84' Honda CB750SC - 32 years and going, what should I be replacing at this point? | GTAMotorcycle.com

84' Honda CB750SC - 32 years and going, what should I be replacing at this point?

JayRad

Member
Hey all,

I'll be beginning my year long project build this month with an 84 Nighthawk. It was last owned by a younger fella who was converting it into a cafe racer; and honestly it looks very good so far thanks to his hard work. However, my first course of action is to put the framework and cafe racer mods on hold, and focus on getting things going on the mechanical and performance side of things. (Not doing air pods or anything fancy; just stock)

As of right now...

- Carburetor is leaking fuel; I intend on taking it apart investing in a carb rebuild kit.
- Exhaust is hanging by some wire right now, and there is no muffler installed.
- Requires a new battery, and some electrical + wiring management

Other these these obvious more matter's, can any of you CB750 owner's/educated users suggest to me what I should be replacing on an old classic like this? I believe most of the parts are all original, or if not were replaced in the last few years; but If I am going to be pulling the carbs and extracting the engine for eventual frame and electrical work, should I just go the full 9 yards and start replacing well-known wearing and weathered parts? (gaskets, cylinder kits, valve kits, wiring harnesses etc etc) I'm willing to spend whatever I need to have her running optimally.

Thank a bunch people

VZ8LhmZ


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Tires would be at the top of my list.

What is your goal here? If you are making it to ride, I wouldn't disassemble much past the carbs and a valve check unless you have a good reason to. You are investing a lot more time and money with literally 0 increase in value at the end (and possibly no improvement in anything else either as maybe it's in good shape inside already).

I would do the carbs, valve check, compression test (or leakdown) and minimal wiring to get it running to see how everthing is working. Use that shakedown to focus your efforts.

EDIT:
Always keep in mind that a cafe'd 750 will probably sell for <$2000 when complete no matter how much time/effort/money went into it.
 
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Tires would be at the top of my list.

What is your goal here? If you are making it to ride, I wouldn't disassemble much past the carbs and a valve check unless you have a good reason to. You are investing a lot more time and money with literally 0 increase in value at the end (and possibly no improvement in anything else either as maybe it's in good shape inside already).

I would do the carbs, valve check, compression test (or leakdown) and minimal wiring to get it running to see how everthing is working. Use that shakedown to focus your efforts.

EDIT:
Always keep in mind that a cafe'd 750 will probably sell for <$2000 when complete no matter how much time/effort/money went into it.

Thanks for your input GreyGhost!

My goal is simply to hold onto something that I put my own time and energy into, and enjoy riding for years to come with my some friends. I am not into flipping the bike for a profit down the road; it would likely just stay in the family and be a hobby bike.

I've heard the engine run once so far upon purchase, and I'll be bringing the ride home on my trailer this weekend. Aside from the carburetor leaking while idling, the engine sounded like it was firing pretty good. Regardless I'd definitely like to run that shakedown just due to the shear age of the bike, and because you can't fully trust everyone's word on vehicle history.

Great stuff, thanks GreyGhost
 
I would first have the bike running properly b4 spending money on anything else.

No sense in doing anything else before you know if you have a good runner or not.

leaking gas - make sure your kit includes new float needles and seats.

The DOHC 750 motor is reliable and easy to work on. It is generally running slightly lean from the factory to pass emissions.
This engine responds very well to jetting and tuning - even on a stock engine with OEM pipe and airbox. Im pretty sure the needles are not set up with slots/clip to adjust their height. Just placing tiny washers (0.6 to 0.8 mm in thickness) under the needles is enough to noticeably improve driveability. Washers cost near nothing, but finding right size tiny washers may be a slight challenge.
 
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Check all the consumables - intake manifolds, etc. for cracks and possible air leaks.
The motor internals are likely okay (if it turns over) and best left alone for the time being.
All the cycle parts - brakes, steering and swing arm bearings, wheel bearings, fork seals and oil should be inspected and changed as required.
 
Those floppy turn signals (if still there) should be replaced. I think Honda used similar for a decade on different bikes.
 
I would first have the bike running properly b4 spending money on anything else.

No sense in doing anything else before you know if you have a good runner or not.

leaking gas - make sure your kit includes new float needles and seats.

The DOHC 750 motor is reliable and easy to work on. It is generally running slightly lean from the factory to pass emissions.
This engine responds very well to jetting and tuning - even on a stock engine with OEM pipe and airbox. Im pretty sure the needles are not set up with slots/clip to adjust their height. Just placing tiny washers (0.6 to 0.8 mm in thickness) under the needles is enough to noticeably improve driveability. Washers cost near nothing, but finding right size tiny washers may be a slight challenge.
I usually use tiny nylon washers from circuit city, cheap and they stock many sizes.

Sent from my SM-A500W using Tapatalk
 
Where is Circuit City?

via Tapatalk
I was referring to "The Source by circuit city", but I guess it's just called "The Source" now. RC related hobby shops carry tiny washers as well.

Sent from my SM-A500W using Tapatalk
 
Check all the consumables - intake manifolds, etc. for cracks and possible air leaks.
The motor internals are likely okay (if it turns over) and best left alone for the time being.
All the cycle parts - brakes, steering and swing arm bearings, wheel bearings, fork seals and oil should be inspected and changed as required.

Thanks for the feedback my friend :)
I've compiled quite a to-do & check list so far.
 
I would first have the bike running properly b4 spending money on anything else.

No sense in doing anything else before you know if you have a good runner or not.

leaking gas - make sure your kit includes new float needles and seats.

The DOHC 750 motor is reliable and easy to work on. It is generally running slightly lean from the factory to pass emissions.
This engine responds very well to jetting and tuning - even on a stock engine with OEM pipe and airbox. Im pretty sure the needles are not set up with slots/clip to adjust their height. Just placing tiny washers (0.6 to 0.8 mm in thickness) under the needles is enough to noticeably improve driveability. Washers cost near nothing, but finding right size tiny washers may be a slight challenge.

Touche, I'll definitely be getting her running smoothly first above all else.

I've toy'd with the idea of jetting, but I'll probably save that for a later project. If I was to jet, I'd probably go down the route of changing the air intake as well. Not a huge pod fan, but I have seen the other aftermarket air boxes that would compliment the bike quite well.

Thanks for your input man!
 
Those floppy turn signals (if still there) should be replaced. I think Honda used similar for a decade on different bikes.

I've still go the old turn signals; though detached at the moment. I may look into another means of turn signals if that's the case. I haven't done too much research on how other owners have handled their floppy turn signals.
 
I was referring to "The Source by circuit city", but I guess it's just called "The Source" now. RC related hobby shops carry tiny washers as well.

Sent from my SM-A500W using Tapatalk
Thanks, I get it now.

via Tapatalk
 
Touche, I'll definitely be getting her running smoothly first above all else.

I've toy'd with the idea of jetting, but I'll probably save that for a later project. If I was to jet, I'd probably go down the route of changing the air intake as well. Not a huge pod fan, but I have seen the other aftermarket air boxes that would compliment the bike quite well.

Thanks for your input man!

Keep the airbox intact. Pods are difficult to tune and do little. IMO.

Would be great if you posted your bike with pics in the "project section". subscribed lol.
I owned two cb750F's, a 1980 in stock cond, and a 822cc 1981 cb750F w mikuni 29mm smoothbores and velocity stacks, and upgraded suspension (race bike). Fond memories.
 
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