Base gasket
- Thread starter Ud_luz
- Start date
blitz11
Silver Level Site Supporter
You can adjust the compression ratio/cylinder pressure by varying base gasket thickness (assuming a constant piston dome to pin height). The more gaskets, the lower the compression ratio. It is easier to add/subtract base gaskets than to actually vary cylinder height.
GasGas and other manufacturers sell base gaskets in different thickness so you can "mix and match" and get the correct compression ratio.
GasGas and other manufacturers sell base gaskets in different thickness so you can "mix and match" and get the correct compression ratio.
GMP
Active member
The squish is set up conservative like this for different fuels around the world. Generally at the first top end I use a single .3mm. There are .3mm, .5mm, and .15mm(to be used along with a .3 or .5mm). As you know a thinner gasket brings comp up slightly and alters port timing slightly. No X and Y worries like a KTM. To get the most out of the motor you can go with a single .3mm and have the head cut to adjust squish and compression based on that gasket, and the fuel of choice.
Usually 91 or 92 octane. I normal don't use a sealer, but I bought some for the thin gasket. It is Permatex High Tack Gasket Sealant #80062. I have run the bike a couple hundres miles like this and it runs great. I also added an 06 pipe to the bike and the fresh top end so of course it is going to run better regardless of gasket. I found a thread here or on the Smackover site with a report of someone else having luck with it.
Paul B
Paul B
I coated the entire surface except a thin band on the inner edge. It kind of went on like rubber cement andthe jug sqished just a bit out the sides. It did a nice job sealing up one of my head studs taht had been weeping as well. I actually pulled the topend after install to double check that my rings were both facing the right direction, one ended up being upside down. Live and learn. Most of the sealant had soaked into the gasket which seemed like a good thing.
Paul B
Paul B
eff
Silver Level Site Supporter
I just realized that I got different gaskets than on my bike. What color is the .3 gasket?
My bike currently has a green gasket and a thicker black gasket. When I order my piston, etc. I ended up with the green gasket and a really thin gasket that is like a piece of brown paper.
I stopped putting my bike back together at that point until I make sure I'm not going to slam the piston into the head.
My bike currently has a green gasket and a thicker black gasket. When I order my piston, etc. I ended up with the green gasket and a really thin gasket that is like a piece of brown paper.
I stopped putting my bike back together at that point until I make sure I'm not going to slam the piston into the head.
eff
Silver Level Site Supporter
OK, just clarify things.
The green gasket is the 0.3mm and the thinner brown gasket is the 0.15mm. The black one that was on my bike originally was a 0.5mm.
According to the manual, you should run the 0.15mm and either the 0.3mm or 0.5mm.
I am running the 0.15mm and 0.3mm combo right now and I'm very pleased with the it.
The green gasket is the 0.3mm and the thinner brown gasket is the 0.15mm. The black one that was on my bike originally was a 0.5mm.
According to the manual, you should run the 0.15mm and either the 0.3mm or 0.5mm.
I am running the 0.15mm and 0.3mm combo right now and I'm very pleased with the it.
skid jackson
New member
so I go out and paw through the parts that came for my top end. I have one base gasket that appears to be the .5. it's black, the bike has two base gaskets on it right now, one green one. I'm guessing its the .15 and the .3. I really wanted to get into this top end this weekend. I'm assuming it is ok to to run the .5 by itself and this should make for a bit less compression than the two that are on there now. which would tame the motor a bit. is htis correct?? what effects will the .5 have on performance
Jim Cook
Platinum Level Site Supporter
When we had the shop going, we tried to run a single .15 mm gasket, but had a lot of trouble getting it to seal. We/I don't like to put gasket sealer on the base gasket, but prefer to let the cylinder nut torque compress the gasket to achieve a good seal.
The .15 mm gasket is provided to work with one of the thicker gaskets to achieve desired compression and port height. The original 300 ('99) came from the factory with a .5 and a .15 stacked together.
On my '99, I ran a single .3 mm base gasket, but on my '06 I use a single .5 mm base gasket.
The .15 mm gasket is provided to work with one of the thicker gaskets to achieve desired compression and port height. The original 300 ('99) came from the factory with a .5 and a .15 stacked together.
On my '99, I ran a single .3 mm base gasket, but on my '06 I use a single .5 mm base gasket.
Jim, Why don't you like the sealer? I ran the .3 by itself for years with no problem, I now am running the .15 with some sealer and it runs great! I have about 400 miles on the .15 with no leaks yet. The performance gained by using the thin gasket has me wanting to sent the head to R&B for his treatment.
Paul B
Paul B
Raising the compression ratio on the GG 250/300 by removing base gaskets is kind of counterproductive since lowering the cylinder shrouds/blocks the transfer ports. The cylinder actually has to be raised 0,5 mm from standard to unblock the transfer ports completely.
On my previous GG bikes I ran just one 0,3 mm gasket and it didn't make any difference whatsoever in the way the bikes ran. Instead, when I raised the cylinder (0,5mm) and modifyed the cylinder head to suit it completely transformed the bike. There is really no comparison to a std GG 300, maybe a bit too powerful for tight woods riding but absolutely wonderful in all other conditions.
Kent
On my previous GG bikes I ran just one 0,3 mm gasket and it didn't make any difference whatsoever in the way the bikes ran. Instead, when I raised the cylinder (0,5mm) and modifyed the cylinder head to suit it completely transformed the bike. There is really no comparison to a std GG 300, maybe a bit too powerful for tight woods riding but absolutely wonderful in all other conditions.
Kent
socalscott
New member
So, 1.45mm is the total?
skid jackson
New member
ok so I know nothing of this stuff ..... by using the one .5mm gasket that I got will these ports line up correctly??
