Author Topic: CB750 Barn find project - First Timer  (Read 34126 times)

Offline Underdog1

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Re: CB750 Barn find project - Where do i even start!?
« Reply #30 on: July 25, 2016, 09:57:13 PM »
This might help finding a caliper.
http://www.sohc.co.uk/index.php/topic,1562.0.html

Cheers

Dennis

Yeah that may well come in handy, cheers bud!

Underdog,  I'm so sorry,  I seem to have inadvertently thrown a metaphorical spanner into your thread, now it's all about that fella on Youtube. Is he Australian Perhaps; and could that be why he builds engines upside down.  8)

I'm new here myself, but from what I've read.on this excellent forum I feel sure that you are eventually going to find all the information and help you could ever want.

Rob

Hah no worries!



So i only managed to get 30 minutes or so poking about the old girl today as i finished work late. Took the ignition off at the block connector, connected a good battery touched the spade connectors for the red and black wires and didn't get anything.. no electrics.



Hopefully this is a fault at my end as the advert did state that the bike turned over with a good battery, is there a better way to bypass the ignition?

Now I've got the lock off anyone know a way i can find the key code (on I'm assuming the lock barrel) without destroying it?).



Now the tanks off I'm a little confused by the fuel line set up.. the petcock has 2 outlets but i can only see one fuel line fitted (nothing was actually connected up though) which has a T junction to seemingly feed a each pair of carbs. So this set up means all the carbs are fed off just one petcock outlet.. I'm probably being an idiot here but whats the other petcock outlet for?  ;D




As a bonus, heres the inside of my petrol tank the dirty old girl


Offline K2-K6

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Re: CB750 Barn find project - Where do i even start!?
« Reply #31 on: July 25, 2016, 09:59:42 PM »
Well I've never seen one built like that before i. e. upside down, seems like he's creating more problems than he's trying to solve. Maybe he can't put the barrels down onto already installed pistons and rods because he's had to cut away the bottom of them to clear the massive alloy rods and lost the taper to help lead the rings into the barrels.

The rods don't even look finished properly with some really big stress raisers built in for good measure, surely if you are going to run an alternative you'd want a better quality than standard.

And he kept rattling those exposed big end bolts against the crank journals!!!  if you drop the rods down onto the crank on a car engine, you'd place something like silicon hose over the threads to avoid contact with the crank.

Offline Underdog1

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Re: CB750 Barn find project - Where do i even start!?
« Reply #32 on: July 26, 2016, 11:14:22 AM »
Another quick question, and inknow this can be a contentious issue...

Is running a 10w40 Semi synthetic oil API SL/CF ok for this bike?

Offline Trigger

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Re: CB750 Barn find project - Where do i even start!?
« Reply #33 on: July 26, 2016, 01:13:43 PM »
It is not contentious, you need 10-40 mineral. The ignition should have a plug on it that plugs into the loom.

Offline royhall

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Re: CB750 Barn find project - Where do i even start!?
« Reply #34 on: July 26, 2016, 01:14:37 PM »
Not seen that video for a while but from memory, I think he does it that way so he can fit one piston at a time instead of having to deal with all four. In avoiding that one small issue he creates many more issues. Really weird way of doing it.
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Offline Trigger

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Re: CB750 Barn find project - Where do i even start!?
« Reply #35 on: July 26, 2016, 01:19:43 PM »
Not seen that video for a while but from memory, I think he does it that way so he can fit one piston at a time instead of having to deal with all four. In avoiding that one small issue he creates many more issues. Really weird way of doing it.

I have never seen so many school boy errors.

Offline Jamesh_sussex

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CB750 Barn find project - Where do i even start!?
« Reply #36 on: July 26, 2016, 04:57:20 PM »
This might help finding a caliper.
http://www.sohc.co.uk/index.php/topic,1562.0.html

Cheers

Dennis

Yeah that may well come in handy, cheers bud!

