Topic: 750 head

[mrbreeze]

I was digging through parts the other day and came across a box that I got a few years back with some parts bikes I bought. I had a K1 and a K4. They both had heads installed when I got them so I don't know anything about this head I found in the parts he gave me. The thing I do know is it looks like it has sat in the bottom of a lake for a decade or 2! Thought about cleaning it up and inspecting for cracks, stripped theads etc. I'm an auto mechanic but not a machinist so I don't know much about cleaning up aluminum heads. I usually ship them off to the machine shop to be be rebuilt or just replace with a reman. I enclosed pics of it as it came to me. It sat outside in a box for god knows how many years in the Sierra- Nevada mts. so it was full of pine needles, spider webs, etc. and has the white powdery stuff from aluminum all over. I know not to put into an acid bath and I think I read not to hit it with a wire wheel either.I would like to strip it down and acess the condition...... remove all valves, spark plugs, etc. How could I tell what year it came from? I enclosed pic. of a marking on it that looks like a backward 79. Any other markings or clues to look for to ID it? What is best for clean-up/ Maybe like simple Green or something? The fins all look good but I still would like to inspect for cracks, bad threads, straightness, etc. It may turn out to be a good core or it could make a nice boat anchor!

[madmtnmotors]

Definitely DO NOT use a wire wheel. I had a head that was nearly destroyed by some ham-fisted goob with a wire wheel.  Combustion chambers were feathered out around the edges, almost beyond the sealing rings in the head gasket. A hand-held wire brush will work well, and aluminum cleans up with less effort than you might expect. Soda blasting also works very well on the softer metals. I have an assortment of round wire brushes that are designed for thorough engine cleaning, ranging from about 3/16" up to about 5/8" that would work well for getting between the fins:

http://www.harborfreight.com/10-piece-tube-brush-kit-95947.html

Others can chime in as far as identifying the year of head you are working with. There are differences that can help tell them apart, I'm just not that familiar with them.

[mrbreeze]

I don't have a bead blaster so maybe just use a household scrub brush with dish soap or would something like Simple Green be better? Still no ideas about what year this head is? I searched cylinder head ID but didn't come up with anything. I'll try again and see if I can refine my search. Thanks for the info guys.

[PeWe]

Go chemical!
That oxide will easy become history with sodium hydroxide, also known as caustic soda. My head cover looked really ugly, polish did not bite at all.

I mixed ~1dl caustic soda with almost half a bucket with water, appr 4Liter. (if it react slow, 1dl more)  Then in with the head cover. I brushed with a dish washer brush everywhere. It started to react really heavy direct, the oxide became black. Rinse it with water after 1 minute. Do not let it react too long time. The black parts easy to clean with steel wool.

Check if it needs more and do the process again. Carefully rinse with water afterwards.

Use long gloves and protection glasses   Do not smoke or use open fire when the process will create a lot of gas,hydrogen.

I did this with all CB750 engine alu parts that had oxide + wheel hubs. You will see that it will react only where the oxide is.
My head cover got a nice old alu look, rather dark possible to polish if I want. Hubs look newer.

But most people I knew back in the days should left it to a professional shop whith glass bead doing the complete head, then fix the valve seats that must look horrible. I small spot of rust on the seat will cause a leak.

[754]

1970-1972 head. . Can probably. Be dated better by the oil jets.

[mrbreeze]

 Thanks for that info!! I'll try PeWe's cleaning method and then take some more pics and close ups of the oil jets. So what leads you to say 70-72 Frank? Did you see the picture with the backward looking 79? What is the telltale sign that its one of those years? It may have some other markings that will show up after I clean it. I'm sure there will be problems with the seats,guides, rust on valves but the first thing I want to do is make sure the casting is OK. Like I said......I got this head with 2 part bikes (K1 & K4) which both had heads installed so I have no idea if this was an old discarded head or a good donor for a reman.

[PeWe]

Just remember the time in the mix. Try with maximum one minute to start with, then rinse with water or even better a big bucket or bath tub where you can drain it completely with fresh water.
More it smokes, better it works

Eye protection glasses. The stuff in your eyes will not improve how the world look like

[754]

I can tell by top front fin and I can see the circular bar between the fins neat the outside corners.

[edwardmorris]

From what you describe, this head may end up at a machine shop anyway for resurfacing. Glass bead might be a bit aggressive, plastic bead blast will clean it up pretty well. I've had some luck with that when I had mine done, saved me a lot of scrubbing. Just my 2c.