2-Stroke Throttle....W.F.O.??

[toolmaker]

My dealer insists that all 2-strokes should be run W.F.O. all the time. No backing off the throttle when just about through the log, no half-throttle on the string trimmer. He tells me it is the best way, and what the engine is designed for in a 2-stroke, to maintain the engine.
Is this true?
What damage could occur if run too much @ half-throttle?
How much half-throttle engine time until damage?
Thanks!!

 

[habanero]

I'm not so sure about running wide-open 100% of the time, but a 2-stroke engine will generally stay in better condition if being worked hard most of the time. Idling around is pretty tough on them, in my experience.

 

[Dan Forsh]

Wide open is bad for an engine if this is in a no load condition.

 

[blis]

full throttle when loaded is the only way, but without load it isnt wise to run on full throttle for long periods..

 

[PA Plumber]

I understand chainsaw at full throttle under load. My other equipment doesn't seem to carbon up at partial throttle, but I run Opti in everything but my chainsaws. Saws are Stihl mix.

 

[ktoom]

I do alot of the engine work for the landscaping company i work for. I find that since we can't run r blowers or string line trimmers wide open, most of the time, that they build up a good amount of carbon in the exhaust ports. Intern, making them run bad, lack in power and start harder. We really can't run them wide open cuz we don't wanna hit cars with debris or rocks and we gotta always watch out for people too:jester: PLus when the guys walk around with them they are constantly idling. Every year, atleast one guy sends a rock through someones windshield . Usually about half way through the season, i have to tear down each peace of equipment and give it a good cleaning. The first season i worked for the company, toward the end of it, the blowers and string trimmers started dropping like flies and nobody knew what it was? We were down to one okay running weed waker and a so so blower(mind you we had about 6 weed wakers and 3 bowers all of different brands). We put new plugs, fuel filters and air filters in every machine and still nothing. Then we took the mufflers of every machine and sure enough all of the machines were either half or 3/4's carboned up. I have yet to run into this problem with any of my personal chainsaws, so you should be fine.

 

[Ed in Maine]

I agree, WFO when under load, no idling for more than a minute or two. It is even more exagerated for outboard motors, run them hard or shut them off, or take the carbs off and clean them up. Always good to check your rpms on any 2 stroke so you know what WFO is putting out!

 

[Crofter]

The carboning up of the screens could be caused by overly rich carb setting (providing you are using a decent quality oil. The caution about not operating a saw for long periods at less than full throttle conditions is because a lot of saws actually run lean in the intermediate speed ranges. Though both high and low jets are set correctly there can be a lean area as you transition from one to the other. Some carbs / saws are more prone to problems than others in this respect and would definitely lean score.

 

[blis]

I agree, WFO when under load, no idling for more than a minute or two. It is even more exagerated for outboard motors, run them hard or shut them off, or take the carbs off and clean them up. Always good to check your rpms on any 2 stroke so you know what WFO is putting out!

The idling itself aint bad, its the middle range that causes problems...

 

[Lakeside53]

Most small ope equipment carbs do not provide the correct mixture at partial throttle -it's just an approximation between L and H, and to get you to a fully operational main jet.

The important issue is to MOSTLY operate the throttle wide open... and control the speed with the load. In the case of a saw - it's the wood, a trimmer - the string length (you will overspeed most trimmers with a short string and WOT, and overheat most with string too long), and a blower is self regulating by design of its fan wheel etc.

Some saws that were being used for limbing ended up with lean seizures or excessive wear, and later carbs included "Partial Power jets.

Of course ,we all use our saws at partial power on small wood, leaving a cut, trimming up etc, but the power used at that time is low and doesn't materially impact the engine. Same with using a blower at low throttle (they are designed for that) and a trimmer when doing finishing work. It's the running at some intermediate throttle portion for long periods while developing moderate power that can lead to trouble.


This has been thrashed out many times before on AS - Search is in order...

 

[ktoom]

Lakeside, that would make sence cuz when we r at a job site the guys r always running mid throttle to be safe, but to also have enough power. They aren't so much idling or toping out.

 

[bump_r]

What is W.F.O.? I've heard of W.O.T. for Wide Open Throttle, but W.F.O. eludes me. "Wide the F$&@# Open?"

Nevermind - I see it's "Wide Full Open" (and my hypothesis was correct, as well!)

http://www.acronymfinder.com/af-query.asp?acronym=wfo

 

[Crofter]

What is W.F.O.? I've heard of W.O.T. for Wide Open Throttle, but W.F.O. eludes me. "Wide the F$&@# Open?"

Nevermind - I see it's "Wide Full Open" (and my hypothesis was correct, as well!)

http://www.acronymfinder.com/af-query.asp?acronym=wfo

Nope! Its Wide fff'ing open, Lol!

 

[Stihl #1]

Another aspect of running WOT is the vaporization cooling the fuel provides to the piston. This is necessary to cool the piston, and this is why adjusting the carb lean or having an air leak that changes the air/fuel ratio will cause the piston to overheat and score up on the exhaust side, the hottest area, first.
And yes, as said, it should be WOT under load, then back off until ready for the next cut or the next area to trim.
Older carbs were usually tuned to run rich, like my old XL-12, where I would tune it to just 4 stroke a little at WOT with the bar and chain on it. Now of course, with EPA stuff, everything is leaner, with limiter caps, so the new carb designs may have a part load jet, like Lakeside said. This is a fixed jet about half way between the idle discharge holes and the main nozzle, so as the throttle is opened and low pressure moves back through the venturi, the part load jet will kick in some fuel to help the carb transition from idle to WOT. This jet will have a check valve in it, like the high speed nozzle does, so if it is leaking, it will mess up the idle and cause trouble. Many new carbs also have an accelerator pump that pushes a small amount of fuel through the main nozzle when the throttle shaft turns. It doesn't squirt fuel, just richens up the mix when the throttle is snapped open. All of this makes the carb more complex, and if the acel pump o-ring or any of the check valves leak air, or stick shut, running problems happen. I have had very good success by using STIHL fuel stabilizer additive and 89 octane fuel. No more gummed up carbs on units that sit for even 3-4 months.
These are not the carbs we used to work on years ago.

 

[Ed in Maine]

WOW, note to self, do not take apart carb on 361 and buy some stihl fuel stabilizer!