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300 falling on its face


MarkinAR

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So here's one I haven't beat yet, could use some input. Honda 300FW was running fine when one day it started bogging at WOT. Figured dirty carb so I cleaned it and still the same. Cleaned again once more by soaking overnight in thinner and then compressed air. Back together tonight and still falling at WOT. Tried a known good plug...nothing makes sense here. The float bowl does seap a bit due to old gasket, could it draw vacuum enough to interrupt fuel? 

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Absolutely will draw air intake on the bowl with a bad bowl gasket.  What happens is you get a corrugation of fuel and air going up into the needle.  Its like a carbonated effect. 
I would shut the fuel off and run the engine dry. Unscrew the bowl drain screw on the bottom of the carburetor to get all the fuel out. Wipe down the edge of the bowl where it meets the carburetor and run a beed of silicone around the seem.   Let it dry good over night and reset everything back as it was and fire it up.  If it runs good then you need to put a new rubber gasket on the carb. 

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Think it may have been the bowl gasket. I drew a bead of ultra gray and let it dry. Put it together and it seems to be back to normal. I also made a pump block off out of thin steel. The diaphragm looked a but rough and we never need the manual pump so it's just blocked off now. I left the pump so I could reuse the original screws but it's just decorative. 

20200409_144535.jpg

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