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My tuning journey

  • Dr.Phatpants

    8/23/26  My current ride is an 07 Spirit vt750c2. I picked her up last summer. Right now she has between 17k and 18k miles. I absolutely love riding this bike. Decided Im going to customize her to my liking. As of today I haven't riden her in almost 4 weeks and to be honest, its starting to bother me. Anyway, I have installed open exhaust and v stack. Couple other shiny cosmetics that dont apply to this. 

    Took the carb off, took it apart and cleaned it, used the performance kit from tjbc. Started with the 50 pilot jet and 148 main. Double shim on the needle. Reinstall carb and she'll only idle with the enrichment value pulled out. Running lean, cool. 

    Today I have time to work on it. Switch out the 50 pilot for the 55. Still will only idle with enrichment valve pulled out. So now im going to take the carb off again, clean everything again, and check the float height this time. When I get paid Thursday I'll probably buy some new spark plugs just to have them.

    Anyway, thats where im at right now. If anyone has any suggestions im open to them. Ill post on here again and hopefully she'll be idling properly.

     

    **UPDATE ** 8/29/26

    I finally got the bitch running today and I am over joyed! Pulled the carb, took it apart, and gave all the pieces a good soak for about 30 minutes in a big ass can of carb cleaner. Then took my time with a brass brush, spray can carb cleaner, and canned air i cleaned everything up and sprayed all the holes and crevices out. Reassembled everything. Started the 50 pilot and 148 main. Float height is JUST below 18.5 mm. Used my stock gas line. (Originally I had used new line I cut longer because the stock is a bitch to get on.)

    Forgot about the choke and she fired right up and idled. After fucking with the air/fuel screw and idle screw for a couple minutes I got idle is sit around 1200. (Bought a cheap tach that wraps around the plug wire.) Little bit of black smoke out the exhaust and possible afterfire. Partial throttle seemed good to go.  Was getting dark so im done for the day. Tomorrow going back at her. Might be a little rich at idle. 

    **note** vstack, exhaust, and performance kit are all tjbc. I did Originally replace the carb boot. I did remove and install exhaust gaskets**

    I'd rather be mediocre at fixing my motorcycle than great at pickleball
  • Dr.Phatpants

    8/30/26

    Turned the air/fuel screw IN to about 2 1/4 turns out and again to about 2 turns out. She's idling fine, quarter throttle sounds fine. At idle there is still a little black smoke coming out the exhaust. Doesn't seem to be any smoke when the throttle is applied. Any advice or words of encouragement are appreciated.  Im going to take her out on the road and see how she does 

    I'd rather be mediocre at fixing my motorcycle than great at pickleball
  • Dr.Phatpants

    8/30/26

    Turned the air/fuel in to about 1 3/4, she starts and idles great. Apply throttle still good to go. If there's any black smoke coming out the exhaust its very hard to see. Turn bike off. Remove the  tachometer, attach the speedo to the tank, attach the seat. Go to start up, won't start. Rock the bike there's fuel in the tank, feels low. Switch to reserve, try again,  nothing. Use the choke, still nothing.

     

    So now im stumped. I dont have time to today but at some point this week imma check the plugs. Is there anything else anyone can think of?

    I'd rather be mediocre at fixing my motorcycle than great at pickleball
  • TJ

    @Dr.Phatpants check the clutch safety switch, neutral safety switch, and the kickstand safety switch, also, try leaving speedo unplugged before you try to start. you did something between your testing and your reasembly. 

    DO FUN SHIT!
    Check the FAQ's here for tons of tuning info and more!! - t.ly/MA6r6
  • Dr.Phatpants

    @TJ really?? Ok, I'll check those out. Ive cleaned 2 of the 4 spark plugs. Covered in soot. Been waiting on payday to buy a 6 inch extension to pull the other 2. 

     

    Thanks for the advice! 

    I'd rather be mediocre at fixing my motorcycle than great at pickleball
  • Dr.Phatpants

    Finally got all 4 spark plugs pulled and cleaned. Bike fired right up! Still running a little rich. Turn the mix screw in a quarter turn at a time. White smoke is coming out. Must be lean now. Bike idles low and then dies. I had/have the idle screw turned all the way in. Gonna turn it out a little bit, see if I can get her to behave properly. Seems to be an extremely fine line between too much and too little air/fuel. 

