mixing ratios for 2 stroke chainsaws

[North by Northwest]

Interesting that you mentioned 'stuffers.' I've been concentrating on other parts of the engine, but have reserved increasing the primary compression figures (crankcase compression) for miserable rainy winter days.
How did you fabricate the stuffers and how did you secure them in place? Did you add any additional weight (tungsten?) to the lobes to help balance the extra weight of the stuffers? Also, did you notice any more torque at higher RPMs due to the higher compression ratios? What kind of ratis did you start with, and what did you end up with? I'm guessing that any small gains would be hard to feel in sawing firewood, but in a saw-mill rig it might be more apparent.
What was your intake duration before your porting? What kind of improvement did you see with the 143 deg duration? More higher-rpm torque?
Thanks NNW!
-doug

It's a 357 xp Doug , quad ports & factory stuffers .It had plenty of grunt from the factory , mid range was its weakness as a stock 57 cc saw . It has decent high rpm horsepower as a xp series saw . I will send you a pm for numbers & compression spec's , so as not to bore the other folks on the oil thread brother !

 

[North by Northwest]

No , i meant when it meets the intense heat of combustion , & falls out of solution , (wetting metal surfaces) it would wet the wrist pin & piston skirt & ring assembly . I would not wish the crankcase being that hot & flashing lol . What other migration potential do you recognize ? lol.

Ben , you did not enlighten us further to your to your other contributing potential for oil migration within a premix 2T engine ? Please elaborate further within the best explanation of this rational brother !

 

[skeet88]

It's a 357 xp Doug , quad ports & factory stuffers .It had plenty of grunt from the factory , mid range was its weakness as a stock 57 cc saw . It has decent high rpm horsepower as a xp series saw . I will send you a pm for numbers & compression spec's , so as not to bore the other folks on the oil thread brother !

What oil thread ? This thing has run off the tracks at least a dozen times! All good though I am learning something new every day. Y’all Be Good!

 

[thenne1713]

Sorry NNW, been busy trying to get my new (stupid) P320 XTen running right. Mags keep jamming-up with 200 gr HC. Sig sucks.
Anyway, the 3120xp:
Exhaust opening = 98 deg ATDC, duration = 164 deg.
Intake duration = 135.7 deg
And oops, looking at my spreadsheet on the engine, squish is actually 0.580mm = 0.0228" (still kinda tight for the compression and squish-band width of 9.5mm)
I've been thinking of getting it just a hair tighter.... but calcs indicate that it's already too tight. No indication of detonation with the fuel being used, though.
Blowdown is just a hair over 22 degrees.
Transfer duration is 120 deg.
Nothing too radical, though I don't know if I want to try 93 octane as before. Seems to run smoother and harder on 100LL for the time being. And Aviation fuel is no more expensive than the available non-alcohol 93 pump gas around here.
I've been thinking of increasing intake duration to around 140 - 142 deg.
The head, piston deck, and intake and exhaust ports have had the 350 deg baked Cerakote Piston-Coat applied and it does seem to help with keeping the heat inside the combustion chamber rather than getting the piston undersides and head too hot.
I use pretty cool plugs -- B10HS.

Funny (not), I have the engine apart again, checking things out. I purchased an OEM piston last year to put on the shelf for a snowy day. I just weighed it and it's a whole 2.3g lighter than my messaged and lightened OEM piston that I had been running. WT....? Measured it all over and found some of the webs are slightly thinner, but the big surprise was some minute cracks in the casting right at the window/skirt corners just under the lower ring, on two sides. Bugger. Good luck exchanging that piece of junk AL.

The OEM rings (junk) that I had in there lasted maybe 1.5 hrs. Initial gap was something like 0.445mm, should have been closer to 0.21mm. I ran them anyway because I couldn't find any G15H cabers at the time. Everyone was selling those F-Cast rings.

