Author Topic: CB750 Barn find project - First Timer  (Read 32971 times)

Offline Underdog1

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CB750 Barn find project - First Timer
« on: July 23, 2016, 09:45:10 PM »
Hi guys,

I taking delivery of a 1976 CB750 tomorrow which is a non runner from a dry US state, something for me to spend my spare time tinkering with. Needless to say i have naff all history with this bike.

According to the seller it has good compression and when fed a few squirts of ether it fires and tries to start & run. My mechanical expertise are basic from doing various jobs on cars, and I've bought this bike to actually develop some better mechanical know how.

As i don't know the history of why this bike was stored in the first place I'm a little reluctant to start trying to fire her up straight off the bat - Can anyone give me any damage controlling tips on what i should check beforehand?

My first job will be to tear down and refurb the carbs, hopefully this will get her at least ticking over. Only time will tell hey!


« Last Edit: July 28, 2016, 08:34:41 PM by Underdog1 »

Online Jamesh_sussex

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Re: CB750 Barn find project - Where do i even start!?
« Reply #1 on: July 23, 2016, 09:51:28 PM »
Welcome to the forum, and looks like you've bought a DK special. Looks like a good base to start with....

Offline Johnwebley

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Re: CB750 Barn find project - Where do i even start!?
« Reply #2 on: July 23, 2016, 09:52:26 PM »
first,

  get a manual,with that read it and check ALL the bike over,

 renew brake fluid,engine oil and filters,

 beware of stripping the carbs if you don't know what you doing,

 spend time learning about the bike,before you touch it,


BTW,we love pictures on here,the more the merrier,

PS,Welcome the the wonderful world of sohc,lots of friendly people here,with stacks of expert advice,
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Offline Underdog1

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Re: CB750 Barn find project - Where do i even start!?
« Reply #3 on: July 23, 2016, 10:11:02 PM »
Welcome to the forum, and looks like you've bought a DK special. Looks like a good base to start with....

Hah yeah bang on. Pretty much the same description on all their imports!

first,

  get a manual,with that read it and check ALL the bike over,

 renew brake fluid,engine oil and filters,

 beware of stripping the carbs if you don't know what you doing,

 spend time learning about the bike,before you touch it,


BTW,we love pictures on here,the more the merrier,

PS,Welcome the the wonderful world of sohc,lots of friendly people here,with stacks of expert advice,

Cheers mate, yeah I've got a tatty second hand haynes manual ready for it. Im pretty mechanically minded so will hopefully get things figured out. Just didn't want to make a catastrophic mistake at the start line firing it up when theres no engine oil or something  ;D

Online Trigger

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Re: CB750 Barn find project - Where do i even start!?
« Reply #4 on: July 23, 2016, 10:11:40 PM »
Welcome to the mad world of the SOHC. Met a guy a couple of days ago at a café on the coast that just bought a CB750K1, USA import. He was telling me that he only rode the bike 7 miles to the MOT station when the top end went wrong, due to the oil jets blocking. So, at least remove the sump to see what state the engine is in. Enjoy :)

Offline MarkCR750

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Re: CB750 Barn find project - Where do i even start!?
« Reply #5 on: July 24, 2016, 12:25:51 AM »
Trigger is talking about the most worrying feature of these engines, if the jets are blocked it'll eat it's cam, so you either take the engine out and strip down to check the jets are clear, or clean the carbs change the oil and fire it up with a couple of tappet covers removed to see if there is oil splashing about the rocker area, if you remove the tappet covers before you do anything else and see residual oil in there it's a positive sign but not a guarantee, as trigger said it can get nasty!, I took the risk on mine and fired it up, happily plenty of oil getting to the top, but it's a call only you can make!.
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Offline AshimotoK0

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Re: CB750 Barn find project - Where do i even start!?
« Reply #6 on: July 24, 2016, 07:12:50 AM »
Hi welcome from me too .. a nice friendly bunch on here.

Start by downloading this. It's a big file but has the relevant parts/service manuals.

https://www.dropbox.com/s/anpzqn2r55f1o9k/CB750%20Mega%20Parts%20Service%20and%20More.pdf?dl=0

I recognize that turntable at DK !

