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Vapor lock with a clarke tank and cap??

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I just put a Clarke 2.6 gal tank on my 08 CRF450R.. Rode it for the first time on sat and about an hour into the ride, pretty slow tight technical stuff, It started to stall and fall on its face whenever i would hit the throttle.. I stopped and heard a hissing noise, Took the gas cap off and it had a ton of pressure in it, I looked at the fuel and looked like it was boiling, or like somebody had a blow gun at the bottom of the tank blowing bubbles into the fuel. i went back to the truck and disassembled the gas cap. reamed the vent hole out a bit and removed the check ball, rode the rest of the day without a problem.. Has anybody else ran into this with a clarke tank or gas cap??

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Here's my 2 cents.

The vacuum that gravity caused by not having a clear vent held the fuel up and out of the petcock which stalled out the bike. When you released the cap, The VACUUM was released and fuel was allowed to fill up the hose past the petcock which was being starved. The bubbles was the air getting replace by fuel in the lines. Normal if your cap doesn't vent properly. Sounds like you fixed it. -BIG DAN:thumbsup:

PS: vapor lock occurs with fuel injected models where a rigid line that contains fuel and a small amount of air/water reaches a temperature where the air can expand to a point where fuel cannot be pushed past the bubble.

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Here's my 2 cents.

The vacuum that gravity caused by not having a clear vent held the fuel up and out of the petcock which stalled out the bike. When you released the cap, The VACUUM was released and fuel was allowed to fill up the hose past the petcock which was being starved. The bubbles was the air getting replace by fuel in the lines. Normal if your cap doesn't vent properly. Sounds like you fixed it. -BIG DAN:thumbsup:

PS: vapor lock occurs with fuel injected models where a rigid line that contains fuel and a small amount of air/water reaches a temperature where the air can expand to a point where fuel cannot be pushed past the bubble.

I thought about that,but it bubbled for 15-20 min, I dont think there was that much fuel in the line, and the vapors were being pushed out of the vent tube, nothing was being sucked in, thats what led me to beleive that there was pressure in the tank... Carbed vehicles/bikes can vapor lock too..

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on any big four stroke most check ball type vents will not flow sufficiently, those vents were made for pitbikes.

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I thought about that,but it bubbled for 15-20 min, I dont think there was that much fuel in the line, and the vapors were being pushed out of the vent tube, nothing was being sucked in, thats what led me to beleive that there was pressure in the tank... Carbed vehicles/bikes can vapor lock too..

I agree. Reading your post again, you have quite the perdicament... -BIG DAN:thumbsup:

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Have you contacted Clarke?...You said that once you opened up the cap that it ran fine.

Was it positive or negative pressure in the tank?

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Have you contacted Clarke?...You said that once you opened up the cap that it ran fine.

Was it positive or negative pressure in the tank?

Positive pressure in the tank, like it wanted to push the fuel out the top of the tank.. Once i removed the check ball out of the cap and made the vent hole bigger it didnt do it again fot th rest of the day..

As for absorbing heat, it most certainly feels hotter, the bigger tank extends out behind the radiator where the original tank did not, so it seems to me that the heat being removed from the radiator is being blown into the tank instead of blowing thru the rad shrouds and probably being absorbed by the tank..

Ill get some heat tape and wrap the exhaust.. that will help too.. Thanks Dwight..

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This is a common issue on KTM bikes. Take the checkball out of then cap and ride. Some line the bottom of their tanks with reflective tape. I have seen the aluminum duct work tape used and works good. Your bigger tank is prob riding closer to the pipe and engine causing it to get hotter.

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