Author Topic: DOHC cb750 just purchased.  (Read 1600 times)

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Offline le_sterls

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DOHC cb750 just purchased.
« on: July 11, 2010, 10:32:06 PM »
I just bought a DOHC 750 from a friend for $150. It's in relatively good shape, just needs a new tank. Which brings up my first question, which tanks will fit on this bike? It's an '81. Engine runs, needs the carbs gone through, and I'm going to repaint, as well as get a new seat. Can't stand the one that's on it. If any of you have a tank and sidecovers for sale that will fit this model, let me know. Also, what seems to be problematic on these bikes? Never had experience with a DOHC.
That's what I'd like to hear.
'77 CB550k - running... For now...

Offline Alan F.

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Re: DOHC cb750 just purchased.
« Reply #1 on: July 13, 2010, 08:40:37 PM »
All of that info can be found at http://www.cb1100f.net/

Offline bikebitzofvt

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Re: DOHC cb750 just purchased.
« Reply #2 on: July 14, 2010, 05:47:36 AM »
I just finished resurrecting a 1981 CB750C from the grave.  The bike hadn't run in years.  The fuel tank had gotten rusty inside, fouling the carbs.  I de-rusted and etched the tank with muratic acid, then lined it with POR-15. Then I cleaned the carbs, replaced fuel lines, and installed new carb to airbox boots upon re-assembly.  Upon running the bike it wouldn't rev over 7K rpm.  After months of troubleshooting in my spare time including 2 more carb overhauls, bypassing the air cut-off valves, bypassing the vaccum fuel valve, checking valve clearance, installing new plugs and plug wires, installing a new battery, checking timing, replacing ignitor boxes, checking the charging system, rechecking everything again and again and again I stumbled onto this site: www.cb750C.com .  Following a suggestion there I checked voltage drop at the coils and found a loss of 2.1 volts!  Installing a relay from the battery to the coils resulted in the bike revving right up to red line as it should!  In 20+ years of working on motorcycles it's probably the most frustrating problem I've ever had to overcome, but certainly one of the most satisfying now that it's done!

I finshed up with a new clutch, new tires, flushed the front brakes, new chain and sprockets and some TLC.  The owner is picking it up this afternoon.

Do you have a C, K, or F model?  The fuel tank is pretty model specific, as are the side covers. 


Good luck with your new bike!!!
Tom
"If it ain't broke you aren't riding it hard enough!"

77 CB750K7, 77 KZ1000B

Online bryanj

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Re: DOHC cb750 just purchased.
« Reply #3 on: July 25, 2010, 07:46:05 AM »
Some 900 cosmetics fit, if its a real early one there was a recall to fit a modified oil passagway inside the sump to stop the sprocket seal blowing out meaning an engine out stripdown
Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

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