bdreed

My Feedback: (-1)

Hello -

I've got an Evolution 26GT that I cannot get to run properly. I'm using high quality 2 stroke 100% synthetic racing oil and premium gasoline. The ignition system is being powered by a 7.2 volt 1500 milliamp battery. The engine runs and does not die. I have adjusted both the high and low settings and have them where the engine sounds like it should. ( to me anyway). The problem is persistent throughout the entire RPM range. It sputters, sounds like it is missing. In the air with the plane pointed down the engine stops sputtering and runs just fine. On the ground I try to replicate this by holding the plane at a 45 degree angle UP and then move it to a 45 degree angle down; the engine continues to sputter. I cannot replicate in flight on the ground.

Any ideas as to what I should try?

Thanks for any and all suggestions!!!


Brian

Zippi

My Feedback: (10)

I had a similar problem with my Brillelli 26cc on the front of a Giles 202. It ran good on the ground but once it broke ground and got in the air it would spit and sputter like it was flooding out and if I cut it to idle it would die. To make a long story short, it ended up being the air flow coming around the cowl to the carb. To fix the problem I made an air induction out of a 90 degree brass elbow that came off the carb and faced towards the prop. Problem solved.

Scott Ellingson

My Feedback: (146)

I am not farmiliar with the ignition system on an Evolution, but isn't 7.2volt too high? I think the max voltage is 6v on them. Do you have a regulator? I could be wrong though.

bdreed

My Feedback: (-1)

The Evolution 26GT won't run properly on 6 volts. The manual says 6 to 8 volts. I tried 6 volts and it would only run for a couple minutes and then the battery was used up.

BaldEagel

It sounds to me like Diaphragm buffeting, on the side of the carb is a metal plante held in postion by 4 screws, this plats has a circular rim and if you look carefully, a hole in the metal plate. This hole vents the diaphragm to atmospheric pressure.
Note the positon of the hole its different on different models of carb (this is assuming a Walbro carb) its imortant to get the hole back in the same position it came off.
Take off the plate leaving the diaphragm and springs inside the carb and solder a small length of brass tubing or a pressure nipple to the plate, ensuring that the hole in the brass tube or nipple is not blocked, Refit the plate on the carb exactly in the same position it came off.

Either fit a trumpet to the carb and join the new palate nipple to the trumpet,
or simply lead a length of fuel tubing to the inside of the model's fus.

I cannot claim originality for this cure as it came from the late Paul Landers of Just Engines in the UK.

MIke

bdreed

My Feedback: (-1)

Tried taking the carb apart and cleaning/inspecting it. Put it back on and still the same. The hole in the metal plate seems plenty large and is free of obstruction.

Will probably try Horizon tech. Maybe, have heard they are not that helpful.

DKjens

My Feedback: (50)

bdreed,
Nobody said there may have been obstructions in the hole in that plate on the carb. What Mike was explaining was how to fix a possible fuel metering problem that's causing your problem. Wenting that hole to an area with the same pressure as the intake (need to use a trompet and run line to same) or to a more constant pressure area, as in inside the fuse, will make the carb. meter the same no matter the airplanes situation and attitude, i.e. on the ground or in the air, pointing up or down.
DKjens

NM2K

My Feedback: (14)

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Or, put another way, the diaphragm under that hole controls how much fuel gets into the carburetor, like a float bowl on an old car carb. Sometimes oncoming air during flight can throw off the calibration of this regulator. One fix is to fasten some kind of nipple or pipe to the hole on the cover and then hook up a piece of tubing that is ran to another location in front of the firewall, or to penetrate the firewall with the tubing and utilize the "dead air" inside the fuselage to help stabilize the diaphragm's movement.