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Beta Evo 250 4T exhaust backfiring

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I have a '13 Beta Evo 4T trials bike that likes to backfire on deceleration, it's pretty annoying. Looking at the parts book, there is no gasket, o-ring or anything else that goes between the exhaust port and the headpipe. The  headpipe isnt deformed or damaged, nor is the sleeve at the exhaust port that the headpipe fits over. Does anyone else have the same problem? What did you do to fix it? 

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Typical setup on those is to install the blue carb diaphragm spring

http://shop.americanbeta.com/p/beta-trial-4t-carb-spring?pp=12

From there adjust the fuel screw. It's a huge pain in the ass to get to on the bottom of the carb so you'll want to get one of these if you don't already have one

http://shop.americanbeta.com/p/evo-4-stroke-fuel-screw?pp=12

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8 hours ago, rrefugee said:

I have a '13 Beta Evo 4T trials bike that likes to backfire on deceleration, it's pretty annoying. Looking at the parts book, there is no gasket, o-ring or anything else that goes between the exhaust port and the headpipe. The  headpipe isnt deformed or damaged, nor is the sleeve at the exhaust port that the headpipe fits over. Does anyone else have the same problem? What did you do to fix it? 

what type of gas are you running? octane? ethanol content? dealer mentioned race gas might be needed if problems arise typically on deceleration 

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10 hours ago, ccullins said:

Typical setup on those is to install the blue carb diaphragm spring

http://shop.americanbeta.com/p/beta-trial-4t-carb-spring?pp=12

From there adjust the fuel screw. It's a huge pain in the ass to get to on the bottom of the carb so you'll want to get one of these if you don't already have one

http://shop.americanbeta.com/p/evo-4-stroke-fuel-screw?pp=12

Hm...I get the impression that this is a common problem for Beta 4Ts.

The previous owner didn't say anything about fuel, so I have been using 87 octane unleaded gas with 10% ethanol. I thought the deceleration backfiring was caused by an exhaust leak. The only leak I could find is where the headpipe connects to the exhaust port, the rest of the system is tight.

I'll get the spring & fuel screw (thanks for the link) does it need a leaner mixture?

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Actually back firing is usually due to a lean condition on motorcycles. It could probably be adjusted out with the fuel screw. 

I recommended the spring becuse that's the common setup to get optimal performance out of Beta 4t's. 

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I finally got off my lazy and installed the fuel mixture screw. The end result was worth the time it took to get the job done. Thank you Ccullins for your sound advice and directing me to the right part.

 

 

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I guess decel popping would be a more accurate term than backfiring. No biggie though, it didn't do that anymore.

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