Topic: Just bought a replacement motor - how should I prep for install?

[Tugboat]

So I had been planning on swapping out the top-end from a donor 750K motor onto the bottom-end of my 750F. That part's no problem. But there are probably a bunch of metal flakes in the bottom from where I dropped a valve(s) that would require complete teardown to clean up (judging from the amount of "glitter" that came out of my oil filter). That work, plus the cost of a valve job & (at a minimum) honing of the cylinders PLUS the fact that the more I read about it, the more I feel like I'm in over my head with the complete teardown have led me to look for known runners that I can just drop in and go. Enter this (please don't swipe it out from under me!):

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=220703932650&ssPageName=ADME:X:RTQ:MOTORS:1123

Any advice? 11k miles is pretty low.. 140psi is great.. I've emailed back & forth with the guy and he seems to be honest. What would you do?

[lone*X]

Over 7000 feed back with 100% positive pretty much indicates the seller is honest.  The price is good, even with shipping, for a motor in the condition described.  Buy it.  After you get your bike back on the road you can part out the old motor and make back some of the cost.

[KingCustomCycles.com]

Replace.  At that price you will not be sorry. I have purchased about 35, 750, SOHC engines and 2 out of that batch were unusable.  Honda built a very good engine that can take sitting and neglect for years. 

[Tugboat]

Thanks for the advice fellas! I did indeed end up buying this motor - $400, including shipping. Not too bad!!

So any recommendations as to how I should prep this thing before I install it?

[Tugboat]

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[Tennessee]

eFFin' score!  I had nothing to contribute to the thread but I had to express my excitement for a local soon ot be back on the road again.  I have been looking for a K motor for my potential F-bomb grenade also... just not as dilligently as you I see. 

[Kong]

Well, there's not much to say.  If you plan to start it right away put a set of carbs and some sort of exhaust on it, a set of plugs in it, put in fresh oil and a filter, and kick it over ten or twenty times by foot to get oil distributed, then fire it up.  If you wanted to be completely anal about it you could take a blow nozzle and blow air in through the spark plug holes while someone kicked the engine over so as to blow any garbage that might have found its way in through the open ports (as the valves opened and closed) back out into the cruel cruel world.  

When you think about it, and this is particularly true of a dry sump engine, if no water got to it there isn't much to go wrong with an engine no matter how long it sits.  The seals and gaskets deteriorate to some extent but they are all replaceable if the need be, other than that about the worst that happens is a little surface rust forms on the cylinders where either valve was partially open all those years.  But if there was no actual flow of water into it that stuff will scrub itself right off with the first few thousand revolutions of the engine.  I do think that once you get it running you should change the filter and oil at a pretty short interval the first time, maybe after the first 500 miles, just to catch any scrapings and bug nests that might have found their way in there and got mixed with the new oil.  After one change and a good tuneup you should be in good shape.

On Edit:  Now is the time to clean and paint it, not after it is in the frame!

[CycleRanger]

Thanks for the advice fellas! I did indeed end up buying this motor - $400, including shipping. Not too bad!!

So any recommendations as to how I should prep this thing before I install it?

While you've got the engine out of the bike don't forget to scrub it down and repaint.

Assuming the oil is already drained remove the filter and oil pan and clean.
Pull the stator, shifter, valve, and clutch covers and clean out the sludge that will be there. Pull the oil gallery plugs and clean.
Basically remove all the covers and clean and replace with fresh gaskets/o-rings.
Flush the engine with some solvent to help remove the sludge.
When you do get it fired up I'd run it only until the oil is hot then shut it down and drain it and change the filter.  Repeat at least once more.  After that I'd run it maybe a few miles then change the oil again.
If the bike sat for a number of years there's gonna be a lot of sludge in the bottom of the engine that will dissolve/break up when it gets hot.

At least that's pretty much what I did my used motor that had been sitting for years before I bought it.

Seriously, looking at the motor it's been sitting outside for a number of years. You may even want to pull the oil pump apart and make sure it's clear before you try to start it.  Post some photos when you get the motor.

[Spanner 1]

Way to go Tug  .... I'm facing the same dilemma myself; got the '78K motor totally apart and need new mains, big-ends, pistons, rings, gaskets. 'Prolly more economic to get a complete motor and replace it. We'll see when the weather warms back up in a few weeks.... anyone got a low milage '78 motor to sell 

[Tugboat]

Thanks for the advice & encouragement fellas! Now we're getting somewhere!

I totally dig what you're saying about flushing the motor out. I've pulled the oil pan off a couple of cars before and can only imagine what kind of sludge is down in this thing after having sat for a while. Couple of questions about that though:

OK - so after cleaning the pan, checking the oil pump and cleaning out my oil tank, I just fill it with oil and seafoam or something? Then run it for a bit, drain, repeat?

Any advice about pulling the pan? After you get the screws out it's stuck on with the gasket and whatnot - and I don't want to mar the mating surfaces. Just knock on it with a mallet or something and it comes right off?

Also, what are the oil gallery plugs?

[CycleRanger]

The pan should come right off pretty easily. 
You should consider putting the engine on a stand so you can more easily access it while you're working on it.
There's several threads here about building or adapting an stand for use with a CB motor. Just do a search.
As for the rest, please reread my earlier post, you want to pull ALL the covers off.

[Tugboat]

I've got an engine stand that I made out of 2x4's that I'll be using, so that's taken care of. And I'll be removing all of the covers & cleaning out all the gunk collected there.

So what about my proposed flushing method (oil + seafoam.. run, drain, repeat)? Does that sound okay?

Also still wondering what the oil gallery plugs are..

[y2kc0wb0y]

Way to go Tug  .... I'm facing the same dilemma myself; got the '78K motor totally apart and need new mains, big-ends, pistons, rings, gaskets. 'Prolly more economic to get a complete motor and replace it. We'll see when the weather warms back up in a few weeks.... anyone got a low milage '78 motor to sell 

Sure do. I think it's got 7-8K on the clock. Him me up off line if you want to chat about it.

[Kong]

I would not put SeaFoam or anything else in the oil.  Clean the pan and put it back up, put in oil, run the bike, change the oil.   The oil has detergents in it to lift the varnish that is left, the filter is there to capture any particles.  Let them do their job.

[CycleRanger]

Also still wondering what the oil gallery plugs are..

#5 in the drawing.