Stihl chainsaw cutting issue

[spudulike]

I have a 16inch stihl saw which has a fairly new chain and bar. It gives some nice chips when cutting at the top end of the bar and I can cut through large logs. However, when cutting back on the handle end it cuts about an inch deep and then struggles. any ideas?

 

Well - did we get anywhere with this??? The most logical reason for this issue is that the bar has been worn by the engine where it does most of its cutting action takes place and the chain is now sitting at an angle in the bar and is therefore not being held by the bar correctly in the cut.

 

Options are:-

 

Dress the bar

Replace the bar

Knock the rails together if worn

 

It depends on what you find but it may be nice to give us some feedback:001_rolleyes:

[Dazonit]

To me, this sounds like lack of power otput or a slipping clutch - power output being the most likely.

 

It sounds, from your description, that your saw is revving and idling OK but when you go to cut wood, the saw slows and boggs in the cut.

 

If you have bar/chain issues, you usually get the saw revving its nuts off but very little cutting action - a bit different from bogging in the cut.

 

My advice is to ensure your saw has compression, check the piston through the exhaust port (should be smooth with no vertical scores). If this looks good then check the fuel system. It is likely you have a partial blockage - probably the internal gauze strainer under the single screw cover.

 

A sliping clutch would cause the revs to continue or soar as the chain slows in the cut and possible excess heat/smoke from the clutch side. A worn sprocket will cause rough chain rotation but shouldn't cause this issue.

 

Engine wear/partial seizure/ fuel/ bad spark plug are most likely IMO!

The revs die as the saw bogs the saw dose not seem to bog if I cut with the tip of the bar but I don't know if this is because there is less chain/bar in contact I striped and cleaned the carb a few weeks ago when the saw refused to start and found the gauze fully blocked and it starts sound now . I use stihl one shots so don't think its the fuel it starts and runs sound so I presume the plugs ok I'll remove the exhaust tomorow and have a look cheers

[Rob D]

If you could post a vid then I reckon would make diagnosis very quick.

[Dazonit]

If you could post a vid then I reckon would make diagnosis very quick.

 

Good idea rob I'll give it a go cheers:thumbup1:

[spudulike]

The revs die as the saw bogs the saw dose not seem to bog if I cut with the tip of the bar but I don't know if this is because there is less chain/bar in contact I striped and cleaned the carb a few weeks ago when the saw refused to start and found the gauze fully blocked and it starts sound now . I use stihl one shots so don't think its the fuel it starts and runs sound so I presume the plugs ok I'll remove the exhaust tomorow and have a look cheers

 

Cutting with the end of the bar will put less strain on the engine and possibly hide the fact the engine is lacking guts. I think yours is more engine related than clutch as when you have the OPs fault, the saw revs like it should but you literally polish the wood away rather than chipping it out of the cut - I have had it a couple of times and it throws you at first!

 

If your saw has one of those early steel wire airfilters, they can let a lot of fine dust through leading to wear on the inlet side of the cylinder. Once through the plating, the cylinder is scrap!

 

One thing to point out is cutting with the tip of the bar can be dangerous - NEVER cut with the top end of the bar on the bar sprocket as it can lead to a bad kickback!!

 

If you know this then ignore - if you don't, make note!

[Dazonit]

I am going to strip it today and have a look so I may be a new pot and piston. I was cutting to end of the bar but bottom side if you know what I mean but cheers anyway

[Dazonit]

striped it down and there is scoring on the exhaust side pic 1 but the air intake side seem fine . Would this make the saw loose power if so Found a cylinder and piston kit on ebay for £40 so I'll give that a go as the saw owes me nothing really and would be a good spare .

[Dazonit]

Pic one

[Tom D]

Even a slight bend in the bar can give these symptoms, take it off and look at it very closely....

[Stubby]

striped it down and there is scoring on the exhaust side pic 1 but the air intake side seem fine . Would this make the saw loose power if so Found a cylinder and piston kit on ebay for £40 so I'll give that a go as the saw owes me nothing really and would be a good spare .

 

Check to find out what caused the damage first . If you have an air leak fix that first or your new parts will end up the same . Check your mix as well . Dont use cheap mineral based 2 stroke oil . Use good quality and dont use mix that is over 4 weeks old ...or dare I say it use aspen !