Pa-18cub150

I have a Home Light trimmer motor on a Sig 110 Rascal. The motor will idle ok but die as I transition. As I have things adjusted now. If I go slow it will run for a short time at high rpm and then fall off. If I pull back to idle quickly the motor will continue to run. The High needle has little to no affect.
The motor faltered a little a couple of weeks ago but a little tuning and then I had three good flights. today I can't get this thing to transition for love or money.
I didn't do the conversion or mount the motor.

Pa-18cub150

its a wt 439 carburetor

Pa-18cub150

went back after supper. it will not run above 1/3 throttle agene. No adjustments were made. I'm beginning to think that I don't have a tuning issue. where should I start? Carburetor kit, Carburetor, fuel lines, or filters? what should I look for. started with a 1 1/8 out high needle setting.
In-line filter is clean
running 80:1 AMSOIL and premium fuel no ethanol

pe reivers

Clean the carb filter screen.
While at it, check integrity of diaphragms (supple) and gaskets. Replace if needed.
Be careful to fit the pumper diaphragm towards the body before you fit the gasket, and the regulator diaphragm with gasket to the body.

Tidnab

My Feedback: (51)

You don't have to run high test in a Homelite and most other 2 cycle engine.The lower octane gases run well even in most race engines.To get rid of ethanol put some Startron in each gallon. I have a friend that runs it in his weedeaters and his full size car and gets better gas milage. You must be running Amsoil Saber 100:1 and at your 80:1 ratio that would be 1.25 oz per gallon. I run Amsoil 100;1 in all my 2 cycles whether in my r/c boats or wacking weeds,but I put 4 oz per gallon and my engines are clean inside and not much smoke.
http://www.walmart.com/ip/Attwood-8o...itive/16351036

pe reivers

The fuel never is the problem with these symptoms.
A good walbro writ-up is:
http://www.drystacked.com/Walbro%20C...027Jun2010.pdf

Pa-18cub150

Hear is where I am at tonight. Tank was clean, clunk filter clean, In-line filter clean, carburetor screen 85-90% covered with a black crumbly substance.
Replaced screen removed needles blasted with carb cleaner and air.
results: if I have the low needle rich enough to transition it is hard to start and it floods at idle. also rpm falls off on the last little bit of the high end travel. I think something is still restricted .

pe reivers

Spend a diaphragm/gaskets update kit on the carb. All moving parts must be flabby flexible.

captinjohn

+1

Pa-18cub150

Well this is where I'm at this afternoon. cleaned carb and replaced diaphragm, needle and check valve wafer. (used the mash looking one as the proper rubber one was missing from my kit)

motor will rev up and die at idle.

I am assuming that I may have an induction leek?

I have checked the insulator block and gasket. no cracks. checked and double checked all screws. I'm at a loss

I was planning on flying this tomorrow in a demonstration, but its not looking good.

propellantchem

I would bend out the metering arm under the diaphragm just a little, sounds like you're leaning out. Moving the meter arm up will richen at all screw settings, lowering arm leans at all screw settings. Getting it set right is a bit fiddly about 0.030" might separate too rich from too lean. If you apply choke (like putting your finger over the intake) does engine run OK, or does it immediately die? If it runs Ok, you need to richen up, if it dies, lean out. If you have new internals in carb, look for other air leaks, a loose muffler can make tuning impossible. Bad bearing seals can be a problem.I would also inspect fuel lines for cracks and kinks. Just had a fuel line coupler plug the other day, and saw another flyer with a kinked hose after some field repairs.

azalner

My Feedback: (8)

In my experience, once you start to "fiddle" with the metering arm you're screwed. Without the proper equipment (depth gauge & pressure tester) you will spend hours taking the carb off, tweaking, putting it back on, testing, then repeating the process.

What brand carb is on the engine and what is its displacement?

BertZ

propellantchem

Yes, once you start fiddling it does get a little time consuming, but it's a good learning experience. I keep a modified 31cc Ryobi handy for rough tuning carbs. I also found that having a fuel tank on a stand with a long fuel line is nice to test the metering arm height/fuel flow. When the carb doesn't leak fuel with a 2'-3' pressure head and it pulls fuel with the choke set and engine "cranking" the metering arm is good to go. (YMMV) Then you can set the hi and low needles.I figure 30 - 60min to setup the carb, faster once you get the hang of it. Test motor is nice because you can keep carb on and only pull off 4 screws over metering diaphragm. I found that the Ryobi likes a little pipe especially when you get above 150 degrees duration on the exhaust otherwise it's impossible to tune. (It can run with the carb inlet plugged/choked because of exhaust reversion with an open exhaust)I bought a 10 pack of diaphragms for my walbros, but they are not an exact replacement for some of the carbs I have, so I got pretty good at tweaking.The carbs came from a pile I found at the local scrap yard, brought home about 30 assorted diaphragm carbs,

Pa-18cub150

I haven't had time to fiddle with he carb for the last week and wasn't sure what I needed to be looking for.

Propellantchem. Yes when choked, it dose run better and longer but at a high idle, the exhaust is nothing more than a copper elbow on a plate. It ran strong before I started having problems
I replaced the needle so it makes sense that I may have inadvertently bent the metering arm down.
Azalner it is a 25 cc home light. The carb is a Walbro WT439

Flathead

My Feedback: (11)

I am retiring from modeling after 65 years. Age is catching up to me. Engine conversions have been my passion for some 20 years.
My problem? I have a bunch of engines, probably mostly RYOBI's that I never got finished. If anyone is interested, and I will make
a count of what I do have. Give me a shout here. I live in Western Kansas, 190 miles East of Denver, 250 miles West of Salina, KS

propellantchem

Hi PA-18,Alright, so you applied choke and the motor ran better (don't worry about speed yet)That would indicate that you are running too lean. All the intake and carb screws are tight, you have new diaphragms (stiff metering diaphragms cause lots of problems) and gaskets in the carb, and you cleaned the inlet screen in the carb. You've verified that the fuel lines are not cracked, kinked, or plugged and fuel flows easily from the tank to the carb. The exhaust system is tight and so are all of the screws on the engine (jug, back plate, spark plug, etc. )Make sure that the crankshaft doesn't have much play in it (leaking bearing seals)I want you to work through the tuning on this link and report back.http://www.footflyer.com/fix/motor/carburetor/walbro.htmI'm thinking that the metering arm is out of adjustment, but work through the link above first.