mixing ratios for 2 stroke chainsaws

[bwalker]

Some time back I was flushing out the bottom end of a 385 & realised that when I transitioned between different mixes I could feel the difference in how freely the crank spun. This lead to a bit of experimentation & what stood out to me was how much of a difference I could feel rotating the crank with a case full of 32:1 vs 50:1.
In heind sight I should have tried it with different oils too.

Tom, as far as real world testing goes, I would set up a motor running at constant load. Once warm set rpm as desired for the 50:1 mix. Then over a period of time (while the motor runs continuously) raise the oil mix ratio up to around 20:1. Then over the same period of time reduce the mix back to 50:1.
Monitor cylinder temperature & rpm throughout.
While you won't be measuring a direct correlation between a specific mix ratio & rpm (as the mix will be varying) you should see a meaningful trend.
Repeat as many times as possible using as many different oils as possible

And what would this tell you?
Sounds like a waste of fuel and time to me.

 

[bwalker]

Yeah, and I'm sure the mix ratio or type of oil was the reason why. Yeah, I believe that.

Miraculously failures stop once you up the oil..
And why wouldn't they given a modern strato saw has the same or similar bearings as the older saws, but uses drastically less oil due to fuel efficiency.
Even Husky 3xx series saws crank bearings lasted longer when ran at 32:1. In a logging setting this is pretty apparent.

 

[MacAttack]

The Japanese bikes were all 32:1 except for Yamaha which speed 30:1.

Which decade are we talking about?

60's / 70's or even 80's that wouldn't surprise me at all.

 

[bwalker]

Which decade are we talking about?

60's / 70's or even 80's that wouldn't surprise me at all.

90's to present.
Might also note that KTM's since forever have came from the factory so damn rich they are probably burning the equivalent of well below 32:1. The guys that leave them like this have a long lasting motor that requires frequent power valve cleanings and silencer repacks.. The guys that tune them properly for certain have decreased big end and crank bearing life.
One mod that guys are doing to to new KTM TPI motors is to bump the oil pump up as they aren't lasting either.

 

[MacAttack]

When I got my KTM it already had a full FMF exhaust and had been re-jetted, it ran kinda lousy. I re-re-jetted it with a larger main jet and smaller pilot and it woke up. I also decided to mix it 32:1 with full synth because that was what I used in my Banshee.

For the heck of it I looked up a Banshee manual and I was surprised, 24:1 with Yamaha oil or 20:1 with other brands, of course when I had my Banshee I never looked at the manual.

 

[bwalker]

When I got my KTM it already had a full FMF exhaust and had been re-jetted, it ran kinda lousy. I re-re-jetted it with a larger main jet and smaller pilot and it woke up. I also decided to mix it 32:1 with full synth because that was what I used in my Banshee.

For the heck of it I looked up a Banshee manual and I was surprised, 24:1 with Yamaha oil or 20:1 with other brands, of course when I had my Banshee I never looked at the manual.

If your KTM has a Mikuni carb the best thing you can do is chuck it in the trash and run a Keihin PWK. JD sells prejetted ones that are close. The PWK is very easy to tune compared to the Mikuni.
I believe in latter years Yamaha speced 30:1 for the banshee as well.

 

[MacAttack]

I think it has a Mikuni but would need to check, I've never had trouble with Mikunis, the tune is actually good now. If it wasn't just a heavy trail-banger enduro bike I'd maybe be more picky about tuning it haha.
The bigger issues are the fork seals puking oil and the front brakes need fixing, brake lever goes right to the handlebar. I think the master cylinder needs rebuilt.
I need to find a good source of parts, which for those KTMs is not as easy.

 

[bwalker]

I think it has a Mikuni but would need to check, I've never had trouble with Mikunis, the tune is actually good now. If it wasn't just a heavy trail-banger enduro bike I'd maybe be more picky about tuning it haha.
The bigger issues are the fork seals puking oil and the front brakes need fixing, brake lever goes right to the handlebar. I think the master cylinder needs rebuilt.
I need to find a good source of parts, which for those KTMs is not as easy.

Is this an older bike with Marzocchi forks?

 

[MacAttack]

Is this an older bike with Marzocchi forks?

Yep. And an Ohlins in the rear, Brembo brakes.

I recall having a tough time finding a rebuild kit for the forks.

 

[J D]

And what would this tell you?
Sounds like a waste of fuel and time to me.

Some time back I was flushing out the bottom end of a 385 & realised that when I transitioned between different mixes I could feel the difference in how freely the crank spun. This lead to a bit of experimentation & what stood out to me was how much of a difference I could feel rotating the crank with a case full of 32:1 vs 50:1.
In heind sight I should have tried it with different oils too.

