What was the factory finish on these engines?

tacoswild

Wondering how Yamaha finished the cylinder, head, and cases. Was it bare metal, or painted grey? I have a 71 so if anyone knows how those were done originally please let me know.

gordo

taco, I believe that they were just clear coated on the side cover's only.

nudude53

The top half of the engine case was painted silver from the factory, the bottom half was left bare metal. I just repainted mine today with Duplicolor hi-temp engine paint. I painted another engine 2 years ago with the same paint and it still looks like it did when I pulled the masking tape off. It's also good to use for frames, brackets and other small parts.

tacoswild

Hmm, so what about the top end? Just blast it and leave it bare?

nudude53

Yes, the cylinders are raw casting, glass beading would look great, I would do that to mine if I had the engine apart. You might even shoot some hi-temp engine clear on them after they're cleaned up too.

nudude53

Tacoswild
Here are some pics of the engine painted 2 years ago, no chips, no flakes, still cleans up well.

tacoswild

Alright thanks fir the advice. Makes sense because the top case on mine has always had a weird tint to it compared to the other aluminum parts, sort of yellow. Almost 40 year old paint I guess.

dpmphoto

The yellow can be caused by the heat from the cylinders if engine is running hot

tacoswild

That's a possibility too. No other aluminum parts (including the cylinders themselves) have that tint though. I can't say what all went on in the history of the bike but when I took it apart this year the left piston had an odd mark about half an inch wide and an inch tall on one part of the skirt. The machine shop thought it had probably gotten too hot at some point in the past and didn't recommend reusing it unless I was planning to be back in there in a couple seasons. I had trouble finding standard size pistons or rings for this bike at reasonable prices and then I found a set of 1st over pistons for only $50 for the pair so I went that way.

tuffbuilt

If you can find a place in your area that does glass beading it is the best way to go. It leaves a very clean but not polished finish with no haze and doesn't remove much material at all. It is the original finish for most alum. valve covers. For very stained pieces I use HVAC condenser coil cleaner The mild acid type(it will also take rust stains off of a garage floor) wet the piece first and then spray and don't let it set any longer than it takes to brush it. Don't mix it strong use light doses or it will turn the part white and you will have to polish it with something like Mothers to bring it back. We use this in muscle car restoration.

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