Stihl 044 Ring Gap

[Indy Red]

Hi All, the rebuild of my 044 is going well and really enjoying the learning experience, whilst waiting for parts thought I would ask what the piston ring gap should be? The current ones have a gap of 0.40mm, they may not even need replacing but wanted to give it a right good freshen up as compression test was at 140 and was expecting higher tbh

Also was checking Piston for wear and I have a reading of 0.10mm gap between piston and cylinder, acceptable?

Cheers,
Rob

 

[Mad Professor]

Hi All, the rebuild of my 044 is going well and really enjoying the learning experience, whilst waiting for parts thought I would ask what the piston ring gap should be? The current ones have a gap of 0.40mm, they may not even need replacing but wanted to give it a right good freshen up as compression test was at 140 and was expecting higher tbh

Also was checking Piston for wear and I have a reading of 0.10mm gap between piston and cylinder, acceptable?

Cheers,
Rob

Rings are getting a little worn I'd replace those anyway. New P/C clearance is ~0.0025", yours is ~ 0.004" so has some wear.

 

[Indy Red]

Rings are getting a little worn I'd replace those anyway. New P/C clearance is ~0.0025", yours is ~ 0.004" so has some wear.

I absolutely suck at this inches thing my feeler gauges sadly only go up in .5 so 0.10mm 0.15mm etc etc, what one in mm would you say would fit the best for that 0.0025"

Will get myself a better set at some point.

 

[atpchas]

I absolutely suck at this inches thing my feeler gauges sadly only go up in .5 so 0.10mm 0.15mm etc etc, what one in mm would you say would fit the best for that 0.0025"

Will get myself a better set at some point.

Try
https://www.rapidtables.com/convert/length/inch-to-mm.html

 

[Mad Professor]

I absolutely suck at this inches thing my feeler gauges sadly only go up in .5 so 0.10mm 0.15mm etc etc, what one in mm would you say would fit the best for that 0.0025"

Will get myself a better set at some point.

1 inch = 25.4 mm Either multiply (inches to mm) or divide (mm to inches) by 25.4

Forgot you were in the UK. 0.0025" = 0.0625 mm so 0.05 mm = 0.00197 " 0.10 mm = 0.00394"

 

[Indy Red]

Thanks for the help guys

 

[Wizard]

Alternatively, you can use mm x 0.039

 

[Indy Red]

I have purchased a set with dual readings on to take the math out of it

 

[Wizard]

To calc the area of a circle;

Most use PI x radius squared. There is a better way. Anyone care to chime in?

 

[Gord404]

in a new set of rings on a bore that size I usually set them to about 10 thou for new rings in a fresh cylinder cleaned up or new- usually use cabers - have a box full or various sizes - use a piston to push the rinin the cyliner to make sure they are streight- imo

 

[Mad Professor]

Alternatively, you can use mm x 0.039

That is only two significant figures and less accurate. 0.0390 is better. The 1/25.4 ratio is exact to 3 figures.

I forgot. Do You understand precision vs accuracy? You can have one , the other, or both, measuring things.

To calc the area of a circle;

Most use PI x radius squared. There is a better way. Anyone care to chime in?

I can use calculus to derive it. Don't need to memorize formulas.


I can lay out timber frame joinery with a compass, plumb bob and snap line. No rulers or squares needed, perfectly square.

Can You:

1) a Layout a perfect 1,1, root 2/45o 45o 90o knee brace and tenons, just using a compass and straight line? (A 3 4 5/30o 60o 90o brace, takes a bit more work....)

b) How about the mortices? In a post and tie beam to accept the brace you made in a above?


2) Can you layout a perfect "Star of David" using a line and a compass? Then use it to layout a perfect post,tie beam and connect them?

I can here is a hint, but then the cat is out of the bag..... Drawing copyright MP



It's just basic geometry.........

