Part Seven: Carburation

[huskihl]

Or a carb kit

 

[MattG]

Or a carb kit

Dude, were trying to answer my earlier post #78 ? It's already had a carb kit, etc. etc. and is generally in very good shape. I just wondered what things make saw carbs ultra sensitive on the H side adjustment. You know like....spring strength, jet diameter, control lever height or whatever. Someone must know.

I don't think it's due to my altitude (sea level) since the other stuff I own doesn't have the behaviour.

 

[huskihl]

Dude, were trying to answer my earlier post #78 ? It's already had a carb kit, etc. etc. and is generally in very good shape. I just wondered what things make saw carbs ultra sensitive on the H side adjustment. You know like....spring strength, jet diameter, control lever height or whatever. Someone must know.

I don't think it's due to my altitude (sea level) since the other stuff I own doesn't have the behaviour.

It was in response to you, but I didn't see the part about you already servicing the diaphragms. In my experience, a good cleaning and new diaphragms and needle usually takes care of it. But on some, nothing seems to fix them

 

[exSW]

?
Kindly elaborate please dear sir....

Octane rating. Just a SWAG.

 

[MattG]

Octane rating. Just a SWAG.

Same as I use in all my other stuff. I think we've 95 RON here in UK.

My guess it's due to the inlet control lever height or something....

I does tune alright, its just a little bit fiddler because of the sensitivity.

 

[Fruecrue]

600 rpm in 1/16 turn doesn't sound to far out the norm. If there's nothing else wrong, and it holds a tune I wouldn't worry about it.
I would imagine this varies from carb to carb due to thread pitch, seat angles, and other design features.

 

[astnmacgto]

If you have a saw that's been modified pretty heavy and you get done with it and it starts great cold but once it's warm and you shut it off and try to restart it it's a pain in the butt and just fires a couple times but won't stay running but if hold the throttle open it fires right up. Perhaps a bigger carb and intake would help?

Everything has been changed when i built it, new seals, fuel lines, filter, carb kit, plug, it's got 210psi and I've only made about 3 cuts with it.

The oem carb and intake are very small for a 54cc saw, like they are the same as the one on my ms170.

I just don't think it's getting enough air to make it happy

 

[astnmacgto]

Also, has anyone successfully switched carbs on a saw that the crankcase pulse is in the top cover and modified one that has the pulse port cast into the carb body, and made it work?

 

[Fruecrue]

I had a saw act the way you describe. Owner rebuilt the carb with the diaphragm inside the gasket. Acted like a high metering lever.
Would usually start cold, sometimes flood.
Wouldn't restart hot.
Ran fine once it started.

 

[astnmacgto]

I had a saw act the way you describe. Owner rebuilt the carb with the diaphragm inside the gasket. Acted like a high metering lever.
Would usually start cold, sometimes flood.
Wouldn't restart hot.
Ran fine once it started.

I will have to double check my gaskets, I must admit I did put that kit in kind of a hurry

 

[MattG]

If you have a saw that's been modified pretty heavy and you get done with it and it starts great cold but once it's warm and you shut it off and try to restart it it's a pain in the butt and just fires a couple times but won't stay running but if hold the throttle open it fires right up. Perhaps a bigger carb and intake would help?

Everything has been changed when i built it, new seals, fuel lines, filter, carb kit, plug, it's got 210psi and I've only made about 3 cuts with it.

The oem carb and intake are very small for a 54cc saw, like they are the same as the one on my ms170.

I just don't think it's getting enough air to make it happy

All I can add is that with a decent airtight engine, with a re-serviced carburettor; then decent cold starts and good running and throttle response......but WON'T restart when hot WITHOUT fully open throttle sometimes means a slightly too rich L screw setting. My 064 is notoriously sensitive, and after setting up the L for a nice response and idle, I've found that I need to just lean it back a tiny amount on the L side to get hot starts to work nice.

Just my couple pence there

 

[astnmacgto]

All I can add is that with a decent airtight engine, with a re-serviced carburettor; then decent cold starts and good running and throttle response......but WON'T restart when hot WITHOUT fully open throttle sometimes means a slightly too rich L screw setting. My 064 is notoriously sensitive, and after setting up the L for a nice response and idle, I've found that I need to just lean it back a tiny amount on the L side to get hot starts to work nice.

Just my couple pence there

Appreciated!

 

[astnmacgto]

Well, I checked my gaskets, they are on correct, so I have a bigger carb that I'm setting up to go on it, I'm going to order an oe intake boot that is larger and see how it mates up and if I need to go bigger then I believe I know what I need

 

[I Know Something]

Things I didnt see discussed in here at all.

1. Drilling out main jet. Which one is it. And how big do you go. Also, metering spring mod needed? If so, remove how much?

2. How exactly do you increase the venturi size? Just drill press with correct size drill bit?

3. If you change out the carb for another one. Do you just reattach the old ones things that hook up to your choke/throttle and other things?

4. Carb brands that work better then others? Walbro over Zama? Tillotson?

5. Family or class of carbs that are interchangeable? How to tell if they are?

6. Blowdown. How to measure and how to know what you have is appropriate. Or...what exactly is it?

7. Pulse line. My only experience thus far is a hole in the carb that goes below the piston. I'm assuming that's the same thing. Is that modded for any reason at all?

All I could think of in my quiet time away from my kids. Any other rookie got a question they can add? I'm new to 2 strokes. And dont know jack about their carbs. Please help me and my education.

 

[Deets066]

 

[cgraham1]

Now let's spend a little time on carburation

I hate to be that guy, but you spelt carburetion wrong. I miss Jonathon... he used to take care of this sorta stuff.

 

[Mastermind]

I hate to be that guy, but you spelt carburetion wrong. I miss Jonathon... he used to take care of this sorta stuff.

Repped.

 

[5000+]

026's can go from alittle rich to screaming with the slightest turn.

 

[Mastermind]

Things I didnt see discussed in here at all.

1. Drilling out main jet. Which one is it. And how big do you go. Also, metering spring mod needed? If so, remove how much?

2. How exactly do you increase the venturi size? Just drill press with correct size drill bit?

3. If you change out the carb for another one. Do you just reattach the old ones things that hook up to your choke/throttle and other things?

4. Carb brands that work better then others? Walbro over Zama? Tillotson?

5. Family or class of carbs that are interchangeable? How to tell if they are?

6. Blowdown. How to measure and how to know what you have is appropriate. Or...what exactly is it?

7. Pulse line. My only experience thus far is a hole in the carb that goes below the piston. I'm assuming that's the same thing. Is that modded for any reason at all?

All I could think of in my quiet time away from my kids. Any other rookie got a question they can add? I'm new to 2 strokes. And dont know jack about their carbs. Please help me and my education.

I wish I had time to address your questions with detailed answers.

Sadly, for me, those days are long gone.

Saws.....pastures....hay ground....tractors, and of course cattle. These things take all my time. When I can sit down, I spend that time with my family.

 

[I Know Something]

I wish I had time to address your questions with detailed answers.

Sadly, for me, those days are long gone.

Saws.....pastures....hay ground....tractors, and of course cattle. These things take all my time. When I can sit down, I spend that time with my family.

Spare time exists? *feints*