Stihl Carb query

[Hedge Chopper]

Just wanted to satisfy my curiosity more than anything else,bought a MS250 as I needed something a bit bigger than the 171's I normally use.Reading the book I noticed that there seems to be two options for carbs on the saw,

 

H1 and L1 where you turn the screws clockwise until stop then back one turn

 

H3/4 and L1 where the H is turned counterclockwise until the stop and the L screw clockwise until stop and back one turn.

 

With the first option I'm assuming you can make the H and L screws leaner or richer but with the second you can only make the H screw richer as its on the stop with the standard setting?

 

I'm guessing that it depends which country you are in as to which one you get.Was hoping someone who knows more than me about these things(not difficult)could enlighten me!

 

I'm considering doing a muffler mod on it more out of the fact that I like tinkering than anything else and wanted to be sure about the carb settings before I did anything as I haven't got a Tacho.

[blazer]

If it's running ok why touch it but if you feel the need - just turn each screw clockwise untill it stops and note how far it goes - then turn it back to the same position to find the setting.

Mufflers are more important on a 2stroke then any 4 stroke as the provide some back pressure to help volumetric efficency, as any moped rider knows more noise often equalls less power. I have had no probs with most of my saws, just the little ms170 lost power caused by the muffler chocking up.

[spudulike]

I have yet to see a carb tuned in this way - all I have ever come across are tuned by turning the screws in all the way and then out by a specified number of turns.

 

Just found the document - almost definitely a missprint or badly written - remember Stihl is a German company!

 

A muffler mod will ned the mixture richened slightly - the outlet should be no more than 80% of the exhaust port area!

[Hedge Chopper]

I have yet to see a carb tuned in this way - all I have ever come across are tuned by turning the screws in all the way and then out by a specified number of turns.

 

Just found the document - almost definitely a missprint or badly written - remember Stihl is a German company!

 

A muffler mod will ned the mixture richened slightly - the outlet should be no more than 80% of the exhaust port area!

 

Cheers spud,just found the handbook on line-if you go down to page 43 of the manual it shows the two different options for the carb.

 

http://www.stihlusa.com/stihl_ownersmanuals/ms210230250_manual.pdf

[Megatron]

Like you have found out, the two different specs/settings are for two different carbs.

H=1, L=1 is the standard setting for the Walbro WT-215 and WT-286A carbs which do not have a limiter capped H screw. These stopped being used in 2003.

 

H=3/4 (counter-clockwise as far as stop), L=1 refers to carbs with a limiter capped H screw and is the standard setting with the H screw limiter cap in place. The standard setting with the limiter cap removed is lightly seat both screws and then open the high speed screw 1 and 1/2 turns and the low speed one full turn. A new limiter cap should be installed afterward.

(Also, i have seen a carb for this series where the actual stop pin had to be removed as the limiter cap was actually metal and part of the H speed screw.)

 

The purpose of the limiter cap is to stop people richening up their saws and thus polluting more.

Edited September 20, 2011 by Megatron

[Hedge Chopper]

Like you have found out, the two different specs/settings are for two different carbs.

H=1, L=1 is the standard setting for the Walbro WT-215 and WT-286A carbs which do not have a limiter capped H screw. These stopped being used in 2003.

 

H=3/4 (counter-clockwise as far as stop), L=1 refers to carbs with a limiter capped H screw and is the standard setting with the H screw limiter cap in place. The standard setting with the limiter cap removed is lightly seat both screws and then open the high speed screw 1 and 1/2 turns and the low speed one full turn. A new limiter cap should be installed afterward.

(Also, i have seen a carb for this series where the actual stop pin had to be removed as the limiter cap was actually metal and part of the H speed screw.)

 

The purpose of the limiter cap is to stop people richening up their saws and thus polluting more.

 

 

Thanks Megatron,thats what I was after-if i want to richen the saw after modifying the muffler I need to do as you say and remove the limiter cap.If i've got a wet day I may put it on the bench and tinker about with it.