So I'm a car guy and a diesel engine engineer...so have pretty good understanding of 4 stroke IC engines.  But I don't have much when it comes to little 2 strokes like used in small garden tillers.   We have a Echo tiller that has never really run right since we've owned it.   Compared to our Stihl weed eater, which starts within 3 pulls even when cold, the tiller would take 20-30 pulls to finally start and keep running.  I've taken it to the shop we bought I from and they've replaced the plug, air filters, fuel filter screen, and adjusted the carburetor and usually it runs well for a few weeks after we get it back, but eventually reverts back to running very poorly.

Symptoms:

VERY hard to start, especially when cold (say <50F)
Will start with the choke lever closed, and after priming the primer bulb 10-15 times.
Once running, will die as the choke is slowly opened up, but with each start will run probably 30 seconds longer before dying
Once running there are clear mis-fires and low idle stability issues.  Exhaust smells of fuel.  Its like it wants to be a Harley engine or something!  
Would immediately die with any application of the throttle.  Not even a slight increase in speed, just a muted groan as it died.


So this year rather than pay $50 for a tune up, I decided it was make or break time and I'd fiddle with it.  It was either going to run, or not run when I was done, and seeing as though it didn't run well to begin with, the risk was low I'd make it much worse.

I pulled the plug and cleaned some carbon from it and checked the gap was .026" as listed in the manual.   I cleaned the air filter and put fresh gas in it and tried to start.  After 30 minutes and a heckuva an arm workout I couldn't keep it running for more than 30 seconds.   Subsequent tries to restart could get it to fire for maybe a couple seconds eventually not firing at all.

I pulled the plug and it was covered in a fuel / oil mix.  I'd clean it, put it back in, and could get it to run again and then it would revert back to not running.    To me all signs pointed to being too "rich" to run correctly.   I took apart th carb and cleaned it well, removed the muffler and checked to make sure the exhaust port was clear (was oily, but not carboned up).  I put back together and it didn't help.   So I looked at the manual and saw where I had two carburetor adjustments, one for high idle and low idle.   Both were set as recommended at about the middle of their allowable adjustment range.    Thinking it was running rich I turned both in (CW) to the limit to attempt to lean it out.

I restarted and could get it to run better at idle, but it would still die as soon as any throttle was applied.  I pulled the plug and it was again heavily coated in fuel /oil mix.   I decided to play around a bit and opened the gap up to about to just over .030" (my .030" wire on my plug too would slide freely) and replaced.


After opening up the plug gap I restarted it on like the 2nd or 3rd pull (instead of the 20th) and the thing runs like a scalded dog now!   I played around with idle mixture and opening up the low idle screw makes it flatten out a bit but screwing back in seems to make it run better.  I also adjusted low idle speed a bit and that seems to help too.


So...the $64,000 (ok, really more like $50 since that was what the tune ups cost) questions are"

1)  What does opening the spark plug gap up mean in terms of overall performance?  Does that improve the "heat" of the spark so to speak and help combust the rich start up mixture a bit better?
2)  By leaning out my low idle (whithin adjustment range on the screws) do I need to worry at all about hurting the cylinder at all?    As I said, I'm a diesel guy so used to running very "lean" but know that in a gasoline engine too lean can be bad, and wondering with a 2 stroke that needs the oil for lube if I'm hurting anything there.



Any thoughts?  Should I open up the gap a bit more or leave it where it is for now?

This interests me as well.  On a whim I bought a small 2 stroke generator, $120 at Harborfreight and it is like a torture test to get the dang thing to start.  Just wanted a lightweight supply to run some lights and ceiling fans at the hunting cabin.

It's the identical twin to this


I'll have to try the steps you did.   When it is running no-load it burbles, pops and misses but put just a couple hundred watt load on it and it smooths right out.

I like your determination.

My weed wacker is some off brand engine and is several years old.  Runs just like you describe.

My leaf blower is a nicer Husky unit.  Runs like a normal two stroke should.

I always just figured one being a POS and that was that.


I rebuilt the carb on the weed wacker once and it improved a bit, but I never have messed with the jetting.  Don't care enough.  Run her till she blows.

Needs the richer mix of the choke being on until it has warmed up enough.

This sounds like pretty standard 2-cycle warm up behavior.

Give it more time.

You can start to use it almost as soon as it starts but leave the choke on.

I was wondering about that...but it won't stay running even with the choke on.  It runs longer, but will not maintain idle and just dies.    Last year I could run it when warm with the choke about 50%.

