Weird mid range issues.

Stephen Douglas /

Hi guys, I have a ZA50 with a basic 70cc Airsal kit, long intake, fancy exhaust, pretty well tuned Bing 14.

It was working amazingly for miles until I developed a crunchy mid range. It's just kucky enough now that I can't get to that higher 2-stroke "nirvana" in second gear.

I know you guys want to tell me to do all the simple stuff right-off the bat, but I did. Checked gap, replaced gas (found a little water and crap), cleaned carb, played with different plugs, played with needle. Still same problems.

So, any fancy theories? Thinking of taking the cylinder off and checking for scratches... ?

Re: Weird mid range issues.

More info...timing,degrees/cdi/points ? jetting ? pipe ? gearing ? load weight ?...

Re: Weird mid range issues.

which Jet/needle/atomizer/slide in your 14 Bing

Re: Weird mid range issues.

Overpriced Parts /

Ya Take off the cylinder and inspect

Re: Weird mid range issues.

Stephen Douglas /

OK, sorry. I do have a CDI. Which all I did was install it. I didn't set anything. Needle I THINK is original. My friend who had a similar set-up gave me that carb because he had it nearly perfected. I will ask though.

Re: Weird mid range issues.

Stephen Douglas /

Oh, and the jet is a 76. Going to have to look at the needle size later but will get back.

Re: Weird mid range issues.

Brent Bublitz /

The carb might have been set up for your friends bike, that means nothing on yours. Even if it's the same exact setup it still has to be re-tuned. Every engine is different.

Tune the carb for good performance at WOT, then mess with the needle for idle to 3/4 throttle. If you do it the other way around you will be going in circles for days.

Re: Weird mid range issues.

Stephen Douglas /

Yep. Did that.

Re: Weird mid range issues.

Stephen Douglas /

OK guys. I found the problem. It was a culmination of help from a few of your that got my brain in the right direction.

What it was: It was the air filter. I looked at my long home-made thick-walled intake and noticed all the condensation on it. I was warm at the bottom and way cold at the carb end! It finally hit me that it might be making (condensing) it's own water from the high summer humidity in the air! That is when I started having probs.

So, I swapped it for a denser foam one. Completely solved!

I did notice though, that the old filter seemed wet with two stroke oil and fuel. Definitely worth considering that as a contributor also. It has such high flow though, that I would think a lot of air would be getting in anyways. It still shows a lot of light through it..

Lesson for my moped: KEEP A SPARE FILTER IN THE REAR COMPARTMENT.

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