Harbor freight compression tester

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woodeneye

woodeneye

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So I recently had a 30% off coupon for Harbor Freight and decided to get a compression tester. Well, no surprise, it shows all my good running saws at anywhere from 90 to 115 psi. Is there any fix for this or should I just get a refund or should I try for a replacement unit? I know there is a lot of harbor hate on this forum and I probably should have at least got a craftsman if not snap on but the price was so tempting! Could I just replace the pressure gauge maybe? Any thoughts appreciated and if you have a good used one to sell me, I'd love it.
 
CTYank

CTYank

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An educated consumer can do very well at HF. Some of their bargains are not real bargains, IMHO. Case in point- their all-plastic chain grinder. In some cases, mediocre tools just won't do. Comp tester is one of those.
 
watsonr

watsonr

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you need one with a schrader valve in the tip, you probably got a car tester. The one for a two stroke has the valve to prevent the air escaping the rubber hose as a chainsaw doesn't have much volume on each stroke. Pull until the gauge stops climbing.
 
fearofpavement

fearofpavement

Trying them all
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you need one with a schrader valve in the tip, you probably got a car tester. The one for a two stroke has the valve to prevent the air escaping the rubber hose as a chainsaw doesn't have much volume on each stroke. Pull until the gauge stops climbing.

Show me a picture of a compression tester that doesn't use a schrader valve because I've never seen one. they all need it to record the reading. (not counting the ones you hold against the plug hole)
 
watsonr

watsonr

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Me either... just that some have the valve near the gauge and not in the tip. The one with it in the tip prevents the pressurized air from escaping the hose. The one with a valve near the gauge... has to fill the hose before it can fill the gauge... and those typically read low @90-115psi when used on a saw.

If the hose only fills 1/2 way, the down stroke pulls the compressed air down with the piston and not much actually makes it to the gauge. But a valve in the tip never lets the pressure go until you release it.
 
LowVolt
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I have been there and done that with harbor freights tester. It only read 90 psi on all my great running saws. I exchanged for another with the same results. I ponied up the extra cash for the craftsman (mityvac) one that comes in a kit and have not looked back. It is a good quality tool.
 
watsonr

watsonr

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Same here with the HF compression gauge with the hose. The tester seems ok if I have someone hold the gauge, with the valve in the end of the metal tube, against the plug hole.
The one that I got, http://www.harborfreight.com/compression-test-kit-8-pc-69885.html

That one has the valve near the gauge. Using the one with rubber tip makes the tube shorter and will work, but not optimal since it takes two people.
Go get a better gauge. I bought a used Snap on for $60 on eBay.... I just searched there and it has a bunch listed for cheap money!
 
OC455

OC455

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I bought the more expensive compression tester from Advanced Auto.....it has the hose and the metal tube. It also has different sized fittings too. I used the metal tube and put the gauge on it, much easier to get the reading on it. $41 and some change plus tax....
 
pops21

pops21

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The tester I got from HF is http://www.harborfreight.com/quick-connect-compression-tester-95187.html This one. I leave mine connected since there is mainly only one plug size for chainsaws. Just make sure not to screw it into the cylinder too tight. Its uses a oring to seal so just snug it tight. Mine has been checked with other testers in the past and was within 5psi.
 
Wood Doctor
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OP, you might be able to live with it. Most measurement errors are a constant multiplier and the error increases as the pressure increases. The percent error, however, remains the same along the scale. In your case, the multiplier is about 1.4. For example, if the gauge reading is 100 psi, the actual pressure is 140 psi. If the reading is 50 psi., the actual pressure is 70. So, simply use that multiplier to convert the gauge reading to the correct pressure.

You would be surprised at how well that will work.
 
lone wolf
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