Underdog,  I'm so sorry,  I seem to have inadvertently thrown a metaphorical spanner into your thread, now it's all about that fella on Youtube. Is he Australian Perhaps; and could that be why he builds engines upside down.  8)

I'm new here myself, but from what I've read.on this excellent forum I feel sure that you are eventually going to find all the information and help you could ever want.

Rob

Hah no worries!



So i only managed to get 30 minutes or so poking about the old girl today as i finished work late. Took the ignition off at the block connector, connected a good battery touched the spade connectors for the red and black wires and didn't get anything.. no electrics.



Hopefully this is a fault at my end as the advert did state that the bike turned over with a good battery, is there a better way to bypass the ignition?

Now I've got the lock off anyone know a way i can find the key code (on I'm assuming the lock barrel) without destroying it?).



Now the tanks off I'm a little confused by the fuel line set up.. the petcock has 2 outlets but i can only see one fuel line fitted (nothing was actually connected up though) which has a T junction to seemingly feed a each pair of carbs. So this set up means all the carbs are fed off just one petcock outlet.. I'm probably being an idiot here but whats the other petcock outlet for?  ;D




As a bonus, heres the inside of my petrol tank the dirty old girl


Good news is the carbs are probably original to the bike. The K5/6 US models switched the petcock (fuel tap) to the LHS with a single fuel outlet. They did this as a safety update so if a rider hit reserve they could switch the tap with the left (non throttle) hand.

Looks like you have a K2 tank and seat fitted. The K2 tank has the fuel tap (with two outlets) on the RHS.

Given the rusty fuel tank, get yourself one of these so you don't contaminate the carbs (once you've checked and cleaned them) when you first run the bike after basic inspection / servicing..:

https://www.ebay.co.uk/itm/351510130564

I've recommissioned several US import 750's and they are generally pretty bullet-proof. Do yourself a favour and get her running nicely first before you start spending out too much...

James

Offline Underdog1

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Re: CB750 Barn find project - Where do i even start!?
« Reply #37 on: July 26, 2016, 05:30:54 PM »
Looks like you have a K2 tank and seat fitted. The K2 tank has the fuel tap (with two outlets) on the RHS.

Given the rusty fuel tank, get yourself one of these so you don't contaminate the carbs (once you've checked and cleaned them) when you first run the bike after basic inspection / servicing..:

https://www.ebay.co.uk/itm/351510130564

I've recommissioned several US import 750's and they are generally pretty bullet-proof. Do yourself a favour and get her running nicely first before you start spending out too much...

James

Ah that would explain it, i take it i can just run two fuel lines from it (one to each pair of carbs)?

Just bought that remote fuel tank, was literally about to bodge one together out of an old petrol can and hosepipe  ;D

Started work on cleaning the rust out the tank



Gwarn science lad!

Offline Underdog1

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Re: CB750 Barn find project - Where do i even start!?
« Reply #38 on: July 27, 2016, 11:54:57 AM »
No real progress so far, the key i ordered still hasn't turned up and i haven't been able to get the ignition on by using a decent battery and connecting the red and black ignition wires.

Wish i had just bought an aftermarket ignition and key as it would have been the same price and would be here by now!

The 40 year old wiring looks crusty and a lot of the connectors look well past there prime, i think I'm going to rewire the entire bike at some point as it looks like the wiring can be simplified a bit and will at least last a while then.

I found this schematic online, is this a good place to start?

« Last Edit: July 27, 2016, 11:59:44 AM by Underdog1 »

Offline AshimotoK0

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Re: CB750 Barn find project - Where do i even start!?
« Reply #39 on: July 27, 2016, 12:15:59 PM »
Looks OK ..no horn or indicators though. If I was doing a non-standard rewire I think I would use sealed Deutsch connectors for perfect weather protection
“Alright friends, you have seen the heavy groups, now you will see morning maniac music. Believe me, yeah. It’s a new dawn.” Grace Slick, Woodstock '69 .. In the year of the Sandcast.

Offline Underdog1

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Re: CB750 Barn find project - Where do i even start!?
« Reply #40 on: July 27, 2016, 01:29:48 PM »
yeah I'm going to do away with indicators, no time for that nonsense.