The thing ran really powerful for about half hour straight out of the shop (typical break-in stuff, short bursts up to roughly 11000rpms). Then the rpm's started slowing down roughly 200-300 rpm's lower (tinytach). No big deal though. After 1.5 hrs, took the pipe off and saw minute scratches on the cylinder on the intake side. Fug!
Took the top off and found minute scratching on the exhaust side too. Double fug! Ring gap grew to 0.650mm on both rings! Max-gap replacement time should be around 0.60mm. These husqvarna OEM rings suck. They're lazered 'KO B8' for Komarov s.r.o. The circumferential exterior edges of the rings looked a bit chipped in some places, but not really localized to the ports. Initially the edges were quite sharp, not chamfered.
Finally got some G15H cabers in yesterday. Nicely chamfered edges. Gaps acceptable at 0.253mm.
Crankcase has been thoroughly flushed, all bearings look and feel good, seals are 1.5hrs old, so going to slap on the rings and see how she goes. Again.
Anyone know where I can find a Meteor piston for the 3120, or should I just get another OEM at inflated cost?

re: scratches, did you pull air filter and see if fines/ debris getting past the filter?

 

[ApePilot]

re: scratches, did you pull air filter and see if fines/ debris getting past the filter?

I was stupid. I used a brand-new K&N filter. They're fine for keeping big gravel out of the carb, but anything than smaller than gravel flies right through like pollen through a screen door, like a c19 cyst through a face-diaper, etc, etc. I'll never ever use K&N filters of any kind again.

I flushed the crankcase with low-pressure kerosene propelled by a 12v diesel vane-pump, with the crankcase suspended upside-down while rotating the crank, pouring into a bucket with a bunch of rare-earth magnets taped on the bottom exterior surface of the white-plastic bucket. The alarming thing was there were some very minute ferrous particles caught by the magnets. At first I thought the rod and crank bearings were going south, but inspection revealed they were good. The way I have the carb (WB37) situated with the linkages and K&N pod filter, there could have been plenty of steel filings from the clutch and/or chain making their way easily through the K&N. At least that's what I hope; the alternative would mean $$$$. The K&N has big enough holes in it's gauze weave to see through, even when oiled.
If there were scratches above the transfers, I'd be worried about the bearings. No scratches are present above the transfers. Just very minute scratches above the exhaust and inlet ports, as well as some very small scratches on the inlet-side piston skirt. Hardly anything to miss sleep over. The piston deck looks fine as did the rings' surfaces.
The fuel filter is a new pleated paper filter designed for small aircraft engines; the fuel was fresh 100LL straight from the local airport contained in a new, thoroughly cleaned-out polyethylene fuel jug. So the filings were likely not from the fuel.

A little side-note: The diesel vane-pump was purchased at Car Quest. Made of chinesium. Also a pleated-paper pre-filter. After noting a visible quantity of extremely minute ferrous particles being collected by the magnets with only the kerosene cycled through the pump, I decided to put a big diesel spin-on filter after the pump. The first base and filter purchased at CarQuest had a supposed filter micron-rating of 10um particle size. Even with the kerosene being recycled through the pump system, there still were those super-minute particles. After a lot more research on the filter, I found Baldwin (the manufacturer) rated these at 20um @ 75% efficiency rather than what Carquest's verbiage indicated. I exchanged that base for another base (Baldwin FB46185) that would fit a Donaldson P551313 filter rated at 5um @ 99.9% efficiency. That's the filter most of the tractor-trailer and heavy equipment mechanics suggest using for a 1-14 thread-size base . That setup pretty much cleared up any remaining ferrous debris in the kerosene, and anything that was being shed by the chinese vane-pump. After success there, I re-flushed the crankcase with and found no more ferrous debris in the flushing.
So was the initially-detected ferrous debris really coming from the crankcase or was it coming from the chinese vane pump? Other than the super-fine ferrous powder, I did initially find a couple of larger particles, though quite small. Still, those larger particles could have been the pump breaking-in. Whatever. I think (hope) it's all good now. Lesson: Never use K&N!

