How Dumb Do I Feel? And Saw Tuning Advice Needed Immediately

[CT-Mike]

So I posted on another thread about my Jonsereds being very hard to start. My father-in-law used these saws while working as a lumberjack in NH, and they have had a hard life but always work.

Anyhow, I found the manuals online, and while reading through it I noticed that there is a decompression valve on the side of the cylinder. Imagine how much easier they are to start now.

On to saw tuning:

Started the saw for the first time since this past spring, and noticed that the chain freewheels while the saw is idling. I followed the instructions in the manual and backed the idle screw all the way out, to no avail. Due I need to turn in on the low speed screw?

I did check and the throttle returns to the stop when released.

Help please, I need to be cutting trees tomorrow morning.

Thanks,

Mike

 

[CT-Mike]

Well,

I think I got it running basically ok. Turn both High and Low screws all the way in, then 1 turn out each. Saw seems to idle fine, has good acceleration and lots of power.

Still feel dumb about the decomp valve, woulda been nice to know when I was pulling it over 30-40 times on cold mornings.

Mike

 

[LLigetfa]

High and low screws are for mixture setting, not speed. Of course, if you affect the mixture, you affect the speed. There should be another screw to adjust the idle stop for the butterfly.

The usual cause of a low idle spinning the chain is that the clutch spring is weak and needs replacing. If the chain is loose and you have a roller nose bar, try taking up the slack.

 

[CT-Mike]

LLigetfa,

Thanks for the reply. Part of the problem was that the throttle butterfly would stick and that was causing the chain to freewheel. I did take up the slack on the bar (it is a roller nose) to the point where the drive lugs can't be pulled clear of the bar. Is that too tight? I did adjust the idle screw all the way out as I stated above, but the throttle was sticking.

I found a website online that had a parts manual for the Jonsered so I ordered some small parts that I am missing to get the saw back in tip-top shape.

Thanks for the help,

Mike

 

[struggle]

What I have always done with the high speed screw is to warm the saw up and then run it wide open and turn the high idle screw out to where it just starts to sputter a bit and then leave it. It will run smooth under load then at high speed.

Then adjust idle mixture screw to where it idles good with a the nidle screw stop adjustment in just a little bit so you have some area to adjust that further.

If you lean out the high idle to much you can seize the motor so it is better to error on the rich side a little on the high speed adjustment.

 

[LLigetfa]

I did take up the slack on the bar (it is a roller nose) to the point where the drive lugs can't be pulled clear of the bar.

That is how I check the tension but I guess it depends how hard you have to pull to see the ends.

You made it sound like you were adjusting the low speed mixture jet and not the idle stop screw. I adjust the low mixture for a smooth idle that doesn't bog when you open the throttle.

 

[Gooserider]

LLigetfa,

Thanks for the reply. Part of the problem was that the throttle butterfly would stick and that was causing the chain to freewheel. I did take up the slack on the bar (it is a roller nose) to the point where the drive lugs can't be pulled clear of the bar. Is that too tight? I did adjust the idle screw all the way out as I stated above, but the throttle was sticking.

I found a website online that had a parts manual for the Jonsered so I ordered some small parts that I am missing to get the saw back in tip-top shape.

Thanks for the help,

Mike

That sounds a bit to tight... You want it so there is JUST no slack, but minimal drag... IOW while pulling up on the nose of the bar, tighten the chain until the links in the center just touch the bar's bottom. If you spin the chain around, it should be pretty close to the same tension all the way around, and at any point you should be able to pull the chain off the bar a little way, but snap back into contact with it when released... Try dragging the chain around when it's way loose, it shouldn't feel much more drag than that when tightenned properly. On ArboristSite they say "No Sag, No Drag" is the right point.

A couple of other notes -

1. Only adjust the chain TIGHTER - If you get the chain to tight, back it way off untill it's really loose and then try tightening it again. This keeps the slack in the adjusting mechanism from letting the chain loosen up in use.

2. Long bars (i.e. 28" +) will need to be adjusted a little tighter than shorter (16-20") bars as their chains get more stretch as they heat up.

3. Only adjust chains when they are thoroughly cold. If you notice a LITTLE slack after it warms up, don't worry about it. If you get a lot, you may need to tighten while hot, but in that case it is very important that you slack back off when done cutting before things cool back down - otherwise the chain may get over-tight when it cools down and shrinks, which puts undue strain on parts at best, and has been known to bend cranks at worst - again, this is more of an issue with long bars.

4. ALWAYS pull up on the nose of the bar when tightening the chain and while locking down the bar nuts - this is the way the slack in the bar mechanism will want to go when the saw is in use, not doing this will tend to make the bar want to shift a little bit while cutting and change the chain adjustment on you.

