New to me bike on the way

S

Scottz

Active Member
I will be getting an '80 CB750 from my wife's uncle in the next week or two. At this point, all I know is that it has been garage stored and not run for several years, and will need some work before it will run. I should find out more details on Thanksgiving. I was wondering if there are any common problems with this model that I need to be aware of. My plan is to get it running and safe before I do anything else to it. After that, I'd like to do a scrambler/brat style makeover on it. He has a repair manual for it,and I've already either downloaded or linked everything I can find.

Thanks!

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Valve adjustment is criticle on those old DOHC 4's. If you have never set clearence on a shim and bucket type, read up and check out youtube, there are some decent videos on how to do it.
Ignore what the manual says, you're looking for .004 to .006 Inches or .10 to
.15 mm clearance.
Click to expand...
Also the cam chain tensioners have been known to wear, the old rubber gets hard and shreds / crumbles. Mine were fine.
Stick with the factory airbox... those CV carbs HATE pod style filters.
Do you know what model? there were 3... K , C, and F K was the standard, C was a Cruiser and F the Sport. Engine wise they are all the same. The K had a single front rotor while the C and K had dual, rear drum brakes on the K and C but the F got rear disc.
 
Its the K model, with a Vetter fairing and bags, so it will need to go on a diet. Thanks for the tips.
 
+1 to above.
Also check out your charging system carefully.
The rotor brushes wear, and rotors sometimes go bad. Reg/Rec is also suspect at this age...
 
Bozz said:
+1 to above.
Also check out your charging system carefully.
The rotor brushes wear, and rotors sometimes go bad. Reg/Rec is also suspect at this age...
Click to expand...
Yep, Yep....
I loaded a link to free downloads of the Factory Service Manuals on our Technical Documents page just for your bike.
It includes the charging system link to the CB1000 that is a little more detailed and apples to apples.
 
I hope everyone had a good Thanksgiving. I got to speak with my wife's uncle about the bike tonight. He said that it ran fine when he parked it and its been indoors since. He said he was embarrassed to ride it because the seat was ripped and planned to get it fixed but never did. So, it should be a good candidate for me. It has around 30k miles on it. It may be a week or two before I can go get it but my plans are to change out the fluids, put some penetrating oil in the cylinders just for insurance and then after it sits a day or two I'll see if it will turn over. After that, check the valve clearances and clean the carbs. Once its running I'll get the rubber and brakes up to date. I plan to spend the next season just riding, with no mods until next winter. I'll post pics once its home.

Where's the best place to order carb rebuild kits? Anyone ever try the outlaw kits on Amazon? I have some amazon credit I could use if their ok.
 
+1 on Randakk.
His kits aren't the cheapest, but are quite possibly the best.
All viton rubber than can handle the ethenol in modern fuel.
An Ultrasonic cleaning and one of his kits and you are probbaly good to go.
 
Well, this took a lot longer than I planned due to the weather and a pregnant wife but I finally picked up the bike today. Turns out it's not a 750k, it's a 750 F. It was last plated in 99. Gas tank is clean inside, no rust.
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Looking better with the fairing off, but now I need a headlight.

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Ok, my known issues...
Tires dry rotted
No brakes (both are dry)
Exhaust rusted through on both sides
Key will turn to lock position but not to on
No battery, turn signals or headlight
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Went after a K and come back with an F Super Sport? DAMN GOOD FOR YOU!!!
Those known issues of yours are perfect for a bike build... you'd be changing them all anyway.
 
I dont know why, but I love the stock bodywork on these bikes. Find a 750sc headlight cowl, throw on some lowrise superbike bars, updated shocks and an 80s-90s non usd CBR front end. Instant vintage superbike.
 
Well, I've only gotten to spend about an hour messing with it so far, so those are the issues I'm certain of so far. I hope to change the oil and try to turn it over this week. I know I'll be rebuilding the master cylinders at some point. They were both dry. After filling them up, I started bleeding the rear and had fluid coming out of the bleeder but now the caliper is locked up. I probably just need to flush it all out good. The front still has no pressure going anywhere at all.
 
Scottz said:
Well, I've only gotten to spend about an hour messing with it so far, so those are the issues I'm certain of so far. I hope to change the oil and try to turn it over this week. I know I'll be rebuilding the master cylinders at some point. They were both dry. After filling them up, I started bleeding the rear and had fluid coming out of the bleeder but now the caliper is locked up. I probably just need to flush it all out good. The front still has no pressure going anywhere at all.
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You'll probably need to rebuild the carlipers.... and maybe the masters cylinders.
Concentrate on getting her running, not stopping. Squirt a little oil in the 4 sparkplug holes before cranking her over.
 
To be honest the exhaust has me worried. That's not a cheap item to replace, and it's kind of important. Any chance of me being able to cut them at the rusted area and adapting some kind of slip on muffler?
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