Author Topic: need help testing CB750 motor  (Read 576 times)

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Offline Jcold98

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need help testing CB750 motor
« on: September 10, 2018, 08:10:38 PM »
HI, still new to the forums and first real discussion starter.

I have 1978 cb750 frame and have recently obtained a CB750 1972 motor along with the receipt from a reputable motorcycle shop showing that the motor had been rebuild back in 2007 and i was told it has yet to see any miles in a bike yet (supposedly).

I have basic mechanical knowledge (more so with cars) but i would like to know if there are any kind of tests or things i can do to check to see where i stand with this engine while i finish working on repairing the wiring harness. I was also told by someone in the motorsports department of Clawson Honda Fresno that a compression test would not give me the information im looking for if it had not been broken in after the rebuild. I was also told that it is impossible to start the engine outside of the frame? how true is this? what makes this engine different from an old car engine that you can start on an engine stand?

Any help or advice is appreciated

Offline 754

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Re: need help testing CB750 motor
« Reply #1 on: September 10, 2018, 08:27:28 PM »
First, check intake ports and exhaust for carbon..
 Check pistons thru plug hole for carbon and evidence  of big bore or higher compression.
 In a darkened room with a strong light you can see the piston and maybe parts of the bore with the light outside the hole.
 I just installed one that had likely not been started, but had a natural mistrust.
 I pulled valve cover on mine,  everything new , clean and stock, and had red assembly oil.
Seller said it may have had hotter cam. If you pull cover and its a hotter cam, check valve clearances,
 
 Can you have or make a test or run in stand....easily..
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way