What is involved in a 2 stroke engine "tune up"

[Jim 5]

My father has a 2 stroke John Deere walk behind mower with a Briggs 2 stroke "Duraforce" engine. This mower is around 20 years old. It still runs like a champ, but when it was new it would start on the first pull, and now it takes 5.

He picked the 2 stroke because he wanted "no maintenance" and that is what this mower has received for the last 20 years. No filters, spark plugs, not even draining the fuel before winter. I would like to restore it to a one-pull start.

I have in mind to change:
- spark plug
- air filter
- fuel filter (if equipped)

Can anyone add to this list, including parts like carburetor parts/gaskets that should be replaced to do it right? What about things like ignition/condenser. Is this worth changing if the engine seems to be running OK?

Thanks in advance for your thoughts!

 

[Tom_T]

I could be completely wrong about this but the Duraforce engine was a Lawnboy product. Parts are now being made by Briggs. The engine design is not 20 years old. The same engine in a piston ported design is used by Toro on snow blowers. The Duraforce is a reed valve induction design.

But as far as a tune-up goes -
1)Change or clean the air filter
2)Change the plug
3)Remove the muffler and clean the carbon from the exhaust port with a wooden dowel. Keep the piston up so carbon does not fall into the cyl. Use wood as not to scratch the piston.

If the ignition has points, replace them. If the ignition is electronic no service is needed other than replacement upon failure. Carb service is not part of a regular tune but at the age of your unit I'd suggest it while you have the thing apart. Change the float, needle and seat on the carb; set the float to spec. Blow out all the passages with carb cleaner. Brush off any fuel strainers. If you don't tear any gaskets they can be re-used but if you're ordering other carb parts why not go ahead and get new ones. I'd recommend installing an in-line fuel filter and fuel shut off valve as additions.

 

[Jim 5]

Not sure about the "duraforce" but it's definitely a Briggs 2 stroke.

Thanks for the tips!

 

[dwendt44]

What is he using for a fuel mix?
Many mowers can run on 40:1 instead of 32:1.
Is there a primer system? That could be the reason for hard starting.
Air hole in the primer bulb, collapsed hoses in or out of primer.

 

[Tom_T]

Is this your engine?

http://www.odref.com/briggsandstratton/model-09/95720-ms9168-0891.pdf

If so I doubt you can get replacement parts easily. From a practical standpoint I'd give it a tune, run it till it quits then give up and get another. For a project you could try getting a 2 stroke Lawnboy as parts are generally avaliable and either restoring that or FrankenMower the lawnboy engine onto the John Deere deck.

 

[daman]

Rings!!

rings are the heart of any 2 stroke engine..

 

[Tom_T]

As well as the oil seals, but we're talkin tune-up here.

 

[ksJoe]

I have a question, that I'll ask here since it may be relevant to the op...

I assume that using any carb cleaner fuel additive, or spraying carb cleaner into a running 2 stroke is a huge no-no. My reasoning is that a two stroke gets its oil through the fuel, so adding harsh solvents to the fuel (oil) would be bad.

meaning that the only safe way to clean a carb on a 2 stroke is to remove it.

Is this correct, or am I being paranoid?

 

[XS650]

Originally Posted By: Tom_T
As well as the oil seals, but we're talkin tune-up here.


I thought rings and seals were regular tune-up parts for a 2-smoke

 

[Mamala Bay]

Originally Posted By: Jim 5
My father has a 2 stroke John Deere walk behind mower with a Briggs 2 stroke "Duraforce" engine. This mower is around 20 years old. It still runs like a champ, but when it was new it would start on the first pull, and now it takes 5.

He picked the 2 stroke because he wanted "no maintenance" and that is what this mower has received for the last 20 years. No filters, spark plugs, not even draining the fuel before winter. I would like to restore it to a one-pull start.

I have in mind to change:
- spark plug
- air filter
- fuel filter (if equipped)

Can anyone add to this list, including parts like carburetor parts/gaskets that should be replaced to do it right? What about things like ignition/condenser. Is this worth changing if the engine seems to be running OK?

Thanks in advance for your thoughts!


