Stihl 024 hard to pull

[Tendika]

I have a Stihl 024 that hasn't been run in 20+ years. I put some 25:1 in it and it was hard to pull. With the plug out it is easy to pull so I put a few drops of mixed fuel into the cylinder and it started 1st go with not much resistance and I let it idle for a few mins.

I came back to it a few days later and it was hard to pull but started, I had to keep the throttle open a little to stop it stalling.

From a warm start I could pull single cycles on the cord and it would fire each time but not enough to actually start. A normal pull would probably break something.

Any ideas? Pics below
Thanks

 

[pioneerguy600]

Your cylinder is too wet, the carb is leaking fuel when sitting, common problem when carbs sit for lo0ng periods. A thorough cleaning and a new carb kit would fix it in most cases.

 

[Oldsawnut]

Hard to tell if it's the carb or ignition timing from what you said. Definitely looks wet in the pictures but not sure if you took them before or after you were playing with it with the plug in and the lever off does it still pull over hard.. If it pulls over easier in the off position it's your ignition.

 

[Tendika]

Thanks for the replies. If I take the air filter off should I be able to see fuel leaking in?

Is the carbon buildup causing too much compression? I thought maybe I should try using less oil but there is a sticker on the saw saying to use 20:1.

I'll try it in the off position and report back

 

[Bob Hedgecutter]

Thanks for the replies. If I take the air filter off should I be able to see fuel leaking in?

Is the carbon buildup causing too much compression? I thought maybe I should try using less oil but there is a sticker on the saw saying to use 20:1.

I'll try it in the off position and report back

So you are currently running 20-1 fuel mix because of a sticker on the saw?
Got a photo of that sticker?
Usual Stihl recommendation is 50-1 with THEIR oil and 25-1 with "other" oils. Other oils is polite language for those people in the World that do not have access to Stihl dealers on every other block corner store and use the like of 30wt engine oil in low octane gasoline mix.

20-1 could well be part of your problem, I imagine any spark arrestor screen is well plugged, the crankcase is possibly full of oily sludge and hydrolocking mildly as you try to start it.
If you feel inclined, remove the cylinder and clean everything up- get rid of any sludge, any carbon and look at both the exhaust port and muffler to see how restricted they have become- desgunge everything internally, shout yourself a new sparkplug, mix up some fresh fuel with a quality oil designed for air cooled 2 stroke engines at 40-1 or 50-1 if the saw is well tuned and see if things become easier for you.

EDIT: I went back to the top of the thread and see you are using 25-1, same applies. If you are using a good quality synthetic 2 stroke oil designed to be mixed 50-1, you are A: running the saw lean (too much oil = not enough gasoline) and B: unburnt oil sitting in the case, semi burned oil becoming carbon deposits.

 

[HarleyT]

Sounds like you ought to clean off the carbon from the combustion chamber.

 

[Tendika]

The muffler was lined with carbon but it doesnt seem that bad and has no arrestor screen.
I took the head off and the bottom of the engine is almost spotless. The connecting rod and crank have a strange yellow patch and the crank weight also has a flat spot. The fuel mix seems to have softened up a lot of the carbon but there's some crusty deposit by the spark plug, not sure how to deal with it.

Going to get a new plug, carb and head gasket. Is there anything I should check before I put it back together?

Thanks

 

[atpchas]

I've not seen a single ring piston in an 024 (or virtually any Stihl models). Could it be a "foreign" piston causing your issues?

 

[Bob Hedgecutter]

I've not seen a single ring piston in an 024 (or virtually any Stihl models). Could it be a "foreign" piston causing your issues?

Over the life of their production, I believe the 024 had four piston variations- two were single ring and two were double ring.
Some 041's also have a single ring piston.

 

[Tendika]

Cleaned the carb, replaced diaphragm (was still quite flexible), new plug, new fuel bulb.

Would not start, pulled it over about 50 times, although much easier to do than before. I put some mixed fuel into the cylinder and it started after 7 pulls and ran fine.

I think it may have been a bad plug causing it to flood? The carb wasn't visibly gummed up.