Help Tuning Tillotson Hl166
- Thread starter doodlebug6.5
- Start date
- Tags hl166 tillotson tuning
Assuming that it is mounted ok and no air leaks and pulse port is getting pulsed there is a popoff setting that should popthe needle off the seat at around 10 psi for what you are doing. Next there are drillings for idle, low speed and hi speed. If the low speed drilling is too small you may not get enough adjustment to richen it up. The lo speed works all the time and when airflow is high enough it starts pulling fuel from the hi speed. I usually start with each needle out 1turn and adjust lo speed so it will start and idle then test and adjust from there. The low needle on mine alsoaffects idle. I had to turn mine so stack is on the bottom as the other way when you stop it fuel runs out into air cleaner and also the idle was eratic withstack on top.
Tillotson HL CARBha
Carb should run IN ANY PPOSITION with NO ill effects.
No such thing as upside down. Its what works for you.
Carb should run IN ANY PPOSITION with NO ill effects.
No such thing as upside down. Its what works for you.
Last edited:
I have run them stack up and stack down on clones ( and I am talking about the 166 now ).
I prefer stack up because it will dribble some fuel and that makes it easier to start without the choke installed.
The other way you going to want to keep the choke.
Drilling and pop off on the 166 and 166B are very close to where you want to be as built.
I would not mess with it and try and lighten the setting ( makes the little carb twitchy for little gain ).
Yes you could probably improve it but I would not mess with what works unless you are a carb drilling expert like Korndog or others here.
You can't undo what you remove without a lot of trouble and you need jigs and special tools to do this right anyways.
There are ways to mount a tilley that are wrong...
Adjustment needles up is wrong ( on its side )
This mounting will allow an airlock under some conditions in the metering chamber and you will get a hesitation until you suck out all the air under load.
The correct way to set this car up is with the throttle completely closed when off the throttle ( no idle at all when fully adjuested ).
Set the low side rich about 1/8-1/4 turn more from best idle ( contradictory I know you will want to idle to set the low side but not drive that )
The idea is you will tap the throttle at low speeds to keep the engine running and this will always leave you with enough excess fuel for a quick snap of the throttle and no stumble.
The high side will pick up most of the fuel delivery about 1/4 throttle but the low side will continue to deliver fuel.
This mean the factory suggested setting may not be the same when this carb is mounted on a clone!
The carb was designed for a denser fuel mixed with oil and the clone will try and pull more air through it than a 2 stroke half its size would have.
They way this work out in the wash means the idle setting will be more than you might expect on a big chain saw ( where this carb was designed to be used ) and potential less on the high side.
My 2 cents....
Its a good carb, but I find I can make a float carbs work better for my own engines.
There are always other choices.
I prefer stack up because it will dribble some fuel and that makes it easier to start without the choke installed.
The other way you going to want to keep the choke.
Drilling and pop off on the 166 and 166B are very close to where you want to be as built.
I would not mess with it and try and lighten the setting ( makes the little carb twitchy for little gain ).
Yes you could probably improve it but I would not mess with what works unless you are a carb drilling expert like Korndog or others here.
You can't undo what you remove without a lot of trouble and you need jigs and special tools to do this right anyways.
There are ways to mount a tilley that are wrong...
Adjustment needles up is wrong ( on its side )
This mounting will allow an airlock under some conditions in the metering chamber and you will get a hesitation until you suck out all the air under load.
The correct way to set this car up is with the throttle completely closed when off the throttle ( no idle at all when fully adjuested ).
Set the low side rich about 1/8-1/4 turn more from best idle ( contradictory I know you will want to idle to set the low side but not drive that )
The idea is you will tap the throttle at low speeds to keep the engine running and this will always leave you with enough excess fuel for a quick snap of the throttle and no stumble.
The high side will pick up most of the fuel delivery about 1/4 throttle but the low side will continue to deliver fuel.
This mean the factory suggested setting may not be the same when this carb is mounted on a clone!
The carb was designed for a denser fuel mixed with oil and the clone will try and pull more air through it than a 2 stroke half its size would have.
They way this work out in the wash means the idle setting will be more than you might expect on a big chain saw ( where this carb was designed to be used ) and potential less on the high side.
My 2 cents....
Its a good carb, but I find I can make a float carbs work better for my own engines.
There are always other choices.