Carburetor slide stopper

[keith0alan]

The little button is pressed in. I have made some brass rivets to replace them. It does involve drilling a hole where the current button is located. This is something that I do during rebuilds. They only hold the slide up when the engine is not running. This allows some air in for starting. They have no effect on mixture at any speed. As needles and nozzles wear the carbs get richer at idle. If you are going to set the needle out I would recommend that you lay a feeler gauge on the face of the piston and press the needle in with a straight edge to the feeler gauge rather than the face of the piston. This way it can be fine tuned consistently.

[Ted928]

I took a look at the carbs today. The front carb bumper/stopper was flush and the rear carb was proud about 25 mils. Since I had set the needles according to the ZTherapy instructions, the needles were offset relative to each other. The front needle shoulder was flush with the piston bottom (slightly proud of the brass insert which is what the Clymer manual says to use) while the rear was proud ~25 mils. I noticed that my choke was hung up on the rear carb so I cleared it and retuned the mixture knobs.
I am now happy with the idle mixture and fueling while under load although I still think that the idle is slightly off.
I don't know if it is necessary or not, but I plan to fab a new button/stopper for the front carb this winter so that the two carbs are consistent and retune in the spring.

Thanks to everyone for the help.

[notoptoy]

Glad you got it running acceptably. Thanks for getting back to us with your results!

[Ted928]

Glad you got it running acceptably. Thanks for getting back to us with your results!

Thank you for your help. It is running so much better.
I like the Z-Therapy method for setting the needles since that sets the needle height relative to the nozzle regardless of piston height (variation will be due to buttons/stops). I still think I need to make a new buttons/stop so the two are consistent. I suspect that all is still not perfect.
Ideally, small changes to either carb idle speed screw or mixture nut will result in the same response regardless as to which carb was tweaked. For example, a quarter turn of idle speed (+/-) should result in the same change in idle speed regardless of which carb screw was tweaked. Same for the mixture screw.
I'll report back.
Thanks to all. This forum is extremely helpful.