Head gaskets

F

Flathead

Member
New rings ,gaskets-top and bottom ,cdi ,cilinder hone . Tight to129 inch pounds !! I will ride light( 15 to 20 mph) till rings seat ,however long that takes ? She still has power low and high end ! Just glad to have my bike on the road again Happytime
 
Use some full throttle along the way or the rings won't really seat, they will just glaze up and leak. The trick with break-in is to vary the speed and load. You need some full throttle to push the rings out firmly. A little blast here and there, more as time goes on.

Steve
 
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The real question here is how did you blow your head gasket? It's actually been a question of mine for a long while when it comes to these little engines. How the heck do people blow their head gaskets?
I think the answer boils down to one of two possibilities. First is that the head is not tightened properly and thus distorts over time. The second is that people may try to torque them without a torque wrench. Either way the head will distort and make the gasket (which is just aluminum sheet, btw) blow out.

Your best bet is to get a mirror or piece of glass and tape some 100 grit to it. Sand the head in short circles, rotating the head 90 degrees every few passes. When you think it's flat, color the sealing surface with some magic marker, then do a few lights strokes on the sandpaper. If there aren't any low spots, continue on to 220, then 500 grit paper. If there are still low spots, sand away.

You can make a head gasket from a coke can and scissors. For what it's worth, I don't use one.
 
first, take out gasket and clean it well - if you see no burn marks or cracks you can use it again

look for the indent where the compression ring of the head bit into the gasket, turn gasket over and let it bite other side this time - with a used gasket, I'll usually torque to 12# instead of 10#
 
I didn't torque the head down enough in the front and the ring in the gasket almost disintegrated where it was loose. I can post a picture of the gasket. I have a Monster can if that will work. Do I just use this gasket as a template?
 

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I'd just buy one as that one may not be right size/shape for a template after all that damage - wouldn't hurt to try though.
 
Ok, so there is this guy who thinks I'm completely ignorant in the field of minor engine work, like making gaskets. He says these soda can gaskets don't work at all because the combustion will blow it out. Is this true, or just stubbornness? He is in his late 50s early 60s, and has done a lot of engine work. Oh, and he refuses to give it a try, because he apparently has done that before.
 
I guess that guy tried and it didn't work for him. I wonder if he tried it on a head of this size.

People here on this forum have done it for sure. No harm in trying and you'll increase your chance of success if you mill the head like agreen said above. But don't forget to do the head and the jug surface as well, which is probably what agreen meant to say.

A new gasket is cheap enough, five bucks at sick bike parts. Still a good idea to mill the surfaces with a new gasket.
 
some cans are sealed in plastic coating that could burn off - a piece of disposable aluminum baking pan is thicker and nice and soft
 
Yes, lap both the head and cylinder. The cylinder is less prone to warping though, but still couldn't hurt.

You can use whatever you want, so long as it's a malleable metal like aluminum or copper. Or buy one. Shipping could be a week or longer, so in the down time you can try it out and see if it works for you. Prove someone wrong.
 
Good stuff here. Yes, soda cans will work as gasket material for these engines.
Definitely lap the head and cylinder flat on sandpaper on glass, and torque it.

If you have enough squish room you can run without a stock gasket using teflon tape.
Use a piece of lead solder to see what your squish is:
16386959_10154822927490803_1070217359875522370_n.jpg

Bolt the head on. Turn the engine over top dead center to compress the solder and measure it.
You should have at least 0.020" clearance. 0.035" would be even better.
Twist a piece of teflon tape into a string and use grease to hold it in place.

This is what a typical blown headgasket looks like:
1915345_10153717745465803_831898121014901090_n.jpg
 
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Turns out there is a strange rectangular hole traversing the compression ring diagonally from one side to the other. Zero compression, and the smell of gas as it cranks over. Anyone know what can cause this? It is small and only allows the very tip of a toothpick in. I'm guessing no taller than 32ga wire, but as wide as 16ga.
 
Those holes are there because the gasket I made is too thin. I have no sandpaper to mill the head, so I'm going to save a few bucks and buy a proper gasket. If that still doesn't work, then I will buy high temp material and make a squishy one.
 
xXNightRiderXx said:
Those holes are there because the gasket I made is too thin. I have no sandpaper to mill the head, so I'm going to save a few bucks and buy a proper gasket. If that still doesn't work, then I will buy high temp material and make a squishy one.
Click to expand...

All of that kinda goes against what all the experienced people here told you.
Sure, go ahead, and please, tell us how it works out.
 
Yeah, but I don't exactly have a few heads laying around to practice milling it down, and this being my only motor, I don't want to run the risk of permanently damaging the head and jug. Also, at TDC, the edge of the piston sits pretty much right at the top of the cylinder, so I'm sure if I try milling the jug down, I will also wind up damaging the piston head. My best bet is using a pre-made gasket or make one that is extra thick and can squish down quite a bit. Also, is the inner edge of the gasket supposed to hang slightly over the cylinder wall, or is it supposed to be flush with it?
 
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