Stihl 025 runs 1000 RPM too fast

[Bubba scooter]

Stihl 025 should max at 12,500 RPM, but turns 13,500 to 14,000 RPM. I have replaced the seals and pressure tested, rebuilt the carb and the saw runs great both in and out of the cut. Fuel lines have been pressure tested and are good. It has only a low speed jet adjustment and I have richened that as must as I can and still get good idle and decent throttle response. Should I just run the saw and keep an eye on the spark plug color? Any suggestions other than buy a carb with two adjustable jets?

 

[Brushwacker]

I haven't put a tachometer to any saws since working at a dealer, pre 1990s. I prefer getting the burble sound out of the cut, but in the case of non adjustable carbs don't worry about it much unless it is not accelerating and deaccelerating normal. If it was a high dollar saw i might be more concerned. I have an 023 and ms180 non adjustable and 1 or both of them sound like they rev very high . I use 50 to 1 in both because they don't get enough fuel flow with 28 to 1 that I use in most my personal saws.

 

[trains]

Stihl 025 should max at 12,500 RPM, but turns 13,500 to 14,000 RPM. I have replaced the seals and pressure tested, rebuilt the carb and the saw runs great both in and out of the cut. Fuel lines have been pressure tested and are good. It has only a low speed jet adjustment and I have richened that as must as I can and still get good idle and decent throttle response. Should I just run the saw and keep an eye on the spark plug color? Any suggestions other than buy a carb with two adjustable jets?

Replace with a genuine WT 215 carb, its fully adjustable, and listed for your saw.

Tune in the cut as Brushwacker mentioned.

I had a 180 with a fixed jet carb that was up at near 16000, put in a larger jet, but had issues with stihl sending the correctly labeled package, with incorrect contents, took several attempts to deal with it till something that worked arrived, lets just say, after 4 attempts, I still had not been sent what I ordered, and made do with what I had available.

 

[Bubba scooter]

I haven't put a tachometer to any saws since working at a dealer, pre 1990s. I prefer getting the burble sound out of the cut, but in the case of non adjustable carbs don't worry about it much unless it is not accelerating and deaccelerating normal. If it was a high dollar saw i might be more concerned. I have an 023 and ms180 non adjustable and 1 or both of them sound like they rev very high . I use 50 to 1 in both because they don't get enough fuel flow with 28 to 1 that I use in most my personal saws.

Thanks. I guess we have to trust Stihl knew what it was doing with the fixed jet saws. I have three 018C with fixed jets and I've only melted one of them using it like it was a 088. I'll just run the 025 the way it is and keep an eye out for signs of it running too lean.

 

[J D]

I'd give the carb a good going over as that in itself might make a good difference.

I guess we have to trust Stihl knew what it was doing with the fixed jet saws.

I suspect they knew full well they would be cutting costs, appeasing the EPA, & limiting engine life. Everyone I know that I would consider "knows what they're doing" tunes their saws appropriately for an oil ratio of at least 40:1.
As trains mentioned, there are larger replacement jets available. The ms170's & 180's I see tend to either get a bigger jet or the original one drilled out by 0.05mm & they run much better for it.

I'll just run the 025 the way it is and keep an eye out for signs of it running too lean.

If it's turning 14000RPM I think it's fairly clear that it's running lean... additional signs that it is in fact too lean will include lower compression, harder starting, unsatisfactory power & the need to replace piston, rings, & possibly the cylinder

 

[Jed1124]

The max rpm on a ms250 is 14k. I didn’t know there was much difference between the 025 and the ms250, but you are correct the o25 spec is 12,500.
I would go for the solution you don’t want to do, buy an adjustable carb.

 

[Okie294life]

Stihl 025 should max at 12,500 RPM, but turns 13,500 to 14,000 RPM. I have replaced the seals and pressure tested, rebuilt the carb and the saw runs great both in and out of the cut. Fuel lines have been pressure tested and are good. It has only a low speed jet adjustment and I have richened that as must as I can and still get good idle and decent throttle response. Should I just run the saw and keep an eye on the spark plug color? Any suggestions other than buy a carb with two adjustable jets?

Is it still four stroking at full throttle ?

