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Discussion Starter #1
2006 Bruin 250. Will only throttle to 1/2 - 3/4 throttle then cuts out. Thought it was carb main jets so I put on new carb. Still has issue. Found I can remove the air cleaner cover and it will throttle up full. Not remove air cleaner, just cover. If I leave the cover on I can shoot some air down the intake tube and it throttles up full. Just doesn't like cover on. Is there some kind of vacuum that helps assist intake or a PCV valve or something similar I'm missing?
 

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Have you done an engine rebuild or power mod increase? or live a high elevation?
 

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Discussion Starter #5
Yes, filter clean. It operates same way whether air filter is in or out. Throttles to 1/2 - 3/4 then cuts out when filter box cover installed, throttles fine when cover removed. When cover is installed can give a small amount of air from compressor down intake tube and it throttles fine. Air intake tube is clean. Also, altitude is sea level.
 

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Staving for fuel.
Clean the fuel tank and pay close attention to the fuel shut off. The shut off can plug with dirt and rubber if the gasket is failing.
If you have an inline fuel filter replace it.
 

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Starving fro air or gas?
Is the choke in the full open position?
so when you have it throttled up without the cover, is this while riding?
And have you read the plug?
 

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Discussion Starter #8
Plenty of fuel flow. Starving for air. Does it in the garage. Haven’t tried riding. Only does it when cover on. With cover on I can also blow a little air down the intake tube and runs fine. I haven’t read plug because it appears to be an air issue.
 

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Yes, low air, high gas so a black plug?
I was wondering if riding or not for the load on the engine, so the valves may be out of adjustment.
 

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Should check that the air intake duct before the air box is clear.
Also check that all of the ducting between the air box, the carb and the engine are air tight.
Does the idle seem kind high.

Adjusting valves is always a good idea but normally hard starting is the first symptom.
 
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