Primers vs. Chokes

Arborist Forum

Help Support Arborist Forum:

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

bplust

Addicted to ArboristSite
AS Supporting Member.
Joined
Dec 28, 2010
Messages
1,750
Reaction score
678
Location
WHEELOCK
Hi all,

What are the advantage/disadvantages to each one? My intuition tells me that a choke would last longer than a pump, but I've been wrong before.

I'm sure this question has been asked before, someone redirecting me to a previous thread (I couldn't find what I wanted) would work.

Thank you,

Bryan
 
Hi all,

What are the advantage/disadvantages to each one? My intuition tells me that a choke would last longer than a pump, but I've been wrong before.

I'm sure this question has been asked before, someone redirecting me to a previous thread (I couldn't find what I wanted) would work.

Thank you,

Bryan

As far as I can tell, the "primer" on most OPE is basically a "purge pump" that gets the carb full of gas without having to pull the starter cord. So more "first-pull" starts.

However, even saws with this "primer" need the choke to enrichen the mixture enough for it to start.

In my limited experience, OPE without primer bulbs start better than OPE with...
 
As far as I can tell, the "primer" on most OPE is basically a "purge pump" that gets the carb full of gas without having to pull the starter cord. So more "first-pull" starts.

However, even saws with this "primer" need the choke to enrichen the mixture enough for it to start.

In my limited experience, OPE without primer bulbs start better than OPE with...

You're basically right. Most of the bulbs you see on small OPE (chainsaws, hedge trimmers, blowers, whackers, etc) are indeed purge pumps (and not primers, despite what people call them). They push or pull fuel through the lines and carb, purging the air out. Makes for quicker starts. The downside of 'em is that they tend to develope air leaks after a while. I'm not a fan of them. Just my opinion, based on my experiences...

True "primers" on small OPE are usualy piston pumps that spray a shot of fuel into the carb throat or intake manifold as a means of enriching things for cold starting in place of a choke. You won't see that on much 'modern' small OPE. Back in 'the old days', McCulloch chainsaws were where you'd find the most primer systems. Many lawmowers do still have bulb type primers in place of chokes.

A purge pump can be pressed 100 times without flooding the engine. Once the air is purged, all you're doing is passing fuel through the lines and carb and back to the tank. The bulb feels 'harder' to push once the air's out.

A primer bulb or pump will flood the engine if it's pressed too much. For the most part, you won't find a primer on a piece of OPE with a choke. You will find a choke on a purge pump/bulb equipped piece of OPE, as it still needs some method of cold start enrichment.
 
You're basically right. Most of the bulbs you see on small OPE (chainsaws, hedge trimmers, blowers, whackers, etc) are indeed purge pumps (and not primers, despite what people call them). They push or pull fuel through the lines and carb, purging the air out. Makes for quicker starts. The downside of 'em is that they tend to develope air leaks after a while. I'm not a fan of them. Just my opinion, based on my experiences...

True "primers" on small OPE are usualy piston pumps that spray a shot of fuel into the carb throat or intake manifold as a means of enriching things for cold starting in place of a choke. You won't see that on much 'modern' small OPE. Back in 'the old days', McCulloch chainsaws were where you'd find the most primer systems. Many lawmowers do still have bulb type primers in place of chokes.

A purge pump can be pressed 100 times without flooding the engine. Once the air is purged, all you're doing is passing fuel through the lines and carb and back to the tank. The bulb feels 'harder' to push once the air's out.

A primer bulb or pump will flood the engine if it's pressed too much. For the most part, you won't find a primer on a piece of OPE with a choke. You will find a choke on a purge pump/bulb equipped piece of OPE, as it still needs some method of cold start enrichment.

That's spot on. In addition to air the metering chamber can also have a fuel vapor bubble, especially after heat-soaking when a hot saw is shut down. The purge pump will pull that through as well.
 
last saw I heard of with a primer

I have a Makita DCS 520, just a choke, the 520i had an prime injector
carburetor, think some Dolmar i models did too.
I have some OPE equipment with purge bulbs, when working properly, they seem
to help starting by flushing stale fuel out of carburetor, but more lines & a flimsy
bulb to crack & fail.
 
Back
Top