 

[Bubba scooter]

it does four stroke/burble. I discovered my cheesy chinese tachometer is all over the map, so I'm going to splurge on a good tach (like I should have in the first place) to be sure it's not running too lean. I suppose the Stihl tach is built in China too (what isn't?) This is a cool website, thanks to everybody for their help! I'll try to attach a video... sorry, video won't load.

 

[Okie294life]

it does four stroke/burble. I discovered my cheesy chinese tachometer is all over the map, so I'm going to splurge on a good tach (like I should have in the first place) to be sure it's not running too lean. I suppose the Stihl tach is built in China too (what isn't?) This is a cool website, thanks to everybody for their help! I'll try to attach a video... sorry, video won't load.

As long as it’s four stroking and passed a vac and leak test probably okay. Did you do both tests or just one?

 

[Bubba scooter]

As long as it’s four stroking and passed a vac and leak test probably okay. Did you do both tests or just one?

Yes, had the piston out, replaced both crank seals which were both leaking. Did pressure and vacuum tests, rebuilt carb, tested all lines and filter. Saw has 135 psi compression and now starts and runs wonderful, four strokes at max RPM. I just allowed myself to be misled by a defective tachometer. Thanks for the input. I'm gonna run the heck out of this saw first chance I get. My nickname isn't "wood whore" for no reason!

 

[J D]

For future reference, if you have a pressure/vac tester you can check the carb too... Put it on the fuel line & pump it up, should hold 10-12PSI all day. Somewhere above that it should "pop off" as the metering valve pops open.
If it doesn't put a little fuel down the line as the metering valve doesn't always seal dry. If it still leaks drop it in a bucket of water to see where the bubbles are coming from & diagnose from there

 

[Bubba scooter]

For future reference, if you have a pressure/vac tester you can check the carb too... Put it on the fuel line & pump it up, should hold 10-12PSI all day. Somewhere above that it should "pop off" as the metering valve pops open.
If it doesn't put a little fuel down the line as the metering valve doesn't always seal dry. If it still leaks drop it in a bucket of water to see where the bubbles are coming from & diagnose from there

Yep, I did that before I rebuilt the carb. It would not hold pressure but it would still run even though the needle would not hold and it had two leaky crank seals. Kind of surprised it would run at all but it ran pretty good. I try not to put much more than 7 psi on the carb inlet for testing. The reason I starting working on this saw was because it would not idle down as low as it should have, probably due to being lean as it was pulling air into the crankcase? With repairs all done the raw now runs really nice, and I'm a little bit smarter than I was before. And I also have one more homeowner saws to add to my collection! How many shoes does a woman need?

 

[J D]

One can always justify having more (shoes... saws... women...)

 

[Okie294life]

It’s not how many saws it takes to do the job that matters it’s how many your going to bring.

 

[Brushwacker]

Yes, had the piston out, replaced both crank seals which were both leaking. Did pressure and vacuum tests, rebuilt carb, tested all lines and filter. Saw has 135 psi compression and now starts and runs wonderful, four strokes at max RPM. I just allowed myself to be misled by a defective tachometer. Thanks for the input. I'm gonna run the heck out of this saw first chance I get. My nickname isn't "wood whore" for no reason!

The tach being cheesy China crossed my mind . I had a compression gauge as such caused me to misdiagnose a number of saws as low compression I was selling on ebay. I expect it cost me several hundred dollars in sales before I caught it. There should be laws to prevent crap like that which cost the consumer many times over its price so chi chum can screw us to start with.

 

[lone wolf]

it does four stroke/burble. I discovered my cheesy chinese tachometer is all over the map, so I'm going to splurge on a good tach (like I should have in the first place) to be sure it's not running too lean. I suppose the Stihl tach is built in China too (what isn't?) This is a cool website, thanks to everybody for their help! I'll try to attach a video... sorry, video won't load.

Test the Tach on a few other saws and see if it accurate.

 

[Okie294life]

For future reference, if you have a pressure/vac tester you can check the carb too... Put it on the fuel line & pump it up, should hold 10-12PSI all day. Somewhere above that it should "pop off" as the metering valve pops open.
If it doesn't put a little fuel down the line as the metering valve doesn't always seal dry. If it still leaks drop it in a bucket of water to see where the bubbles are coming from & diagnose from there

Heat cycle her a couple times and check your head bolts.