Metering Lever Question

[Vintage Engine Repairs]

Hi Chaps,

I get that If the metering lever is too low it will cause the saw to run lean.

However, if the metering lever is too high, so long as you have a fully adjustable carb, is there any reason that you can’t just tune the saw a little leaner to compensate for the extra fuel in the metering chamber?

I imagine if it has an additional fixed bypass jet then it would be trickier as a set amount fuel flow can’t be controlled, but for carbs without bypass jets where all the fuel goes past the H and L screws, I’m scratching my head as to why a higher lever would be an issue?

Thanks in advance.

 

[CausticUC]

If it's too high you will have no fuel shutoff and it will drool.

 

[Vintage Engine Repairs]

If it's too high you will have no fuel shutoff and it will drool.

Correct, but if the diaphragm isn’t touching the lever, but it’s still higher than it should be, any reason it can’t be tuned out?

 

[CausticUC]

This is only if the diaphragm touches the lever though right, but if it’s not touching?

If the needle does not seat, there is nothing restricting the fuel. On a diaphragm carb that also means there is no pump pressure because it can not seal off one end to create the effect.

The diaphragm is typically attached to the lever via the nipple. This is on most equipment that is made to be inverted. Lawnmowers and trimmers may not have the clip.

 

[RED-85-Z51]

Ive experimented with this. Running it a touch high can...CAN make it a shade more responsive in a situation where it needs more fuel than the needle can reasonably provide at the stock position, at the cost of random flooding and a tricky idle...

Sent from my LM-G820 using Tapatalk

 

[farmguywithasaw]

Ive experimented with this. Running it a touch high can...CAN make it a shade more responsive in a situation where it needs more fuel than the needle can reasonably provide at the stock position, at the cost of random flooding and a tricky idle...

Sent from my LM-G820 using Tapatalk

You can also stretch or trim the spring to adjust when the needle pops off but it’s not recommended on a work saw. A stiffer spring will give you less fuel at the top end. You will find that there is way less adjustment possible on the high side.but much finer adjustments So if your building a race saw I imagine you would play with this. A softer spring will open sooner and give more fuel at high rpm and allow more adjustment ( but less fine tuneable) as I understand

 

[sean donato]

In my experience, you have a little wiggle room, for setting the metering lever. Although I normally set mine with the gauge, i have had a few instances that setting it a tad higher, or swapping out for a lower pressure spring was advantageous. I can really only think of 2 times that I changed lever height and not the spring under the lever. Neither application was saw related.

 

[rupedoggy]

Tom aren't you the guy that has given people advice on carburetors in the past?

 

[CausticUC]

There are lots of different types of carburetors, and there is no harm in asking if you've forgotten, unsure about, or drank too much to remember which side is up!

 

[stihl86]

If it lower, it will definitely affect acceleration. Never notice an improvement setting it higher. Too high and it leaks.
But, tbh, if you have to screw around that much with a carb for more power, just buy a bigger saw. Performance will increase. Guaranteed.