Will look up those connectors you mentioned.

As I'm waiting out on this key to arrive I'm just familiarising myself with the bike. Came across this tube which looks to be some sort of breather or overflow tube. Not quite sure what its for though.

Top end is near the battery



Other end comes out next to the centre stand


Offline AshimotoK0

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Re: CB750 Barn find project - Where do i even start!?
« Reply #41 on: July 27, 2016, 02:09:40 PM »
I may have some of those connectors somewhere,  if I can find any I will dig a few  out for you (free) . Good thing is you can solder them  as well as crimp. I have the hand crimper in the loft somewhere ...today that tool costs over 350 quid!


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« Last Edit: July 27, 2016, 02:14:45 PM by AshimotoK0 »
“Alright friends, you have seen the heavy groups, now you will see morning maniac music. Believe me, yeah. It’s a new dawn.” Grace Slick, Woodstock '69 .. In the year of the Sandcast.

Offline Jamesh_sussex

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Re: CB750 Barn find project - Where do i even start!?
« Reply #42 on: July 27, 2016, 02:38:41 PM »
Looks like you have a K2 tank and seat fitted. The K2 tank has the fuel tap (with two outlets) on the RHS.

Given the rusty fuel tank, get yourself one of these so you don't contaminate the carbs (once you've checked and cleaned them) when you first run the bike after basic inspection / servicing..:

https://www.ebay.co.uk/itm/351510130564

I've recommissioned several US import 750's and they are generally pretty bullet-proof. Do yourself a favour and get her running nicely first before you start spending out too much...

James

Ah that would explain it, i take it i can just run two fuel lines from it (one to each pair of carbs)?

Just bought that remote fuel tank, was literally about to bodge one together out of an old petrol can and hosepipe  ;D

Started work on cleaning the rust out the tank



Gwarn science lad!

Yeah - just run a pair of individual lines and you'll be fine.

That overflow tube by the battery tray is for the battery overflow (for lead-acid batteries). If you use a sealed / agm battery you can do away with it.

Offline Underdog1

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Re: CB750 Barn find project - Where do i even start!?
« Reply #43 on: July 27, 2016, 04:30:12 PM »
I may have some of those connectors somewhere,  if I can find any I will dig a few  out for you (free) . Good thing is you can solder them  as well as crimp. I have the hand crimper in the loft somewhere ...today that tool costs over 350 quid!


(Attachment Link)

(Attachment Link)

That would be awesome, cheers bud!
Yeah - just run a pair of individual lines and you'll be fine.

That overflow tube by the battery tray is for the battery overflow (for lead-acid batteries). If you use a sealed / agm battery you can do away with it.

Yeah took the rear fender off and there was a little sticker underneath with a diagram of it  :D

Offline Underdog1

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Re: CB750 Barn find project - Where do i even start!?
« Reply #44 on: July 28, 2016, 01:14:32 PM »
So another day and the replacement keys still haven't turned up! The doubt the set i ordered from the code on the tank lock are even going to fit now as (a previous poster alluded to) the ignition should have a code on it somewhere unless it is aftermarket.. and i can't find one. Called a local locksmith and he quoted me some silly price to cut a key so I've just ordered an aftermarket ignition and key from eBay. If it turns out the set of keys I've ordered do fir then i can just return it i suppose.

So with not really much else i can do right now I've looked at the tank this morning, its been on the electric chair for over 2 days and I've conditionally ben scraping all sorts off the sacrificial anode so its definitely done something. I emptied it out sprayed some WD40 inside and swilled it out with methylated spirt before drying it out with a hair drier.

Suprisingy it doesn't actually look any better than before despite the crap that came out of it



and after looking deeper inside with a torch i found what looks like some sort of old sealant inside towards the front end of the tank




so with my best screwdriver i tried to scrape it off and found it to be quite hard



only managed to get a small bit out




Any tips on how i can strip all this shite out? Its probably the reason why the electrolysis didn't work as well as i thought it would