Topic: Source for CB750 top end...

[dthohler]

Hello again,

My '78 CB750 frame with a '76 motor ground to a halt on the freeway a few months back and I finally got in there to see what the problem was. Lo and behold the oil galley on the 3-4 side was clogged and the cam dried and burnt to a crisp.

Anyone have any suggestions on where to look for another cam/holders/rockers? Someone told me I should search for an aftermarket cam setup, but I am not seeing many good options. Would like to replace all the pieces from the same engine, if possible.

Any words of encouragement? Thoughts? Anyone have an engine sitting around I can buy? I am in California, but am looking for any excuse to go on a road trip.

Thanks again, this site has been a great resource since I started riding Hondas at 16.

I guess until I get this sorted, I will be riding my CB350.

[Mo]

Well, I'm not entirely sure what parts you are looking for, but cycle x sells a lot of top end stuff for the 750.

http://www.cyclexchange.net/Engine%20Parts%20Valve%20Trane.htm

Lots of members here have used CycleX for a lot of stuff, and they have a pretty good reputation around here.

You could always source stock parts from ebay, craigslist etc. When I needed a new head for my CB500, I picked one off ebay for $30 shipped (complete with valves, springs, etc).

As for words of experience: YOU CAN DO IT! DONT GIVE UP!

[bjbuchanan]

I have all the top end pieces from a 76 750k engine minus the cam which was unfortunately badly rusted and pitted on the top of the lobes from sitting out unoiled. Cam towers, shafts, that kinda stuff is good and is from a 15k~ engine

Pm me if you want to talk more about it, see pics etc

[754]

The rusty cam may clean up...

[bjbuchanan]

It probably would but I'm not sure about selling a cam that "should" clean up, you get me?

[Mo]

Well, if its just the cam, a CycleX one should do the trick. A pretty easy fix if that's all that wrong, right?

While you're there, make sure you check for bent valves (lay them on a mirror, or some glass). If you're pistons aren't showing any damage, then you should be good.

Wisdom would dictate doing a top end job just to be sure. New rings, honing the cylinders, and lapping valves, followed by proper timing etc. If you're ambitious, this can be done in a weekend but patience is always a good thing with something you're relying on for a couple thousand miles.

[Don R]

I've always been big on spares.  It may be cheaper to buy an entire used engine than parts. I'd give BJ a call too.

[ekpent]

If you buy good used cam towers make sure you have the matching caps and try to keep them in order for all to work best. Most cams will drop in.

[Red Good]

Where do you think all the material that is missing from the cam and cam towers went ? I would split the cases and clean  everything very well .

[dthohler]

Thanks for getting back to me guys. This will not be the first time I have rebuild this motor, and I am hoping I did not get too crazy with the gasket maker when I was sealing the cases or gaskets. In the end I most likely rode it a bit too hard before fully letting it get broken in..

The rebuild I did last year included- honing the cylinders, new rings, cleaned the head (and everywhere else obviously), cam chain, tensioners, guide...I also split the cases to see what was going on down there. Pretty interesting motor to get into. I will certainly split them again to make sure something is not going to get stuck in there again.

Thanks for the suggestions everyone, I will check them out. I did not see cam towers/holders on the cyclex website, just full racing kits (pistons,springs, cam..)

Thanks again!