Topic: 750 DOHC Project

[ljonny18]

more parts arrived today

[FrankenFrankenstuff]

Such a great feeling getting new motorcycle parts!

[mono]

wow jonny, this is a really great thread.  i'm glad you're going into such detail and posting so many good pictures!  thanks

[ljonny18]

wow jonny, this is a really great thread.  i'm glad you're going into such detail and posting so many good pictures!  thanks

Welcome - im happy you enjoy it !!! watch this space there is more on the way

[ljonny18]

I have been making slow but good progress on the engine, however I (only just :S ) figured that I would either have to wait until the frame is complete before I install the engine, or install the engine and test it's all ok and then remove it again, complete the frame and running gear and then re-installe the engine etc... both of which I dont really want to do!

The ideal position would be to have the frame and (most) running gear finished and ready before the engine is finished (or at least before fitting the engine).

I have therefore invested a little time getting the bike back on its feet as I have quite a lot of plans / changes / modifications remaining before its anywhere near finished / how I want it:



As you can see I have (temporarily) put the front end (forks yokes etc..), back end (swing arm, rear shocks) and wheels back on the bike. I basically want to get a "rough" idea of what I can get rid of, what I want to add and what this requires (fabrication wise) and how I want the bike to sit etc ....

This is how the bike currently sits on the old original shocks that it came with:



It sits quite low at the back, I am guessing this is because the shocks have seen better days, and I believe these bikes so actually sit pretty low at the back ?

This is how I want the bike to sit (if possible):



You can see that it is quite a bit higher (a fair few centimeters). I guess I will have to start looking into some aftermarket shocks to achieve this (although this is not a bad thing as the shocks need replacing in any case) ?

My aim to to have the seat section of the frame (the bar that sits behind the tank, directly beneath the sate) to be straight / level, e.g. :



I have a few concerns about doing this, e.g. this is changing / adjusting the original (designed) level of how the frame sits on the running gear, and im not sure what this will do to the handling of the bike etc... and also (mainly) if I will run into some issues with the chain once the engine is fitted, e.g. if the chain will rub on the sing arm pivot when such an angle is introduced etc....

Any inputs / thoughts / advice would be appreciated here!!! As well as any advice / recommendation re what rear shocks to go for

The reason I want the frame to sit level is that I want the bottom of the tank to sit level with the frame:



As described in a previos post, I have gone for a tank from an earlier (SOHC) CB750 (K Series). The tank needs some slight modification before it can be fitted correctly. Once the tank has been modified it should sit lower and the bottom should (hopefully) line up with the described seat section of the frame (if that makes sense) ?

Once all that is sorted, I need to sort a seat out (will pb have to make one), the fenders, then work out all the electric's etc .... fun and games

[mono]

i've been working on my DOHC project lately, and am going for the same "level" look.  Looks like yours is almost the same as the '81 750 Custom that i'm working with, and mine sits pretty much the same.    The front end was made to sit high, since they were going for that "cruiser" look.  on the DOHC forum a lot of people talk about dropping down their front end 1" on the forks, and i did that on mine and it looks OK, although i don't know how it affects the ride.

i just picked up a '78 750K roller with a 17" rear, and i'm going to try and swap out the wheels (the K wheels are spoked), in the hopes that the 17" rear will finish the compensation and level out the frame without making the ride weird.

**edit -- i also have a friend's '81 650custom in my garage, and it sports the dual front discs and the same forward-mounted axle as the 750.  the shocks look shorter, but i haven't measured them.  if they are shorter, i think they may be a good swap, but i don't know if they are a weaker shock than the 750... the 650 is WAY smaller.  anyone know about that?

[ljonny18]

i've been working on my DOHC project lately, and am going for the same "level" look.  Looks like yours is almost the same as the '81 750 Custom that i'm working with, and mine sits pretty much the same.    The front end was made to sit high, since they were going for that "cruiser" look.  on the DOHC forum a lot of people talk about dropping down their front end 1" on the forks, and i did that on mine and it looks OK, although i don't know how it affects the ride.

Hey Mono, thanks for the input !!! your project(s) sound v-interesting !!! Do you have any threads / pics of them ? I would be interested to see them

[mono]

thanks   yeah i have my thread links in my signature if you want to check them out - the DOHC thread is pretty bare, but so far it's just been a bunch of polishing and stuff that people already know about - didn't feel the need to do a lot of before/after pics for that stuff.  give me about 10 mins and i'll post the pic of the LED  indicator light assembly that i finished last night

[ljonny18]

I have (again) not been up to much in the garage recently after feeling guilty about neglecting my project, I decided to identify what parts I wanted / needed to remove from the frame. This basically included all fairing mounts and center stand brackets. Some of which you can see in the following pic (painted in grey primer) :



As my mate works in a metal shop, with a selection of tools at hand, I took the frame to work with me, and called by on the way home :



Sorted

[ljonny18]

Next up, I decided to remove all the broken / bad parts form te running gear.... This basically included discs sprockets, rubbers etc etc.... I then started to rebuild the frame with running gear, so I can (try to) work out what is all require before the engine cane be re-mounted. I now have basica running gear that I can work with re planing the rebuild and (another) long list of parts to find, salvage and order

Front wheel:









Rear wheel:

[mono]

are you doing a dual-disc rear brake ?

