# 631929 Equivalent Carburetor Replacement



## Throughthefire (Jan 14, 2013)

Hi,

Just spent the weekend fighting with a Toro 421 Snowblower with the Tecumsah engine and 631929 carburetor. 

My problem seems to be with the carburetor; if I spray starting fluid into it, it will run for 10 seconds, then stops. My reading of this is that I have a fuel supply problem. 

I had the carburetor off and soaked in carb cleaner, but I left it too long - about an hour whilst I ran to the store to buy some rubber gloves (my latex gloves were dissolved by the carb cleaner!). I see in the Tecumsah manuals that I shouldn't soak the carb for more than 30 minutes in cleaner.

After cleaning it, I get exactly the same result; runs for 10 seconds, then it stops. My options appear to be to buy a service kit for the carb, or replace it with a new one.

If I replace it, is there a standard, cost effective and easy replacement out there? I can't find the original except at a few places for over $100 - not worth it for a $50 snowblower, but I do want to keep this one working!

Thanks in advance.


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## detdrbuzzard (Jan 20, 2012)

hello throughthefire, welcome to SBF. you have to pull the jets and clean them just soaking in carb cleaner won't do that


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## bwdbrn1 (Nov 24, 2010)

Hi Throughthe fire, welcome to the group. We feel your pain, because we've all had an experience like yours. You put all that time and effort into it thinking, boy this is sure going to run now, only to have the blasted thing seem to be fighting you all the way. 

First, I'd recommend using brake and parts cleaner in an aerosol can. That's what I use myself, having picked up on it while working at a motorcycle repair shop for a summer couple of years ago. It's not as harsh on the hands, and the gloves hold up longer. I'm going to guess Tecumseh says not to leave them soaking for more than 30 minutes because the rubber bits will start to break down.

Second, like detdrbuzzard said, you have to take the jets out and shoot the cleaner through the openings, and clean the tips off.

Don't know if this is the manual you were referring to, but scroll down the pages and you'll get some pretty good visual aids to taking the carb apart to clean it.

http://www.barrettsmallengine.com/manual/tecumsehcarburetormanual.pdf

Look into a carb kit for the carb before looking to buy a whole carb. You should get everything in a kit you need to rebuild the one you've got, and it should be a lot cheaper than a carb.

Let us know how it goes for you.


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## td5771 (Feb 21, 2011)

If you soaked the carb did you take the float needle out? There are 2 types....one that has a rubber tip on the end and another that has a metal tip and a small rubber donut with a tiny hole that the needle sits in. It regulates the flow of gas. The carb soak would expand the tip or the donut and close off the fuel supply. A rebuild kit would come with a new rubber tipped float needle or a metal tip needle with the matching seat (donut).

There are also o rings on the 2 needle valves that would be ruined with the soak as well. 1 high and 1 low


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## HCBPH (Mar 8, 2011)

*Carb problems*

First off, welcome to the forum

If you're soaking the carb, strip it down first assuming it's a metal frame.
Pull the float, needle valve seat along with the jet needles.
Now on your issue, one thing I've found is there are 3 small holes in the throttle bore behind the welch plug in the side. If they're plugged it causes issues running. I have taken a piece of phone wire, put a 90 degree bend in it and work it through those holes (assuming you didn't remove the welch plugs.
I also use spray brake cleaner to clean them out. I spray the heck out of everything prior to putting in a carb kit. I've done that on over a dozen carbs successfully.
In all fairness I've had 2 carbs off Ariens blowers - 8 hp with Tecumseh engines that absolutely wouldn't work for me. I ended up getting replacement carbs for them. I looked for a carb for a comparable sized engine, cost about half the money as a service carb. If the choke linkage is different, you have the choice of either swapping out the choke arm off your original carb or get the correct linkage for your carb - I've done both. Here's a thread that touched on the various options I ran into for a 8 HP:
Scrap that problematic carb

Hope that helps. If you try something like this, look for a replacement carb for an engine your size. For some reason, replacements for Ariens go for alot more than the same engine on other brands.


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## Throughthefire (Jan 14, 2013)

Thanks everyone!

A bit more detail; I did strip down the carb before putting it in cleaner, but I think the O-ring for the main needle valve (the one at the bottom) got left in. Also, I didn't have a service kit, so didn't punch out the Welch plugs. 

Today I'm going to get hold of a service kit for it, have the plugs out and see what other gunk I can find in there. 

The previous owner had left the gas in it for several winters, and I found the fuel lines completely stuffed up with bitumen, so I think the channels below the plugs will also be suffering.

Your help is gratefully appreciated! Hope to get this Snowblower running by mid-summer at this rate... <g>


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## bwdbrn1 (Nov 24, 2010)

Hopefully before then! Let us know what sort of critters you find residing in that carb.


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## Throughthefire (Jan 14, 2013)

*Time for an update!*

So I got hold of a carburetor service kit, and installed it. Daughter didn't like me using her pink glittery nail varnish to seal the new welch plugs, but tough.. 

It now runs, and cuts snow nicely. My only remaining question is, I'm not sure what rpm to run the engine at (nor how to attach a tachometer to measure it). Any ideas? When I have the engine running at slow idle, it turns over nicely, but wouldn't have any power to push snow - is that correct?

Thanks for all the help so far!

Pete.


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## HCBPH (Mar 8, 2011)

*Welch Plugs*



Throughthefire said:


> So I got hold of a carburetor service kit, and installed it. Daughter didn't like me using her pink glittery nail varnish to seal the new welch plugs, but tough..
> 
> It now runs, and cuts snow nicely. My only remaining question is, I'm not sure what rpm to run the engine at (nor how to attach a tachometer to measure it). Any ideas? When I have the engine running at slow idle, it turns over nicely, but wouldn't have any power to push snow - is that correct?
> 
> ...


Pete
I've never sealed the welch plug, just seated them well on the install. I use a metric socket when seating them and it seems to work just fine.
There are tachometers available, one is a wire setup that when rested on the machine somehow indicates the speed, another uses a light similar to the old timing lights except it reads a white strip added to the pulley etc.
There's another one similar to the 2d one except it is pressed against the pulley or crank - I cannot recommend that 3d one, doesn't work well.
As far as I remember, I think the RPM's are supposed to be set around 3400, but it's in the Tecumseh manual.

Paul


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## bwdbrn1 (Nov 24, 2010)

There's lots of tachs that you can use for small engines. I have one that has a clip that goes onto the sparkplug wire so it can be used on all the small engines I have. Looks like this one, but I don't remember now who I ordered it from. I know it doesn't have the Matco name.

Google Image Result for http://www.matcotools.com/ProductImages/etp328.jpg

As you can see, there's lots to choose from, and a pretty broad range of prices.

small engine tachometer - Google Search

I've heard Tiny Tach mentioned a lot.

Design Technology, Inc., Home of Tiny-Tach


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## Throughthefire (Jan 14, 2013)

Thanks! The Tiny Tach looks just like what I need - I was already looking for an hour meter anyway, so both in one device looks like a good deal!


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## Shryp (Jan 1, 2011)

3600 RPM is usually the normal.


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