Newbie CB750 Cafe Project

[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:

 

[SilkySmooth750]

Great progress!

 

[Hoosier Daddy]

I like watching the filthy old whores come apart, the changes are like night and day!
Keep it up

 

[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 !!!

 

[SilkySmooth750]

Don't say that! OK, I'm starting a list!

 

[Hoosier Daddy]

 

[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.

 

[SilkySmooth750]

Welcome back!

 

[Hoosier Daddy]

Are you back?

 

[ljonny18]

Are you back?

I sure am !!! Merry Christmas every one !

 

[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.

 

[SilkySmooth750]

Congratulations!

 

[notlob]

Good to see your going to back at it and congrats on the little addition.

Your ideas on the frame stance may have a problem.
I lowered my front forks internally by 45mm, you cant slide the stanchions through the triple clamps as they will hit the handle bars and raised the back 35mm, I still had good trail which is what you need as these old hondas have a lazy steering angle anyhow. However raising the back any higher will make the chain rub on the top of the swing arm, there is a piece of metal for it to slide over but constant contact with it will destroy your chain and the swingarm in no time at all.

 

[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

 

[ljonny18]

As I am still waiting for a tool to re-fit the valves and rebuild the top end of the motor.... back to my frame / tank issues. You may remember that I want to fit a different tank, taken from an older (SOHC) CB750 to my (DOHC) frame, but the problem is that the inside of the tank is completely different, is too small (thin) and needs quite some modification to allow it to sit correctly (lower) on the frame without rubbing. As you can see its too high on the frame:

I spent a long time trying to find someone local (here in Germany) to do this modification. I was told it was not possible, its not worth doing, it will just be problematic, it will damage / break the tank and will not be usable etc etc... I appreciate and understand these comments but I have my heart set on this tank I did eventually find a custom bike builder who said he can do it, but will need at least 203 days work and at 75 Euros / hour would add up to almost 2000 Euros which is out of my budget

I contacted a bike builder in Italy (FranzGarage) who has completed such a modification on two bikes previously, and he very kindly gave me some advice and pointed me in the right direction to try and complete the modification.
Basically the inside of the tank needs widening in the areas where it hits the frame:

It is not actually that much it needs, about 2cm (1 cm either side) would be sufficient.

It also needs bringing back a couple of cm so that the bars don't hit the tank of full lock, therefore ill somehow have to move the mounts for the fram rubbers back a couple of cm:

 

[ljonny18]

I basically had two options that I could do with the tank (which is good as I have two tanks to play with ). The first / easiest option is to beat the indies in the correct places until the tank fits (not the most elegant solution I agree). The second option is to cut out the sections of tank that hit the frame, and that fill / cover and weld the cut areas with shaped metal to fit accordingly.

To get the ball rolling, I took the first tank and first solution so I could see if once the tank is fitted if all my other ideas related to the tank (seat, bars, riding position etc...) would work, at least this way I had and working base ad something to start with. Its it all works out well, I will complete the tank properly by cutting and welding the underside to fit properly (watch this space).

I filled the tank to the brim with water to prevent damaging the tank when beating it with a rubber mallet - this did not work as I created extra dents in the tank, and cracked the inside of the tank although this is not the end of the world as I can weld up the cracks and the tank was already dented and in need of some TLC (just needs more now).

I also had to babysit while doing this:

I have now beat the top inserts into shape (red) and will now move onto beating down the blue bits.

Finished, the tank now sits nicely on the frame with no rubbing or contact to the frame, it just does not look very nice, is dented and cracked

 

[ljonny18]

I found a guy in the town I live who has a Kawasaki Zephyr Club and small workshop that he has very kindly said I can use for my project. He is very interested in the project and is willing to help out

I took the tank down to try and fix what I had broken while beating it into shape.

First up was to repair the cracks in the bottom of the tank:

Next was to clean up and sand blast all the dented areas of the tank so I could try and pull them out :

Homemade blasting machine

The sand could not take the stickers off so I had to do this manually:

Once ready, we tried to pull out the dents using an adhesive based puller:

This sadly did not work dues to the strength of the metal used for this tank - as I d=found out while beating the tank, these old CB tanks are solid !!! a lot more robust than other tanks !!!

I therefore had to weld rods to the tank and pull the dents out this way. Although messy, this worked well ! - Pictures to follow.

 

[ljonny18]

Good to see your going to back at it and congrats on the little addition.

Your ideas on the frame stance may have a problem.
I lowered my front forks internally by 45mm, you cant slide the stanchions through the triple clamps as they will hit the handle bars and raised the back 35mm, I still had good trail which is what you need as these old hondas have a lazy steering angle anyhow. However raising the back any higher will make the chain rub on the top of the swing arm, there is a piece of metal for it to slide over but constant contact with it will destroy your chain and the swingarm in no time at all.

This is great to know !!!! I will be coming back to this topic soon, so would appreciate a chat with you - PS love your build !!!

 

[ljonny18]

Started working on building the top end of the motor and getting the valves in. I think im getting old as it was too cold to work in the garage over the weekend. Luckily (thanks to a neighbor) I have access to the workshop at one of the local car garages and can use the workshop when its not open for business. I therefore loaded the engine into the back of the car headed down and got setup:

https://lh6.googleusercontent.com/-
Zh_ejvUWoxI/UosoMqRGlaI/AAAAAAAAKtM/rYpxxuHq_tc/w1000-h750-no/IMG_5358.jpg

First off I founds some old gaskets that id missed I thought I had finished the long and mind numbingly boring process removing the old gaskets, apparently not ! and these 4 were the worst of the lot

and then I started the valves:

You can pb tell by the pictures that this process was a lot more tricky than I expected. It took me a while to get the hang of it and in turn took me ages for each. I am not even half way done so will have to go back down to complete it.

 

[ljonny18]

Spent a bit more time on original tank and original idea. Here is the tank looking in a bit of a mess after I managed to pull most of the dents out. These tanks are really solid and it took quite some effort getting the dents out. We welded a threaded rod to the tank in many places one at a time and slowly worked through each dent until it was at a state where it was a good as could be and at a stage where it could be easily filled to finish etc... The onlt problem is that it looks a right mess

This is the worst / biggest dent on the top of the tank. The tank also has 2 small dents on the right and a small but nasty one on the front right


After the dents were pulled out to (what I guess) the best they could be, I sand blasted away any dirt and took another couple of cm of paint off around each dent to try to make the filling / finishing process easier:

Instead of using filler, we decided to fill the holes with metal. Never doe this beofre, and was the first time id heard of it, but it was recommend as its a much more solid solution so I thought id give it a go.

I bought a load of metal rods, heated them up and melted them into the dent:

I let it cool down and then started to sand down the added metal and re-apply accordingly...

I have only so far worked on one dent (the smallest) and this still needs quite some work (sanding and re-applying metal etc) but it seems to be working out well... I think I can get it exact, but may also need a touch of filler at the end