Sounds kind of like it has some sort of fuel flow problem.  Not completely plugged but impeded.  After starting and running, it starves itself for fuel and quits.  You pull on the cord 30 times, enough fuel builds up for it to start then the process repeats itself.

I'd start looking in the carb and anything between the fuel tank and the head that could cause you to be impeding fuel delivery.

i used alot of shit lawn equipment. between me buying a house, using my dads old shit and buddies tools.
i bought a new stihl kombi km90 and its been great. the old echo i had would do the same, tuned it up, sent it to the shop etc, piece of shit, got tired of it and bought a stihl.  no issues. same with chainsaws, blowers etc.

buy a new one.
i know people that rely on stihl premixed gas (ethanol free) but ive been running 93 with stihl 2 oil, and my huskys get husky 2 oil with no issues.

you can buy ethanol free gas if you look around (not just 110 octane) there is a website that has a search feature for it.
ive also heard the ethanol will wear out carburetors when used hard and a long time. something due to grit being in it or some shit heard it from a reputable shop.

I had wondered about that so cleaned the fuel system and carb really well.  After it would die I pulled the plug and it was saturated, so seemed to be getting fuel.   What I need to do is pull the plug now that it is running better to see if it is more clean.

I think that is a good idea.  Once this thing is done I'll likely replace with a different brand.  The other Stihl items I've used have been much more reliable.

Carb is plugged.  Next

I took it apart and cleaned it and didn't get much improvement until I opened up the gap on the plug.   It does certainly run better now so not discounting a dirty carb as part of the issue.

Cracks in fuel lines are common as dirt.

It does not take much air leakage to not have enough carb suction to pull gas from the tank.

The ethanol added to gasoline now plays havoc with the older seals in 2-stroke engines.

Wonder if the spring under the needle and seat lever is to weak. That can cause an overly rich scenario especially when you have the limited adjustment stops on the high and low speed screws.

On my 1/5 scale rc (30cc 2 stoke with a walbro carb) I lowered the pop off pressure to increase the amount of fuel. You do this by clipping coils off the spring that sits under the needle and seat arm.  You use a hand pump and gauge hooked up to the fuel inlet. Then remove the diaphragm on top of the needle and seat. Lube the needle up a little with a light oil. Then start pumping up the pressure on the fuel inlet. You keep pumping it until the needle pops open and releases the pressure. At what psi it pops off is the pop off pressure.  Usually it's pretty high 25-30 psi.  If you have a mighty vac with a pressure gauge you might test your carb to see if it's exclusively low which would explain the excessive rich condition.


If is overly rich it will be rough and sound like a 4 cycle. If it's lean it will be lazy and zinggy. Also check your muffler to see if there is a spark arrestor screen and if it's plugged.

I think you are on to something there wiht the carb.   I tried to start it tonight wiht no luck.   Pulled the plug and it was saturated.   Cleaned it up and before installing cycled the engine without the plug, and it puked out a ton of fuel thorugh the spark plug hole.   I pulled off the air cleaner which was saturated and there was standing fuel in the housing.

I'm wondering if that spring and arm assembly is just leaking fuel all the time and essentially makes it way too rich.  I finally got it started with the choke off and a clean plug, and then it ran great.   I let it idle for about 3 minutes and I could here it start to miss more and more.  I went to give it some throttle and it died.   Pulled the plug and it was wet.    Started it, and then ran it up and high idle for a minute and then let come back and stabilize at idle.  Pulled the plug and it was bone dry with a little grey ash.    Think I need a whole new carb or are those spring snad arms easy to change out?

yup

this is a textbook symptom of a clogged jet somewhere in the carb. locate the jets, spray them out with carb cleaner. a lot of it.
blow out with air. this can take a while. Don't just spray some cleaner in the carb throat.

I didn't blow it out with air, but did spray the jet down really good with carb cleaner.  Would a plugged jet cause excessive fuel in the cylinder due to poor atomization?   When I took the plug out after struggling to start it fuel was dripping out of the spark plug hole and air filter housing.

Spring and arm is easy to change out but with these small carbs it's usually best or costs the same for a new carb. A parts kit for the carb might be 15-20 bucks and a whole new one would be in the 30 dollar range.

A new carb would be the way I'd go.

Sounds like a good next step.  At this point not much to lose, and $30 isnt much to spend to see if it fixes the issue.

Don't forget about the spark arrestor screen in the muffler. They can become clogged with carbon which restricts air flow in and out of the cylinder.

It's an easy fix, just remove screen, clean and re-install.

