What's on your bench today?

[UK Guy]

Guys,

Got to say this tread is a wealth of knowledge and Im sure its an inspiration to a lot of us. Spud & GardenKit, your input and the help you give to the forum is second to none and personally I think an ARBtalk award of greatness should be presented to you guys. I have started reading this thread from the start (nightly read before bed..... sad I know) ..... have found the excuse of buying shed loads of tools 'just in case' I need them

Im no pro mechanic but have always serviced my growing list of engine driven 'tools (2T & 4S)'..... now I could open a service shop with the tools I have purchased!

 

Anyway, with all this wealth of experience and advise, together with our resident Aspens preacher Mr GardenKit I can not ignore his experience and expertise in these matters of keeping your kit in tip top shape so I dived in and converted to Aspens for all my 2S kit (for starters!)

 

Aspens seems to run great in all my Stihl equipment apart from my little 7 year old lightly used (apx 20 tanks) MS170 which seems to struggle to tickover reliably. I have tweaked the tickover Screw and set it on 2800rpm (it tops out at apx 13500-14000 and is very responsive) .... read with that tach I bought after reading Arbtalk...!

 

The next time I go to use it a few days later it wont tick over well and measure it at around 2k rpm which is low. I tried changing the Carb (OEM) (they are cheap for these saws), and it seemed to fix the issue, but next time I used it it was low on tickover again.

 

What I have found is if I hold the saw with its bar pointing up or down, it seems to tick over better, not perfect but better.

 

Now - The tickover screw does not seem to do anything, screw it all the way in makes no difference - it does not seem to affect the tickover much (thats on both carbs, so not the carb).

 

With Premium fuel + Stihl HP mix, I did not notice an issue with this saw. I have read on this forum somewhere that with old kit you should replace the fuel lines before using Aspens which I have not done yet.

 

I have NOT put Petrol mix back in to see if its OK with that (which is one thing I will try), but is there anything you guys can advise I should try.... is this a common issue with old chainsaws and Aspens.

 

Thanks in advance.

UK Guy

[spudulike]

Guys,

Got to say this tread is a wealth of knowledge and Im sure its an inspiration to a lot of us. Spud & GardenKit, your input and the help you give to the forum is second to none and personally I think an ARBtalk award of greatness should be presented to you guys. I have started reading this thread from the start (nightly read before bed..... sad I know) ..... have found the excuse of buying shed loads of tools 'just in case' I need them

Im no pro mechanic but have always serviced my growing list of engine driven 'tools (2T & 4S)'..... now I could open a service shop with the tools I have purchased!

 

Anyway, with all this wealth of experience and advise, together with our resident Aspens preacher Mr GardenKit I can not ignore his experience and expertise in these matters of keeping your kit in tip top shape so I dived in and converted to Aspens for all my 2S kit (for starters!)

 

Aspens seems to run great in all my Stihl equipment apart from my little 7 year old lightly used (apx 20 tanks) MS170 which seems to struggle to tickover reliably. I have tweaked the tickover Screw and set it on 2800rpm (it tops out at apx 13500-14000 and is very responsive) .... read with that tach I bought after reading Arbtalk...!

 

The next time I go to use it a few days later it wont tick over well and measure it at around 2k rpm which is low. I tried changing the Carb (OEM) (they are cheap for these saws), and it seemed to fix the issue, but next time I used it it was low on tickover again.

 

What I have found is if I hold the saw with its bar pointing up or down, it seems to tick over better, not perfect but better.

 

Now - The tickover screw does not seem to do anything, screw it all the way in makes no difference - it does not seem to affect the tickover much (thats on both carbs, so not the carb).

 

With Premium fuel + Stihl HP mix, I did not notice an issue with this saw. I have read on this forum somewhere that with old kit you should replace the fuel lines before using Aspens which I have not done yet.

 

I have NOT put Petrol mix back in to see if its OK with that (which is one thing I will try), but is there anything you guys can advise I should try.... is this a common issue with old chainsaws and Aspens.

 

Thanks in advance.

UK Guy

 

 

The fuel line will probably not be the issue unless it was split before you changed to Aspen. The fuel line often hardens once pump petrol is taken from it and then it leaks around the area it pushes in to the fuel tank and that is why they are often changed.

 

I believe that this carb has a weird single screw idle adjustment only and works by bypassing the throttle valve with a bleed screw.

 

If this is so then it needs to be turned anti clockwise until it beds and then turn two turns in (Clockwise) and the saw should run OK on this. If the carb is different then let us know. The fact both give the same symptoms sort of rules out the carb.

 

Has the saw got good compression, have you popped the muffler off to check the piston through the exhaust port? A lower idle than normal may be attributed to a bit of drag on the clutch/needle bearing, worth whipping it off and giving it a clean and see if that makes a difference.

 

The fact the saw has only done 20 tanks sort of rules out that the seals etc have gone or the saw is just worn out!

 

The fact that pointing the saw downward improves the saw looks like it may be the fuel pickup so check the fuel line/filter position and worth pressure testing the fuel line (can be done without removing).

 

If you get he saw idling on the deck, does pulling the rear handle to and from the engine cause the engine note to rise and fall? If it does, perhaps the manifold is holed.

 

When you removed the first carb, did you replace that little plastic ring that stops the manifold collapsing and restricts the impulse line a little? Common for these to go missing

[UK Guy]

Spud

 

I had the issue of low tickover as soon as I first started the saw up with Aspens (I emptied the Petrol mix then run it dry and then filled with Aspens and started it).

