rough 2 stroke engine

[Richard Dooling]

I just bought a 2 stroke string trimmer. I am used to a 4 stroke engine. Do 2 stroke engines typically feel like they idle rougher than 4 strokes? When I rev it there's plenty of power but at idle it feels noticeably rougher than what I'm used to. :confused:

Thanks

.

[AL Ursich]

4 things that go bad on small motors like that are...

1. The Exhaust Spark Screen plugs up with carbon. Remove it and clean it with carb cleaner.

2. If there is a bowl in the carb there is a possibility that at the very bottom of the bowl, sediment has built up. I have seen that in 3 carbs.

3. You need a new spark plug.

4. Carb adjustment too rich.

Good Luck,

AL

[Paul Atkins]

I have a trimmer that has a California mandated 'non-adjustable' carburetor that drives me nuts. In fact this week I'm going to cut off the plastic things so I can get it to run right. Might be an EPA thing on yours too. (I'm going to get my Model A running too just for spite).

[Richard Dooling]

Al, thanks for the info and I'll keep it in mind, but in this case - it's brand new and a Stihl. I may need an adjustment. Ouch.

On older units I'm also hearing that ethanol is causing a lot of carb issues due to its tendency to dry out plastic and rubber components.

Also the planets may be out of whack - this isn't the only yard machine driving me nuts. (BTW different gas sources so that's not it either.)

Paul, "Might be an EPA thing on yours too. (I'm going to get my Model A running too just for spite). "

Good thought; maybe I'll put a small steam engine on this! I just have to configure the firebox.

On the up-side, I'm very happy with my new drill press. Sc*** the yard!


.

[Myk Rian]

I just bought a 2 stroke string trimmer. I am used to a 4 stroke engine. Do 2 stroke engines typically feel like they idle rougher than 4 strokes? When I rev it there's plenty of power but at idle it feels noticeably rougher than what I'm used to. .
Yes, they do idle rougher than a 4 stroke. Probably nothing wrong with it.

[Tom Esh]

...it's brand new and a Stihl. I may need an adjustment...

Not yet - unless it won't start or run properly. FWIW 2-strokes do tend to idle rough and extended idling can accelerate plug fouling and deposits in the exhaust components. It's also typical for new units to be adjusted a tad rich to ensure adequate lubrication during break in. Give your dealer a call. I'm pretty sure they'll tell you to run several tanks of fuel mix through it before bringing it in or adjusting it yourself. Worst case - you foul the plug prematurely, so maybe pick up a spare. (You'll need it eventually in any case. It's a 2-stroke after all :D)

[Scott T Smith]

Not yet - unless it won't start or run properly. FWIW 2-strokes do tend to idle rough and extended idling can accelerate plug fouling and deposits in the exhaust components. It's also typical for new units to be adjusted a tad rich to ensure adequate lubrication during break in. Give your dealer a call. I'm pretty sure they'll tell you to run several tanks of fuel mix through it before bringing it in or adjusting it yourself. Worst case - you foul the plug prematurely, so maybe pick up a spare. (You'll need it eventually in any case. It's a 2-stroke after all :D)


+1. Due to the lower ratio of oil to gas, using a synthetic oil (such as Amsoil) in your pre-mix will help smooth it out a bit, but the rough idle is just the nature of the 2-cycle beast.

[John alder]

+1. Due to the lower ratio of oil to gas, using a synthetic oil (such as Amsoil) in your pre-mix will help smooth it out a bit, but the rough idle is just the nature of the 2-cycle beast.
I agree a good quality synthetic oil makes a big difference on my 2 cycle equip.and has kept them trouble free.

[Peter Stahl]

+1. Due to the lower ratio of oil to gas, using a synthetic oil (such as Amsoil) in your pre-mix will help smooth it out a bit, but the rough idle is just the nature of the 2-cycle beast.

Where do you buy it?

[David Weaver]

Where do you buy it?

It's an MLM and direct marketing thing.

Guys on arboristsite recommend MX2T oil for electrolux (husky, jonsered) and stihl stuff. I think you can get it at autozone.

I wouldn't worry too much about a rough idle. You just want it to be running a little rich at idle and be able to accelerate without bogging out or leaning out when you pull the trigger, and run a little rich at the top. If it does that (accelerates fine and isn't lean at the top), you're good.

Running the trimmer near wide open when you use it (instead of feathering the throttle all the time) will save you trouble in the long run.

Guy at my local shop where I got my trimmer said most of the time when commercial guys bring their trimmers in, they're gummed up from feathering the throttle all the time.

[Ken Fitzgerald]

Another thing to do...


Read the manual on all new gasoline power tools.


My Stihl......IIRC.....in the owners manual says it has to run on medium grade gasoline and it spells out the octage required. It warns that running it on lower octane gasoline could result in the engine overheating and damage could result.

I just checked the owners manual on my Stihl trimmer........minimum octane required is 89.

[Brian Elfert]

All of Stihl products can run a bit rough at idle from day one. I have a trimmer and backpack blower from them.

[Richard Dooling]

Thanks for all the great advice! You all have given me some ideas to work with.

I should also say that I bought this from a locally owned company, Land and Coats. When I called the manager his only concern was that he wanted me to be a happy customer. I'm taking the trimmer in to see if it's a real problem or just my ignorance.:rolleyes:

In any case he's ready to switch out the machine - no problem.

.

[Matt Meiser]

Stihl has a synthetic oil too in a white bottle instead of the old orange bottle. My dealer said that they are phasing out the older oil. Not sure if she meant Sthil or just this particular dealer.

I was going to suggest taking it in. I deal with two Sthil dealers and both have the same attitude as yours. I suspect Sthil requires it based on their advertising.

[Dennis Peacock]

+1. Due to the lower ratio of oil to gas, using a synthetic oil (such as Amsoil) in your pre-mix will help smooth it out a bit, but the rough idle is just the nature of the 2-cycle beast.

+10...!!!!!!! I use it and LOVE it.

BTW, my Stihl specifically states that I must use 91 octane gasoline or higher.
I've also found that running aviation grade fuel (which will require a carb tweaking) will make your machine run much better and the av-fuel will never go bad. Many of the pro-loggers are running aviation grade fuel in their saws and really like how it makes them run both better and cooler.