Gooserider

 

[LLigetfa]

4. ALWAYS pull up on the nose of the bar when tightening the chain and while locking down the bar nuts...

I pull up on the chain at the top of the bar which esentially lifts the bar and snugs it against the adjuster at the same time so that the adjustment doesn't shift as the saw is worked.

When adjusting the carb jets, I set the high on the rich side at full throttle no load. As mentioned, it will be just right when under load. The low jet I don't lean out for a smooth idle either. I set it just rich enough so that it doesn't bog opening the throttle.

 

[Gooserider]

4. ALWAYS pull up on the nose of the bar when tightening the chain and while locking down the bar nuts...

I pull up on the chain at the top of the bar which esentially lifts the bar and snugs it against the adjuster at the same time so that the adjustment doesn't shift as the saw is worked.

When adjusting the carb jets, I set the high on the rich side at full throttle no load. As mentioned, it will be just right when under load. The low jet I don't lean out for a smooth idle either. I set it just rich enough so that it doesn't bog opening the throttle.

Sounds a bit odd to me, seems like it would cause you to get a strange tension adjustment on the chain. However if it works for you, that's what counts.

Gooserider

 

[CT-Mike]

Goose and LLigetfa,

Thanks for the good advice. The saws manual does say to hold up on the nose while setting the tension. I guess I will reset it when I get to the woods this morning.

Thanks again,

Mike

 

[kevin j]

Q the slack on the bar (it is a roller nose) to the point where the drive lugs can’t be pulled clear of the bar. Q




do you mean the side plates, the connector tie straps? that would be a bit tight. If you actually mean the drive lugs, that engage the rim wheel, it would be way too loose.

goose wrote a very clear post.

I hold the saw between knees/thighs, rest the bar tip on a log, and the weight of the saw/bar bends the bar upward when the nuts are loosened. left hand on top of chain to check, right one with scrench to adjust and snug it up. Then lift it up, run the chain free all the way around to find any tight spots, and readjust if necessary. Some people just watch the bottom of chain to snug it up until gravity no longer holds it away from the bar bottom, but that has always been too loose for me.

Long bars heat up and grow more with temperature, but really short bars (12 inch) may need a bit of extra tension also. I don't know why, but they seem to derail more easily with side loads when cutting small stuff, clearing ground brush or limbs less than an inche. I think it has to do with not being guided in the cut, not being held straight when using one hand, or snagging on the thin bark or maybe it is just the smaller chain pitch design.

I think the key is consistency: whatever method works for you, stay with it and you get a certain routine and feel or sound when it is just right.

 

[Bigg_Redd]

So I posted on another thread about my Jonsereds being very hard to start. My father-in-law used these saws while working as a lumberjack in NH, and they have had a hard life but always work.

Anyhow, I found the manuals online, and while reading through it I noticed that there is a decompression valve on the side of the cylinder. Imagine how much easier they are to start now.

On to saw tuning:

Started the saw for the first time since this past spring, and noticed that the chain freewheels while the saw is idling. I followed the instructions in the manual and backed the idle screw all the way out, to no avail. Due I need to turn in on the low speed screw?

I did check and the throttle returns to the stop when released.

Help please, I need to be cutting trees tomorrow morning.

Thanks,

Mike

Unless it's really hauling @$$ I'd let 'er spin.

 

[Gooserider]

So I posted on another thread about my Jonsereds being very hard to start. My father-in-law used these saws while working as a lumberjack in NH, and they have had a hard life but always work.

Anyhow, I found the manuals online, and while reading through it I noticed that there is a decompression valve on the side of the cylinder. Imagine how much easier they are to start now.

On to saw tuning:

Started the saw for the first time since this past spring, and noticed that the chain freewheels while the saw is idling. I followed the instructions in the manual and backed the idle screw all the way out, to no avail. Due I need to turn in on the low speed screw?

I did check and the throttle returns to the stop when released.

Help please, I need to be cutting trees tomorrow morning.

Thanks,

Mike

Unless it's really hauling @$$ I'd let 'er spin.

There's a bit of judgement involved, but having the chain stop moving when the saw is idled is an important SAFETY consideration - you only want the chain to move when you are actually revving the saw up to make a cut, it shouldn't move when idling (though the chain should always be treated as dangerous if the engine is running...)

It also puts a lot less strain on the engine not to be pulling the chain at low revs, and less wear on the clutch components if they are totally disengaged, not half touching and slipping.

Of course the safety purists will say the brake should be on any time you aren't cutting, which is not at all bad advice. Of course if the brake is on, the chain had better not be moving, but if you have to high of an idle, or the clutch springs are weak, you will really be putting a lot of drag wear on the clutch shoes and drum... IOW that chain should NOT move period....

However, w/ all that said, a chain that just "creeps" around the bar slowly is probably less of an issue than one that moves at a fast clip and pretty steadily....

Gooserider