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I work on a lot of different things for a lot of different people. This project is an 81 CB900C,. The carbs were taken out and cleaned, then a rebuild kit was bought (this is where I come in) I rebuilt the carbs. Upon reinstall, everything went smooth until the start up. Sputtering, backfiring, at about 4500 to 5000 Rpm it would gasp. . I know its a lean issue because it will rev high if the choke is engaged about 50%. But its still gutless. The only issue I noticed and didn't think was that big of an issue was the needle diaphragms all had minor scoring/wear. Maybe its not that minor? Could they all be sticking short, could they all have a clogged air bleed jet? Or if one was jamming, would it disrupt the other three from functioning properly? Could this be something else I'm overlooking. Suggestions are welcomed with enthusiasm because I'm looking like I don't know what Im doing to this client/customer.:???:
 

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Even a slightly overrich float bowl was enough to make my B1200 spit and fart as if it was one cyclinder short....which it was. I woud run some heavyduty carb cleaner through it and leve it overnight or longer if possible. I would also re check the diaphragms for tiny pin holes etc. Make sure any small 'o' rings....usually at the top of the carb...under the cap....are insitu as these are for the air supply to the enriching circuits....although if it runs better with the choke/enricher on it tends to show it is working. What about tank venting and fuel filters....evn gunk build up in the tank/lines.

Good luck
 

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I work on a lot of different things for a lot of different people. This project is an 81 CB900C,. The carbs were taken out and cleaned, then a rebuild kit was bought (this is where I come in) I rebuilt the carbs. Upon reinstall, everything went smooth until the start up. Sputtering, backfiring, at about 4500 to 5000 Rpm it would gasp. . I know its a lean issue because it will rev high if the choke is engaged about 50%. But its still gutless. The only issue I noticed and didn't think was that big of an issue was the needle diaphragms all had minor scoring/wear. Maybe its not that minor? Could they all be sticking short, could they all have a clogged air bleed jet? Or if one was jamming, would it disrupt the other three from functioning properly? Could this be something else I'm overlooking. Suggestions are welcomed with enthusiasm because I'm looking like I don't know what Im doing to this client/customer.:???:
 

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I used to be a Honda Car Service Manager. i had 2 motorcycle mechanic working for me. Details. That was the name of the game. -Scott
 
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