Topic: 750 DOHC Project

[ljonny18]

AMAZING!!! Jon, thank you and welcome to the forum. (dont let the "SOHC" in the title keep you from starting a thread for your build! your bike is amazing)

Hi all, I am new to this forum I am posting as recommended by another forum user: "FrankenFrankenstuff".

I am currently working on a 1983 DOHC (not SOHC ) Honda CB750, however want to take it back in time a bit using a SOHC tank and side covers etc...

Do any of you know if a tank from a K series SOHC (the more rounded tank) and side covers will fit on the DOHC frame... The frames (SOHC and DOHC) do look similar to one another - are they the same ? do they have differing mounting bolts / brakets etc ?

I will upload my progress pics shortly - keep posted if you are interested

Note: As I am already a month into the project, I will just upload all progress in one go so you will have a months work uploaded in pretty much one step....

[ljonny18]

Here is my new (and first) project bike: A 1983 Honda CB 750 RC 04.

I got the bike cheap in an Ebay Auction although it is in a lot worse condition than I originally thought and is currently a non starter.

The first step is to try and get the motor started to see what I have, and then strip it down to its bare essentials

As mentioned, this is my first project and I am a bit of a novice but looking forward to seeing what I can do with the bike !!!

Attached is the picture taken from the Ebay Ad:

[ljonny18]

Here are a couple more pics before I started any work on it:





Bit of a neglected tatty mess in my opinion

[ljonny18]

The bike had no power at first I thought it had a flat battery until further investigation proved it had no battery at all :

[ljonny18]

The new battery arrived, so I filled it with acid and let it charge for a few hours before fitting it:





After checking the oil and giving it some fresh petrol, it eventually started





OK, so its a runner (sort of)...  However, there was a not too healthy knocking noise from the engine. The engine is coming out in any case but if anyone has an idea re what it is likely to be im interested. It sounds like a "mechanical" knock so im guessing its going to something like primary chain rattling or crankshaft bearings ?

I will get the engine out and apart and have a further look !

[ljonny18]

I managed to find a bit of time and I started to prepare the engine for removal. Some progress pics:

Managed to clear a bit of space (although not much I have too much junk) so I can work around the bike a bit easier:





The carb rubbers (both sides) were that old and worn they were solid and had now flex in them at all therefore I had to remove / move back the Air box and housing to give me more room to maneuver the carbs and have any chance of getting them out. To enable me to move the air box housing back I had to firstly remove the Battery casing:





Battery casing out:

[ljonny18]

Onto the Carburetors:







Removing the Throttle / Choke cables:



and out

[ljonny18]

Time to remove the scratty old Exhaust:





Tacho cable:





HT leads:



Front sprocket:

[ljonny18]

The motor is now pretty much ready for removal (i hope) its all free of components and cables connecting it to the rast of the bike. I just need to drain the engine oil and somehow get this nut undone:



I cant for the life of me undo it - its solid... I will try and get a nice long(er) breaker bar and give it another shot. If anyone has any ideas re how to get it off, I would appreciate any advice (its the big swingarm nut)

[ljonny18]

I eventually got the bolt off using an extended breaker bar and a little help from a friend  !!!

After another day spent in the garage I managed to get some more progress done (i cant wait for the clocks to change and the weather to get better, so I can get some hours in after work during the week).

My mate T came round to help me get the motor out, but first we had to finish a few bits off to prepare the motor for removal:



This is the bolt I have been having a few issues with re getting it off:



We eventually got it off (after some effort and an additional trip to the DIY store)



Jack in place to take some of the engine weight:



Started to remove the engine bolts:









And frame mountain bracket bolts:





Ready to be lifted out:









Out





Cheers T

[ljonny18]

Next onto stripping the rest of the bike:

First off, the wheels, front wheel:









and the back wheel:

[ljonny18]

Backend / Swing arm removal:

[ljonny18]

I hate electrics....

This will be replaced by a nice round headlight if all goes to plan











Toll the front brakes off while stripping the electrics:











Finally the loom is out:

[ljonny18]

Dismantling the front end:





Garage could pb do with another tidy up at this stage...







Just need to take the yokes off now but need to buy a bigger socket

[ljonny18]

I manage to get a bit further this weekend. I started removing the last section of the frame, the yokes:






















Now the frame is all ready for cleaning, welding and eventually powderconating

[ljonny18]

Here is another little project that I am also working on (as and when time allows), a Pasini Mini Moto:

[ljonny18]

Back to the CB750 I started the "massive" task of cleaning / degreasing the filthy engine:



Until a nice new engine stand was delivered :

[ljonny18]

Time for another re-organise of the garage to make some space allowing for the engine to be worked on easily (enough):



I found an old table in the cellar to mount the engine on:

[ljonny18]

I started stripping the top end of the engine to see what sort of condition things are in:



All of the center head bolts were sheared off will have to replace these (not a great start) ...










In my "novice" opinion, so for so good and the chais seem to be of good / correct tension ...

[ljonny18]

onwards...





releasing / slacking the chain tensioners





both chains are now slack

[ljonny18]

time to get the alignment right before moving the cams, this is the part I was most worried about :S After a lot of reading and asking around I think (hope) I did it correctly ...



















1st one off

[ljonny18]

A few hours later I had the head and main barrel off

[ljonny18]

Is it ok / normal for the connecting rods to have a little play (left and right) ? All of them seem to have a little amount of play, with the second rod in from the left left (looking from the front) having a tiny bit more than the rest ...

[ljonny18]

At this point, seeing although I am this far (and the bike had a knocking noise coming from the engine when running) I thought it made send to go the whole hog and also check the bottom end of the motor to make sure there are not "bigger" issues related to the camshaft / connecting rods etc  before I continue ... it's also pb best as the bike has 60,000km (40,000 miles) on the clock and it appears the the previous owner(s) did not look after it too well
















Now I have hit a wall and conta continue until I get / make a tool to take this nut off:

[ljonny18]

I did not get too much time on the bike this weekend due to catching up on some important jobs and watching the England France Rugby game I did however manage to get a bit done.

I tool Honda tool arrived during the week, but sadly was the wrong one (was too small). They sent me the wrong part (with the wrong part number) so it has to go back... This pretty much stopped my weekends progress :



I did however (instead) manage to get a bit further with my MiniMoto Project. I primed, re-sanded and re-primed the frame and wheels ready for paint: