carb question - primer v.s. no primer - Snowblower Forum : Snow Blower Forums
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post #1 of 15 Old 11-30-2014, 11:01 AM Thread Starter
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carb question - primer v.s. no primer

When I picked up my Tec. HS50 (70's Arien's blower) I immediately noticed the lack of a primer bulb/line and was told it was a 'self-priming carb'.

Almost every carb I see mentioned on this site or on the repair videos all have primer lines/bulbs.

How does a carb 'self-prime' and why don't all carbs use this feature/why the discrepancy between designs?
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post #2 of 15 Old 11-30-2014, 11:09 AM
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The first pull of the cord usually "primes" the carb with fuel and they start on the second or third pull if tuned well.

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1962 Ariens 10ML60
1979 Toro 524
1975 MTD Snowflite 4/22
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post #3 of 15 Old 11-30-2014, 11:37 AM
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Here's my guess.

Usually engines that operate in colder weather need a richer air/fuel mixture to start. That's why on some of the really old Tecumsehs there's a push plate that's a cold weather choke, it has smaller holes than the choke plate does and allows for additional choking when the temps get below 0F.

A bulb primer probably eliminates the need for different diameter holes in the choke plate and allows the engines to be more easily used across a wider range of both summer and winter applications with no changes in carb design whatsoever.

Or maybe the engineers found that the engines start easier that way, who knows
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post #4 of 15 Old 11-30-2014, 11:39 AM
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If your engine is from the 70's, it would\should have a mechanical primer as described and pictured in this thread--

https://www.snowblowerforum.com/forum...-not-bulb.html

Toro 8/24 (38080) 1989
Toro 721-QZR (38743) 2015 (Hemi Predator Power)
Toro 421-E (38585) 2008 (New Owner)
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post #5 of 15 Old 11-30-2014, 11:40 AM
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Did you check the carb numbers to see if it is the right carb for that engine and blower and not replaced with something off a mower or tiller or something ??

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Make sure the windows are up before the snow plow goes by !!

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post #6 of 15 Old 11-30-2014, 12:42 PM Thread Starter
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This is the best I can read the numbers off the carb, the second set is what puzzles me:

568 8J22
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post #7 of 15 Old 11-30-2014, 12:59 PM
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Quote:
Originally Posted by cancon View Post
This is the best I can read the numbers off the carb, the second set is what puzzles me:

568 8J22
The carb numbers indicate 568 is Tecumseh carb number 631914.
The 8 indicates year (68 or 78) Probably 78.
The J indicates month (Jan,June,July)
The 22 is the day of the month.

From Here-
Tecumseh Carburetor Manufacturing Numbers

Toro 8/24 (38080) 1989
Toro 721-QZR (38743) 2015 (Hemi Predator Power)
Toro 421-E (38585) 2008 (New Owner)
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post #8 of 15 Old 11-30-2014, 01:11 PM Thread Starter
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Cool, thanks for that. I thought I was supposed to have only 3 characters in the second bit. So '78 makes sense because it is the year of the blower. The engine is HS50-67008B with the a 1978 serial number and carb #631914 matches this as far as I can tell.

Also, there is no push-plate on this machine.
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post #9 of 15 Old 11-30-2014, 06:19 PM Thread Starter
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But back to the story, what gives?
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post #10 of 15 Old 11-30-2014, 06:39 PM
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In looking up that carb it doesn't have anything other than just the choke. It might be that it was jetted rich enough it started just fine with just having the choke on.

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