I have a ys 63 engine it is new but has about 1 gal of fuel through it. the engine transitions well from low to high and has a good top end. The problem is that when the throttle is advanced a little below 1/4 and left there the engine load up with fuel. upon pushing the throttle to full it takes about 3 to 4 seconds to clear and run fast. at all other settings though letting the engine run for awhile does not cause this problem. Even letting it run at idle for 30 seconds I can still get a fast good transition. Any clues to what is wrong or needs to be adjusted?

rlipsett... I have two YS 63's and two YS 110's... I have not flown with the
110's yet... and I have the samething happen to my 63's.. Not sure if it's
just a trate of the way these engines run or not adjusted right. They tend
to be finicky at times, But for now I love the power/size and throttle
response. They tend to be effected by heat... I believe that the YS's go
from a normal(carb) fuel feed at idle, and "sort" of an injection feed above
idle to top end.. and I'm not sure if this is part of the loading problem at
about 1/4 throttle setting????
I have not had YS's for long, so I'm still learning the do's and don'ts... And
for now:-) I love them.... I have just tuned per the instructions on YS's web
site.. And it works pretty good... But it does run a little rougher when it gets
hotter... And it does here in AZ:-(... Anyway I've never had a deadstick..
Well I've had a few fuel out dead sticks...

Probably the regulator assuming all else is well. First double check that all really is well. Specifically check for

Tank holding pressure and no fuel leaking out of engine (engine off)
Gaskets, o-rings in good condition, etc.
Good plug, OS #F or YS (I'd change if you have a spare, even if it looks OK)
Valve clearance is set properly
Engine is propped correctly
Proper fuel is being used, i.e. 20/20 or similar
Needles and regulator seem to be at a reasonable setting (reg should be roughly even with housing)

If all that checks out, and the engine is still loading up with fuel midrange, start adjusting the regulator. If you are going fat, lean the regulator 1/4 turn. Do this by turning clockwise, which compresses the regulator spring so less fuel is let by. Note you may have to reset your other needles after making a regulator change. Be sure to test with a warm engine, but don't run extended on the ground or it can overheat and then you end up chasing mixture all over the place. If you still need more adjustment, keep turning the regulator 1/4 turn. Fine tune as required. However, if you need to go more than 1 full turn from flush of the housing, something else is wrong IMO.

FYI - every YS I own I've needed to adjust the regulator some, but typically never more than 1/2 turn.

Cheers.