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I previously reported that after almost four years, that I had begun to have trouble tuning my carb. At first I thought the slide was binding. Then I discovered the mixture needle was the cause. The needle would bind once the set screw was tightened and so it appeared the slide was cocking over but it was caused by the mixture needle. I tried new needles, as I had the old brass ones which appeared very loose within the mixture outlet. But, I was still unable to tune this thing any longer except for a specific time or condition. I finally gave up as I was spending too much time on the ground. So, I just ordered a new carb as I thought the mixture needle outlet had become enlarged and therefore unusable. These difficulties had been reported to Sonex tech. What a surprise when I opened the new carb. I immediately noticed that they have INSTALlED A NYLON BUSHING at the mixture needle orifice. This makes it smooth as silk now and I suspect that it may be a replaceable item as it appears. I had not received any word on this from Sonex. It is not listed in the parts diagram either. I do not know if they plan to offer retrofits or kits for the same. I do feel that the reason why so many have had trouble tuning the carbs is that they may just have been unlucky enough to have an off size needle or perhaps mixture outlet anomaly. Just an opinion. But I installed the new carb, had no trouble tuning and flew for about two hours. I always need a little fine tuning after the first few flights to dial it in to my liking but the point is that it instantly solved my problem. Hope this help someone.

GWMotley wrote:I immediately noticed that they have INSTALlED A NYLON BUSHING at the mixture needle orifice. This makes it smooth as silk now and I suspect that it may be a replaceable item as it appears.

I'm pretty sure mine also has a nylon bushing. It is at least 1, maybe 2 years old, so I would think by now a lot of us have that bushing. I haven't been to my airplane to check though and was waiting to see if others knew anything about that bushing.

My AeroInjector has the nylon bushing in the needle orifice. My AeroInjector was delivered in April 2013.

Jake

When I try and tune my aeroinjector I find that the needle, regardless of size number, is loose in the needle orifice. From what you have said, this loose condition is most likely why so many of us cannot get a nice smooth constant rpm setting etc. with our older aeroinjectors. My unit doesn't have a nylon bushing. It looks like some type of brass insert. If Sonex knows about this, why hasn't it been addressed. It seems like a simple problem with a simple fix. Since I've never looked at another Aeroinjector I don't know if the needle is designed to be loose or not. It seems it should be a nice sliding fit. Have I missed something this past year of trying to adjust my carb?

Regarding the needle threads, see the second half of my post for my experience:

http://www.mykitlog.com/users/display_l ... 6134&row=2