Accelerator Pump O-Rings (Carburetor Model Look-Up)

[Vintage Engine Repairs]

I’m a big fan of having an accelerator pump on a carby, but the o-rings are a known weak point.

For your reference, buy them from an o-ring supplier - it’s about 20-30 cents a piece. From Stihl / Zama, you can buy one size and not the other.

Lots of people block off the accelerator pump drillings and in some machines this works well, like the 200t, on other machines, this affects metering chamber volume and will cause strange running characteristics. I have yet to repair a machine with a worn piston or bore yet, but that does happen and is worth checking too. But having the o/rings on hand can make a quick fix for a leaking acc accelerator pump. I hope it helps.

Size One - 3x1 metric fits:



Size Two - 2.3x0.8 metric fits:

 

[EFSM]

We stock 3 different sizes: from smallest to largest 195702308 (most common on Husqvarna products), 195503010 (superceded to Z000-955-Z014-A, the most common), and 195503510 (fits some of the Stihl 4-mix/saw carbs). Replacing accelerator plunger o-rings has drastically improved the success rates of my carb rebuilds.

 

[EFSM]

I should see if I can cross reference the Zama part numbers to Walbro. Their rubber is far, far superior. I have only replaced one or two Walbro o-rings.

 

[Vintage Engine Repairs]

We stock 3 different sizes: from smallest to largest 195702308 (most common on Husqvarna products), 195503010 (superceded to Z000-955-Z014-A, the most common), and 195503510 (fits some of the Stihl 4-mix/saw carbs). Replacing accelerator plunger o-rings has drastically improved the success rates of my carb rebuilds.

Nice, I haven’t come across any 4 mix yet, that’s really handy to know. I’ll keep that in mind, thanks! My guess is 3.5mm x 1mm. Can you confirm that?

Edit: I haven’t come across any walbro carby pump issues come to think of it! Maybe I just don’t see them on carbs as frequently?

 

[EFSM]

Nice, I haven’t come across any 4 mix yet, that’s really handy to know. I’ll keep that in mind, thanks! My guess is 3.5mm x 1mm. Can you confirm that?

Edit: I haven’t come across any walbro carby pump issues come to think of it! Maybe I just don’t see them on carbs as frequently?

They are not as common but Echo uses them extensively on their top-handle saws. 3.5x1 sounds about right. They're barely bigger.

 

[pbillyi69]

We stock 3 different sizes: from smallest to largest 195702308 (most common on Husqvarna products), 195503010 (superceded to Z000-955-Z014-A, the most common), and 195503510 (fits some of the Stihl 4-mix/saw carbs). Replacing accelerator plunger o-rings has drastically improved the success rates of my carb rebuilds.

do you have the o rings for the walbro 199 carb?

 

[EFSM]

do you have the o rings for the walbro 199 carb?

I don't think we stock them. I basically don't seem them go bad.

 

[SteveSr]

I’m a big fan of having an accelerator pump on a carby, but the o-rings are a known weak point.

For your reference, buy them from an o-ring supplier - it’s about 20-30 cents a piece. From Stihl / Zama, you can buy one size and not the other.

Lots of people block off the accelerator pump drillings and in some machines this works well, like the 200t, on other machines, this affects metering chamber volume and will cause strange running characteristics. I have yet to repair a machine with a worn piston or bore yet, but that does happen and is worth checking too. But having the o/rings on hand can make a quick fix for a leaking acc accelerator pump. I hope it helps.

Size One - 3x1 metric fits:
View attachment 419833View attachment 419834View attachment 419835


Size Two - 2.3x0.8 metric fits:

View attachment 419832

@Vintage Engine Repairs Just curious where you got your o-ring dimensions from? Did you measure samples or find actual documentation for the sizes?

I think that your m2.3x0.8 might actually be 3/32" x 1/32" imperial (.094" x .031").

I am getting ready to order some wher the shipping is likely equal to or greater than the cost of the parts and want to be sure I get the right sizes.

 

[Wonkydonkey]

I was looking to get some as well, probably order from China thou , I was wondering what type to get , NBR, EPDM, or those FKM.

The latter is good fuel resistant (ethanol) where as NBR is not so good.

My carb is from a 200t and is a C1q 61 & that is not actually on the list

I have looked around on the net, & seen a few different prices, for the pump piston kit . It would seem the pump is slightly different shape & length.
I know I was actually just looking for the orings…but one search leads to another search.
There is a seller on eBay that sells aftermarket piston pump kits, I’ve been trying to figure out where they com from. It’s not Farmatec thou. As I’ve looked and asked.

 

[DND 9000]

Use O-Ring Z000-955-Z014-A for your C1Q-S61 carburetor.

 

[SteveSr]

Use O-Ring Z000-955-Z014-A for your C1Q-S61 carburetor.

Do you know if any of these tiny o-rings are standard sizes or if they are custom made?

This particular one looks like it is close to M3x1.

Tom's M2.3x.8 is actually close to 3/32" x 1/32" imperial but the imperial cross sections for standard sizes don't go down to 1/32" (0.8mm) so am thinking that these are custom.

 

[SteveSr]

We stock 3 different sizes...

As in buy the Zama part numbers or stock to resell?

 

[Wonkydonkey]

Do you know if any of these tiny o-rings are standard sizes or if they are custom made?

This particular one looks like it is close to M3x1.

Tom's M2.3x.8 is actually close to 3/32" x 1/32" imperial but the imperial cross sections for standard sizes don't go down to 1/32" (0.8mm) so am thinking that these are custom.

I’m sure They will be standard sizes…
most of the world uses the metric system and stihl is German which is part of Europe. Even thou most of it’s made in China.
So my suggestion is buy them from someone that sell them in metric

 

[Wonkydonkey]

On the other hand… you could use a comparison chart on this website to work out what the Oring you need in metric and what it’s imperial size is

British O-Ring Size Chart | BS British Standard O-Ring Sizes

www.allorings.com

 

[DND 9000]

Do you know if any of these tiny o-rings are standard sizes or if they are custom made?

I don`t know if it is a standart size.

 

[SteveSr]

On the other hand… you could use a comparison chart on this website to work out what the Oring you need in metric and what it’s imperial size is

British O-Ring Size Chart | BS British Standard O-Ring Sizes

www.allorings.com

Well, like I was saying, this is the standard imperial chart and cross section doesn't go below .040"

A similar metric chart doesn't go below 1mm (.039") cross section but at least there are more I.D. options. So it would appear that these are custom unless someone knows another rock to look under...

Here is a link to the metric chart:

https://www.allorings.com/Metric-O-Ring-Size-Chart

 

[EFSM]

As in buy the Zama part numbers or stock to resell?

Yes. I'm sure I could get them cheaper custom made in big batches but I never took the time to do so. I replace them in nearly every Zama carburetor I have apart.

 

[SteveSr]

I just disassembled the pump on a C1Q-S174 carb off of a Stihl 4-mix. Here are the relevant dimensions of the piston:

Diameter = 0.215" (5.46mm)
Ring groove diameter = 0.144" (3.66mm)
Ring groove height = .044" (1.12mm)

Based on these measurements it looks like an M3.5x1 o-ring is correct for this carb.

Now to find a reliable source for these. Trying to avoid the Chinese garbage.

 

[pbillyi69]

the local bearing house i go to has o rings too

 

[Al Smith]

FWIW usually if you know the size they can be found on E-bay on the cheap . However just like a lot of things you have to research it .Just remember "google " is your friend .