 

[Indy Red]

Ok so I have just taken another reading with my good set of feeler gauges and it appears they were even more worn than I thought, readings were 0.25" or 0.63mm one ring was much worse than the other

 

[huskihl]

Ring end gap should not be tighter than .004” per inch of bore. So .008” on a 50mm bore is as new

 

[pioneerguy600]

I absolutely suck at this inches thing my feeler gauges sadly only go up in .5 so 0.10mm 0.15mm etc etc, what one in mm would you say would fit the best for that 0.0025"

Will get myself a better set at some point.

Every 044 and MS440 I have built got .008 to .009 ring end gap and each and every saw is still out there working, just one has acquired enough hours to now need a new set of rings and possibly a piston once I get it apart and measure them. With 28 of them out there cutting wood it is a good testament to their toughness.

 

[Indy Red]

Every 044 and MS440 I have built got .008 to .009 ring end gap and each and every saw is still out there working, just one has acquired enough hours to now need a new set of rings and possibly a piston once I get it apart and measure them. With 28 of them out there cutting wood it is a good testament to their toughness.

On a scale of 1 to 10 how worn is 0.25" Have new ones to fit regardless but I am shocked that the saw is fairly worn even though it is very low hours, It was used by the Environment Agency to cut into dirt to remove hawthorn roots with a carbide chain, Stihl made them a special clutch cover with a flap on to empty out the dirt, It has been in storage for over 20 years.

 

[pioneerguy600]

On a scale of 1 to 10 how worn is 0.25" Have new ones to fit regardless but I am shocked that the saw is fairly worn even though it is very low hours, It was used by the Environment Agency to cut into dirt to remove hawthorn roots with a carbide chain, Stihl made them a special clutch cover with a flap on to empty out the dirt, It has been in storage for over 20 years.

Well 0.25 is a quarter inch , that would be beyond any ring end gap I could envision. I would consider .030 totally worn out and would never put a saw back together with rings showing .025 as that would affect compression quite a bit. In my own case I have many new sets of piston rings in my parts compartments so no waiting for parts to arrive, makes saw building so much easier. Because I own and run many of this model of saws I keep all parts on hand and can built an entire saw from just my parts supply. I fully understand most people do not have this supply on hand and may have to put a saw back to work with less than stellar parts.

 

[Indy Red]

Just double checked and confirmed to be 0.25"
On the parts wait, I am totally against replacing parts with non genuine parts, If I did that it would no longer be a 044, but also understand some people just need to get it running again for as cheap as possible due to financial positions etc etc. Also loggers and the like cannot afford for a saw to be down for extended periods, mine just sits on the bench until they arrive.

 

[Mad Professor]

I have purchased a set with dual readings on to take the math out of it

America, besides scientists and engineers, have not fully adopted the metric system. All my devices at home are still in standard measure/inches. Math just need some work on it.

Ok so I have just taken another reading with my good set of feeler gauges and it appears they were even more worn than I thought, readings were 0.25" or 0.63mm one ring was much worse than the other

re- Check measurements and/or math. Always do that. You are off a decimal point in the conversion.

Rings are cheap but good if you get Cabers compared to OEM, but still check/fit them.

 

[pioneerguy600]

Just double checked and confirmed to be 0.25"
On the parts wait, I am totally against replacing parts with non genuine parts, If I did that it would no longer be a 044, but also understand some people just need to get it running again for as cheap as possible due to financial positions etc etc. Also loggers and the like cannot afford for a saw to be down for extended periods, mine just sits on the bench until they arrive.

I recommend OEM parts as a first choice and stock only OEM . but yes there are people and cases where AM parts may make sense for them.

 

[Wizard]

Being a motorcycle mechanic, I took interest when a fellow hotrodder biker told me that new refits didn't need any end gap at all, and to run at full throttle at first start up. He said the resultant end gap therefore would be optimal (minimum tolerance or thereabout).

I have never tried this, but I believe it might have merit, as my rering jobs would open the gap up closer to max tolerance on next disassembly. If a cylinder has been honed, as many are, you are , right from jumpstreet enlarging the bore diameter as you curl over the peak heights as piston reciprocates.

A hone manufacturer will verify that this occurs.