mooseflier

Hi. I have an OS 46fx that I am having a problem tuning. The problem started with this... when the engine would idle for more than a few seconds, when I would flick the throttle to full the engine would studder a bit and then slowly spin up to full RPM. I was unsure of how to clean that up so that it was much more responsive... faster throttle up. So I read through the engine manual and talked to some folks out at the air field andI thought I had a decent understanding of how to use the idle setting (the screw that's 'inside' of the throttle arm). My understanding of what was going on here is that it was too rich at idle and would slowly flood the carb... so the longer it idled, the less responsive it would be when Itry and throttle up quickly. That seemed to make sense and match the symptoms.

So, I slowly closed (clockwise) that screw... about a quarter turn at a time to lean out the idle. It seemed to work fairly well... the engine would be more and more responsive after leaving it in idle for 20 or 30 seconds and then quickly throttling up. But, the manual seemed to suggest that the propper setting for this would be about 2 full turns open. When I got it set as best as possible, that idle screw is fully closed on my engine. Again, seems to work ok, but I've only had a few short flights when I was testing it... and still noticed some sputter on throttling up while in the air.

Can anyone make any suggestions as to what I might be doing wrong or what Imight try? Not sure if it matters, but I'm using 15% fuel.

Thanks!

w8ye

My Feedback: (16)

Part of the trick is to set the high speed correctly first

ceecrb1

Also, I learned that, while you are tuning the low needle.. dont turn a 1/4 turn at a time... it can be even as little as 1/16th or 1/8th that is needed...

when tunning my 55ax.. the sweet spot was found by giving the screw the tinyest of tiny nudges in one direction..

rcdude7

My Feedback: (264)

Set your HS needle first then set the LS. Let the engine idle for a few seconds then "roll" on the throttle, excessive smoke and sputter, too rich. Engine dies suddenly, no smoke, too lean. Adjust and reapeat.
These carbs don't respond as well to flicking as they were not designed for that. Car slide type and YS carbs will respond lightning quick, but you are asking too much of a .46fx carb if you expect that kind of response.

mooseflier

"These carbs don't respond as well to flicking as they were not designed for that. Car slide type and YS carbs will respond lightning quick, but you are asking too much of a .46fx carb if you expect that kind of response."

Very cool to hear! I think I was expecting it to be too perfect then. Glad to hear about the YS too... I have a new YS 110 for a bipe SkyBolt that i'm making. It's my first four-stroke. They always sound so smooth out at the airfield... have always wanted one. I can't wait to get it broken in!

Thanks for all the advice!

rcdude7

My Feedback: (264)

You will like the YS, once broken in and tuned right it will spin up and down the rpm range just as quick as you can move the throttle stick, a great running engine.