40:1 Poor Man’s Richen Carb

[leeave96]

If you have a chainsaw that is running lean and adjusting the carb is not an option, would changing the mix from 50:1 to 40:1 or 32:1 essentially richen the carb without touching any carb settings?

Just curious - thanks!

 

[epo]

If you have a chainsaw that is running lean and adjusting the carb is not an option, would changing the mix from 50:1 to 40:1 or 32:1 essentially richen the carb without touching any carb settings?

Just curious - thanks!

No. Quite the opposite.

 

[Vintage Engine Repairs]

Raise the metering lever a little. Changing oil ratios between 50:1 - 25:1 doesn’t produce a noticeable change in lean or rich running.

 

[huskydave]

You have to find out why its running lean and fix the problem, plugged jet, leaking seal, gasket or carb boot are some things to consider. In reality, changing from 32:1 to 40:1 for example is so small of an amount, it's not going to affect the F/A ratio enough to notice. Going from 40:1 to 60:1 might, but probably not.

 

[Gord404]

what is the saw in question that you can't ajust the carb and why

 

[DND 9000]

Changing oil ratios between 50:1 - 25:1 doesn’t produce a noticeable change in lean or rich running.

Oh yes, it makes a significant change!!! I`ve tested it by myself and my saw (MS 361) turned around 1500 rpm higher without adjusting the carburetor using 25:1 instead of 50:1.

 

[Vintage Engine Repairs]

Oh yes, it makes a significant change!!! I`ve tested it by myself and my saw (MS 361) turned around 1500 rpm higher without adjusting the carburetor using 25:1 instead of 50:1.

No it doesn’t. The heat soak of the engine, temperature, humidity, how much fuel in the tank, even slightly more or less tension on the chain all make a drastically bigger difference to rpm than fractions of a ml.. if you’re getting 1.5k difference in rpm, it’s not the oil.

 

[stihltech]

It is not the oil. It is the air to fuel ratio. That is why a vacuum and pressure test is so important. Trying to richen a too lean saw without repairing the actual issue (leaks, fuel system, etc) results in melted pistons.
You have to diagnose and repair.
Magic wands don't work.

 

[bwalker]

No it doesn’t. The heat soak of the engine, temperature, humidity, how much fuel in the tank, even slightly more or less tension on the chain all make a drastically bigger difference to rpm than fractions of a ml.. if you’re getting 1.5k difference in rpm, it’s not the oil.

@Vintage Engine Repairs is correct and this can easily be proven using simple math.

 

[Gord404]

It is not the oil. It is the air to fuel ratio. That is why a vacuum and pressure test is so important. Trying to richen a too lean saw without repairing the actual issue (leaks, fuel system, etc) results in melted pistons.
You have to diagnose and repair.
Magic wands don't work.

my mitivac is one of my most used tools- lets me get to the souce quickly, bandaids don't work

 

[SAWMIKAZE]

Oh yes, it makes a significant change!!! I`ve tested it by myself and my saw (MS 361) turned around 1500 rpm higher without adjusting the carburetor using 25:1 instead of 50:1.

No it doesn't.

 

[stihltech]

I wish I could get through to owners the answer is not how cheap you can buy an after market part. As pros, we know the value of diagnostics. We have all experienced the "that part did not fix it" syndrome.
We don't get those special diagnostic tools for looks. They get used BEFORE we put on parts.
Fuel quality is #1. Leakage of the bottom end is a close second. There is a reason manufacturers have diagnostic sheets.