If the outside of the spark plug hole on the cylinder of the Stihl 390 has some oil build up, will this effect the way it starts?
It's not farting until the 10 or 11 pull
zap
It's not farting until the 10 or 11 pull
zap
Thanks fox9988. I'll test the compression later tomorrow then post.Sounds like you are losing some compression. That usually leads to hard starting. I would clean it up and reseat or replace the sparkplug.
What should the compression be 120 and up, it's about 5 years old.Sounds like you are losing some compression. That usually leads to hard starting. I would clean it up and reseat or replace the sparkplug.
If the outside of the spark plug hole on the cylinder of the Stihl 390 has some oil build up, will this effect the way it starts?
It's not farting until the 10 or 11 pull
zap
Usually farts after the second pull, not sure if the 362 is different being a newer saw.Sorry I can't help you with your problem except to mention my saw never farts, no matter how my times I pull it. Do I have a problem?
Zap, it sounds like your plug may not have been in tight enough which caused fuel mix and/or exhaust to escape around the plug lowering your compression and causing that build up.
I'd take the old plug out, clean everything up real good, and put it back in. If it still starts hard you may have a different issue.
lukem, it seemed to be in good and tight but will check it tonight.More than likely the issue. Have seen the decomps weep oil also.
Is that 120 psi the most it'll do or did you stop after 6 pulls? Should pull until the needle stops rising completely. Zip tie on the trigger will hold the throttle wide open and reduce the number of pulls it will take to obtain a max reading.The first thing I did tonight was check the compression (the stihl 390 was cold) it tested 120 on six pulls, the second thing I did was take a new spark plug an gap it like the local shop does, damn thing never started (pissed) grabbed another new spark plug (never gapped it) put the second new one in, the 390 took off on the second pull.
The 390 manual recommends 0.02 inch gap, the shop recommends a 0.26 inch gap. I'm thinking out of the box the new Bosch is gapped at 0.02 so I'll stick with that.
zap
.Push down compression button,
So damn use to pushing that when starting, we'll see tonight. I had emailed Stihl about compression testing, they said the throttle should be in the I position and don't press in the decomp!Now why would you do that, you are after all trying to see the maximum compression the saw makes right? That button will get you a much lower reading. I would start it normally until it "pops" and then pull the plug and repeat your test.
Throttle position doesn't really matter, so long as you max the psi reading on the gauge. But I do have a preference.
120psi with the de-comp pressed in is pretty darn good. I still don't think compression/ignition is the issue here.
I read your post, just came back in from starting the 390 on one pull without the decomp pressed in, I'll post how it runs tomorrow in some ironwood.More better. Your 390 is doing fine with that compression. I found that the 310s will not start as well if they are modified, as when they are all choked up from the factory. 4-5 pulls is on full choke is typical on my modified 310 here for it to rumble, and then another 1-2 at half choke. No decomp on a 310. Decomps can be the casue of flooding though, especially if you are not used to feeling the rumble of a full chike start and stall. Usually the decomp button will pop at that point, but not always. At that point you should flip the lever to half choke, or it will flood. Flooding is common when starting the 361 with the decomp button pressed in, and for that reason I do not use the decomp when starting the 361s when they are cold. The LA fire department put zip ties around the decomp buttons on all their 361 rescue saws to keep them from being used becasue of flooding problems starting the saws cold.
Pulled the 390 out of the back of the Rhino once I was at the cutting area, pushed in the compression button, started on the second pull. Used it like that all day.More better. Your 390 is doing fine with that compression. I found that the 310s will not start as well if they are modified, as when they are all choked up from the factory. 4-5 pulls is on full choke is typical on my modified 310 here for it to rumble, and then another 1-2 at half choke. No decomp on a 310. Decomps can be the casue of flooding though, especially if you are not used to feeling the rumble of a full chike start and stall. Usually the decomp button will pop at that point, but not always. At that point you should flip the lever to half choke, or it will flood. Flooding is common when starting the 361 with the decomp button pressed in, and for that reason I do not use the decomp when starting the 361s when they are cold. The LA fire department put zip ties around the decomp buttons on all their 361 rescue saws to keep them from being used becasue of flooding problems starting the saws cold.
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