[ljonny18]

are you doing a dual-disc rear brake ?

nope - just a single, keeping it standard in that sense

[ljonny18]

Sadly not much progress recently, mainly due to lack of time amongst other things I did however manage to get my hands on a cheap donor bike which I picked up ealry yesterday morning:





apart from the engine broken (cam chain snapped) the rest of it seems complete and in pretty good nick (at least better condition than mine)   I will be stealing some part from the donor bike, and will also have a lot of parts / spares left over if anyone needs / wants them !!!

[Magpie]

It's amazing how cheap these DOHC'ers are! And how many have broken cam chains. Cliff.

[Marco83]

cool project. planing to work on the 1979 cb750 DOHC and will love to see the early 750K tank install on your bike

[vfourfreak]

Hey ljonny,

I was sorting out some boxes of stuff (i.e. mainly rubbish) the other day and found a Haynes manual for the DOHC 750. You are welcome to it if you want it. Just PM me your address and I can pop it in the post.

Kev

[ljonny18]

Hey ljonny,

I was sorting out some boxes of stuff (i.e. mainly rubbish) the other day and found a Haynes manual for the DOHC 750. You are welcome to it if you want it. Just PM me your address and I can pop it in the post.

Kev

Cheers, I jut sent you a PM !!

[ljonny18]

Sorry for the lack of updates recently - I have been in south India touring of Goa and karnataka on a Royal Enfield:



I will start updating the thread again ASAP !!!

Cheers,
Jon.

[mono]

wow that's awesome!   

[ljonny18]

Hi guys, im back !!!

Sorry for not posting the last months, we had a little boy !!! This is the little chap who has been keeping me busy:



Now he is a bit older I am managing to get a few (not many) more hours in the garage, so am hoping to crack on and get the project finished

I will get some progress pics updated and post them asap !!!

Cheers,
Jon.

[Roach Carver]

Congratulations!!

[70CB750]

Congratulations!

[VTCBike750]

Congrats! My son was born a little over a year ago and the first year go by FAST.

[vfourfreak]

Hi guys, im back !!!

Sorry for not posting the last months, we had a little boy !!! This is the little chap who has been keeping me busy:



Congrats !! You have been teaching him how to fly like Superman ? Soon you will have a little helper in the garage !

Kev

Now he is a bit older I am managing to get a few (not many) more hours in the garage, so am hoping to crack on and get the project finished

I will get some progress pics updated and post them asap !!!

Cheers,
Jon.

[ljonny18]

Managed to get back in the garage this week

Its been a long time since my last update, and  I have (sadly) not made much progress on my CB project. Winter arrived, baby arrived leaving me no time or chance to get in the garage and get things done, and now winter is on its way again

I currently don't have any electricity in my garage therefore the winter prevents a lot of progress, not because of the cold but because of the light



Anyway a small update of some of the things I have managed to get done:

I managed to clear some more space (that does not exist) and got the donor bike I bought into the garage:





And drained the oil from it:





Although also a mess, the donor bike is generally in considerably better shape than my project bike, with no parts missing and all parts in the right places (ish) ... Thoughts had even crossed my mind to dump mine and move onto this, although then I got a hold of myself and decided to stick to my guns although, im sure I will be steeling a lot of parts from this bike, including wheels, suspension (to rebuild), foot rests, yokes - in fact pretty much all external (unbolt-able parts) as they are all better than mine !

I also took delivery of a new "hebebuehne" (ramp) for my project which should help (a lot) during the rebuild !!!








I took the original tank that came with my project bike to see if it was any good / worth selling only to find out that it was full of filler and justify my thoughts that my bike is a complete nail that has been thrown up and down the road too often:



If anyone whats this tank - it is free to a good home ! otherwise its going in the bin.

I spent a day working on some ideas for the backend (rear mud-guard, seat, number plate holder, lights etc...) but come up with nothing I liked, that was "clean" enough:






Apart from checking condition of parts and ordering new ones that I had not got much more done. On a none related note, I took a trip back to the UK and picked up a new toy to enable a few trips next year:



saw this on the way down, I heard it dragging and scratching along the road before I saw it its pb the lowest legal (apparently) car ive seen on the road:






Waiting for the ferry I met with a Vespa group and there crazy little scooters



On the ferry:





And 1000+ (sore) miles later back in Germany