YZ125 base gasket question

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10/11/2017 6:30 AM

Hey guys it's my first post here, sorry if it gets a little long but please bear with me. Just had a quick question about my 2001 yz125. I am putting a new Athena cylinder kit onto my bike, seeing as my old cylinder was shot from the previous owner. I was going to get it replated but the cost was going to be more than the Athena kit... So I recently got the whole kit in the mail and I already got the piston on. My question is, the Athena gasket kit came with 2 different base gaskets, one is black and looks like the OEM base gasket. The other is green and looks cut out. I have searched the internet for a while and found no clear answer to this. Do I put both gaskets on like the kit included or just one or the other? I know my service manual shows just one gasket but I want to know before I torque the cylinder down. Thanks in advance

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10/11/2017 11:22 AM

The 2 will allow for setting the squish.

Paw Paw

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10/11/2017 11:37 AM

But do I still need to set the squish when it’s a new cylinder? The Athena manual shows one gasket going on but as you can tell this is my first time doing this. Sorry if any of these questions are common sense, I just don’t want to make mistakes.

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10/11/2017 1:29 PM
Edited Date/Time: 10/11/2017 1:30 PM

Anytime you change cylinders and or pistons the squish needs to be checked. Aftermarket and piston create the need even more. Cylinder heights differ as do piston.

Paw Paw

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10/11/2017 1:38 PM

Paw Paw wrote:

Anytime you change cylinders and or pistons the squish needs to be checked. Aftermarket and piston create the need even more. Cylinder heights differ as do piston.

Paw Paw

And you just check that with the soder in between the piston and head?

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10/11/2017 3:43 PM

Paw Paw wrote:

Anytime you change cylinders and or pistons the squish needs to be checked. Aftermarket and piston create the need even more. Cylinder heights differ as do piston.

Paw Paw

Yamahaulin112 wrote:

And you just check that with the soder in between the piston and head?

Yes just make sure it touches the side if the cyl and I lay it across the way of the wrist pin. I make it like a horseshoe (the U of it is in the center of the piston then the 2 "tails" toich cyl) so I can make sure it goes to the edge of the piston and I always make sure the solder ends are flat to get an accurate reading

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10/11/2017 10:19 PM

Athena Top End Race Gasket Kit

Specifically designed for the pro, semi-pro and amateur rider who freshens up their engine prior to a race or during mid season

Kit includes a top of the line MLSS head gasket and premium quality base gaskets of different thicknesses to optimize engine compression ratios

Gives the rider a choice of using standard gas with stock compression or race gas with a higher compression
Photo

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10/12/2017 4:40 AM

Ti wrote:

Athena Top End Race Gasket Kit

Specifically designed for the pro, semi-pro and amateur rider who freshens up their engine prior to a race or during mid season

Kit includes a top of the line MLSS head gasket and premium quality base gaskets of different thicknesses to optimize engine compression ratios

Gives the rider a choice of using standard gas with stock compression or race gas with a higher compression
Photo

So the black one gives you standard compression, correct? Cause I don’t need to run race gas.

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10/15/2017 6:43 AM

Paw Paw wrote:

Anytime you change cylinders and or pistons the squish needs to be checked. Aftermarket and piston create the need even more. Cylinder heights differ as do piston.

Paw Paw

Yamahaulin112 wrote:

And you just check that with the soder in between the piston and head?

ktm-5 wrote:

Yes just make sure it touches the side if the cyl and I lay it across the way of the wrist pin. I make it like a horseshoe (the U of it is in the center of the piston then the 2 "tails" toich cyl) so I can make sure it goes to the edge of the piston and I always make sure the solder ends are flat to get an accurate reading

I got it back together and I now realize that the Athena manual says you need to run gas with at least 96 octane because of the brass dome inside the head. I guess it’s from the higher compression. Do I really need to run 96 octane gas or can I just use the pump gas which has 93 octane? Not sure it would make that big of a difference.

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10/15/2017 8:10 AM

Yamahaulin112 wrote:

I got it back together and I now realize that the Athena manual says you need to run gas with at least 96 octane because of the brass dome inside the head. I guess it’s from the higher compression. Do I really need to run 96 octane gas or can I just use the pump gas which has 93 octane? Not sure it would make that big of a difference.

Don't worry about what the engineers that designed the kit say, just run pump gas and report back after 20hrs of run time... should be fine!

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10/15/2017 11:29 AM

slipdog wrote:

Don't worry about what the engineers that designed the kit say, just run pump gas and report back after 20hrs of run time... should be fine!

Come on man I was asking a serious question. I may be new to this but I’m not that stupid...

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10/15/2017 12:37 PM
Edited Date/Time: 10/15/2017 12:41 PM

I have the same kit on my 2003. It will run 93 pump gas fine, I've never had knock.

The black and blue base gasket should give you the squish you need. I've built a few bikes with this kit and they all work out spot on with that gasket.

Make sure you check your ring end gap, I've had a few of the Athena rings come in a little tight and need to be filed down.

Good choice, that cylinder makes a big difference on those YZs. I found the stock Yamaha pipe with a PC Factory Sound silencer works really well with it.

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10/15/2017 3:38 PM

Jbulz wrote:

I have the same kit on my 2003. It will run 93 pump gas fine, I've never had knock.

The black and blue base gasket should give you the squish you need. I've built a few bikes with this kit and they all work out spot on with that gasket.

Make sure you check your ring end gap, I've had a few of the Athena rings come in a little tight and need to be filed down.

Good choice, that cylinder makes a big difference on those YZs. I found the stock Yamaha pipe with a PC Factory Sound silencer works really well with it.

Funny you say that, I just messaged the Athena guy and he said the 96 octane gas in Europe (which is where the company is located) equals out to only 92 octane in the US. So 93 octane gas from the pump works fine. Thanks for all the help guys, you really helped a noob out.

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10/15/2017 6:32 PM

Jbulz wrote:

I have the same kit on my 2003. It will run 93 pump gas fine, I've never had knock.

The black and blue base gasket should give you the squish you need. I've built a few bikes with this kit and they all work out spot on with that gasket.

Make sure you check your ring end gap, I've had a few of the Athena rings come in a little tight and need to be filed down.

Good choice, that cylinder makes a big difference on those YZs. I found the stock Yamaha pipe with a PC Factory Sound silencer works really well with it.

Yamahaulin112 wrote:

Funny you say that, I just messaged the Athena guy and he said the 96 octane gas in Europe (which is where the company is located) equals out to only 92 octane in the US. So 93 octane gas from the pump works fine. Thanks for all the help guys, you really helped a noob out.

X2

Paw Paw

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10/16/2017 1:26 PM

Jbulz wrote:

I have the same kit on my 2003. It will run 93 pump gas fine, I've never had knock.

The black and blue base gasket should give you the squish you need. I've built a few bikes with this kit and they all work out spot on with that gasket.

Make sure you check your ring end gap, I've had a few of the Athena rings come in a little tight and need to be filed down.

Good choice, that cylinder makes a big difference on those YZs. I found the stock Yamaha pipe with a PC Factory Sound silencer works really well with it.

Yamahaulin112 wrote:

Funny you say that, I just messaged the Athena guy and he said the 96 octane gas in Europe (which is where the company is located) equals out to only 92 octane in the US. So 93 octane gas from the pump works fine. Thanks for all the help guys, you really helped a noob out.

Yup, US uses Antiknock Index 'AKI' octane which is the average of 2 methods. (RON+MON)/2 to calculate while EU uses RON only. It depends on the fuel, but RON 95 is approximately AKI 91.

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