 

[link]

2,5% oil is plenty, because 2% is enough.

 

[ApePilot]

What oil thread ? This thing has run off the tracks at least a dozen times! All good though I am learning something new every day. Y’all Be Good!

yup. Me too. I've found most of my questions about 2Ts here at ArboristSite, and much of the juicy info is hiding in the threads that aren't related to the juicies.

 

[ApePilot]

2,5% oil is plenty, because 2% is enough.

Funny. I guess when all you operate are the small displacement engines at very light, intermittent load (firewood?), or you're putt-putt-putting about in the woods with your 2T bike, then yeah, 50:1 is ok. But dare try making that thing scream on continuous, high-torque operations and high heat and all of a sudden that 50:1 will be your bane. Especially air-cooled engines like most of us run.
IMEO (in my experienced opinion), the F/O mixture should reflect the load-factor at which you're most using the engine. Light to medium torque with intermittent use (firewood, brush-clearing, light weed whacker use, etc) could deal with 50:1, since while idling, the engine is pooling the excess oil in the bottom of the crankcase. But operations (milling, dirt-track racing, kart racing, etc) of high rpm at high torque for sustained periods of time (high heat build-up, no chance of oil pooling) calls for more and higher-quality lubrication.

 

[ZeroJunk]

I have an 056 Mag II that never came with anything but a metal screen for an air filter. Lot of older Stilhs did. No problem, sawdust is not particularly abrasive. Would not try it with a cut off saw.

50 to 1 with new generation lubricants is just fine for anything other than milling. Unless you are just stupid, which is entirely possible.

 

[bwalker]

Ben , you did not enlighten us further to your to your other contributing potential for oil migration within a premix 2T engine ? Please elaborate further within the best explanation of this rational brother !

Things like crank case volume, intake port timing, tuned pipe tuning, transfer port size and orientation.

 

[North by Northwest]

Things like crank case volume, intake port timing, tuned pipe tuning, transfer port size and orientation.

Absolutely Ben , the volumetric efficiency of the crankcase along with enhanced scavenging effects & better flow due to optimal transfer sizing & positioning , will most definitely effect the migration potential . I agree , thanks for the input brother !

 

[North by Northwest]

Funny. I guess when all you operate are the small displacement engines at very light, intermittent load (firewood?), or you're putt-putt-putting about in the woods with your 2T bike, then yeah, 50:1 is ok. But dare try making that thing scream on continuous, high-torque operations and high heat and all of a sudden that 50:1 will be your bane. Especially air-cooled engines like most of us run.
IMEO (in my experienced opinion), the F/O mixture should reflect the load-factor at which you're most using the engine. Light to medium torque with intermittent use (firewood, brush-clearing, light weed whacker use, etc) could deal with 50:1, since while idling, the engine is pooling the excess oil in the bottom of the crankcase. But operations (milling, dirt-track racing, kart racing, etc) of high rpm at high torque for sustained periods of time (high heat build-up, no chance of oil pooling) calls for more and higher-quality lubrication.

I agree Doug , I have always stated that oil ratio in combination with proper tuning of the saw to the application is vital to protecting your investment . I also agree with the analogy which that not only does more oil better seal the rings for optimal compression (proven fact) . But selecting a oil with proper additive packages , can also provide a cleaner & more efficient running engine with better overall performance also !

 

[ZeroJunk]

I would be simply curious if any of you have ever lost a saw doing anything other than milling. Or, are you just babbling ?

I have run all kinds of saws for 50 years and work on them for a living. I go by the manufacturers recommendations.

Do you not find it even a little curious that they just run and run for me and not for you.

Like maybe you have something else going on ?

 

[sean donato]

2,5% oil is plenty, because 2% is enough.

My nitro engines run a minimum of 10% oil. Guess thats too much by your standards.

