty, the rear needed a whole new suspension mount fabricated and welding on to the frame, new spacers needed to be machined.
To use the original CBR triple trees, the upper head bearing cup had to be cut out and a new larger one pressed and welded in its place. I think I will also need to notch the frame for the chain and use an offset front sprocket but I have not got that far yet.

 

[big086]

geez, that's committed! keep the pics up, keen to see how it progresses!

 

[BAHNST]

Geez that stock cbx is high tech compared to my K....with your mods another world.....
Well done....enjoy when finished

 

[BAHNST]

Any updates? .....no pressure.. but we interested.

 

[Kristian750]

In terms of the bike, not much has happened to be honest, it’s been a long run up to Christmas with work and now I am halfway between moving from the UK to Italy. Once the garage is set up and the bikes are here I will hopefully have a bit more progress..

Saying that, I have managed to get the mock up engine in the frame now and been on a bit of a parts hoard and have started to draw up an inlet manifold to get the carbs mounted to the engine…

I’ve been scouring the internet for a set of cams to no avail, in 84, Honda with HRC developed a “power up” kit but They are impossible to find. Some of mates (I work for Honda at the moment), in Japan have even tried to find old stock but all parts have since been thrown out…

 

[R1dude]

How’s the project coming along ?
I’m in Huntingdon in the uk too and have a silver cbx750 but used to own a red one so I wouldn’t mind buying your old tank and panels if you’re not using them mate. Cheers

 

[Kristian750]

Hello all,

So thought I’d add a little update… (it’s only been a year and half since my last post ). After moving away and with work and a flood which wiped my garage out, I’ve pretty much made a full circle to the same point the bike was at before I left, although In reality, I’ve done a few bits which I will share with you all.

The original plan to use the CBR1000 forks had to be scrapped as they where too short and the front wheel was touching the exhaust… In the end I had to have a set of fork clams custom machined as the offset from the cbr fork clamps was too small. I went with an offset that was a tad lower than standard and swapped the cbr forks for some GSX-R ones. The only difference was that the gsxr forks were older and I hadn’t realised that Showa had changed the diameter of the lower clamp point by 1mm so I had to get them turned down slightly for the fork clamp…
(You can start to see why progress has been so slow!). It also had to change the design of the stem as the one I made would not have been suitable. I ended up turning up one out of stainless and used the original diameters for the lock nuts ect…

This is how the bike stands now, but apart from cosmetic work, the front is finished.

The engine is coming along slowly, new sleeves, rods and pistons have been put in as well as the bigger inlet valves and head porting…

And finally some “inspiration” pics

 

[brettp]

Digging that tank. Is it from that bike?

 

[Kristian750]

No it’s from a CBX500

 

[brettp]

Looks really good on it

 

[Rob_CBXGoBrr]

Hello Kristian I flippin love this build, that rear end is spicy.
I working on my own 85' CBX and was wondering whether you still had, and would be willing to share, the CAD files for those lovely billet triple-trees ??

 

[wilso38]

Kristian, where did you get your exhaust from