Maintenance Report - compression - Snowblower Forum : Snow Blower Forums
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post #1 of 13 Old 03-15-2015, 09:55 AM Thread Starter
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Maintenance Report - compression

So as I've posted recently, I was having issues with my ariens 921012 trigger wheel lock. After replacing the cable it worked for a while, but started failing again. To make a long story short, I had my dealer look at it.
In addition to the wheel lock issue, I asked him to go through the whole unit.
So her performed his standard snow blower service.
This included plug, oil, carb kit, lubrication all around. It also needed a new friction disc. I was surprised to hear that all my belts were good after 6 seasons of use. I would guess that proper pulley tension and alignment since new would contribute to belt longevity.

My report states compression to be 85lbs which according to his report was marked OK. Therein lies my question. What is normal or acceptable compression for this B&S 250cc snow series engine? At what point is compression bad and what causes compression to decrease over the years?

Thanks in advance.

2010 Ariens Deluxe 27 (921012)
250cc B&S (1150 ft lbs)
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post #2 of 13 Old 03-15-2015, 10:05 AM
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Normal wear and tear will lower compression but if it's only 6 yeas old that would need to be a lot of wear on the piston rings or valves/valve seats.
Did you notice any lack or loss of power this last season ??

I didn't look up the spec.
Maybe it has lower compressing during testing because of a compression release built into it for easier starting ??

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post #3 of 13 Old 03-15-2015, 10:14 AM Thread Starter
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Originally Posted by Kiss4aFrog View Post
Normal wear and tear will lower compression but if it's only 6 yeas old that would need to be a lot of wear on the piston rings or valves/valve seats.
Did you notice any lack or loss of power this last season ??

I didn't look up the spec.
Maybe it has lower compressing during testing because of a compression release built into it for easier starting ??
So that's my question. Is 85psi considered low? Or is that normal for this engine?
I haven't noticed any loss of power at all over the years. It's a good strong engine. The machine easily cuts through 2/3+ foot hard drifts that the giant plows leave at the end of my driveway on my busy street. I was throwing snow in excess of 30' all winter.

I should mention I didn't report any engine issue to the dealer, he checks it and lists it on the work order as part of the tuneup

2010 Ariens Deluxe 27 (921012)
250cc B&S (1150 ft lbs)

Last edited by Loco-diablo; 03-15-2015 at 10:30 AM.
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post #4 of 13 Old 03-15-2015, 10:52 AM
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Originally Posted by Loco-diablo View Post
So that's my question. Is 85psi considered low? Or is that normal for this engine?
If you posted the engine numbers maybe someone can find the service manual for it and the specs.

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post #5 of 13 Old 03-15-2015, 11:01 AM Thread Starter
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Thanks Frog

15C1 34 0128 E8

I poked around online and couldn't get a straight answer. I guess this engine does in fact have a compression release built in. I read that because of the release, the actual compression numbers are skewed at best during the compression test.

2010 Ariens Deluxe 27 (921012)
250cc B&S (1150 ft lbs)

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post #6 of 13 Old 03-15-2015, 01:47 PM
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Most rope start small engines have a built in compression release system to aid in starting. They have to be running at more than 800 to a 1000 RPM for the release to stop working. I doubt you can pull the cord that fast. The number you get pulling it over will never be real compression figures to the point I would never bother even taking a compression test. If it has some compression it is probably enough. Roger

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post #7 of 13 Old 03-15-2015, 08:09 PM
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Quote:
Originally Posted by Loco-diablo View Post
Thanks Frog

15C1 34 0128 E8

I poked around online and couldn't get a straight answer. I guess this engine does in fact have a compression release built in. I read that because of the release, the actual compression numbers are skewed at best during the compression test.
Here is a link to the Briggs service manual. Page 27 recommends using a leak down tester to test for any compression problems. Actual compression readings will vary because of the quality of the gauges used and as stated, the automatic compression release (ACR). I have had engines with 50-60 pounds compression run perfectly.

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post #8 of 13 Old 03-15-2015, 08:25 PM
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A leak down test will also indicate where the problems are, valves, rings, head gasket.

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post #9 of 13 Old 03-16-2015, 02:27 PM Thread Starter
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Thanks for all the replies folks!!

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2010 Ariens Deluxe 27 (921012)
250cc B&S (1150 ft lbs)
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post #10 of 13 Old 03-16-2015, 04:54 PM
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Quote:
Originally Posted by Loco-diablo View Post
Is 85psi considered low? Or is that normal for this engine?
Seeing as how Briggs & Stratton has never published compression numbers no one ever checks them with a compression tester (and to be totally honest it isn't really possible to anyway)

Briggs & Stratton has always stated (unless something changed recently) to manually spin the engine backwards, when it hits the compression stroke the flywheel should rebound sharply, if so the engine has adequate compression.

You can't test them going ahead as the compression release cam will lower your numbers, this is why you can't really use a gauge, there's no way to turn the engine over backwards long enough to get a number.
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