Cambo

My Feedback: (2)

About a month ago, i was having a problem where my engine would not run above 1/2 throttle. It caused a crash that ripped out the landing gear. It was an easy fix. Either the new spark plug i put in or the fuel line i put it fixed the problem. I have probabley 20-30 flights on the plane since then but just recently it started to get hard to start. Normal starting procedures would get the engine to the point were it usualy starts, however the engine just wouldn't go. It would pop or turn 5-10 times and quit. I could do this like 15 times before it would actually start. Okay, so fastfoward a week. I go out to the field and setup everything. She starts as normal but the second i advance the throttle to around 1/2 it imidiatley quits. After this, it is impossible to start. I got a few more sputters out of it but 35 minutes of flipping and fittling yielded nothing. So i just got back to the plane today. I check everything, fuel filters, spark plug, gas line. Everything checks out great. I try to start it in my driveway and the same thing happens. What the heck is going on here? There is an underlying problem here and i just can't pin point it.

On a side note. I can't seem to get this burbley mid range to go away. One would say just lean in out but i have already had this thing quit on me while inverted. Upside down the engine noticabley smooths out and runs much better. Leaning the low end seems to effect the engine upright and upside down preportionaly but the engine runs leaner upside down. Is this normal?

Should just get a new carb at this point?

Rfabbre

My Feedback: (6)

Cambo,

Why don't you just get a carb kit and do a quick overhaul of the carb before you go to the expense of buying a new one. The kit comes with all the replacement parts you could possibly need and are relatively simple to do.

Bob Pastorello

My Feedback: (198)

Gotta agree. Go to your local chainsaw shop and get a "WT" rebuild kit. Well worth the time and money, and let's you get "intimate" with the innards of a Walbro (not a bad thing). I'd put money on the carb being the issue.

Cambo

My Feedback: (2)

okay, maybe i will do that. Do i need "WT" to be exact?

rangerfredbob

My Feedback: (13)

D20WAT or K10WAT are the carb kits, the D one is just gaskets and such, the K has some metal parts and is somewhat more expensive

Jim Messer

My Feedback: (2)

Sounds to me like you have a plugged screen. Clean it first. If that doesn't solve the problem, then flip out the screen and clean out the hole beneath it. One of these two things should solve your problem.

nitro wing

My Feedback: (1)

Diaphram?

Rfabbre

My Feedback: (6)

The kit will have a new diaphram.

ram3500-RCU

My Feedback: (221)

I agree with this post. I would start with the screen and port before I bought any parts. These carbs rarely need rebuilding, not that it couldn't' happen. I have rebuilt maybe three of mine, in the 18 years of running gas. Cleaning the screen is done much more often.

NUTNDUN

I vote the carb screen from first hand experience two days ago on new motor. My motor would rev past half throttle and I tore the carb apart and there was some junk in the screen and one bigger piece, I swore it wasn't enough though to cause the problem but low and behold it did. She revs like a champ now. Also sounds like you are too lean and I would redo the needles back to factory and do the tune again. Also do you have the diaphragm vent run into the fuse?

OldRookie

My Feedback: (13)

I guess I don't quite understand the diaphragm vent.
Most of the 50cc+ planes I have seen interior, and engine pictures of, don't have the interior of the plane sealed up tight.
It would seem to me, that the air pressure inside the fuselage and wings, would be the same as the pressure inside of the cowl.

Greg

NUTNDUN

I don't think it is so much of a pressure problem. I am sure pressure has something to do with it but I think it is mainly the way the air moves over the vent creating differences in the pulse. I got a carbon graphite carb plate from TBM and all it does is covers the carb plate with a little air gap in between to help keep wind turbulence from effecting the pulse. Also I think most of the people that run the diaphragm vent into the fuse run them into a pill bottle or something. I haven't done this and hopefully won't need to with the carb plate.

OldRookie

My Feedback: (13)

So what does the pill bottle do?
How big of a pill bottle?
Do you drill an air hole in the pill bottle?
If so what size?

I have the SD models Yak 54 50cc size. That big old buckett cowl could scoop up a lot of air. I am planning on blocking the complete cowl opening except for an engine cut out. The engine will be baffled. I am also planning on cutting out the bottom of the radiator box, and put in 4 or 5 louvers, slanting to the rear of the plane. This creates a slight vacuume effect. Should be plenty of cooling for the DL.

Greg

Bob Pastorello

My Feedback: (198)

The pill bottle, film canister, cardboard tube, balsa box all do the same thing... they act as an accumulator/damper to permit gradual adjustments of atmospheric pressure to be felt by the static port of the diaphragm. It makes a HUGE difference on SOME airplanes, not so much on others, and depends on a wide variety of variables which are somewhat totally unpredicatable.

The fact is, that many of the "conversion" gassers have side-induction carbs, whose pressure ports sometimes point directly forward, and are "impacted" by high and changing pressure air masses during various maneuvers.

Symptoms are the same.... can be adjusted perfect on the ground, as soon as climb out, either richen, or begin richening in mid range during abrupt changes in attitude. Seems to also be prevalent in "bucket" cowls like Yaks, etc., althuogh certainly happens on others.

I simply modify all of mine as a matter of course, so I don't have to wonder whether it is going to be affected or not.

rcbill

My Feedback: (1)

I do the same as Bob P.... Bill