Honda CB750 Sandcast

Project CB750-1004286

greggo325 · 52 · 38216

Steve Swan

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If you are not planning to use the engine for yourself and if the alternator cover is a thin lip and if it's in good condition and if you would consider selling the cover, i would be interested in purchasing it.  Lots of IFs, i know......... ;D


kmb69

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kp

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I think the cover is a thickie Sorry to be the bearer of bad news  :(
Yabba Dabba KP



greggo325

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It looks like the Engine # pad changed shape over time, am I just dreaming this?  I look at #100 on MarkB's 97 bike, and it also has the same shape as #371.  Is this a change that's been noted before?  I also see a square shaped raised pad just above the # pad.

http://i1197.photobucket.com/albums/aa424/greggo325/3Gd3M73L55Ld5Mb5J9d5udb0985b5abdb1543_zps4b499320.jpg


cb7504

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greggo325:

      What shipping company did you use to have the motor sent to you? PM me with details. Marty K.  


cb7504

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Yes, the vin pad topic has been brought up before. There were two versions of sand cast case vin pads early version was 11mm wide and later version was 19mm wide. There appears to be no definite vin cut of point for this change. Marty K.   



greggo325

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I've posted lots of pictures of the motor here: http://forums.sohc4.net/index.php?topic=118569.msg1398563#msg1398563  It turns over with great compression, and the top end looked in great shape.  Unfortunately it has a later head...

I'll post a few here, and I'm very eager to hear a verdict on the alternator cover.

Enjoy! I sure did ;)






greggo325

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I've been posting most of my progress over on SOHC4.net, but here's a quick update.

Everything's been torn down to the frame and motor.  The wrinkle tank has been cleaned with Evapo-Rust, and a couple dents were removed by a paintless dent removal guy who goes by Dent Dynamics.  He does great work for great prices.  All the bodywork is ready for paint just as soon as I buy the tank stripes.  Motor 371 is still sitting as is, waiting for an inspection/rebuild.  The running K1 motor that came with the bike is what I'll use until I can do the motor up right.  I found a true sandcast head and cylinder set, and those will be on the way shortly!

So, here's how it sits for now.  I'm working to rebuild the wheels, and front forks so I can put a roller back together after the frame goes for paint.



greggo325

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All my black parts, frame and small bits included are at the painter.  The clear coated aluminum bits, minus the engine covers have gone there as well.  Those should be ready in a few weeks, so I got to work on the engine.  I've copied my post from SOHC4, and Hondaman is a gentleman named Mark Paris, who wrote a book about restoring 750's. 



The cam is definitely not stock, and per Hondaman's book, has more than .370 lift, because a fully backed out tappet adjuster wouldn't let me remove a few of the shafts, we had to rotate the motor until the certain lobes were free from their rockers...if you've read through Mark's book, you know what I'm talking about.  It has an 'O' at one end.



Everything did come out nicely, but the rockers are about halfway worn out, and the cam lobes had some wear as well.



I found a very nice surprise once I got the head off: the original sandcast cylinders!



The pistons are .50 over bores.





greggo325

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The deeper I get into this motor, the happier I am...the pistons look almost brand new, and it turned over like a dream with the alternator bolt...the kick lever not so much, so I'll see if I have problems there eventually.  After about twenty minutes of tapping, razor-blading the gasket, then finally giving up and using a gigantic pry bar at the starter motor and cam tensioner mount (the one place Hondaman says it's safe), I freed the cylinders from the cases.





I got everything required to split the cases, and I stopped before flipping it over and undoing the bottom case bolts...top bolts are off.  I forgot to take pictures, but the tensioner rubbers look BRAND NEW...there was barely one little wear mark on the slider, and the wheel was not chewed up at all.  I've decided to use the new Cyclex parts, and save these nice used ones for another motor.  It looks as though someone rebuilt the motor with the .50 pistons, and barely put any miles on it.  This may turn out to be a really simple refresh for this motor :)



In other news, the painter sent back the battery tray so I could decide on the gloss level...it's perfect, so he'll get started on the rest soon.




greggo325

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I was able to find a no-bolt head through ebay :) :) :)



greggo325

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They're apart!  Everything went relatively smoothly for my first 750 tear-down.  Figured out that the pistons have to come off to remove the crank from the top case. 

I pulled the oil pan first, and only found a few metal scraps, and some primary chain tensioner rubber bits (yes, it needs replacing).  It looked like the bottom end never came apart for the most recent rebuild because I found a riveted cam chain ::) ::)







Found what I think are crank bearing markings on the outer front edge of the top case.



We pulled the cases apart, and my dad immediately remarked: 'You're going to need crank bearings, those are a little chewed up.'




The gears all looked nice



The crank journals looked great



Still need to remove the kick starter spindle, the top half of the gearbox, and the shift linkage.



Removed the oil pump to examine and compare to MarkB's #97.  It looks to be original.