brickhead179

My Feedback: (1)

hey! i ahve an od os engine that seems to have lost its power. At idle the engine is strong and does not miss a beat. But when my throttle increases, even the tiniest bit, the engine sputters or stops all together. this has never happened before and i even ran it about a month ago. what seems to be wrong? is it my carb needles? theres a small blck one on the side of the carb and a big one that twists by hand on the other side of the crab. Which one is high speed and which one is low speed??? PLease help!

eagledancer

the large one you can twist by hand is the high speed, but keep in mind if you adj the other one it can effect the high speed setting

JohnMcGowan

My Feedback: (15)

Hey Brick, give us all a little more detail about your engine, what size is it, 2 stroke or 4 stroke, what fuel is being used, how old is the fuel, how old is the tank plumbing, etc..? maybe we can help out a little more once these are known.
You say it is sputtering when the throttle increases,possiblly making the engine run rich at idle.. it could be the low end needle needs adjusting ( the low end needle is the one in the side of the carb) , as eagledancer stated , once you adjust the low end needle , you then have to go back and adjust the high end needle ( the big once sticking out that you twist) to get the engine to operate properly or it maybe could be as simple as a speck of trash in your carb?
John

Charlie P.

Make sure when you make adjustments to the low end you only change it 1/8th of a turn at a time. It's easy to set the high-end back to a running postition but get the low end goofed up and it can be a whole day of frustration.

Some OS engines (did "od" mean odd or old?) have an air bleed screw for low end adjustments. The air bleed channel could be clogged with dirt or old oil varnish.

Squeeze the fuel line tight enough to block it at low idle. If it stops dead you are lean (back out the low idle screw 1/8 turn). If it runs faster after a few seconds and then dies the low idle is good. If it runs for more than six or eight seconds you are too rich (turn the low idle screw clockwise 1/8th turn). Start the engine after adjustments and take it to half speed for a few seconds and then back to low idle and repeat until you get it set. Then take it to wide open. Set the needle valve to maximum RPM and then richen (counter-clockwise) two or three clicks. Now you have to set the transition. If you can go from low idle to full throttle with no catch or only a slight stutter you are good. If it konks try leaning out the low idle a TINY bit at a time (like 1/16 of a turn or 20ΒΊ or thereabouts).

If the fuel is more than six months old ditch it and start with fresh. And the first thing I do before futzing with a glow engine that has suddenly become a problem child is to replace the fuel tube from the tank to the carb. A tiny hole or tear in this - very common - will make tuning impossible.

brickhead179

My Feedback: (1)

its a 2 stroke engine form 1972 i think lol. The fuel is a couple months old but seems to be in nice running condition. I finaly got the high end needle fixed up and it screamed at full throttle but then died or didnt run for long at all on idle...[&:]. just my luck haha. now i think my glow driver is dead so il recharge it then try to get a perfect idle and only then work on the high speed. Oh and one question, i have to small screws on the side of my carb. One kinda on the top and one on the side right next to the throttle arm. not in it or on it but next to it. Is that normall? the engine has never been complicated before and now i think il have to reset all the needles from zero..sigh..

Charlie P.

I would guess the top is the air bleed screw. I'd also bet a dollar yours is an FP series. Go to the following site and download the 40LA manual. Should get you close. As a rule of thumb, start with the airbleed gap half open (or half closed) and, I think, two turns back out on the low-idle screw after setting the throttle to idle turning in the screw gently. I'm not sure on the initial "factory reset" for the idle - especially not knowing your specific engine.

http://www.osengines.com/manuals/index.html

jay2000dakota

always adjust the high speed first, then adjust the low end

timcat26

I'd check for air leaks from either the exhaustmanifold pressure line or from the gas tank/stopper and lines.

brickhead179

My Feedback: (1)

the underside of my pipe ( right where it connects to the motor) keaks fuel under it when its running