This ^ doesn't tell me anything so far as real world running goes as chainsaws don't tend to run with a crankcase full of fuel.
I did find it interesting tho so thought I would share

Tom, as far as real world testing goes, I would set up a motor running at constant load. Once warm set rpm as desired for the 50:1 mix. Then over a period of time (while the motor runs continuously) raise the oil mix ratio up to around 20:1. Then over the same period of time reduce the mix back to 50:1.
Monitor cylinder temperature & rpm throughout.
While you won't be measuring a direct correlation between a specific mix ratio & rpm (as the mix will be varying) you should see a meaningful trend.
Repeat as many times as possible using as many different oils as possible

This ^ (in my humble opinion) is a better way to demonstrate what Tom was trying to evaluate & show in his video rather than just saying "this is how it is" or "this (unreferenced) study showed"....
It would be pretty simple & relatively inexpensive to do if you already had a selection of oil on hand (although time consuming).
If you could suggest a better/ more effective way to demonstrate what he was trying to show please do... you may even get to see it realised if someone decides it's worthwhile following through with

 

[rogue60]

You could always do something bizarre like follow the owner's manual.

Manuals are good for when you run out of toilet paper in the bush way better than sticks and leaves lol

 

[bwalker]

This ^ doesn't tell me anything so far as real world running goes as chainsaws don't tend to run with a crankcase full of fuel.
I did find it interesting tho so thought I would share

This ^ (in my humble opinion) is a better way to demonstrate what Tom was trying to evaluate & show in his video rather than just saying "this is how it is" or "this (unreferenced) study showed"....
It would be pretty simple & relatively inexpensive to do if you already had a selection of oil on hand (although time consuming).
If you could suggest a better/ more effective way to demonstrate what he was trying to show please do... you may even get to see it realised if someone decides it's worthwhile following through with

I don't see how any of that crap is relevant to real world chainsaw use.
The original test has a plethora of issues and isn't valid.
Any tuner worth his salt knows that anytime you change the amount of fuel flowing through a carb your air to fuel ratio changes. This is pretty elementary and can't be argued.

 

[bwalker]

Yep. And an Ohlins in the rear, Brembo brakes.

I recall having a tough time finding a rebuild kit for the forks.

Those forks are garbage. I had a 200MXC with them.

 

[Ethobling]

Man, for someone who is trying to figure out what mix ratio/tune to use on my saws, I'm still super confused.

I'm pretty set on "X Brand" of FD rated oil (mainly going to run Echo Red Armor, I think). I think I'll run it 45:1 in my standard day-to-day working. But milling? 40:1? 32:1? Just run 50:1 but tune it rich?

AHHHHHHHHHH!!!

 

[bwalker]

Man, for someone who is trying to figure out what mix ratio/tune to use on my saws, I'm still super confused.

I'm pretty set on "X Brand" of FD rated oil (mainly going to run Echo Red Armor, I think). I think I'll run it 45:1 in my standard day-to-day working. But milling? 40:1? 32:1? Just run 50:1 but tune it rich?

AHHHHHHHHHH!!!

I would run it at 40 or 50:1 for normal use and 32:1 and tuned abit rich for milling.

 

[J D]

I run 40:1 day to day, 32:1 + a few hundred rpm fat for milling

 

[ZeroJunk]

Miraculously failures stop once you up the oil..
And why wouldn't they given a modern strato saw has the same or similar bearings as the older saws, but uses drastically less oil due to fuel efficiency.
Even Husky 3xx series saws crank bearings lasted longer when ran at 32:1. In a logging setting this is pretty apparent.

If you have enough data comparing the two to get that result then I believe you. Most of the bearing failures that I see is the cage comes apart and the bearings bunch up and the flywheel bangs the ignition coil or whatever.

I honestly don't know whether that has anything to do with oil or not.

But, you know the drill. Unless you have a group of the same saws running one mix and the same number running another mix for the same amount of time It's hard to prove anything even though you might have a strong opinion about it.

 

[bwalker]

If you have enough data comparing the two to get that result then I believe you. Most of the bearing failures that I see is the cage comes apart and the bearings bunch up and the flywheel bangs the ignition coil or whatever.

I honestly don't know whether that has anything to do with oil or not.

But, you know the drill. Unless you have a group of the same saws running one mix and the same number running another mix for the same amount of time It's hard to prove anything even though you might have a strong opinion about it.

Bearings fail from injesting dirt and from lack of lube.
Some of the strato saws have 20% or even greater fuel economy increase. That means they are using 20+% less oil. It's no stretch to connect those dots.

 

[ZeroJunk]

Bearings fail from injesting dirt and from lack of lube.
Some of the strato saws have 20% or even greater fuel economy increase. That means they are using 20+% less oil. It's no stretch to connect those dots.

More like they are blowing 20% less raw fuel out the exhaust.

 

[camel2019]

More like they are blowing 20% less raw fuel out the exhaust.

If you tune your equipment it shouldn’t be blowing any fuel mix out of the exhaust.