Modifying a saw to make it last longer?

[Crofter]

I see the claim made but I am skeptical. Now dont get the notion that I am knocking the idea of modding saws; mine have been modded and it sure is fun. Of course the catch all term of modifying stretches all the way from merely enlarging the muffler opening to totally carving up its innards from bunghole to breakfast! What mods definitely increase longevity and where is the line crossed. Are there some saw uses that are really hurt by extensive mods!

 

[Sethro]

Anything to reduce heat or restrict exhaust flow helps longevity,fully adjustable carb.switch to 32:1 Mxt2(more oil=less friction=more power) .

 

[PES+]

Then why not more oil?

This question has been bounced around enough that I am thinking about doing some rough tests with various oil ratios with the MX2 and check cylinder and base temps with an infrared thermometer

 

[HiOctane]

I think for a woodsaw,a bit of enlarging,adjusting height ports after a bit of squish tightening as well muffler mod doesnt hurt at all longevity.You go over the line if you add ports,tighten the squish below .018 @ .020,running larger carb,play with timing.Im running a modded 346 done by a builder since two seasons and everything is fine.And im sure she could run with a hotter porting without being hurt.

 

[Four Paws]

I feel anything beyond a mild woods port and a well designed muffler mod will decrease longevity in some aspect. There is no doubt quite a bit of free power hiding on a factory saw, simply because with more power, more fuel is consumed, and the EPA frowns upon that. All will agree, on todays saws, a muffler mod will be the biggest, easiest gain to achieve.

Personally, I feel finger ports have no place in a woods saw. Gains are small and ring wear is accelerated. On saws with 2-ring pistons, it is advisable to flip the piston so ring-ends don't cross the finger. Port shape and width has just as much to do with ring wear.

25-35% gains are reasonable with a woods port. And although the engine will turn more RPM, the lightened piston will reduce internal loads. Productivity will increase, and I think it would be hard to prove any acceralted wear or decreased longevity/reliability as a direct result. It is the last 5-10% gains that come at a hefty price.

 

[Lakeside53]

As pes+ says... need some testing rather then just "intuition".

Sure, opening up a muffler can get heat heat out, but... you end up with ( or the potential for) more power, and more power is more heat. Does the extra power create more heat than is lost though opening up the muffler? Are the heat differences between a muffler modded saw and a non-modded saw really an issue? I'm not so sure.

Port and other mods certainly raise power and consequently heat. I hear lot of talk about power gains, but never any discussion about improving the cooling air flow. Saws are designed to run correctly at a certain duty cycle of their rated HP (not 100%), and there is not a huge margin. The fan, shrouds and cylinder fins are all important, as is "how clean" they are. Then there is that pesty little piston temperature -you can only transfer heat from the piston at a certain rate, and while cylinder wall temperature is part of the equation, the thermal path though the rings is a bottleneck.

 

[kurtty]

more oil isn't always good.
those parts can only take so much lubrication. any extra doesn't do anything but burn.
oil burns hotter than gas which is going to give you added heat.
gas also helps cool the engin. less gas also is going to add to your heat issue.
all this extra heat is going to wear out your saw faster. and give you a slight performance reduction.

run only top of the line sythentic oil at even 50:1 is providing more than enough lubrication while also keeping your saw temp low. this is especially true on newer saws with higher compression.

 

[Steve128]

My reading

Then why not more oil?

This question has been bounced around enough that I am thinking about doing some rough tests with various oil ratios with the MX2 and check cylinder and base temps with an infrared thermometer

Test would be great. Not by any means an engine expert, but if you do some reading on BITOG there is a poster named Cujet who raced and tested two stroke engines for quite some time with a corporate sponsor. Their testing indicated more power up until I think to about 24 to 1. And in cart racing I have attended at the pits, many are running 20 to 25 to 1. Running very high rpm.

There are of course different opinions. In motorcyles the 125 two strokes usually run richer than the bigger bores, but they do run higher rpm.

Now to counter, these are racing numbers, not chain saw engines, and most were water cooled. The ones I asked about were running Motul 800 or MX2T (Racing2t).

I'm the kind of gun who filled up his car oil to the max of the dip stick. I just don't see why when the oil lubricates one would run as high a ratio as possible. Why not run as rich as possible? With a carburetor properly adjusted, I haven't noticed any more smoke or wear from running greater oil amounts. To me, on the edge of lean, burned piston. On the edge of too much oil, spark plug no sparky.

I have read that some members assert aren't modern oils better so we can run leaner ratios. Modern oils are definitely better. Yet, aren't modern oils so much better that we can run them richer with no greater smoke or carbon buildup?

However, there is a good number of members/mechanics here who have seen 50/1 do the job well.

Like I said, I am no expert.

 

[PES+]

It depends on the oil and the additive package

Way back when the only oil that would stay in suspension reliably in alcohol fuels was castor oil the purest was the best and it had to have the best degum ability. Castor seemed by it's nature to have a certain "personality" of it's own.

Castor in it's best form was very finicky in mix ratios and seemed to like a higher ratio when mixed with methanol. If you attempted to use too little the remaining oil would get sticky and you would lose power and lube.

If you added too much it would cause deposits and then starve the bearings of lube.

Castor did not do much actual burning due to it's high flash point but it was real tricky to use.

The MX2T seems to be a very clean oil as far as deposits inside the engine and that is why I am curious to run some simple tests with ratios with it.

