MS 170 Tear-down

[roostersgt]

I think you need to make sure you have spark again. I don't think there is a reason that it shouldn't fire if you did everything we have mentioned. Do you have a compression checker? I thought my 025 was okay but it wasn't till I pulled off the muffler. Maybe there is more to this.

Still have spark. Pulled plug and held it against cylinder head and pulled handle in dark garage. Beautiful blue sparks. Adjusted coil gap w/ guage as suggested. Plug getting wet with mix. Using new can of TruFuel 40:1 mix. Not even getting a bump. Pulled muffler off. Was wet behind it. Piston / rings etc.... looked good. Kill/stop wires all okay. No comp guage, but comp feels really good. Getting fuel, getting spark. Baffling for sure. :msp_sad:

 

[K5krawler]

I wish I had something constructive....I don't. Are you testing with a spark tester??? It could be your plug is sparking out but doesn't have enough "spark" to get the job done when you are under compression etc...????

 

[roostersgt]

Just using the plug it came with. Getting really good strong blue spark. Just seems like its firing at wrong time. If this were a four stroker I'd think I was 180' out, or far out ATDC.

 

[Rookie1]

Take the nut off and check the keyway to make sue its still in time. If you are saying 180 off maybe "key sheared and timing is way off now.:msp_ohmy:

 

[mountainlake]

Even with the slop in the flywheel key on those saws it should still run, try that new plug and make sure it's not flooded. Steve

 

[roostersgt]

Checked key and retightened flywheel nut. All okay. Hoping it was flooded. Will test again this morning before picking up comp tester. Thanks for replies. Will keep updating my progress, if any.

 

[SPDRMNKY]

spark, fuel, air...

if you haven't already, replace that plug...I've had more than one 2-stroke that should have ran, but didn't until I put a new plug(s) in

if that doesn't work it's probably air leak time

 

[roostersgt]

Well, I just got back from my dealer buddy's shop. He said he sees this all the time with rebuilt low compression clamshell/homeowner class saws. He "upped" my compression a bit by adding about a tablespoon of mix oil directly into my fuel resevoir, which already had a tank of 40:1 TruFuel in it. Replaced spark plug, just because. Removed the muffler and put a huge squirt of mix oil directly into the cylinder and then pulled the cord vigorously about 6 times, without replacing the muffler. The saw came to life and began spewing a lot of smoke. Hit 14,400 RPM's and idled at 2800. Now "cold" starts on third or fourth pull since his initial coaxing. :msp_biggrin:

This saw has fixed jets and the only adjustment that can be made is the idle.

 

[SPDRMNKY]

wow...that's one to keep in your noodle

glad she's running!!

 

[roostersgt]

wow...that's one to keep in your noodle

glad she's running!!

Yup, that's why I'm sharing that valuable "Stihl" secret. Sssshhhhhh,,,,don't tell everyone.

 

[Dan_IN_MN]

Well, I just got back from my dealer buddy's shop. He said he sees this all the time with rebuilt low compression clamshell/homeowner class saws. He "upped" my compression a bit by adding about a tablespoon of mix oil directly into my fuel resevoir, which already had a tank of 40:1 TruFuel in it. Replaced spark plug, just because. Removed the muffler and put a huge squirt of mix oil directly into the cylinder and then pulled the cord vigorously about 6 times, without replacing the muffler. The saw came to life and began spewing a lot of smoke. Hit 14,400 RPM's and idled at 2800. Now "cold" starts on third or fourth pull since his initial coaxing. :msp_biggrin:

This saw has fixed jets and the only adjustment that can be made is the idle.

I'll have to try this on an Echo that I put a new ring in.

 

[imagineero]

Nice thread!

I've never done any work on a clamshell before, is the reason that you had to remove the flywheel and clutch to remove the P&C because it was a clamshell?