 

[Kel71]

If you have 89 octane gas and mix it at 50:1, 40:1, and 32:1. What is your octane
with the oil mix?
50:1 ?
40:1 ?
32:1 ?

 

[sean donato]

Quality oil shouldn't effect octane rating much is at all.

 

[rogue60]

I would be simply curious if any of you have ever lost a saw doing anything other than milling. Or, are you just babbling ?

I have run all kinds of saws for 50 years and work on them for a living. I go by the manufacturers recommendations.

Do you not find it even a little curious that they just run and run for me and not for you.

Like maybe you have something else going on ?

Really that's interesting so you work on saws for a living but how/why if the manufacturers recommendations are so good?
I find it amazing a "mechanic" could have such a narrow mind and such little understanding of oil and the benefits of adding more than what the "manufacturer recommendations" and that being 50:1 and tuned lean from the factory more than often now day's.
But I guess if one never strays from what the manufacturer recommends one would never know or learn anything more than what the manufacturer recommends. ignorance is bliss..

 

[ZeroJunk]

Really that's interesting so you work on saws for a living but how/why if the manufacturers recommendations are so good?
I find it amazing a "mechanic" could have such a narrow mind and such little understanding of oil and the benefits of adding more than what the "manufacturer recommendations" and that being 50:1 and tuned learn from the factory more than often now day's.
But I guess if one never strays from what the manufacturer recommends one would never know or learn anything more than what the manufacturer recommends ignorance is bliss..

I have worked on a ridiculous number of pieces of equipment, maybe 30% chainsaws, the rest trimmers, blowers, pole saws, etc.
The majority are simple flooded, set so long the carb has a bugger in it, dropped out of a tree, run over, ignition gone bad, straight gassed. Primer has a hole in it.That type of thing. There are occasional internal defects, ciclips come out. Had two stacked on top of each other a couple of weeks ago. That type of thing. Warranty repairs.

The only oil related issues I see is they forgot to put any in it.

That is the real world .

 

[OM617YOTA]

You're both probably right.

ZJ has said he mostly works on homeowner stuff, if a logger was a part of the group then he had no clue. For almost all homeowners, they will never rack up 250 hours on their saw. If you have a suburban lot and don't heat with wood, you probably don't put 20 minutes per year on your chainsaw. If you do heat with wood, you probably still don't put 5 hours per year on your chainsaw. At 5 hours per year, it would take a person 50 years to rack up 250 hours. 100:1 ratios may well make the saw last just fine at this usage rate. Not ideal, but the homeowner will still never wear the saw out. This backs up ZJ's claims.

We also have people here on the site who are pro fallers and loggers, and will put 250 hours on their saw in a couple months. They will legitimately wear a saw down to low compression in a year or two, plus we have the people who work on these faller's saws. They may well agree, 50:1 isn't enough oil to make the bearings last until the rings are worn and compression is low. This backs up the pro's claims.

 

[North by Northwest]

You're both probably right.

ZJ has said he mostly works on homeowner stuff, if a logger was a part of the group then he had no clue. For almost all homeowners, they will never rack up 250 hours on their saw. If you have a suburban lot and don't heat with wood, you probably don't put 20 minutes per year on your chainsaw. If you do heat with wood, you probably still don't put 5 hours per year on your chainsaw. At 5 hours per year, it would take a person 50 years to rack up 250 hours. 100:1 ratios may well make the saw last just fine at this usage rate. Not ideal, but the homeowner will still never wear the saw out. This backs up ZJ's claims.

We also have people here on the site who are pro fallers and loggers, and will put 250 hours on the you their saw in a couple months. They will legitimately wear a saw down to low compression in a year or two, plus we have the people who work on these faller's saws. They may well agree, 50:1 isn't enough oil to make the bearings last until the rings are worn and compression is low. This backs up the pro's claims.

You actually put some thought into this response . Cudo's I agree with pretty well everything you have indicated . However the professional production felling can actually wear out a saw today within a few yrs even with quality oil at 32:1 lol.