Ive had your issues with 2 strokes for forever. I then switch all of my garden equipment over to a non-ethanol gas. There is a gas station in my town that sells it for like $0.20 more a gallon. Once i did that all my problems went away. Some reacted even better to the blue barrel stuff you get at tractor stores. Which is 100 octance premixed 40:1, 50:1 or 60:1.

may be a better option. Especially for $30.

There is NO reason to pay $50 for a small engine tune up when you can buy a brand new carb for $13+free shipping. I'm sorry but unless your small engine needs a rebuild it's not worth taking to someone else. The labor and parts rate make it worth junking it and buying a whole new piece of equipment.

Edit: NEVER let ethanol touch your small engines. It's like smoking meth. Not even once. Tc-w3 premix and any other fuel additives do nothing to negate the effects of the devils piss.

TC-W3 rated oil is for water cooled 2-strokes like outboards, not air cooled like weed eater, blowers etc. The TC-W3 oils won't take the higher heat of an air cooled engine.

Stihl specifically states to only use oil designed for air cooled equipment as well. I just use the silver Stihl Platinum oil in everything. Also if you use an oil that's is oil injector compatible its watered down with solvents so its pumpable at low temps.  Since you pre mix lawn equipment I wouldn't use an oil that's already thinned out.

You know, I never really put much thought into the gas.  Since I drive a diesel truck, and my wife drives a 2014 m.y. SUV which is tolerant of the newer blended fuels, I honestly pay no attention to what the pump says anymore for gasoline.  Usually I'm doublechecking sulfur PPM and % Biodeisel for my truck.    I'll check to see what I bought and what (if any) Ethanol content it is next time I'm at that same filling station.  Isn't up to 10% or some such supposed to be ok, even in fuel classified as non-blended?


I am running 93 octane as I've always found my lawnmower (26hp Cub Cadet) runs better on the higher octane stuff.   I think 89 octane is the minimum recommended.


I talked to a guy at work today that does a lot of 2 stroke stuff with motor cycles and said he'd replace the plug first, then probably rebuild/replace the carb next, which jives well with the advice here.

Yea and use the same 93 premium stuff in your trimmer with a good air cooled oil. That will help keep the plug from getting loaded up with oil. If you have a Stihl dealer close by they should have the silver platinum oil in 1gal, and 2.5 gallon 6packs.  I normally do the 2.5gal bottles and end up mixing it in a 2 gallons of fuel or a little more.  2.5gal bottle in 2 gallons of fuel is a 40:1 ratio, other wise if you mix it according to the bottle its 50:1.

Ummm, 2.5 gallons of oil in 2 gallons of gas? You must mean ounces.

OP, still check the screen in the muffler. I've fixed many a 2-stroke engines by cleaning the screen, changing the plug and re-adjusting the carb (assuming the carb and fuel sys is ok).

No I ment the pre measured bottle that mixes with 2.5 gallons of gas at 50:1 can be mixed with only 2 gallons of gas to form a ratio of 40:1.

They package their oil in different sized bottles depending on how much fuel want to mixed. 1 gal, 2 gal, 2.5 gal, 5 gal

That's exactly what I use.  My trimmer is a Still and runs 87x better than the Echo tiller, running the exact same fuel.

I did clean both the magnet and the "fan" on the top of the engine.  I did not adjust the gap.  I'm not experienced in that and don't see anything in the owners manual on that.  Any tips?

Put a matchbook cover or business card between the coil and flywheel magnets. Let the coil suck down and sandwich the card between it and the flywheel. Tighten the bolts and remove the card.

Thanks, will take a look at it this weekend then.  I'm going to pick up a new plug for it and air filter.  I didn't realize the coil actually moved, but to be honest didn't play with it much when cleaning.

The mounting holes have slots that allow you to set the gap between the flywheel magnet and coil. I just use a business card for the gap.

Picked up a new plug, air filter, and fuel filter and got them installed tonight.  I set the gap on the magneto (was 2x wider than the business card to start with).    I was able to get it to turn over and fire much sooner with full choke, but did have to pull probably 15-20 times to get it to where it would start and stay running.  I'll chalk that up to maybe the new fuel filter and plug.  Once running I reset the mixture and seem to have decent throttle response, although after idling for 30 seconds I have to slowly apply throttle to it.

Guess that's an improvement and we'll see how it does this season and if it gets better or worse as the year drags on and it warms up a bit outside.  Maybe this thing is just really cold natured and needs 70F+ to run right.

Had a similar problem with an echo chainsaw. Gutted the muffler and it now runs like a raped ape and starts easily. I also only run trufuel or the like.