Scooterotica

Greetings tuners-
I have my hands on a brand new motor setup, and as I am installing the top end, I have a few questions regarding the use of the base and head gaskets for a 225cc ts1. Because this is my first build, I want to ensure that I am doing the assembly and math correctly.

Since I do not have a gasket for the base joint between my gp200 case and the ts1 cylinder barrel, I temporarily put the cylinder on without anything in between, so as to measure the squish.
I placed the thin metal gasket at the top of the cylinder, under the head. I believe that this gasket measures about 2.0mm. I then used a length of soft solder that was 1.5mm in thickness, pushed through the spark plug hole to take measurements of the squish gap between piston and head. In all 5 readings of different areas on the head, the squish was 1.3mm.

This falls within specification for the expected squish tolerance. Yet, I do not have a base gasket as of yet. My plan is to use a rubberized gasket sheet and cut out my own shape to match the bottom of the cylinder and or the face of the case. I expect that I will also be using a flexible sealant compound to assist in the prevention of leakage. The gasket roll that I have measures 1/32", which is 0.03125", or in metric, this is 0.79375mm. When I add this gasket to the assembly stack, I expect the squish gap to rise some, perhaps not to the full thickness of the gasket, as the gasket itself might compress when torqued down with the barrel and head. I do not wish to exceed the advised gap distance of 1.5mm, so I turn to you for advice and options for my setup.
I have just scanned the AF Rayspeed website and I see that there are 225cc base gaskets available, but the thickness of the material is not listed. I have also sent them an email asking much the same as what is here. I'd like to cross reference the answer as I like what I read here.

I could remove the metal head gasket and use the rubberized gasket instead, this would lower the calculation some. I am open to your teachings, and thank you for any info that you provide.

My complete setup is as follows, everything here is brand new.
li150 series 3 frame
gp200 cases, sil
mec eur race crank, stock length rod
all new bearings and seals
16/47 gearing on li150 gearbox, with an 81 link chain, for a final output ratio of 4.99
mikuni tmx 35mm carb, normal manifold, reeds and cage
deepened rear crown wheel, 5 cork plate clutch, yamaha springs
quickslip chain tensioner, no lower chain guide
lightened flywheel
120w bgm stator

I have matched the cases to the ts1 barrel, I did not modify the cylinder itself, nor the piston. I have checked the ring gap and it is as expected, 0.2mm. All I need for my next step is to confirm the squish and the gaskets, and the preferred sealants to use on them.

thanks-

You can safely use silicon sealant as a base gasket, thereby keeping your squish at your desired setting. Have you used Vernier gauges to measue the thickness of the solder, as you state "believe" in your thread. As long as you don't go below 1mm squish gap you should be OK.

I am using digital vernier calipers, as I use them every dang day in my job. The solder measures 1.5mm, it is a cylindrical tube. I had several spools to choose from, I didn't want to over squish material that was much thicker. I thought about putty, but measuring that is iffy.

So, sealant it is, thanks for the answer. High heat I suppose? I have fast drying, semi flexible, loc tite, permatex blue, and copper for the exhaust joint. I have read that hylomar is well liked, I think I can get that too. I suppose that the joint at the base of the cylinder is going to be put to some moderate crank case pressure, I hope that the sealer of choice is up to the task.

Which is more important, head gasket or base? Because, with my measuring, I am only going to be able to get away with using one of the 2 if I want a squish to be between 1.0 and 1.5mm.

RS Components do a high temperature black silicone sealant which can be used for both sealing the base of the cylinder and slip joints on exhausts and exhaust manifolds (although you still need the copper gasket, of course, but ensures a good seal)