All petroleum base 2 stroke oils that I have ever seen do appear to burn to a higher degree than synthetics and even a good castor.

Some of the new saw companies oil does smell like they are blending back in some castor oil because nothing else smells like castor oil

The alcohol suspension aspect is a fact of life for all gasoline now available from normal gas stations here in the US now due to country wide distribution from a very small number of refineries

It doesn't make much difference if the pump is labeled gasahol or not because different blends of gas can use other oxygenates or too much of one that acts in the same way.
ETBE and MBTE have a finite lifespan and degrade back into similar alcohol forms from which they are created
Ethanol and methanol respectively

 

[Al Smith]

I suppose it's all about opinions ,some more stated with great conviction than others.

Cooling and lubrication is often the issue,thus the great oil wars that seem to go on forever .Mine on that issue is good modern mix oils at 32 to 1 and on that I rest my case .Others can do as they please .

More times than not the mufflers on modern saws are restictive which lowers overall power output and raises operating temperatures. I am of the opinion that a simple rework of the muffler followed by a readjustment of the carb would prove beneficial in raising power output with out shortening the life span of the engine.

The notion that attempting to make a 70 cc saw run with a 90 is both preposterious and non realistic .It may do so for a short time but will never make it in the long haul.Of course if a person wants bragging rights about having a super saw and doesn't care how long it lasts,go for an all out modification.Remember though the age old adage that what goes extremely fast does not go extremely long.

 

[Crofter]

I wish Timberwolf was here to give us some figures at where the max piston decelleration is on approaching BDC, also max rod angularity and what position the piston skirt is in relation to the intake port at this time. This is the area that will be affected greatly with modifications that involve enlarging ports to maximum width. It is also an area that must be sealed by the piston skirt to enable base vacumn and compression. There is not a lot of bearing area for the skirt of the pison to ride on either side of the port and it is common to reduce it further to about 25 thou wide to get the maximum port width. The increased rpm that should go with modding, raises thrust forces and wear on the square of the increase. ( piston lightening can help compensate for but not reduce the increased rpm loading). Increased loading from increased output on reduced load bearing area????
I can buy the lower head and cylinder temperature from the initial muffler opening but if you further increase output a lot I bet you are back to higher temps than the bone stock setup was indicating so I am not sure you can claim lower operating temperatures as a longevity factor.
Now as TreeCo suggests, because of the increased speed maybe you can cut more wood overall before your saw wears out but I bet not if the wood cutting was milling!
I'd say Four Paws is on track with saying you can get the first gains of 10% or so (beyond muffler) without bearing too much pain but it gets more involved after that but how do you measure the pain of humiliation when someone outcuts you at the get togethers though? That other guy has a saw that has been taken further or better chain and technique. You just got to go after him!

 

[PES+]

Wut he said

I wish Timberwolf was here to give us some figures at where the max piston decelleration is on approaching BDC, also max rod angularity and what position the piston skirt is in relation to the intake port at this time. This is the area that will be affected greatly with modifications that involve enlarging ports to maximum width. It is also an area that must be sealed by the piston skirt to enable base vacumn and compression. There is not a lot of bearing area for the skirt of the pison to ride on either side of the port and it is common to reduce it further to about 25 thou wide to get the maximum port width. The increased rpm that should go with modding, raises thrust forces and wear on the square of the increase. ( piston lightening can help compensate for but not reduce the increased rpm loading). Increased loading from increased output on reduced load bearing area????
I can buy the lower head and cylinder temperature from the initial muffler opening but if you further increase output a lot I bet you are back to higher temps than the bone stock setup was indicating so I am not sure you can claim lower operating temperatures as a longevity factor.
Now as TreeCo suggests, because of the increased speed maybe you can cut more wood overall before your saw wears out but I bet not if the wood cutting was milling!
I'd say Four Paws is on track with saying you can get the first gains of 10% or so (beyond muffler) without bearing too much pain but it gets more involved after that but how do you measure the pain of humiliation when someone outcuts you at the get togethers though? That other guy has a saw that has been taken further or better chain and technique. You just got to go after him!

A whole nother language *shifts mental gears*

 

[RiverRat2]

Do You mean,,,, Enhance or improve,,,, exhaust flow????

Anything to reduce heat or restrict exhaust flow helps longevity,fully adjustable carb.switch to 32:1 Mxt2(more oil=less friction=more power) .

:monkey: :monkey: BTW I agree on the more oil!!!! for sure no less than 40:1 but mostly 32:1 for me

 

[bobc]

Just a thought, At work I use a lot of titanium nitrate coated endmills and drills in both hss and carbide it really does add life to the cutters. I wonder if this coating could be applied to cylinders and pistons that is if it can be applied to aluminum or possibly over chrome? Might already be done for all I know? I bet this coating would increase longevity of a saw.
Oh yea wouldent more oil equal more carbon?? Wont that cause scoring of piston and cyl?

 

[Al Smith]

Oh yea wouldent more oil equal more carbon?? Wont that cause scoring of piston and cyl?

I suppose there are some that subscribe to that theory,I however do not.

Unlike a few that just talk about,I do believe I can prove it as I have two saws that have ran 32 to 1 in them for the 30 years I've owned them.No carbon that I can see ,still plugging away as good as when they were new.

As I said ,it's just my preference, 40 or 50 to 1 most likely would be fine.32 to 1 doesn't carbon them up but it does oil slick the sides of them just a tad bit.Not a big deal unless you're a fuss budget about a tidy saw.