H70 motor - no primer? - Snowblower Forum : Snow Blower Forums
 
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post #1 of 9 Old 11-24-2014, 09:16 PM Thread Starter
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H70 motor - no primer?

So I've acquired an Ariens H70 7hp motor from a friend's old machine. The heater box was taken off and misplaced, everything else looks complete.
I tried to start it after a carb rebuild and it won't start. I am getting spark to the plug and there is fresh gas.

I have an older 10M-L60 model and it has a primer system. This one does not, and the carb does not have any provision for a primer tube/hose so I suspect it was a plunger style on the side of the heater box, correct? How do you prime this motor to start?

Thanks,
Rob
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Last edited by z31kid; 02-08-2015 at 11:45 PM.
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post #2 of 9 Old 11-24-2014, 09:25 PM
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take off the plate where the primer would go, and place the palm of your hand over the hole and pull it over slowly, this will have the same effect as a spring primer
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post #3 of 9 Old 11-24-2014, 11:29 PM Thread Starter
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Thanks! I will give that a shot this weekend.
Happy Thanksgiving.
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post #4 of 9 Old 11-25-2014, 08:35 AM
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Quote:
Originally Posted by z31kid View Post
So I've acquired an Ariens H70 7hp motor from a friend's old machine. The heater box was taken off and misplaced, everything else looks complete.
I tried to start it after a carb rebuild and it won't start. I am getting spark to the plug and there is fresh gas.

I have an older 10M-L70 model and it has a primer system. This one does not, and the carb does not have any provision for a primer tube/hose so I suspect it was a plunger style on the side of the heater box, correct? How do you prime this motor to start?

Thanks,
Rob
buy a can of starting fluid from the local gas station/mini market. open the choke, open the throttle wide open, give it a quick shot for 1 second, close the choke. this allows the ether to go past the choke plate, past the throttle plate, and get into the intake manifold. closing the choke quickly traps the ether in there. move throttle back to 1/2 way mark, pull. if you have spark it will start.

I have Tec. 3.5, 5, 7, 8HP motors on machines and noticed the smaller ones lack the cylinder draw to pull the fuel in on the first pull when starting them cold, simply because they are so small- this happens especially if they've been sitting for a few weeks. if they only sit a day or a week, they generally do start right up.

the 7's and 8's will generally start on the choke without ether shot by the 2nd pull, but sometimes those need a shot too if they sat outside in the rain. these are old engines with no primer bulb- so if the machine sat a long time and the intake tract and carb is dried out, they need a few pulls to charge the intake manifold.

first off the fuel bowl must fill with gas, then some mixture must be pulled into the carb venture bore, then it must climb upward against gravity using the vacuum draw of the engine to fill the intake manifold, then it has to fill the cylinder, then the spark plug can light it. on some engines that may take more than a few pulls to charge that entire intake tract, especially on an old machine with some wear not drawing as hard as when it was new- and ice cold from sitting for a long time.

giving it a shot of ether makes that happen with 1 pull usually, as the ether is quickly evaporating and fills the intake manifold with fumes almost instantly.

the old style sheetmetal primer plates that pump air into the carb mouth, just don't work all that well. they actually just get in the way. I had the pullcord wrap around the primer on the 8HP I have, and snap the primer handle in half on recoil. so I removed it. save yourself a lot of arm pulling and pullrope wear- just give it a shot of ether.

don't drown it, just one "pssst" will do

that is a cherry Tec. 7 BTW, good score. the paint on it is very nice original. the primer is removed from it. you may as well remove the little primer housing as well, with the 2 little screws that hold it on. it's not doing anything there now but getting in the way. the airflow will be more direct straight in and the engine will breathe a little better too.

serial says it's a 1976 ? because I think a 1966 may have the serial stamped on a sideplate, instead of the top cover. my 1968 7HP is stamped on a sideplate. nice engine.




just say NO to Chinese made ANYTHING !
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Gilson 55012 8/26 gear drive
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Yard-Man Snowbird 7040-0 5/22
Ariens 10M-L35 3.5/24
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(2) AMF Polar Bear 7/26 3-stage project/parts machines

Last edited by greatwhitebuffalo; 11-25-2014 at 08:48 AM.
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post #5 of 9 Old 11-25-2014, 08:47 AM
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You could re-create the plunger primer with a little simple hardware.

'77 Ariens 924032 "Brick House" Re-Powered with a TEC 10HP and oversize auger pulley
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post #6 of 9 Old 11-25-2014, 08:51 AM
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I wouldn't even bother, IMHO those types of primers don't really even work.

OP- there was a primer there but someone removed the pump plate section. or, it broke off and fell off.

junk in front of the carb entrace blocks airflow, and on a small engine like that, it's very detrimental to power.




just say NO to Chinese made ANYTHING !
1967 S-242 Snowbird 4/24
AMF Dynamark Luminaire 5362 8/26 3-stage
Craftsman Drift Breaker 10/32 3-stage
Gilson 55012 8/26 gear drive
Ariens 910010 8/32
Cub Cadet 268 8/26
Yard-Man Snowbird 7040-0 5/22
Ariens 10M-L35 3.5/24
New Holland/Gilson Unitrol 8/26
(2) AMF Polar Bear 7/26 3-stage project/parts machines
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post #7 of 9 Old 11-25-2014, 10:26 AM
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The plunger primers do work, but are often not needed to start a well tuned engine. The plunger seals the carb throat while you crank or pull through the piston. The vacuum caused by the movement of the piston is enough to draw fuel from the bowl into the intake. You may be suffering from low compression which will also make starting difficult. MH

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post #8 of 9 Old 11-25-2014, 03:09 PM Thread Starter
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Thanks for the info everyone.
I'm all too familiar with having to use ether to get these old motors starting at times, but I figured since this motor was so clean I had hoped it would fire right up after a carb tune up.

Anyone got a picture of what this setup SHOULD look like?

My neighbor was able to find the original heaterbox cover and there is no provision for a plunger or primer on it and I don't see anything broken or any other provision for a primer on this carb itself (on my other machine there's a nipple on the carb that attaches to a vac hose to the primer bulb on the heaterbox).

I do have an electric starter that will fit so maybe I will throw that on and try again with a shot of ether.


Quote:
Originally Posted by greatwhitebuffalo View Post
I wouldn't even bother, IMHO those types of primers don't really even work.

OP- there was a primer there but someone removed the pump plate section. or, it broke off and fell off.

junk in front of the carb entrace blocks airflow, and on a small engine like that, it's very detrimental to power.
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post #9 of 9 Old 11-25-2014, 03:56 PM
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Garage
Here you go. There wouldn't be anything on the heater box.
.
.

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

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Last edited by Kiss4aFrog; 12-01-2014 at 11:35 AM.
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