Author Topic: Pull engine or not?  (Read 1059 times)

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Offline zhalx

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Pull engine or not?
« on: June 22, 2020, 03:17:09 PM »
When deciding whether or not to pull and restore an engine, what are the things you'd typically look for other than compression? If compression is good, is it worth pulling the whole thing?

I've had a 78 CB750K for a few years now, and it runs pretty well. I've long had cafe plans for it, but have always lived in a city apartment and have no place to work on it properly. I ride in fear that some old part is going to break and that'll be it. I've done basic maintenance, but not enough to feel super safe.

Well, I just bought my first house and I have a whole bay to devote to motorcycle projects. I'm thrilled, and have been spending more time making tool wish lists and dreaming about mods as our closing date approaches than thinking about the move itself.

Regardless, I want to pull everything apart and restore / replace what needs replacing. I'm still a relative amateur — I've pulled and rebuilt carbs about 7 times on a previous bike (the first 5 times were me learning the hard way that there's no such thing as a shortcut when it comes to old motorcycles), replaced valve shims, etc. Pulling the engine kind of scares me a bit, but a big goal is to KNOW that my bike is solid all the way through. I also want to clean and polish everything up, get rid of the pitting, etc. Half my motivation is aesthetics. Engine's got < 15k miles, but it spent a lot of time sitting (obviously). I'm definitely doing a full restore on all the non-engine parts, going to learn to do wiring etc, but want some advice on whether or not I should commit to going all the way and stripping it down to the frame, or if that's overkill for a bike that doesn't *seem* to have any engine problems.
1978 CB750K

Offline seanbarney41

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Re: Pull engine or not?
« Reply #1 on: June 22, 2020, 03:38:08 PM »
Leave it be.  It is more dependable in the form it left the Honda factory.  Aftermarket parts, inadequate machine shop services, and incorrect assembly are about the only things that screw these engines up.

Trust me.  I have travelled thousands of miles with cb750 engines worn much more severely than what you are reporting and I have NEVER been stranded anywhere ever.

Jump over to the 20 rides for 2020 thread and do a 100 miler.  100 miles in a day, or 500 everyday...don't rebuild it until it needs it.  It is NOT possible to put it back together the way it was at the factory.
If it works good, it looks good...

Offline Stev-o

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Re: Pull engine or not?
« Reply #2 on: June 22, 2020, 03:55:15 PM »
I typically do a leak down test and then go from there. 

But generally speaking, agree with Sean to let it be and "run it"!
'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline zhalx

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Re: Pull engine or not?
« Reply #3 on: June 22, 2020, 08:56:35 PM »
Great, that's what I wanted to hear!
1978 CB750K

Offline bryanj

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Re: Pull engine or not?
« Reply #4 on: June 23, 2020, 11:57:32 AM »
Old saying

"If it a'int broke don't fix it"
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).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline ekpent

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Re: Pull engine or not?
« Reply #5 on: June 23, 2020, 03:43:06 PM »
 + 1 to all you old farts and your suggestions.