Questionable start - Stihl Ms170

[Oletrapper]

WOW, way over thinking again.
The statements that I THINK furl is not the issue always leads me to check it first. If you don;t actually check, how do you know.
Pulling 20 times cold? Check the master control lever and the choke lever and linkage. VERIFY the choke is closing.
Also never trust an old fuel filter because it LOOKS good. It is a maintenance item. And NO aftermarket fuel filters. I am really getting sick of finding them in saws and curing issues because of them.
I also see a few cracked fuel hoses lately. Start simple, work from the outside in.

I'm surprised that nobody has mentioned the carbon going all the way up the spark plug threads. Might be something as simple as a loose plug and losing compression. When I install a new spark plug I tighten then start the saw, warm it up to operating temp, then re-tighten. Same as you would on a new chain. jmho OT

 

[Dacha]

I'm surprised that nobody has mentioned the carbon going all the way up the spark plug threads. Might be something as simple as a loose plug and losing compression. When I install a new spark plug I tighten then start the saw, warm it up to operating temp, then re-tighten. Same as you would on a new chain. jmho OT

good point. thanks

 

[Dacha]

First time took carb off. Does carb usually accumulates this much dust ? Guess so.

Muffler has no muffler screen, so don't have to worry about cleaning it. Took muffler off, looked through, guess it looks ok.









After wiping externally carb with cloth.








And i checked old new spark plug, gap was correct it was just a angle of the photo that made it look crooked.

 

[J D]

If you still have the muffler off post a nice clear pic of the piston through the exhaust port.
Dust on outside of carb is fine... inside of the carb not so much

 

[MacAttack]

I would absolutely be dissassembling and cleaning that carb and install new diaphragms. Then I'd use only canned gas or ethanol-free gas. I bet it would start in just a few pulls after that.

 

[Dacha]

If you still have the muffler off post a nice clear pic of the piston through the exhaust port.
Dust on outside of carb is fine... inside of the carb not so much

I could not see the piston . I rotated drive sprocket hoping it will make piston go up and down. But that didn't happen.

I will look later once again with phone light to see.

 

[Dacha]

I would absolutely be dissassembling and cleaning that carb and install new diaphragms. Then I'd use only canned gas or ethanol-free gas. I bet it would start in just a few pulls after that.

I could order cheap carb kit, as i dont have it. Not sure about the quality of the kit. Only chinese cheap carb kits are available at present.

 

[Dacha]

I would absolutely be dissassembling and cleaning that carb and install new diaphragms. Then I'd use only canned gas or ethanol-free gas. I bet it would start in just a few pulls after that.

It looks fiddly working on that small carb when you are not familiar with carb environment. I could try.

Many options, no difficult decisions. All depends how many hours i have to spend trying different things.

If somehow it all comes together working at the end, sure it will feel rewarding and worthwile.

Thanks for all suport and consultation.

 

[J D]

If you are uncomfortable with rebuilding the carb my suggestion would be to do the following...
Firstly post a pic of the piston... if turning the saw over doesn't bring the piston up then you'll be wasting your time doing anything else.
Assuming P&C is good... empty fuel tank, replace fuel filter, & fill with fresh non-ethanol mix.
Remove carb & clean the outside thoroughly with a toothbrush & the likes of fuel/ WD40/ carb cleaner. Then submerge the carb in a glass of fresh fuel for a good few days. Cover the glass to prevent evaporation & agitate/rotate the carb regularly.
Dry carb & reassemble the saw with your new plug, check the choke is closing properly when set, & fit a clean or new air filter.
It probably wouldn't hurt to remove the coil, thoroughly clean around it & replace it with the correct gap (use a standard business card to set)
If it doesn't run as it should after that the next step is to rebuild or replace the carb

 

[Dacha]

If you are uncomfortable with rebuilding the carb my suggestion would be to do the following...
Firstly post a pic of the piston... if turning the saw over doesn't bring the piston up then you'll be wasting your time doing anything else.
Assuming P&C is good... empty fuel tank, replace fuel filter, & fill with fresh non-ethanol mix.
Remove carb & clean the outside thoroughly with a toothbrush & the likes of fuel/ WD40/ carb cleaner. Then submerge the carb in a glass of fresh fuel for a good few days. Cover the glass to prevent evaporation & agitate/rotate the carb regularly.
Dry carb & reassemble the saw with your new plug, check the choke is closing properly when set, & fit a clean or new air filter.
It probably wouldn't hurt to remove the coil, thoroughly clean around it & replace it with the correct gap (use a standard business card to set)
If it doesn't run as it should after that the next step is to rebuild or replace the carb

I put new air and fuel filter just today.

Choke is closing, would assume properly.

Will try the rest.

 

[Dacha]

hope these pictures give the right info

 

[MacAttack]

It looks fiddly working on that small carb when you are not familiar with carb environment. I could try.

Many options, no difficult decisions. All depends how many hours i have to spend trying different things.

If somehow it all comes together working at the end, sure it will feel rewarding and worthwile.

Thanks for all suport and consultation.

In all honesty, when a saw starts to have problems starting or running properly, more often than not it's the spark plug or carburetor, it would be well worth the effort to dive into the carb and replace the diaphragms. It's not nearly as intimidating once you've done it, there's tons of YouTube videos to help.

 

[Dacha]

In all honesty, when a saw starts to have problems starting or running properly, more often than not it's the spark plug or carburetor, it would be well worth the effort to dive into the carb and replace the diaphragms. It's not nearly as intimidating once you've done it, there's tons of YouTube videos to help.

Everything looks quite new.

 

[Dacha]

My saw starts hot on very first pull. Or it used to before i started this maintenance thing lol.

So i see as being a bit proactive. All i could have done is warm spark plug before starting cold. But i decided to try to maintain it a bit better.

Appreciate all the help.

 

[J D]

P&C look good.
Looks like there may be some fines in the mesh inlet filter. Remove it carefully with a pick, usually you can blow any crud off them with a can of carb clean using the little straw. Be careful not to just blast it off into the nether regions of the workshop.
If any of the diaphragm material feels "crinkly" in any way get a carb kit & replace them.
The brass fitting with the flathead screwdriver slot is the main jet & can be unscrewed. Often (especially on the later varients) it is beneficial to replace them with a jet one or two sizes larger (or drill them out by a thou or 2 if you have the bits to)

 

[MacAttack]

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Everything looks quite new.

Here's the critical thing...it's not how the diaphragms look...it's how they feel. They should be very pliable, if they're at all stiff / crispy, they're shot.
You've already done the work to take it apart, it would be a great idea to put new diaphragms in the carb.

 

[Oletrapper]

I could not see the piston . I rotated drive sprocket hoping it will make piston go up and down. But that didn't happen.

I will look later once again with phone light to see.

Just pull on the starter handle and the piston will move up and down. Drive sprocket will not make it move.

 

[Oletrapper]

I could order cheap carb kit, as i dont have it. Not sure about the quality of the kit. Only chinese cheap carb kits are available at present.

https://www.ebay.com/itm/1865289747...hwcRqRNJu6qbvBuq46xkUUPfMk5OWlCUaAqbZEALw_wcB

 

[Chainsaw Pete]

https://www.ebay.com/itm/186528974705....

He lists his location as Belgrade. Unless he is in Montana or Maine, a kit sold from ebay in the US might not get to him.

 

[Dacha]

Just pull on the starter handle and the piston will move up and down. Drive sprocket will not make it move.

Thats what i figured eventually. Thanks. Lol on my part.