Hello all, ok, I've searched every thread that I can get my eyes on and I can't find the answer to this question. I have a Mcculloch/Troy Built 25cc leaf blower engine that I converted for a Sig Rascal 110, I'm running a Zama 10mm carb with a Zenoah carb adapter, velocity stack and header pipe for a G-26. everything fits and runs like a dream until I line up (nose slightly down) for a landing, then the engine stalls..... DEADSTICK. No matter what I try, it will not idle with nose down attitude (not nose straight down, anything less than horizontal). I thought it might be my tank placement but since it's a pumper carb that shouldn't matter (at least in my head) I tried the original carb but with the mods to it, it won't give it enough fuel to transition. At first I suspected I was just running it out of fuel as if the clunk was dry. it does it full tank or partially full. I am one more deadstick away from buying a Zenoah and a new plane but I hate to spend the money on a plane I already have. HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!11[]

With it running on the ground, move any and all electrical items for the ignition around. (It's called the "wiggle test" in automotive troubleshooting.) Be careful of the prop.

Will it even do it at a fast idle? Does it do it on the ground if you lower the nose, or only when flying? Got a pic of your installation?

AV8TOR

there are only two wires under the cowl, the kill switch leads from the mag to the switch and from the switch to engine ground. I tried increasing idle speed to 2500rpm and it still does it. It will do it on the ground just by tilting the nose down, when I rotate nose high engine rpm increases for a short time and then smooths out. sorry, I don't have a camera at the moment, but my installation is very simple, engine inverted, side carb and exhaust, fuel tank outlet line approximately 1.5 in. below carb. Fuel lines are one supply, one return, and a vent. No choke, no primer bulb and magneto ignition.

This is a wild shot.... Sometimes these engines will run just on fuel draw; like a glow engine carb. Are you sure your pulse holes are lined up and working, and that the fuel pump is working? If the fuel pump is working, no attitude change should make the engine run differently.

Are you positive that Zenoah carb adapter is feeding a crankcase pulse to the carb fuel pump??

Also, if you are not running a primer bulb, there should be only one fuel line to the carb; the one from the fuel tank clunk to the fuel line on the carb nearest the fuel pump. If there is another line fitting on the carb, it was for an external primer bulb, and it needs to be blocked off.

AV8TOR

WOW!!!!!!! talk about a boneheaded move, I had the thing plumbed as if it had a bulb but I forgot that bulbs have a check valve in them, I plugged off the return line and the engine idles the same straight down as it dose straight up, thank you for your insight and help. I am so thankful for your input, if you're ever near Prescott Valley and need a cup of coffee just holler. I can't thank you enough!! Keep the shiny side up!!!!
Jeff

You're welcome. I figured that would fix it. Glad to help.

Prescott Valley heh? I used to live there, and also up in Groom Creek up the mountain out of Prescott. I have a niece in Prescott Valley, and one in Paulden too. I used to own property up in Ash Fork, and flew my ultralight airplane all around those areas. I used to manage Anaco aircraft maintenance out on Love Field.

This was all years ago. I've seen that Chino Valley flying site on the web, but never in person. Looks nice. One time I was flying a Phantom ultralight from Phoenix to Ash Fork for a rancher that bought it. We arranged to stop at a field near Prescott Valley so I could fuel back up. I got the wrong field and landed at a model airplane field!! I never saw a model in the air, but several were flying and boy were they mad at me. Thought I was going to get into a fist fight before we got it all sorted out and they realized it was just a mistake and not a "stunt".

AV8TOR