Topic: Free After One Year!!!

[chewbacca5000]

I am so excited I just unstuck my first engine from a 76 CB750.  I got it a about a year ago as part of a package deal with a 73 cb750 and I could not get it to budge an inch so I put marvel mystery oil in there and after several weeks the kick start would not move till I tried it again tonight.

This time I dumped in some Berryman chem tool and let that do it's thing for awhile an still nothing.  So I remember a post that I read sometime ago that said to try turning the alternator nut on the crank.  So I took the covers off, and low and behold she turned over!!!  I am so excited like a kid in the candy store Merry Christmas to me!!

Ok, now here is my question what this engine stuck in the first place?  Turning with the alternator nut on the crank was easy.  Is this how you guys do it with the engine out of the bike?

Also, the intake valves on 2 and 3 look have some rust should I care?  Can I suck the junk out with a vac and call it good, or am I asking for trouble.


 

[dave500]

anything you cant get out becomes grinding paste and get all through the motor,i always dissemble a stuck engine.

[K5owner]

+1 with dave500; I'd take the engine out and go through it. Look on the bright side...  makes for a good winter project. At the end you'll know you have a sound reliable engine.

[chewbacca5000]

I know Dave is probably right, but I am not sure the engine was stuck in the first place.  Since the engine was out of the bike when I got it I only tried using the kick to turn it over and it would just rock back and forth.  I am almost thinking putting the breaker bar on the alternator nut made the difference.  What do you think?  With the engine out I am not sure the kick start is the way to go to see if an engine is free.

[simon#42]

dave isn't probably right , dave is definitely right .... take it apart now or take it apart after you have gone to all the trouble of fitting it , starting it , and damaging it more .

[rb550four]

I think that you have some really good answers here . I have run into this same thing a time or two before, even when I pick up a running 35 year old machine, there is too many unknowns . I want a reliable machine every time I get on it, don't like getting stranded, and too old to push a 500lbs machine back home. I have a strict policy , tear it down- clean the rust out of the gears,bearings,and oil ports, clean the oil pump so there is no junk floating around, get new gaskets for everything case related especially shifter rod ,they always leak and are not included in the gasket kit usually. This will also give you a chance to check the condition of your clutch and kick start action. I always get a new timing chain and check the main drive chain before it's apart  , quick hone ,a new set of rings will do you right. No skimping now, reseat your valves, check the springs and before you do the valves...very important , especially on an unfamiliar engine, be sure that the former owner didn't strip out the spark plug threads! This happened to me last year, forgot to check,got to do it twice , can do it in the cradle on a 550, it'd be allot harder on the 750. I know this is long winded,  you wouldn't be asking everyone if you should be riding around on 35 year old tires would you? It's kinda the same to me, it just seems that you owe yourself the best ride possible,with no regrets. Of course it's your choice, I' just sayin.

[chewbacca5000]

Thanks for all the great replies!  I think I will add it to my engine tear down / winter project list.  The only thing I don't like about the engine so far is how dark the oil is.  I took the valve cover off and the oil is dark as coal.  Have never seen oil that nasty looking in the top end before.  Makes me wonder if the PO ever gave this bike an oil change. 

I don't like the idea of getting stranded either so a rebuild it is.  Heck I scored a complete Vesrah gasket set for $29 bucks on Ebay so why not do a rebuild! I have 3 extra CB750 engines so I might rebuild all and so an engine build project thread.  I know I will need your guys help along the way with things like top end, 3 bond, rings etc..

Thanks Again for all the replays I will post a link to my build thread once I get started.

[Hush]

You may have found your own answer Chewy, the PO who had my bike removed the engine then gave up on the project and I inherited it. He said the motor always leaked oil and it peed him off. I found out why it always leaked oil, I always but always do an oil and filter change on old bikes as a first move to any other. I removed the sump screen and it was a solid mass of like varnish so nothing was getting through that! Wondering if the engine was any good I put it back into the frame just to see if it ran, loud clanking and grinding noises would have it back on the shed floor straight away. That motor ran sweet as for me for the 3 years I had the bike, it is still running for the collector who bought it off me, never ever has it leaked a drop of oil, some people do not deserve a bike...they are too thick!!!
But I was lucky and mine wasn't "stuck" so best you be guided by the 750 boys on here, happy wrenching.

[faux fiddy]

I figure at least do a top end if the motor was stuck for any period of time.

I took apart a STUCK 350f this week, got the pistons out, and now going through heating and dunking them (repeatedly for months perhaps) so the rings are free in the grooves to stop blow by. Other than that things measure up okay and pretty look clean, so a bit of honing bores and  a top end is all I will probably do.  Might as well clean up the seats a bit while it's apart, but for a stuck motor it must have been given up on with very few miles.