Shaun

 

[mountainlake]

Well, I just got back from my dealer buddy's shop. He said he sees this all the time with rebuilt low compression clamshell/homeowner class saws. He "upped" my compression a bit by adding about a tablespoon of mix oil directly into my fuel resevoir, which already had a tank of 40:1 TruFuel in it. Replaced spark plug, just because. Removed the muffler and put a huge squirt of mix oil directly into the cylinder and then pulled the cord vigorously about 6 times, without replacing the muffler. The saw came to life and began spewing a lot of smoke. Hit 14,400 RPM's and idled at 2800. Now "cold" starts on third or fourth pull since his initial coaxing. :msp_biggrin:

This saw has fixed jets and the only adjustment that can be made is the idle.

This saw burnt down from a lean sieze and at 14,400 RPM I'd think it will be headed the same way. Carb might be partially clogged on the high speed. New plugs help sometimes. Steve

 

[mountainlake]

Nice thread!

I've never done any work on a clamshell before, is the reason that you had to remove the flywheel and clutch to remove the P&C because it was a clamshell?

Shaun

Sure looks like you could leave the flywheel on , on smaller Echo saws you can but need to pull the clutch to get the motor out. Steve

 

[TJ-Bill]

Good job on the rebuild. Interesting trick on the oil fron the dealer, I wonder if it was to seat/break in the rings?

the High Temp RTV you used is it good for contact with gas.. The stuff I used from Prematex was grey I think for 2 cycle engines. Just curious.

 

[mountainlake]

I'd guess adding oil to the fuel did nothing as that fuel sure didn't make it to the carb for starting it the 1st time. The NEW PLUG and shot of mix helped. Steve

 

[imagineero]

Sure looks like you could leave the flywheel on , on smaller Echo saws you can but need to pull the clutch to get the motor out. Steve

On most of the saws I've worked on you could remove the P&C just by removing the muffler, unscrewing he intake boot, removing the top cover and then undoing the 4 cylinder bolts. The motor stays where it is, and the cylinder just slides right out the top.

Shaun

 

[mountainlake]

On most of the saws I've worked on you could remove the P&C just by removing the muffler, unscrewing he intake boot, removing the top cover and then undoing the 4 cylinder bolts. The motor stays where it is, and the cylinder just slides right out the top.

Shaun

Not on a clamshell motor, the bottom cap is screwed on from the bottom on most. Steve

 

[roostersgt]

This saw burnt down from a lean sieze and at 14,400 RPM I'd think it will be headed the same way. Carb might be partially clogged on the high speed. New plugs help sometimes. Steve

Perhaps, but my dealer buddy completely pulled apart, cleaned and pressure tested the carb. Nothing more could be done to service the carb. Carb kit would be a waste of money in the dealer's opinion, as the parts included in the kit would be in no better condition than the parts presently in the carb. Fuel line pressure tested as well (new one ordered, just because). The only other "leak" sources could be either the crank seals and/or intake boot. The crank seals were replaced and the intake boot was visually inspected and found to be without cracks or holes and in new condition. I probably could have pressure/vac tested the seals prior to the teardown, but was operating under the assumption that I was replacing them anyway. With absolutely no way for anyone (my dealer included) making any adjustments to the carb, other than modifying the jets with a drill, I think all of my bases have been thoroughly covered. This saw was built and set up by the factory and EPA to run lean. I wish I could fatten it up a bit to save it from itself, but that's not an option.

To the person asking if the flywheel needed removal, it does. Not to get it out of the saw's chassis, but to allow the installation of the crank seal. For my first rebuild, this was an easy one. I didn't have any leftover parts either! That almost never happens no matter what I'm doing. Many thanks to all those who helped me with this rebuild. It's appreciated. I love this site!

 

[sefh3]

Glad to see you got the saw running. If you want you can install a carb from an 026 in there. You will need to mod a few parts as the carb is bigger but it allows for H and L adjustment. You will also need to drill a hole or two to allow a screwdriver in the to adjust it. I remember seeing this done here but I don't remember who did it. PM BSNELLING. It might have been him.

When you put the piston in, did you put some 2 stroke oil on the cylinder wall? This usually bumps up the compression a bit and protects the piston on itintial startup.