Aero 750 Single carb


  • Yo! First of all this forum is a hidden gem with lots of great information, and in thankful this community exists. 

     

    Unfortunately I didnt find any information specific to my problem.

    I am a massive fan of the products and literature TJBC produces on the shadow and other machines, and I wish to continue to purchase more products in the future like the grips and bar risers, this is in no way an attack on your product/s and I am overall pleased with the quality of the items I received, im just a guy begging for help.

     

    A few months ago I ordered the TJBC carb rebuild kit, AIS blockoff plates, and velocity stack from the site for my 2007 Shadow Aero VT750. I meticulously rebuilt the carburetor and replaced every piece I could during the process, when attempting to tune the bike i ciuldnt get it to idle, i recall watching the how-to videos and polishing the float plunger seat which i did, and i cleaned every oriface out with carb cleaner ensuring a clean stream from the ither side. I am absolutely certain I do not have a vacuum leak anywhere.

     

    Yet for some reason the bike still blows black plumes of smoke out at idle, which indicates an insanely rich condition.

     

    When shutting the fuel off there are a few moments of clarity where the bike is idling perfectly before running out of fuel, which points to an over-filling bowl, well I checked the float level with a clear tube on the outside of the bowl and the fuel stops before the gasket surface. I also checked the choke/enrichment circuit plunger multiple times, and removed it completely to open the port and test the plunger passage. when doing this it seemed to clear up nicely due to the added air from the open port where the choke plunger should be, but after plugging the port with my thumb the flooding idle returned, meaning my choke plunger is not to blame.

     

    I also pulled the long handled mixture screw supplied in the rebuild kit to check if the passage was blocked or scored or if i forgot the old O-ring or washer and found nothing, while doing this i took note of the condition of the screw and the order of the washer and O-ring, and from what ive found i cant tell if the tip is correct or blunted, ive supplied pictures.

     

    Also worth noting is that when I tighten the mixture screw all the way in until snug the bike still idles, which points to three possible failure points; choke plunger, over flowing bowl, mixture screw not seating correctly, or an issue with the pilot circuit/jet.

     

    Any help/advice at all would be greatly appreciated as ive spent over a month trying time and time again to fix this issue.

     

    I have videos of the problem as well that I can link if needed!

     

    Thank you in advance, Chris



  • @Christopher Layciak your mix screw is fine. did you get a stock tuning kit or a perfoirmance tuning/rebuild kit? what size jets did you use? honestly every time someone does this, its ainstaller error. over 20 years, its usually a step that you missed being your first time. 
    did you lose the needle jet? the little brass part that goes in the venturi of the carb? 

    needle jet


  • @TJ I appreciate the reply, i got the performance rebuild/tuning kit, I wound up going with the #50 slow jet, 148 main, the bike runs great past 1/4 or just barely cracked open. No i did not lose the needle jet, I took some pictures during the breakdown to ensure it was facing the right way when putting it back in. Which if i recall is the large port facing up. I used 2 shims on the jet needle, it really feels like the float is overflowing but everything ive checked doesnt point to that, is it possible I bent the pilot jet during install? I was trying pretty hard to just "snug" them instead of cranking them down. Im just so confused why its still idling with a closed choke and closed mixture screw. 

     

    Couple odd notes, idle also improves if I plug the float bowl vacuum tube/drain tube with my finger. 

     

    It also idles well if I shut the fuel off as the float level comes down it finds a happy place before putting out.


Please login to reply to this topic!