HS40 carb ?

[El Tigre]

Having too many problems with carb tuning, bike idles and runs but acts differently each time I start it... my carb has 2 adj at bottom 1 is main Im guessing other is float adj. I also have an idle air on the side. What is the "best" replacement/upgrade to use... one to get more HP preferably.

Thanks
Bill

 

[The Restore Kid]

Could be just the carb is semi gummed up, and with each run gets cleaner and cleaner. Thats not uncommon.. I guess Tillotson carbs will bolt right on and give ya more (potential) power.. But on a Stock HS40, probably nothing you will notice over the original carb.. For the price of a Tilly big enough to work RIGHT for the motor, I'd keep messing with the tecumseh carb.. :shrug:

 

[doubletrouble]

If you know this then ignore my comments. The bottom adjustment is the high speed mixture, the screw on the side is the idle mix. Run the engine and warm it up. Run it at high speed first and adjust the bottom screw for max steady rpm, next allow it to idle and adjust the low speed (side) screw. Its essential to do the high speed first, if you do them reverse or otherwise the settings wont work, and it will run weird.

 

[minibikedude]

You said you have two adjustments on the bottom, Have you open up this Carburetor! That sounds like a older Tecumseh carburetor with the fuel drain on the bottom of the bowl toward the outside of the bowl, It not a float adjustment.You do that with the tab on the float before putting the bowl on. Middle one is the main jet adjustment, Main jet is usually about a turn and half out.