Chainsaw Carb Adjustment ... Idle (T) vs Low (L) - Echo CS400

Arborist Forum

Help Support Arborist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

buxfan1911

ArboristSite Lurker
Joined
Jan 7, 2019
Messages
7
Reaction score
10
Location
Colorado
I've been researching the best way to dial in the carb on my newly purchased Echo CS400 chainsaw and there is a lot of good info here on the forum. I keep getting stuck when adjusting the L screw because of the T screw. I seem to have to simultaneously adjust both screws to the the Low end to even out and Idle smoothly. I've been using a tach to help get my idle @ 2700 RPM and I am very close. But my problem now is a saw that surges at idle ranging from 2500rpm to 3100rpm. The ECHO manual is pretty weak when it comes to proper tuning information

The Question: What's the proper procedure to adjust the T (Idle) screw and L (Low) screw when setting the idle? Everything I read ignores the T until after the L is adjusted, but doesn't say where we should start with the T screw?

Thanks for any help.
 
turn the idle down until the chain stops turning on its own, ignore the rpm's

then lean out the idle until it starts to die, then back it off 1/8-1/4 turn, readjust idle so chain isn't engaged

blip throttle and see what the response is, may need to adjust idle a little more to get good off idle acceleration, usually a little fat on idle gives the saw a better acceleration (and keeps the skeeters at bay)

biggest thing is to ignore what the RPM's are set at at idle, as long as the chain isn't turning and it stops in a fairly short time from full throttle to no throttle, then the idle screw is fine.

The RPM gauge has more to do at wide open throttle then anything, and in reality at wide open and no load saw should start to "4 stroke" or miss a little at the top end, but still pull hard in a cut

Its really easy to lean a saw out too much and burn it up, max revs isn't necessarily good if its getting hot in the process
 
Back
Top