New Member from south coast NSW Australia CBX750F 1984

Quadbuilt

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Hi everyone,
I just purchased this CBX750F 1984 model here in Australia; compliance plate/frame number (RC17-2005966) 3/1984.
I have a few questions for those experienced CBX750/CB750 DOHC owners. The guy I bought this bike from said it was running 10 years ago had a recent top end rebuild then but had some electrical problems hence he stopped riding it. It also had a small gasket leak and the engine had a rattling noise when not under load that went away under acceleration. I assume the rattle is either a cam chain tensioner issue or the cam chain has stretched and needs replacing. So I have ordered a new one and full gasket kit but I want to sort the electrical issue out before I tear the engine down (this will be my first road bike tear down) I have experience with dirt bike engine rebuilds.
Electrical Issues
I intend to drain the tank and refurbish the caby's. Buy a new lithium battery spark plugs and begin tracking down the electrical issues.
Any common failure points to look out for?
Exhaust System
I also noticed most images and videos of this model have a 4 into 2 exhaust system. This bike has a 4 into 1 (is that an after market system and muffler) or was there a choice when purchasing for or were there variations in different country's build years etc??

Any help in getting me started in the right direction would be very helpful. I am keen to get cracking on this custom build.

Cheers,

J
 

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amc49

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Not going to find much on this site on them, I don't think I saw 5 of those since 1984. The exhaust came only 4/2 and that exhaust exit says custom for sure. I myself would never buy a bike that somebody has been through the 'top end' on, it bespeaks too many things wrong. Cam chains make more noise at speed than they do down low at least in my view.
 

Quadbuilt

CB750 New member
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Not going to find much on this site on them, I don't think I saw 5 of those since 1984. The exhaust came only 4/2 and that exhaust exit says custom for sure. I myself would never buy a bike that somebody has been through the 'top end' on, it bespeaks too many things wrong. Cam chains make more noise at speed than they do down low at least in my view.

Well it has over 46000 Kms and the work was done by a qualified Honda motorcycle shop so I have no problem with professional top end rebuilds. Thanks for your input.
 

fg1972

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Hi there and welcome.
In regards to electrical issues, on the dohc cb750s, the charging system seems to be a common problem. The rotors can fail to produce AC volts particularly when hot and also regulator/rectifier failure where it won’t charge the battery.


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Galeforce

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Hi Quadbuilt,
Mate, I just got the same bike! 1984 CBX750F R17
There doesn't seem much support online for this model. I don't think they sold in the USA. The nighthawk was the closest model.
First things first, Do you have a service workshop manual? If you don't, I will organize one and share it with you.
What's your plan? are you going original or custom?
Mine is in pretty good shape so I'm keeping it original. I see you have a 4 into 1 exhaust. nice.
The cam chain would be a good place to start. possibly valve gaps. I'm no guru but I'm willing to help.
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