Fuel Mix Ratio for McCulloch PM 605

[kattcutter]

Hi all,

I have been lurking here for awhile, & I must say this is an excellent site for learning! I tip my cap to all you knowledgable fellows! Now for my question; I recently purchased a (used) McCulloch PM 605, looks to be in great condition. Still has the original bar.

It did not come with an instruction manual.
Does anyone know of the proper fuel mix ratio for this saw? I have done some searching & have found everything from 16:1 to 50:1 recommended. I would like to confirm the correct one so I don't burn this thing up!

Thank you, kattcutter

 

[blis]

And here we go again... 50:1 is ok on ANY saw long as you use MODERN oils...

 

[Just Mow]

That saw was out when mixture was 40:1 ratio. Be sure and use a good oil. No junk from W-Mart, H-Depot etc.

 

[ozflea]

40-1 is the correct ratio for the 605, 610, 650, timberbear, PM5700 and Eager Beaver 3.7.

Do not use 50-1.

Mc Bob.

 

[blis]

40-1 is the correct ratio for the 605, 610, 650, timberbear, PM5700 and Eager Beaver 3.7.

Do not use 50-1.

Mc Bob.

Care to give us any scientific proof of that 50:1 isnt suitable??

 

[kattcutter]

And here we go again... 50:1 is ok on ANY saw long as you use MODERN oils...

Okay...so a 15 yr. old saw that is rated at 16:1 in the owners' manual (as my eager beaver 3.4 is) can now be run on a 50:1 mix?

Sorry for being so niave, but I just wanted to be sure not to burn up my saw. The reason that I question it, is that there is so much fuel mix info. floating around on the web, that I am not sure what to go with.

regards, kattcutter

 

[Austin1]

Oil mix

I have been using 40-1 for years in my sp105 with good 2 stroke oil it calls for 32-1 but I do not like to have a bunch of gas can's for all my 2 strokes. Never had a problem with anything evan the stuff that calls for 50-1, I just run 40-1 in every thing.

 

[mbopp]

My old PM650 owners manual says 20:1 with non-McCullouch oil or 40:1 with genuine Mac oil. I use ISO - JASO rated oil since it's better than what anybody had in 1980. And I run 32:1. Let the debate rage (again.)

 

[blis]

Okay...so a 15 yr. old saw that is rated at 16:1 in the owners' manual (as my eager beaver 3.4 is) can now be run on a 50:1 mix?

Sorry for being so niave, but I just wanted to be sure not to burn up my saw. The reason that I question it, is that there is so much fuel mix info. floating around on the web, that I am not sure what to go with.

regards, kattcutter

Dont worry, i understand that it might get confusing at times, its just that in every two weeks or so someone asks the same question in this board...

 

[ozflea]

Dont worry, i understand that it might get confusing at times, its just that in every two weeks or so someone asks the same question in this board...

Thats why you should believe the manufacturer of the saw for the correct ratio, not hearsay.
Quite a few years ago when the HI-PO Mac's where around Mac recommended 32-1 but this was for the likes of the old SP81, SP81E, 805, 800. For these were high reving and Mac seen the need for more oil, if you increase the oil ratio to ie 16-1 then you get very high oil deposits and heavy carbon build up.

Mc Bob.

 

[Lakeside53]

I used 50:1 Stihl and Echo oil in my pos 605, and 610, for 10 years, and they were like new when I checked them over. Backup saws, but they sure cut a lot of big wood.

2 saws isnt a big sample though, and 40:1 won't hurt anything.

 

[ozflea]

Sorry Lakeside but thats why these threads become confusing maybe 50-1 doesn't hurt the saw as in your case but does that mean everyone should run around willy nilly testing their saws to see if a leaner ratio does harm or not don't think so after all neither Stihl or Echo make their own oil out here in OZ most Stihl used Castrol to make up the 2 stroke oil.

I have not experianced and problems using the correct ratio in my Mac's so why should i tempt fate.

Mc Bob.

 

[Lakeside53]

I agree...

I tempt fate often 'cos I'm too lazy to have mutiple fuel can mixes... but I don't tune mine to absolute max performanace either (for the "fate" reason"). My best advice, which I take, is Stay away from the edge.. all of them.

 

[ozflea]

The only one of the 600 series of Mac's that could be placed in the high performance group was the PM650 as it used a few mods that Mac used to up the power and RPM THE REST WERE DETUNED TO INCREASE LIFE of these saws thats why there's so many still running around how many PM650's are still out there ?

If at anytime you are not sure of the mixture go and read the owners manual before it goes bang.

Mc Bob.

 

[kattcutter]

Dont worry, i understand that it might get confusing at times, its just that in every two weeks or so someone asks the same question in this board...

:deadhorse: Yeah, I noticed that! I was thinking that maybe a member might have the same saw as mine, & could post the ratio from their manual/personal experiences.
Years ago, a retired repairman told me to mix it rich, the back off on the ratio until it stops smoking...

 

[Lakeside53]

That techique will be a problem with low smoke oil..

 

[ray benson]

Intertec chainsaw manual lists the ratio as 40/1 just as Ozflea stated.

 

[Tzed250]

Ratios

What is the reason not to run more oil than less oil? You could say it is becase of deposits. Or the fact that the more oil you cary into the cylinder, the less gas you carry in. Many dyno tests were made years ago that determined that the amount of oil in the premix made very little difference in the power level that the engine would make, as long as the correct gasoline/air ratio was maintained. This proved true down to about 16:1 fuel/oil ratio. Obviously to much oil is better than to little. Many "lean mix ratio" oils were tried in the eighties and nineties, but the majority of folks kept coming back to 32:1. It works, and its easy to mix(4 ounces per gallon). Now modern saws have run for years on 40:1 and 50:1. But the PM605 is hardly a modern saw. McCullochs QC was nowhere near that of the European saws, so we might give the reciprocating assembly a break by giving it a little extra lube. All of my two-strokes burn 32:1 and I sleep great at night. Feedback?opcorn:

 

[buzz sawyer]

Not to get this thread off track, but if a manufacturer recommended 16:1 with oil that was available forty years ago, how could the better oils today cause any problem at the same ratio as long as the mixture is set correctly?