My advice is to strip the motor, at least the top end. My mate bought a 3k mile 500/4 from them a few months back but it didn't have a centre cable in the speedo cable ! It's obviously a very low miler but not 3k). He's fannied around trying to get it to run properly without stripping any of it but he's now stripping it. Same with the 9k mile CB350 I got from them . 'Weather seized from standing for umpteen years' , in their description. When I stripped it I found a big split pin jamming the gearbox (none used in that engine !) , so not weather seized at all ( Oh and a dried up wasp in the gearbox). I wish they wouldn't give bikes ' a few snort of ether' . God knows what damage it would do if the engine starts up after being stood for typically 30 years..
Don't get me wrong, I think the bikes from DK are sometimes great deals and the guys there are great to deal with, but some of their bikes look like them came from open air USA scrapyards plus they remove/swap bits themselves, plus the Yanks are notorious for not changing oil and tinkering, giving up and ditching the bike. After all the bikes were not work transport but mainly recreational vehicles.
“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 onethumb

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Re: CB750 Barn find project - Where do i even start!?
« Reply #7 on: July 24, 2016, 10:20:19 AM »
Welcome to a new world order where old bike rule.
Thanks for the link ashimoto.
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Offline Honda Al

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Re: CB750 Barn find project - Where do i even start!?
« Reply #8 on: July 24, 2016, 10:35:11 AM »
Welcome. What's not known on this site about our bikes isn't worth knowing!

I've bought two DK specials now. Pleased with both of them. My CL350 was described in exactly the same way, but after checking it over and putting a new battery in it started straight away and I rode up the road with it. I'm not sure how much effort they put into trying to start them so you might be surprised when it arrives.

Alan


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Offline AshimotoK0

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Re: CB750 Barn find project - Where do i even start!?
« Reply #9 on: July 24, 2016, 01:36:05 PM »
Welcome. What's not known on this site about our bikes isn't worth knowing!

I've bought two DK specials now. Pleased with both of them. My CL350 was described in exactly the same way, but after checking it over and putting a new battery in it started straight away and I rode up the road with it. I'm not sure how much effort they put into trying to start them so you might be surprised when it arrives.

Alan


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Don't know if you are aware Al but there is an M6 bolt on the cambox on the CB/CL350 twins. It's purpose is to check oil feed to the top end. Funnily,  only about four years ago,  I asked DK why they never imported smallish Honda Twins and they told me it wasn't worth it / No demand. They obviously had a rethink!I was really pleased with the the '69 350K1 I got from them. They had removed bits from it and it never sold so I picked it up in a 'deal'  for less than £1K but it had the nicest chrome of any other twin I have seen them selling. I literally had nothing to re-chrome on it.
“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 #10 on: July 24, 2016, 02:51:05 PM »
So the bikes just been delivered, cosmetically it looks in reasonable nick.

The first obvious issue is it didn't come with any keys, i presume theres some sort of way to order them through Honda?

Offline MarkCR750

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Re: CB750 Barn find project - Where do i even start!?
« Reply #11 on: July 24, 2016, 04:23:27 PM »
You could Hotwire it for now, pul the plug out of the ignition switch and connect red to black, ages since I did mine, someone correct me if I'm wrong!
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Offline Chris400F

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Re: CB750 Barn find project - Where do i even start!?
« Reply #12 on: July 24, 2016, 04:57:01 PM »
Not sure about the 750 but on smaller models the key number is often marked on the body of the ignition switch somewhere.
I have used this guy a couple of times to order keys by number.
http://www.ebay.co.uk/itm/281030401159?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Offline Underdog1

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Re: CB750 Barn find project - Where do i even start!?
« Reply #13 on: July 24, 2016, 05:05:32 PM »
You could Hotwire it for now, pul the plug out of the ignition switch and connect red to black, ages since I did mine, someone correct me if I'm wrong!

Yeah ill give that a go for now, cheers bud.

Not sure about the 750 but on smaller models the key number is often marked on the body of the ignition switch somewhere.
I have used this guy a couple of times to order keys by number.
http://www.ebay.co.uk/itm/281030401159?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

The only code i can find is on the seat lock, I've messaged the seller and hopefully the seat lock is the same as the ignition.


Other things I've noted so far:

No front brake calliper! Bit annoying as looking on bey I'm going to be spending £80+ replacing it.. Does anyone know if I can use any CB750 SOHC calliper or do they differ year to year?

Inside of the tank is mega rusty. Going to try some electrolysis to see if i can bring it back to life.

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Re: CB750 Barn find project - Where do i even start!?
« Reply #14 on: July 24, 2016, 06:23:29 PM »
Let the fun begin  ::) Not all SOHC calipers are the same, don't rush as you will need to get the old girl running before worrying about getting her to stop.
The seat key is very rarely the same as the ignition.