I would change what you have listed. Usually on 2 stroke engines carbon buildup does occur as it does get dirty. I liked the old Amsoil PI especially for small engines as a preventive measure. It does help in the long haul. Is the fuel old causing the 5 stroke pulls? Try adding fuel additive in small amounts and see if that helps. I've added Amsoil 2cycle oil 5 drops(eye drops) in 1/2 gallon of gas and that helped fire away on one pull.

 

[dwendt44]

Low dose treatment of carb cleaners or even MMO might improve things.
MMO use to advice a dosage for 2 cycle engines but I can't find it today.
Pulling the adjusting screws for the low and high speed jets and giving each a shot of carb cleaner (spray) won't hurt.
Most of it will evaporate before you start the engine and, if you keep the doses small, won't hurt the running at all.
IMHO.

 

[daman]

Originally Posted By: XS650
Originally Posted By: Tom_T
As well as the oil seals, but we're talkin tune-up here.


I thought rings and seals were regular tune-up parts for a 2-smoke

^^they are in a 2 smoke engine,it's easy to do and cheap to do..

 

[FZ1]

Simple is better. Just do 1 thing at a time. Change the plug. DO NOT over tighten the plug!!!! See how much better it starts. Check and/ot replace the AF. See how much that helps. I'd do the FF last only if I wasn't satisfied with the way it ran.

 

[Jim 5]

Thanks for all of the tips everyone. I will start with the small things one at a time and go from there.

This mower is 150 miles away at my parent's house and I want to gather the parts before I get there. That's why I can't remember any of the particulars about the engine.

I do know it is a briggs 2 stroke that uses 50:1 gas, and I know it was purchased new in around 1992. So I suppose that makes it only 16 years old.

It was the best JD walk behind mower you could buy at the time. Aluminum deck, self propelled. I will see if my mother could go out to the shed to get the model number so I could post some particulars after doing a little internet research.

Anyhow, the problem is that my folks are getting older and mowing the lawn for them really needs to be farmed out. My dad has trouble with his legs and can no longer really walk. My mother has problems with her shoulders and can't really start the mower if it takes 5 pulls. If they can get it started, my mother really enjoys walking behind the mower (it's a pretty small lawn, and the neighbor mows the side yard). I am starting to see that getting old is a b*tch and not for faint-hearted. Wish my job was closer to their home. For some strange reason I enjoy mowing the lawn and would be happy to add another lawn to my job-jar.

 

[Jim 5]

More info.

This is a John Deere 12SB 21" cut walk behind mower.

There is no primer bulb, and it is a 2 stroke briggs engine. I am going to change the plug and filter. My dad tells me he is using at least 3 year old gas in it. I'll mix him up some new gas with some stihl 2 stroke oil I have and remind him to dump the rest in his full truck tank after the season is over. Part of the problem looks like he is mixing his 2 stroke mix in a 4 gallon fuel can and he is trying to use it for too many seasons. I'll get him a 1 gallon can and mix it every spring for him.

 

[Mamala Bay]

Originally Posted By: Jim 5
More info.

This is a John Deere 12SB 21" cut walk behind mower.

There is no primer bulb, and it is a 2 stroke briggs engine. I am going to change the plug and filter. My dad tells me he is using at least 3 year old gas in it. I'll mix him up some new gas with some stihl 2 stroke oil I have and remind him to dump the rest in his full truck tank after the season is over. Part of the problem looks like he is mixing his 2 stroke mix in a 4 gallon fuel can and he is trying to use it for too many seasons. I'll get him a 1 gallon can and mix it every spring for him.


2 cycle mixture or gas itself is not recommended to kept longer than 1 month especially with the new 10% ethanol gas. This can cause vanish build up and poor start up with old gas. A fuel stabilizer is recommended for longer storage. Stihl has a fuel stabilizer in their 2 cycle oil.

 

[Jax_RX8]

Originally Posted By: dwendt44
Low dose treatment of carb cleaners or even MMO might improve things.
MMO use to advice a dosage for 2 cycle engines but I can't find it today.


Yes, use MMO in your fuel, it does wonders for 2-cycles - replace 25% of your 2 cycle oil with MMO -this is the standard recommendation from Marvel.

I think you could go even higher, say 50%, especially for the first few tanks that you are trying to clean things up.