 

I will have to take a quick look to see if that plastic ring is still there (you never know I may have lost it when I pulled the carb).

 

The needle bearing - I have just had a few of those delivered (OEM) which I was going to change (as Ive never greased it in 7 years!) - and after reading ARBTALK I see its a common issue on the new MS261cm so ordered a few for both saws I have.

 

I will have a look over the weekend and let you know what I find.

 

P.S I will do a pressure test on the fuel lines and check piston compression over the weekend (with my new tools! )

 

Thanks

UK Guy

[Sawchip]

[/ATTACH]

Iv not had such a "original " and from what i can see"new regardless of age" 024 on the bench. This saw seems to have hardly any use in its life and has hardly a mark on it ! Its the closest to a NEW mid 90s o24 iv had eyes or a spanner on. There are even the assembly paint dots on some screws still showing they haven't moved.

Even has some of the protective film attached to the rivets on the top cover and pull cord cover and not any parts that aren't genuine Stihl! So nice to work on something that has nothing broken or worn on it.

[GardenKit]

 

Anyway, with all this wealth of experience and advise, together with our resident Aspens preacher Mr GardenKit I can not ignore his experience and expertise in these matters of keeping your kit in tip top shape so I dived in and converted to Aspens for all my 2S kit (for starters!)

 

Aspens seems to run great in all my Stihl equipment apart from my little 7 year old lightly used (apx 20 tanks) MS170 which seems to struggle to tickover reliably.

 

Crikey, after all these years of preaching I have my first convert!!!!

 

Seriously though, I am glad you have tried it and liked it. Your 170 is a bit of a mystery. It does on the face of it look like it does not like Aspen. Sure, there is a slight difference in the density and gas pressure of Aspen which means that some saws need a bit of a tweak on the L screw, but of course that single screw carb does not adjust well, was the replacement also single screw?

 

But there could be other influences other than the Aspen and this could be pure coincidence, as, believe me, the 170 will run on Aspen without any trouble.

 

Try the options that Spud has given and keep us informed.

[UK Guy]

The fuel line will probably not be the issue unless it was split before you changed to Aspen. The fuel line often hardens once pump petrol is taken from it and then it leaks around the area it pushes in to the fuel tank and that is why they are often changed.

 

I believe that this carb has a weird single screw idle adjustment only and works by bypassing the throttle valve with a bleed screw.

 

If this is so then it needs to be turned anti clockwise until it beds and then turn two turns in (Clockwise) and the saw should run OK on this. If the carb is different then let us know. The fact both give the same symptoms sort of rules out the carb.

 

Has the saw got good compression, have you popped the muffler off to check the piston through the exhaust port? A lower idle than normal may be attributed to a bit of drag on the clutch/needle bearing, worth whipping it off and giving it a clean and see if that makes a difference.

 

The fact the saw has only done 20 tanks sort of rules out that the seals etc have gone or the saw is just worn out!

 

The fact that pointing the saw downward improves the saw looks like it may be the fuel pickup so check the fuel line/filter position and worth pressure testing the fuel line (can be done without removing).

 

If you get he saw idling on the deck, does pulling the rear handle to and from the engine cause the engine note to rise and fall? If it does, perhaps the manifold is holed.

 

When you removed the first carb, did you replace that little plastic ring that stops the manifold collapsing and restricts the impulse line a little? Common for these to go missing

 

I pressure and vacuum tested the saw today, pressure was perfect but had a very very slow leak down on vacuum.

The fuel pipes were perfect (held pressure on test) and no scores on the piston (looks like new!)

I took the side off and it was apparent that the intake rubber tube where it meets the engine was the culprit. I could see sooty oily deposit buildup (not a lot) around the intake pipe where it meets the engine.

I give it a good clean with break cleaner and pushed it tight on the engine. Vacuume test passed...!

So I need to change this intake boot (the saw now tuned up perfect and I managed to retune to 2800 rpm and runs sweet)

 

The carb is the one with only Tickover screw by the way.

 

I did try putting pressure on the back handle to see if this affected it again but it ran spot on perfect.

 

Question.... What's the procedure of changing the intake manifold pipe, do I need to take the engine out? Any help on how to strip it down appreciated.

 

I will get a new intake manifold pipe and plastic rings ordered... Where would you recommend I can buy thiese from (Stihl original).

 

Thanks for the advice

UK Guy

Edited January 23, 2016 by UK Guy

[spudulike]

Saw this, liked the simplicity of design: -

 

[biggarlogs]

Oh dear very camp indeed!

[spudulike]

Been on Husqvarnas "Big Lump" 3120XP, came in with zero compression and could see that it looked seized. On taking it apart, I found that both rings had broken and pretty much destroyed the cylinder and piston.

 

I fitted a new OEM kit, a pressure check showed a BIG leak, traced this down to the clutch side seal that was actually rotating in its seat and had worn it to the point that air was pissing past it.

 

I put a new seal in but it dropped through the pump casing so cleaned it and smeared a little JB weld around the seal and seat then refitted and let it go off, refitted the pump and all good.

 

On this model there is a rather weird valve in the crankshaft that puts a little fuel air vapour through the crankshaft and in to the clutch needle bearing. This causes the saw to leak under pressure but seal under vacuum and is accommodated for in the carbs jetting so is quite normal.

 

The piston photos show that the exhaust top edge of the piston has almost carbonised and granulated. All I can put this down to is the heat from the air leak. Not seen it before and almost looks like detonation but there are no signs on the piston crown.

 

The saw is now sorted, clean and fires up well.

[spudulike]

Another pic of that piston: -