Hard to start MS391

[Gav73]

Hi all, looking for some tips on startIng my MS391. I bought it new a couple of months ago and am finding it hard to start. The guys I work with seem to be able to start it - but I always seem to struggle. My other chainsaws  haven’t had the compression value and I don’t know whether this is causing my challenges. Any tips gratefully received!

[rapalaman]

Full choke, compression valve pushed in, couple of pulls it should cough, half choke then you need to properly commit to a pull - can bite knuckles if you don’t! Should fire up within a pull or three

[openspaceman]

2 hours ago, rapalaman said:

Full choke, compression valve pushed in, couple of pulls it should cough, half choke then you need to properly commit to a pull - can bite knuckles if you don’t! Should fire up within a pull or three

Yes but why not press the decompression valve back in after it "coughs" on choke and then start it? I find I now prefer to do this on bigger saws as I haven't the energy to "beast" them.

[rapalaman]

Yes this - sorry should have added the second press as well. Early morning post over breakfast ?

[Stubby]

2 hours ago, openspaceman said:

Yes but why not press the decompression valve back in after it "coughs" on choke and then start it? I find I now prefer to do this on bigger saws as I haven't the energy to "beast" them.

Remember its a DE compression valve .

[openspaceman]

13 minutes ago, Stubby said:

Remember its a DE compression valve .

Swot I sed

[Stubby]

4 hours ago, openspaceman said:

Swot I sed

Yea sorry . Gav ( the OP ) called it a " compression value " ☺️

[Gav73]

33 minutes ago, Stubby said:

Yea sorry . Gav ( the OP ) called it a " compression value " ☺️

Thanks for all the suggestions!

 

Just to clarify, my phone decided to autocorrect decompression valve into compression value - sometimes phones just aren’t smart! ?

[spudulike]

The decomp valve knocks off the compression to make it easier to turn over but also can cause starting issues if the saw isn't pulled over hard enough.

Personally, I don't tend to use the decomp valve unless the saw is something like a MS660 or 395XP or larger.

I do test saws using the decomp when I have worked on them to ensure they start freely using the valve.

If you can pull the saw over with the valve out, try starting it without it to see if it helps - When cold, use choke, pull it over till it coughs, push the choke lever up one notch (fast idle) and then pull it over (1-3 pulls) until it starts.

If the saw is warm/hot, put it on full choke and then push it up to fast idle and THEN try to start it, never use full choke on a hot saw unless it is an Autotune model and even then I try to start using no choke.

[peatff]

My MS460 with new piston and cylinder needs the decomp valve or it kicks back at me but my old 044 with no decomp is an easy pull and starts with no fuss. I've tried the Ms460 without it but I just seem to miss the cough then flood it.