    **edit** air/fuel is 1 turn out

    I'd rather be mediocre at fixing my motorcycle than great at pickleball
  • Dr.Phatpants

    I seem to be stuck now. Im making very small turns (⅛ to 1/16 turns)  in and out on both the air/fuel and idle screws. Keeps jumping between slightly lean and slightly rich. Low to right idle speed. I can hear the carb over the exhaust.... maybe a vacuum leak???

    Ill figure it out eventually 

    I'd rather be mediocre at fixing my motorcycle than great at pickleball
  • Dr.Phatpants

    Really dont know what's wrong. When I have time I'll take the carb off and check if the diaphragm is seated properly. Might clean the carb again. If that doesn't work, I'll haul it over to my mechanic who works on bikes for a living. Because, by then, I will be completely tired of fucking with it.

    I'd rather be mediocre at fixing my motorcycle than great at pickleball
  • TJ

    @Dr.Phatpants dont run the bike with air fuel mix screw all the way in. id stop messing with the idle screw. Just bench set it so you can just see the emulsion hole in the venturi peeking out from under the butterfly. you can see this looking at the back of the carb right under the butterfyly, thats essentially the correct idle spot. 

    DO FUN SHIT!
    Check the FAQ's here for tons of tuning info and more!! - t.ly/MA6r6
  • Dr.Phatpants

    @TJ I haven't touched the bike all week and im about to go pull the carb again. So when I set the idle screw and the emulsion hole is barely visible under the butterfly (just like your video) I really shouldn't need to adjust the idle screw again? Maybe a very minuscule turn in or out. Ok, good to know. 

    I'd rather be mediocre at fixing my motorcycle than great at pickleball
  • Dr.Phatpants

    Pretty sure i was trying to tune with a vacuum leak at the boot. Took the carb off but didn't disconnect the throttle cables. Figured i would bring the air/fuel and idle screws back to their starting points. Reconnected everything and REALLY tightened down the intake boot. Pulled the choke and fired her up. No whine from the carb and the exhaust was a little quieter. No black or white smoke out the exhaust. Push the choke in and it dies. Too lean. Turn air/fuel out to 3 turns. Again starts and runs with choke. Dies without choke. Same thing at 3 1/2 and 4 turns out. Still too lean. Gonna switch the pilot jet from 50 to 55 sometime this week or next weekend. AND MAKE SURE THE BOOT IS SEALED TIGHT.

     

    I'm almost there. Wish I had more time to work on her more regularly but that's what happens when your kid has a busy schedule and isnt interested in motorcycles lol

    I'd rather be mediocre at fixing my motorcycle than great at pickleball
  • TJ

    @Dr.Phatpants great work man! glad you nailed down one of the issues!

    DO FUN SHIT!
    Check the FAQ's here for tons of tuning info and more!! - t.ly/MA6r6
  • Dr.Phatpants

    Switched the pilot jet from 50 to 55. Only runs with choke pulled out. Tighten the boot until it won't tighten anymore. While running, sprayed carb cleaner at the boot, Rpm gets wonky. Stalled the bike at one point. So I have a vacuum leak i cant get ride of. Don't know what my next move is right now. Maybe gasket maker, maybe buy another new boot from Honda. All I know is winter is around the corner and im running out of time. 

    I'd rather be mediocre at fixing my motorcycle than great at pickleball
  • Dr.Phatpants

    I believe the culprit of the vacuum leak is the aftermarket carb boot. When I got home from work I took the carb off and checked the boot. I wanted to make sure I didn't put it on upside-down or backwards. (The OEM boot has notches and one side is marked carb.) The aftermarket boot is smooth, no notches. Should fit any way you install it. The boot sits snug on the intake manifold but sits loose on the carb. I think when the boot is clamped to the carb, the boot folds up over so slightly, creating the vacuum leak. I will be ordering an OEM boot on payday. 

     

    I then will hopefully be able to tune this cocksucker. 

    I'd rather be mediocre at fixing my motorcycle than great at pickleball
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