Sealed bearings/crankcase compression

[Terry Syd]

Gawd I hate getting old, nothing works anymore. I got to thinking about the area inside the crankpin and 'ding' - don't forget to add the Pi function!

The area in the pin is not 1.68 cc, it is 5.3 cc. That puts the stuffing around 40% of the material I took out. I'll put the saw together that way and decide after testing if I want to stuff the scallop in the cases.

 

[tdi-rick]

Gawd I hate getting old, nothing works anymore.
[snip]

Well, there's no hope for me then, I'm quite a bit younger than you and my brain went to mush years ago.

I keep telling the management in the local nursing home to make up a room for me, just in case......

..at least I can still work the key pad to get out of the dementia section, for the time being at least.....

 

[Jacob J.]

I was leaning towards the shielded bearings. They have a small gap (no contact seal, low friction) on the inner race. The mixture in the crankcase would work its way into the bearings and the petrol would boil off leaving the oil behind. The shields would act as a reservoir for the oil to pool in.

I'm not poo-pooing your idea of using shielded bearings in your saw, but Stihl went through these motions years ago and tossed the idea of shielded bearings in a saw. Sawdust and other debris builds up behind the shields and leads to premature failure.

 

[Terry Syd]

Rick, yeah the wife tried that BS line with me - "Don't worry, you've probably forgotten more than most people will ever know" Which I replied, "remind me how that is a GOOD thing". (I remember some stuff, anybody want to learn celestial navigation?)

Jacob, if that much crud got past the gap on the shields, I'd hate to think how much got flushed through the engine. Where did you pick up this bit of Stihl history?

 

[Jacob J.]

Rick, yeah the wife tried that BS line with me - "Don't worry, you've probably forgotten more than most people will ever know" Which I replied, "remind me how that is a GOOD thing". (I remember some stuff, anybody want to learn celestial navigation?)

Jacob, if that much crud got past the gap on the shields, I'd hate to think how much got flushed through the engine. Where did you pick up this bit of Stihl history?

I worked in Stihl dealerships on/off for seven years...

Saws do eat a lot of debris through the course of their use, it's a part of the wood cutting animal. You Aussies have it the worst, with your dry conditions and super hard wood...

 

[pioneerguy600]

I'm not poo-pooing your idea of using shielded bearings in your saw, but Stihl went through these motions years ago and tossed the idea of shielded bearings in a saw. Sawdust and other debris builds up behind the shields and leads to premature failure.

My 044`s are still doing fine.
Pioneerguy600

 

[Jacob J.]

My 044`s are still doing fine.
Pioneerguy600

You're the exception to the rule though Jerry. The "average" user isn't nearly as meticulous as you are.

 

[pioneerguy600]

You're the exception to the rule though Jerry. The "average" user isn't nearly as meticulous as you are.

One is nearing 500 tanks of fuel, actually at 493, the other has 346 run through it. Give them another 2 years, we will see then.
Pioneerguy600

 

[Terry Syd]

The stuffed crankpin was enough to bring the torque peak up a little higher in the powerband. Previously when I dogged the saw in the revs were lower, now the revs are higher and the saw is doing more cutting. The powerband is still wide enough to be a good work saw. I don't think the engine needs anymore crankcase compression, good thing, can't get the sealed bearings anyway.

I thought that the idle might get a little bit richer from the increased compression in the case blowing back through the carb, it did, in fact more than I had anticipated.

I had to lean out the low speed needle and it adversly affected the acceleration and torque off the bottom. I'm going to drill a small bypass hole in the throttle plate to allow more air at idle. Then turn the low speed needle out again to pick up the acceleration off idle.

I'll try the bypass hole rather than enlarge the cutaway in the throttle plate. The cutaway allows air to move both ways across the idle circuit, out, then in again, thus picking up extra fuel at idle. With the bypass hole the air can move through without 'double-dipping' on the idle circuit. The smallest drill I have is .75mm, so that's what I'll try first.

EDIT: I got to thinking about it and the extra crankcase compression shouldn't have made that much change in my low speed jetting. Then I remembered I had changed the crankseals because both of them had been damaged by sawdust getting under them. I must have had a small leak that leaned out the idle. - Now I have to properly set up the carb with good crankseals in the engine.

 

[AUSSIE1]

The stuffed crankpin was enough to bring the torque peak up a little higher in the powerband. Previously when I dogged the saw in the revs were lower, now the revs are higher and the saw is doing more cutting. The powerband is still wide enough to be a good work saw. I don't think the engine needs anymore crankcase compression, good thing, can't get the sealed bearings anyway.

I thought that the idle might get a little bit richer from the increased compression in the case blowing back through the carb, it did, in fact more than I had anticipated.

I had to lean out the low speed needle and it adversly affected the acceleration and torque off the bottom. I'm going to drill a small bypass hole in the throttle plate to allow more air at idle. Then turn the low speed needle out again to pick up the acceleration off idle.

I'll try the bypass hole rather than enlarge the cutaway in the throttle plate. The cutaway allows air to move both ways across the idle circuit, out, then in again, thus picking up extra fuel at idle. With the bypass hole the air can move through without 'double-dipping' on the idle circuit. The smallest drill I have is .75mm, so that's what I'll try first.

EDIT: I got to thinking about it and the extra crankcase compression shouldn't have made that much change in my low speed jetting. Then I remembered I had changed the crankseals because both of them had been damaged by sawdust getting under them. I must have had a small leak that leaned out the idle. - Now I have to properly set up the carb with good crankseals in the engine.

Great to hear it worked out Terry.

 

[Terry Syd]

Yeah, it didn't need as much stuffing as I thought in order to bring the torque peak up where I wanted it.

That's about all the mods I can make to the engine without the rev limiter being a problem. The last time I was cutting I was finishing up with a dull chain and the limiter was making itself known all too often.

Hmm, maybe that will become my Homeowner 'Dull Chain Indicator'. If anyone asks why the engine is missing - I'll tell them it is the DCI.

 

[tdi-rick]

[snip]

Hmm, maybe that will become my Homeowner 'Dull Chain Indicator'. If anyone asks why the engine is missing - I'll tell them it is the DCI.

I love these threads, some good lateral thinking.

 

[Terry Syd]

Instead of drilling the bypass hole, I took a rat tail needle-file to the top of the throttle plate (on the side away from the idle circuit). There was already a very small cutaway so I decided to enlarge that instead of drilling the throttle. If I went too far with my enlargement, it would be easier to solder a thin bead on the edge of the plate - I wouldn't have to heat up as much material. I could also do it without disassembling the carb.

I didn't take much out the first time. There was a slight improvement, but now I had an idea about how much I might need to remove.

I think the second filing of the notch is pretty close. I opened the LS screw almost 1/4 turn and turned down the idle. The saw will smoothly idle in any position - and when I hit the throttle the response is instant.

Next mod is to englarge the air filter element by 50%.

 

[AUSSIE1]

Good to hear Terry.

Silver solder is a stronger solder to use over the soft electrical solder I found when soldering throttle plates.