Stihl 025 has me stumped.

[Tyler Shelton]

I recently bought a stihl 025 off a guy that had low compression for $30. I put a new p/c on it and tried to start it up but I could not get it to fire. I pulled the plug and I'm getting good spark. I tried a shot of starting fluid in the carb just to see if I could get it to fire that way I would know if it was a carb or impulse line issue but still no bump. I tested the compression and got 105psi. I know my gauge reads low but I went ahead and put another p/c on the saw but still no bump. This p/c also reads 105psi. I have rebiult probably 6 025's and have never had this issue. Is there a possibility the coil is bad and has a good spark out of the saw but not under compression. I have never had a saw that wouldn't at least bump with starting fliud or mix gas put in the carb. I don't want to keep throwing money at it. Any help or ideas is greatly appreciated. This one has me stumped.

 

[dmb2613]

put a little oil in the cylinder and pull it over with the plug out. Put the plug back in and spray some mix in the carb it will fire I bet then

 

[HarleyT]

You may have insufficiently torqued the flywheel nut, and your key is sheared.

 

[Vintage Engine Repairs]

I’m with Harley on maybe a sheared key. If not that maybe a blocked muffler / air filter?

 

[Matt Coolen]

+1 on checking the flywheel key. I have built several 025’s as well. Can be a finicky little saw for some reason.
Is there any fuel on your plug after trying to start? Are you checking spark with a spark tester, or with a plug grounded to the head? Plug wire good? Not shorting on cylinder fins?

 

[rupedoggy]

Send me the saw. I will fix it and tell you what was wrong. Then I will keep it!

 

[RED-85-Z51]

Ive had blown out crank seals cause low compression and no start even with help

Sent from my LM-G820 using Tapatalk

 

[SteveSr]

I recently bought a stihl 025 off a guy that had low compression for $30. I put a new p/c on it and tried to start it up but I could not get it to fire. I pulled the plug and I'm getting good spark. I tried a shot of starting fluid in the carb just to see if I could get it to fire that way I would know if it was a carb or impulse line issue but still no bump. I tested the compression and got 105psi. I know my gauge reads low but I went ahead and put another p/c on the saw but still no bump. This p/c also reads 105psi. I have rebiult probably 6 025's and have never had this issue. Is there a possibility the coil is bad and has a good spark out of the saw but not under compression. I have never had a saw that wouldn't at least bump with starting fliud or mix gas put in the carb. I don't want to keep throwing money at it. Any help or ideas is greatly appreciated. This one has me stumped.

Is this an AM replacement engine?

These saws tend not to bump unless you pull it very hard. The way you know it fired is if it tries to dislocate your shoulder or pulls the starter handle out of your hand. This is your one and only invitation to take the choke off and pull until it starts.

 

[a. palmer jr.]

Generally, if you put fuel mix in the cylinder through the spark plug hole and it starts then it eliminates everything but the fuel intake. If not then you have a compression or spark issue, or maybe the fuel is bad...

 

[59Billy]

Send me the saw. I will fix it and tell you what was wrong. Then I will keep it!

I've had days when that would have been a tempting offer.