2 stroke head gasket question

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12/30/2018 2:51 PM
Edited Date/Time: 12/30/2018 2:54 PM

Rebuilding my 88 RM250. I have a Cometic head gasket and an Oem Suzuki gasket that has been superseded, but according to Suzuki is correct. Question? Why would the superseded Oem gasket block off water passages on the Right/water pump side? Cometic on the left, Updated Oem center with "E" facing north & the old one I removed. Photo

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12/30/2018 9:40 PM
Edited Date/Time: 12/30/2018 9:41 PM

I’m definitely not an expert...but I just ran into this exact thing on some old KTM 125 head gaskets. Turns out the one that seemed to be missing the holes was intended to direct water better...to get the cooled water to the hottest area first (exhaust port).

Possible that Suzuki figured something like that out and updated the gasket with the superseded number.

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12/31/2018 6:50 AM

wpark89 wrote:

I’m definitely not an expert...but I just ran into this exact thing on some old KTM 125 head gaskets. Turns out the one that seemed to be missing the holes was intended to direct water better...to get the cooled water to the hottest area first (exhaust port).

Possible that Suzuki figured something like that out and updated the gasket with the superseded number.

Thanks for the reply wpark89. You are correct, the smaller holes should be at the exhaust area to slow down coolant flow to help aid cooling. I found a good explanation for the reduced holes at the water pump/rt side of the head. " reducing the holes in the water pump side of the head gasket will help flood the cylinder with coolant before it goes straight through the head." Seems logical, apparently Suzuki engineers felt this was needed. Now, the funny part...I found this on a quad site! I will use the updated Suzuki head gasket, after all I paid 30.00 for it!!

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12/31/2018 3:24 PM

wpark89 wrote:

I’m definitely not an expert...but I just ran into this exact thing on some old KTM 125 head gaskets. Turns out the one that seemed to be missing the holes was intended to direct water better...to get the cooled water to the hottest area first (exhaust port).

Possible that Suzuki figured something like that out and updated the gasket with the superseded number.

sandman768 wrote:

Thanks for the reply wpark89. You are correct, the smaller holes should be at the exhaust area to slow down coolant flow to help aid cooling. I found a good explanation for the reduced holes at the water pump/rt side of the head. " reducing the holes in the water pump side of the head gasket will help flood the cylinder with coolant before it goes straight through the head." Seems logical, apparently Suzuki engineers felt this was needed. Now, the funny part...I found this on a quad site! I will use the updated Suzuki head gasket, after all I paid 30.00 for it!!

To be more accurate the reduced outlet sizes from the head will aid in cooling by raising the pressure in that local area, thereby reducing the chances of boiling in that area. Slowing the coolant down does not aid in cooling the engine.

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1/1/2019 6:09 AM

wpark89 wrote:

I’m definitely not an expert...but I just ran into this exact thing on some old KTM 125 head gaskets. Turns out the one that seemed to be missing the holes was intended to direct water better...to get the cooled water to the hottest area first (exhaust port).

Possible that Suzuki figured something like that out and updated the gasket with the superseded number.

sandman768 wrote:

Thanks for the reply wpark89. You are correct, the smaller holes should be at the exhaust area to slow down coolant flow to help aid cooling. I found a good explanation for the reduced holes at the water pump/rt side of the head. " reducing the holes in the water pump side of the head gasket will help flood the cylinder with coolant before it goes straight through the head." Seems logical, apparently Suzuki engineers felt this was needed. Now, the funny part...I found this on a quad site! I will use the updated Suzuki head gasket, after all I paid 30.00 for it!!

Matt Fisher wrote:

To be more accurate the reduced outlet sizes from the head will aid in cooling by raising the pressure in that local area, thereby reducing the chances of boiling in that area. Slowing the coolant down does not aid in cooling the engine.

Sounds reasonable...I read that slowing down the flow from the exhaust area will let the coolant absorb/ transfer more heat before it moves back to through the system.

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1/1/2019 1:13 PM

sandman768 wrote:

Thanks for the reply wpark89. You are correct, the smaller holes should be at the exhaust area to slow down coolant flow to help aid cooling. I found a good explanation for the reduced holes at the water pump/rt side of the head. " reducing the holes in the water pump side of the head gasket will help flood the cylinder with coolant before it goes straight through the head." Seems logical, apparently Suzuki engineers felt this was needed. Now, the funny part...I found this on a quad site! I will use the updated Suzuki head gasket, after all I paid 30.00 for it!!

Matt Fisher wrote:

To be more accurate the reduced outlet sizes from the head will aid in cooling by raising the pressure in that local area, thereby reducing the chances of boiling in that area. Slowing the coolant down does not aid in cooling the engine.

sandman768 wrote:

Sounds reasonable...I read that slowing down the flow from the exhaust area will let the coolant absorb/ transfer more heat before it moves back to through the system.

Very common misconception. Faster moving water will absorb more of the heat than slower moving water (yes, there are lots of other variables to consider such as heat transfer back into the air through the radiator). A simple example is standing in 30 mph winds will make you much colder than 3 mph winds.

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1/1/2019 2:47 PM

Matt Fisher wrote:

To be more accurate the reduced outlet sizes from the head will aid in cooling by raising the pressure in that local area, thereby reducing the chances of boiling in that area. Slowing the coolant down does not aid in cooling the engine.

sandman768 wrote:

Sounds reasonable...I read that slowing down the flow from the exhaust area will let the coolant absorb/ transfer more heat before it moves back to through the system.

Matt Fisher wrote:

Very common misconception. Faster moving water will absorb more of the heat than slower moving water (yes, there are lots of other variables to consider such as heat transfer back into the air through the radiator). A simple example is standing in 30 mph winds will make you much colder than 3 mph winds.

A local higher pressure makes no sense, it defies the laws of physics.

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1/6/2019 3:35 AM

sandman768 wrote:

Rebuilding my 88 RM250. I have a Cometic head gasket and an Oem Suzuki gasket that has been superseded, but according to Suzuki is correct. Question? Why would the superseded Oem gasket block off water passages on the Right/water pump side? Cometic on the left, Updated Oem center with "E" facing north & the old one I removed. Photo

The rule of thumb is you look for the name on the head gasket and it faces you when you put it on. At least with my experiences with head gaskets that's always how it was. I wouldnt want my ports blocked at all

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1/6/2019 7:09 AM
Edited Date/Time: 1/6/2019 7:10 AM

Lasse wrote:

A local higher pressure makes no sense, it defies the laws of physics.

Just curious as to why you say that.

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