Carb wizards commence... Looking for answers...

[Cobby08]

Looking for knowledge from a carb wizard that can explain something. So as a Stihl dealer I can get a Stihl branded carb kit for around oh... $25 or get walbro ones for practically nothing. So as I was in my Wackin' Shack coloring my coloring books I had a random thought which has crossed my mind a few times. How come with like 99% of the carb kits I've used they don't come with a new spring? I mean naturally a metal is going to lose its strength over time and so ideally popoff would lower. Then one would say, "duh *pretty boy adjust your metering lever retard." I understand you can increase it but seems like the spring will still be weak. For the 1/9 of a cent that it would cost for them to include them in the kit it doesn't seem to make sense. Please... discuss and spread your wealth of knowledge to a fellow tard here.

 

[andyshine77]

Well I could be wrong, but I believe they're diaphragm kits and rebuild kits. The rebuild kits come with springs and welch plug.

Sent from my LG-H871 using Tapatalk

 

[Cut4fun]

Dont ever recall the spring being in any kits that I can think of. Complete rebuild or dia kits.
But you can buy spring kits if I recall right. That way you have them on hand.

 

[jackjcc]

They are in the walbro kits aren’t they?


Sent from my iPhone using Tapatalk

 

[huskihl]

Some kits have the springs, some don't. Maybe other models that that kit fits don't all use the same spring. Not sure.

The kits I get from Dave all have had springs in them so far

 

[andyshine77]

Dont ever recall the spring being in any kits that I can think of. Complete rebuild or dia kits.
But you can buy spring kits if I recall right. That way you have them on hand.

Some of the rebuild kits I've had, came with the spring, meetering lever, meetering valve and welch plug. For whatever reason some kits don't have everything some do.

Sent from my LG-H871 using Tapatalk

 

[huskihl]

@Poleman or @Terry Syd may be able to help

 

[earlthegoat2]

The 044 Walbro kits I have gotten do not have a spring but do have the needle and lever. The kit I just got for my 261 from Stihl by the way, only had the gaskets and diaphragm. A Stihl kit I got for an MS460 had the spring, lever, needle, gaskets, and diaphragm.

 

[Stump Shot]

It's very rare that you would actually need a new spring, unless it's corroded.

 

[Bilge Rat]

Some kits have springs and some don't. Had a kit for a weedeater that had a very different spring than the one in the carb so i tend to reuse the origional spring.
Save your springs!

What happens when you dissassemble anything with a spring??? Where do they go when they jump out and hide?

After i am gone someone will clean out the shop and find a pile of springs and clips.

 

[Terry Syd]

Whereas the diaphragms, lever and needle are common to a model of carb, a metering spring is related to the carbs JETTING. In other words, it is specific to the engine, it is not universal.

I remember getting a carb kit that had a spring in it and the spring wasn't even close to the stock spring, it was way too weak. I expect people were putting those springs in and then wondering why their engine wasn't running as well as it used to.

The metering spring is used to 'ramp in' the low speed circuit. There are three things that determine the ramp. First is the pre-load on the spring (sometimes referred to pop-off). The pre-load of the spring determines when the needle will LIFT off the seat. The ramp begins when the needle is lifted off the seat.

If you want to lean out the idle, but want to keep the richer low speed fuel flow, you can increase the pre-load on the lever. For example, you can use a longer spring or extra shims under the spring to increase the pre-load.

The RATE of fuel flow as the air flow increases needs to be controlled. The fuel flow looks like a RAMP, that is it can be steep or shallow depending upon the requirements. That ramp, or rate is determined by two things, one is the size of the metering orifice and the other is the rate of the spring (pitch and wire size).

On a kart or boat, the ramping in of the fuel is very important. It controls the part throttle power out of turns. A Mikuni carb for a boat engine even has removable needle seats of different size orifices to help dial in the jetting.

A chainsaw doesn't have to run at part throttle, so we can get by with horrible jetting off idle (bogging) and still cut wood. As such, tweaking the pre-load is about all we do.

 

[Cobby08]

Thank you Terry! I THINK I'm picking up what your laying down. So ideally should there be a "spec" that could be checked for each unit? or is my theory of a spring getting weak so dumb I should just relax and leave it alone?

 

[Mastermind]

Whereas the diaphragms, lever and needle are common to a model of carb, a metering spring is related to the carbs JETTING. In other words, it is specific to the engine, it is not universal.

I remember getting a carb kit that had a spring in it and the spring wasn't even close to the stock spring, it was way too weak. I expect people were putting those springs in and then wondering why their engine wasn't running as well as it used to.

The metering spring is used to 'ramp in' the low speed circuit. There are three things that determine the ramp. First is the pre-load on the spring (sometimes referred to pop-off). The pre-load of the spring determines when the needle will LIFT off the seat. The ramp begins when the needle is lifted off the seat.

If you want to lean out the idle, but want to keep the richer low speed fuel flow, you can increase the pre-load on the lever. For example, you can use a longer spring or extra shims under the spring to increase the pre-load.

The RATE of fuel flow as the air flow increases needs to be controlled. The fuel flow looks like a RAMP, that is it can be steep or shallow depending upon the requirements. That ramp, or rate is determined by two things, one is the size of the metering orifice and the other is the rate of the spring (pitch and wire size).

On a kart or boat, the ramping in of the fuel is very important. It controls the part throttle power out of turns. A Mikuni carb for a boat engine even has removable needle seats of different size orifices to help dial in the jetting.

A chainsaw doesn't have to run at part throttle, so we can get by with horrible jetting off idle (bogging) and still cut wood. As such, tweaking the pre-load is about all we do.

Bingo

 

[Mastermind]

Thank you Terry! I THINK I'm picking up what your laying down. So ideally should there be a "spec" that could be checked for each unit? or is my theory of a spring getting weak so dumb I should just relax and leave it alone?

Stop over thinking stuff.

Have a beer, maybe a nice glass of wine and relax.

 

[TJ the Chainsaw Mechanic]

I find more Walbro kits don't have the spring and Zama kits do have the spring. Probably because zama tends to be more specific.

 

[Cobby08]

Stop over thinking stuff.

Have a beer, maybe a nice glass of wine and relax.

Don't judge me... overthinking is my gig leave me alone...

 

[Adirondackstihl]

Springs can be different......I get that.
But there isnt a model specific spring for every model of saw out there.
There might be 4-5 different ones.......yes. But not 2458 different springs.

 

[Mastermind]

Springs can be different......I get that.
But there isnt a model specific spring for every model of saw out there.
There might be 4-5 different ones.......yes. But not 2458 different springs.

There are eleventy million springs........that disappeared into the floor of my shop.

#youdontknowthestruggle

 

[Stump Shot]

There are eleventy million springs........that disappeared into the floor of my shop.

#youdontknowthestruggle

No E clips? Lol

 

[MustangMike]

Slightly different subject, but a while back I had to replace the springs under the Hi + Lo screws of my 044, the saw would not hold a tune. So yes, springs do wear out, the new springs (50 cent each) cured the problem! I had to order them through a dealer, they also do not come with a rebuild kit.