Dave,

Took my plane with 120 SF out to fly yesterday and the engine would not run full throttle. Idles and mid range great but full open and it dies out. I can watch the fuel flow to the engine at idle and half but at full throttle the fuel with air bubbles reverse and head towards the tank. Took and cleaned out the check valve, installed correctly but no luck. The engine did sit up all winter (Oct - Jan) without running. I haven't checked the tank or lines yet. Any ideas?

Thanks,
Mike

Might be a worn out NV assembly. Does the NV body bottom out against the hex on the spray bar? If so that could be the problem.

Dave,

I closed the needle all the way and there is about 1/32 gap before it touches the hex part. Another thing I just remembered was when the engine ran up full throttle the needle didn't seem to effect it much. Once I even open it up about 3 turns and it had little effect on the RPM. Course it didn't run really long enough at full throttle to make heads or tails of what was going on.

Thanks,
Mike

I still suspect that the NV assembly is worn out, or after your note maybe full of some junk. Pull the NV body and make sure it's clean. Also the passages in the throttle body where the barrel feeds the carb. Lots of little nooks and crannies in a YS fuel system to plug up!

Thanks Dave, I'll pull it apart this weekend and clean it and see what happens.

Mike

Mike,

Is the tank holding pressure? Use your fuel pump and when full of fuel pump some more in and it will expand the tank and pressurize it. Look for leaks. I know it was not holding pressure on Sunday at the field so make sure of that.

Since all was working back in Sep and now its not. Something is a little squirlely. Another thing I thought of is that the regulator may have some thick oil sitting in it from back in Sept

I know we checked the check valve but if the regular is a little gummed up with thick oil it might not be sending it back to the tank via the check valve.

You don't need new parts just to clean it out. We can flush it with a little fuel and that should help. If its really bad then we may have to open it up and wash it with lean fuel to to clear out the thick oil.

The Pressurized YS engines run on suction at idle as as you open the throttle they rely on the pressure in the tank to force feed the fuel. No pressure means no fuel at the needle valve. Bring it out on Sunday and we'll get it going for ya along with your new 160DZ.

Troy Newman
YS Performance Field Rep

Thanks Troy,
I'll pressure test Sat and make sure the tank and lines are not leaking. I'll bring it out Sun and we can work with it again.
BTW - I ever so slightly loosened that screw on the carb of the 160 and the throttle barrel works sooo much easier now. Thanks for the tip.

Mike

Update: I took the needle valve out and pumped fuel through carb till it flowed well, replaced all lines and pressure tested the tank, hooked everything back up and the engine ran like a scalded dog again !!! Must have had some gunk in the carb from sitting up all winter and was dislodged with the flushing.

Thanks for the help Troy !!! - everyone looking for help in this forum is definitly going to benefit from having Troy as the moderator, I'm lucky in that I can have his expertise at the field any weekend. For those that have never had the pleasure of meeting and flying with Troy, you will never find a more friendly and dedicated pattern flyer to help you with a problem. Last weekend Troy assisted me with a new 160DZ on my Focus, the throttle was sticking and I did not have the knowledge or parts at the field to fix it, so Troy took the throttle wire out of his front line plane and gave it to me so I could fly !! - that meant his plane sat idle while he flew his biplane. He also completely disassembled the carb to diagnois the problem and ended up swapping a part from his spare 160 and installing into mine -- again -- just so I could fly and break the engine in for our upcoming contest. Darn impressive in my book.

Mike Austin

Thanks for the kind words.

But the better news is that means we'll see you at the field next weekend to practice!

I'll be going out this week almost every afternoon. Weather looks a bit iffy...but what can you expect of Phoenix in February. Last Thursday and Friday it was over 80deg.

Troy

Mike I hate to break this to you, but Troy will just have to pack up and move to Alabama!!! LOL
I need him down here if he is going to help out like that. I'll even teach him to eat bbq and say y'all.
I think the weatherman is calling for lows in the mid teens toward the middle of the week. Today was 65. Do you think he will notice?
He sounds like a great guy to know as I have asked him a question or two about my 120ac already and he has been quick to reply.
Hey Troy, had a chance to find your diagram for the 120ac yet?(you were going to look at the plumbing diagram for me because my engine that I bought used had 2 checkvalves , 1 for exhaust side and 1 on the fuel side)) My pushrod set came in the mail today from Central so I am good to go .
I will wait on your email or pm . Thanks guys!!