Questionable start - Stihl Ms170

[Dacha]

i did some cutting yesterday and stihl ms170 served me well once it started.

it took 20 pulls to start it. Storage and outside temperature was in 20s and 30s.

i have it for 3 years. First 6 months from new was starting poorly, like 20 pulls.

than i decided to drop warranty and took whole thing apart and cleaned it, replaced only spark plug. Since then saw was starting almost for 3 yrs on 3rd pull. In both hot and cold.

I kind of feel i now all possible routes to deal with it, but thought i would consult the forum.

I will try replacing the spark plug first.

Will replace air filter too.

If can find a dealer that can measure compression, will do that too.

Will buy new gas mix, but am sure gas is not the issue.

Sure i can pull out spark plug and warm it and than put it back, before cold start, but would like to have cahinsaw ready like it was before.

Chainsaw has around 40 working hours on it. Someone mentioned that these are 40 hours saws.

Any suggestions welcome.

 

[J D]

Flush out fuel tank, check/replace fuel filter & lines. Clean out carb & if necessary put a kit in it.
The more recent ones are set very lean, if compression doesn't feel good probably be worth doing a compression test or pulling the muffler to inspect piston, etc.

 

[Dacha]

Flush out fuel tank, check/replace fuel filter & lines. Clean out carb & if necessary put a kit in it.
The more recent ones are set very lean, if compression doesn't feel good probably be worth doing a compression test or pulling the muffler to inspect piston, etc.

I inspected fuel filter, looks fine, for what its worth.

 

[irhunter]

To the OP:

So, you are saying the problem is that it takes 20 pulls to start it...and, once started, it runs and hot-starts correctly?

I would not worry about the 40-hour thing.

Roy

 

[Dacha]

Flush out fuel tank, check/replace fuel filter & lines. Clean out carb & if necessary put a kit in it.
The more recent ones are set very lean, if compression doesn't feel good probably be worth doing a compression test or pulling the muffler to inspect piston, etc.

I inspected fuel filter, looks fine, for what its worth

To the OP:

So, you are saying the problem is that it takes 20 pulls to start it...and, once started, it runs and hot-starts correctly?

I would not worry about the 40-hour thing.

Roy

Yes, that is the case.

I will inspect spark plug tomorrow to see if that gives any clues.

 

[buzz sawyer]

Are you sure the choke is closing completely? You have to open the throttle for the choke to close. You can check with the air filter removed. I don't think you have a compression problem buy if you run a test, make to use the correct compression tester - with the Schrader valve in the end that screws into the spark plug hole. Don't expect much more than 130 psi.

 

[irhunter]

I would get the shop manual, if you don't already have it. Then, adjust the carb as per manual.

https://www.arboristsite.com/forums/chainsaw-equipment-manuals.170/

 

[J D]

Carbs on these are fixed.
You can raise the metering lever slightly to richen them a fraction, or replace the jet with a size larger, or drill the jet out a few thou, or replace the carb with an aftermarket adjustable & drill holes in the cover

 

[Dacha]

new vs old spark plug

 

[Dacha]

I intended to post this thread in Homeowner helper forum section, but have just realized somehow it ended up in Arborist 101.

 

[Patrick1903]

Will buy new gas mix, but am sure gas is not the issue.

Why do you think fuel is not an issue? When was the fuel dispensensed from the fuel pump into the fuel can. And was the fuel can clean and dry to begin with? Really make sure your fuel can is clean and no water before refilling it. Or go with a metal premixed fuel can like moto-mix.

For fun you should bring the saw in overnight and see if it starts better than when it is stored at 20 degrees.

As was previously said by @buzz sawyer please ensure the lever is fully in choke position. Our ms180 easily slips up into high idle if I’m remembering correctly.

Regarding the fuel pickup (filter) - it’s really hard to visually inspect the pickup to see that it’s not obscured. But not sure that’s your issue if the saw is running fine after starting. I’m not a mechanic btw…just a hobbyist. So perhaps others can see when they need to be replaced. But I can’t!

 

[irhunter]

Carbs on these are fixed.

Humm, that's too bad. On inexpensive saws, especially, it is always tough to decide: carb kit, Ebay carb, adjustable Walbro (assuming one is available).

But, since the saw recently was OK. And, the saw is still OK when warm. One might start by a carb disassemble, clean, reassemble-with-same-parts. I, personally, wouldn't do that...I'd put a kit in it...but, it would not be unreasonable.

new vs old spark plug


View attachment 1229910

Looks like that was not the problem. But, of course, plugs can still be an issue while looking good.

Roy

 

[buzz sawyer]

new vs old spark plug


View attachment 1229910

The gap on the new plug is too small. I don't know if anyone pointed that out yet. Power isout here so I am on my phone and cant see other replies. I also had trouble on my 170 due to choke linmage and not closing fully.

 

[Dacha]

The gap on the new plug is too small. I don't know if anyone pointed that out yet. Power isout here so I am on my phone and cant see other replies. I also had trouble on my 170 due to choke linmage and not closing fully.

Gap spec is

0.027" ( 0.7mm )

I will double check it tomorrow, just to make sure.

 

[stihltech]

WOW, way over thinking again.
The statements that I THINK fuel 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.

 

[BeatCJ]

I agree with @stihltech. Fuel is ALWAYS the first item to check/replace until you have known fresh good fuel. With the stuff available from the pump now it oxidizes so quickly that it's not a bad idea to dump it and replace it on a regular basis. It's why so many recommend the canned fuels now. Even those have a fixed life after they are exposed to air/opened.

 

[buzz sawyer]

Gap spec is

0.027" ( 0.7mm )

I will double check it tomorrow, just to make sure.

The gap should be even across the opening. Unless this pic is before you adjusted it, it's not right. The old plug has nice, even gap. You may have to bend the side electrode back and the over.

 

[capetrees]

My 170's always need 7-8 pulls to start with the choke closed when they're cold or have sat for a few days. Even brand new. I do believe it has to do with the cold and compression combined, even new.

Once they start, they run right away first or second pull no problem.

And whats a 40 hour saw? I've had my 170 saws for years.

 

[Dacha]

My 170's always need 7-8 pulls to start with the choke closed when they're cold or have sat for a few days. Even brand new. I do believe it has to do with the cold and compression combined, even new.

Once they start, they run right away first or second pull no problem.

And whats a 40 hour saw? I've had my 170 saws for years.

During break in period i ran first 2 tanks at 1:33 mix ratio. First 6 months it was taking minimum 7-8 pulls to start it, often more.

Than i did something to it, not sure what, other than took apart everything, cleaned it and put a new spark plug.

After that saw was starting on 3rd pull for over 2 years straight. I could not believe my luck.

I will add new fuel and air filter this time around, even though i think old ones are fine.

WIll put one more new spark plug with right gap, before i start bending the other new spark plug, lol.

Will see how that goes. Than if need be, i will play with carbouretor cleaning and stuff.

Thanks for advices.

 

[Dacha]

Spot on 0.7mm (0.027"). Got new one today.