08 CRF450R Fouling Plugs

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1/14/2018 1:49 PM

We just put a carb kit and a FMF slip on my 08 CRF450. If I understood FMF right we shouldn't have to rejet for just the slip on. The fuel screw is very sensitive, if I turn to far in it pops terribly upon decel and you can see a flame coming out. If I turn it out bike runs fine but fouls plugs within minutes of riding. Put a new plug in and adjusted fuel screw to where no decel pop and bike ran perfect for three laps. My son went to roll a table top, said when he pulled in the clutch the bike shut off and will not restart.

Like I said with a fresh plug bike runs great and fires right up.

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2020 YZ450F
2018 KTM 450SXF FE
2016 YZ250F 2008 CRF450R
2015 YZ250F 2008 CRF250R
2001 CR250R
2010 YZ250 2012 CRF150R
2009 YZ125 2010 KX109.5
SSR Motorsports Dealer
TAGMX Suspension & Graphics! www.tagmxsuspension.com https://www.liquidskinzdesign.com/



1/14/2018 3:46 PM
Edited Date/Time: 1/14/2018 3:47 PM

Sounds like you have float sealing issues or it is not set correctly. Either will cause flooding.
Decel poping can be caused by and bad exhaust gasket/seal at the head or at the joint of the head pipe to the slip on.
Also, adjusting the fuel screw to correct for the poping will make it too rich. You should be about 2 turns out from sealed.

Paw Paw

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1/15/2018 2:10 AM

Thank you Sir!

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2020 YZ450F
2018 KTM 450SXF FE
2016 YZ250F 2008 CRF450R
2015 YZ250F 2008 CRF250R
2001 CR250R
2010 YZ250 2012 CRF150R
2009 YZ125 2010 KX109.5
SSR Motorsports Dealer
TAGMX Suspension & Graphics! www.tagmxsuspension.com https://www.liquidskinzdesign.com/



1/15/2018 6:47 AM

When I put my FMF slip on my 08 yz450 It did not have a clamp like the stock one so I used some high temp permetex to seal the connection. You may have an air leak there.

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1/15/2018 9:29 AM

make sure the oring on fuel screw is good also

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1/16/2018 3:50 AM

lcgordon711 wrote:

When I put my FMF slip on my 08 yz450 It did not have a clamp like the stock one so I used some high temp permetex to seal the connection. You may have an air leak there.

We had that discussion yesterday! I will check that!

Upon talking with my mechanic at the shop yesterday I am suspecting the bowl gasket as well we are going to take it down today and check!

Thanks for the replies!

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2020 YZ450F
2018 KTM 450SXF FE
2016 YZ250F 2008 CRF450R
2015 YZ250F 2008 CRF250R
2001 CR250R
2010 YZ250 2012 CRF150R
2009 YZ125 2010 KX109.5
SSR Motorsports Dealer
TAGMX Suspension & Graphics! www.tagmxsuspension.com https://www.liquidskinzdesign.com/