Copper Gaskets: Where to purchase extra thin or assorted sizes?

[Chainlube]

Well I'm all about doing it right. The trouble is, this hobby has very few scientifically proven ideas associated with it. People tend to do things because everyone else does it. Nothing is sure except that the opinions are popular. I'm not arguing that squish isn't a thing, I just have to wonder if it's actually important for people who aren't racing bikes. And lets say it is. All the advice you get through forums and videos and written word seems to be based on tradition or accepted practice but with no clear cut methods or proof to come with it.

What's the right way to go about this now? I've taken about all I can take off the head. Should I remove material from the top of the jug now to get me where I'm trying to go? What are you thoughts on not using a gasket?

There is no need to modify the engine in any way if you are happy with it's performance, I built a few bikes that were bone stock. The guys that ended up buying them had lots of fun riding that way.
The one thing that I would recommend to everyone building a bike is to take off the head and cylinder and clean all the casting flash from the ports. There is nothing worst than a small piece of metal coming loose and rattling around in there and messing up your engine.

Before you started you should have checked the clearance from the top of the jug to the top of the piston with it at TDC, that way you would have an idea of how much material you're going to have to remove to get the desired squish. If the piston is more that 1mm below the deck, your not going to able to take the head down and achieve any good squish. It would all have to come off the jug.

Playdoh is a valuable tool for measuring depths.

A head gasket is important because of thermal expansion, if the jug or head expands more than the other then one part has to bend/warp. With no gasket, where is going to bend to?

 

[yuckfoo]

There is no need to modify the engine in any way if you are happy with it's performance, I built a few bikes that were bone stock. The guys that ended up buying them had lots of fun riding that way.
The one thing that I would recommend to everyone building a bike is to take off the head and cylinder and clean all the casting flash from the ports. There is nothing worst than a small piece of metal coming loose and rattling around in there and messing up your engine.

Before you started you should have checked the clearance from the top of the jug to the top of the piston with it at TDC, that way you would have an idea of how much material you're going to have to remove to get the desired squish. If the piston is more that 1mm below the deck, your not going to able to take the head down and achieve any good squish. It would all have to come off the jug.

Playdoh is a valuable tool for measuring depths.

A head gasket is important because of thermal expansion, if the jug or head expands more than the other then one part has to bend/warp. With no gasket, where is going to bend to?

The engine is new so I won't know anything about how it performs until I get it on the bike. I measured the squish before I started. It was over 1.5mm and after removing almost all the material on the head it's still over 1.5 mm. My piston seems to sit about 0.7 mm below when at TDC. It's a bit tricky to measure with calipers. I've heard some people don't use a gasket and instead use copper paint gasket. I wouldn't think a motorized bike would get hot enough to warp the head or the jug. My understanding is they run about 180 degrees when running correctly. I'd think if it ran hot enough to warp head or jug it's already a destroyed engine. Playdoh sounds like a good idea. I will start removing material from the top of the jug tomorrow. Thanks!

 

[Chainlube]

The engine is new so I won't know anything about how it performs until I get it on the bike. I measured the squish before I started. It was over 1.5mm and after removing almost all the material on the head it's still over 1.5 mm. My piston seems to sit about 0.7 mm below when at TDC. It's a bit tricky to measure with calipers. I've heard some people don't use a gasket and instead use copper paint gasket. I wouldn't think a motorized bike would get hot enough to warp the head or the jug. My understanding is they run about 180 degrees when running correctly. I'd think if it ran hot enough to warp head or jug it's already a destroyed engine. Playdoh sounds like a good idea. I will start removing material from the top of the jug tomorrow. Thanks!

Easy job to take the head and jug off after you have had a chance to ride it, that way you'll see if you like it the way it is or need to improve it.

 

[Wrench]

My understanding is they run about 180 degrees when running correctly.

Yes 180*C = 356*F but actually if ya sit at Idle with a warmed up engine you temps will spike up past 400*F
So keep it in the wind and try not to sit at idle for more than necessary 3 mins.

 

[Street Ryderz]

I'm just about out of room on that head. I suppose I should move on to sanding down the top of the jug? What are your thoughts on not using a head gasket?

I deck the the jug so that the piston crown is flush with the deck, the gasket thickness then becomes the squish and ideally we find .7 of a mm in copper sheets or aluminum if making your own or there are some copper ones available and the stock works but can be a little thicker. To use no gasket both surfaces need to be machined flat and true to one another and even then theres no guaranty, a bead of twisted teflon tape works well for tight clearance sealing.

 

[Street Ryderz]

The engine is new so I won't know anything about how it performs until I get it on the bike. I measured the squish before I started. It was over 1.5mm and after removing almost all the material on the head it's still over 1.5 mm. My piston seems to sit about 0.7 mm below when at TDC. It's a bit tricky to measure with calipers. I've heard some people don't use a gasket and instead use copper paint gasket. I wouldn't think a motorized bike would get hot enough to warp the head or the jug. My understanding is they run about 180 degrees when running correctly. I'd think if it ran hot enough to warp head or jug it's already a destroyed engine. Playdoh sounds like a good idea. I will start removing material from the top of the jug tomorrow. Thanks!

That's quite common for the piston to sit lower in the cylinder than an effective squish clearance. I just deck the jug to bring piston flush, There is thermal variance between the head and cylinder to where these stock heads have been known to warp then leak and that's what kills the engine. 180c is a bit high imo I like to see them sustain under 300f so 148c my own with sustained wot runs and a constant hour's ride is around 240f or 115c measured between the cylinder and head with an IR gun. Playdough, modeling clay, electrical solder all work well to measure squish clearance placed across the piston top just short of touching the cylinder walls, rotate the piston through tdc remove and measure at the ends with caliper.

 

[Wrench]

Temp readings of a 4 stroke Flathead 138cc Whizzer M/B with average speeds of 35 to 45 MPH
The only way I could get accurate temp readings of my M/B engine was to take the temp readings while I was going 35 MPH in the wind
I rode my M/B for 10 miles before taking the temperature. It was a *82F day I used a hand held temp gun. I held it 1' away from the head and I aimed the laser at a flat spot next to the spark plug. The head temp was average *300F in the wind @ 35 MPH. But while sitting at idle for 3 to 5 mins my temps spiked up to *425F On cooler days the head temps are *275F in the wind. The case temps are much lower @ *150

It's kind tricky to be going over 30 MPH and use a hand held temp gun.