A late thought. Say you buy a HF, or generic tool of sorts to save maybe $20 or so. You're feeling great in saving a bit of green, but "what if" that tool causes a miss-diagnosis......Or chasing good parts because.....
Importance of vacuum/pressure testing
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Most gauges, even on name brand items in the automotive world have a + or - 5-10% accuracy range. Let alone most don't have a way to compensate for elevation changes, hence why the "0" is usually so large. It's considered perfectly acceptable. You're more so after consistency. Does it hold vacuum? Doesn't really matter if it's 5-8"hg. Does it hold pressure? Again, doesn't matter if it 7-10 psi for the work being done. We're not in a lab environment working on small engines and non of the parameters are so critical that the cheaper Guage sets can't be used for accurate diagnosis. Truthfully, if I didn't already have a lot of high end tools from being a professional mechanic I wouldn't be wasting the money on name brand stuff that would spend 90% of it's life collecting dust.
You’re not wrong. The QA/QC on those tools is hit-or-miss and that’s why they’re so inexpensive. So yeah some percentage of those tools straight up fail the first time they’re used. Just a fact.
A pro tech (somebody like you for instance) if you were on a desert island and forced to use HF or made in PRC tools.. the pro tech I think would recognize the readings didn’t make sense and he/she would be frustrated as all git out but pro tech would figure it out somehow… because he’s a pro. Maybe not ALL pro techs… but say… most pro techs.
But the *beginners* for sure would be screwed if they bought an out of the box lemon comp tool or vacuum tool. (Not a dig at the beginners—we were all new to this once—it’s just a fact)
Beginner wouldn’t know what to look for. And yeah beginner would NEVER get a diagnosis right and would also be frustrated as all git out… but I’m trying to think of a way that ends up damaging the saw…. (Shrug)
The takeaway: my advice to *everyone* beginner or not—buy the highest quality tools—even if you have to buy them used. High quality made in USA, Switzerland, Germany among others… if you buy top of the line tools used, if you later discover you don’t like wrenching you can sell the tools probably for what you paid for them. Because used high quality tools pretty much hold their value IME.
But again, IME most beginners don’t want to hunt down used tools out of the classifieds or whatever the modern equivalent is—they just want to get to it and want tools in their hands quick. So they go to HF or they go to local hardware store that rhymes with “base” and they think “oh these hardware store wrenches and tools look good. The price isn’t exactly ‘cheap’ so they must be better than HF and pretty good right? And those guys end up paying a higher price for tools made in the PRC… LOL. But at least (I think?) they can return the tool to hardware store and get a replacement or their money back or something (? I think—I know sears still does that even though their craftsman tools aren’t made in USA anymore… which is really a shame).
But I’m trying to think of a situation where a bad reading from a leakdown test or compression check ends with a destroyed saw but yeah maybe he’s using a vacuum gauge that is busted and once pumped up to 15 it just sticks there no matter how leaky the motor is… maybe the cost is frustration wasted time and having to pay a pro to diagnose it.
But maybe there’s a nuke scenario from a PRC tool… idk it’s a curious good question. I’m gonna noodle on it.
HAGD everybody!
You are the pro tech case in point… on a desert island you’d be annoyed but if you had a pile of chainsaws and nothing but coconuts and a HF store you could make them all run no problem. But you know what you’re doing…
I ran as a road tech for many years. One of our saying was "if we don't have it, we didn't need it." There are plenty of ways to skin a cat, even on much more complicated engine (systems) then to get worked up about accuracy of a cheap gauge used on a small 2 stroke engine imo. If it's off a few psi, or 2"hg doesn't really matter. Another case in point, I have a very nice opama spark tester. Beautiful high tension leads, scaled needle adjustment which corresponds to spark kv rating. Think it was around $60.00 a $10.00 harbor freight spark tester will get you to the same point.
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That particular "what if" is pretty rare- as stated above, the gauge reading is not really particular and perhaps not "true" but if it is constant it is constant.
If the saw itself and the usual culprits of air leakage test fine and the system is still not holding pressure- then test the delivery line, then the tool.
It is more likely if pressure cannot be held in the system and the saw components do not show leakage, the delivery line is compromised at a join, or a line perish/split.
No argument there. I have a German durometer (tool for seeing how soft or hard motorcycle roadracing slicks are) that the Pirelli guys left in my cart years ago… I’m told it’s super expensive… and yeah I’ve used it a few times myself… but the fact is I know when tires are “done” and I don’t need their fancy machine to tell me
I think the key is to know what you're testing, why you're testing it & how the test actually works in relation to your equipment... I check the lead resistance every time I turn a multimeter on, regardless of whether it's a fluke or a cheap disposable multimeter. With regards to vac/pressure testing, I rotate the crank while testing & look for fluctuations that tell me I'm actually testing the motor (not a kinked like or blocked impulse port). Carb testing, I like to manually release the metering valve to ensure I'm testing the entire circuit. As others have said, the exact values aren't that important as long as its within a reasonable range & doesn’t leak. If I were pumping all day to get to that "reasonable range" I'd confirm the tester before pulling down the motor regardless of it being a harbor freight special or a snapon
There is some knowledge AND common sense that must go with testing. JD got it right. Without the knowledge behind the test, the results say nothing.
Well. I made it through another dozen or so pieces of equipment repaired without vacuum or pressure testing anything.
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Just like Gilligan and the Professor...... (60's television series)
LOL yeah… I watched it when I was a kid… on a black and white TV with no remote control
Edit: actually the remote control was the youngest brother… we’d make him stand there holding the twisty knob and shout at him “change it to” whatever… he’d get frustrated and would start spinning it around (I think we got like 5 channels out of a possible 7 or whatever) and my dad would come in and start screaming “you’re gonna break the TV!”
This from the guy whose idea of TV repair was to hit the side of it until the channel came in clear… LOL… oh the good ole days… thanks for the trip down memory lane
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LOL yeah… I watched it when I was a kid… on a black and white TV with no remote control
Edit: actually the remote control was the youngest brother… we’d make him stand there holding the twisty knob and shout at him “change it to” whatever… he’d get frustrated and would start spinning it around (I think we got like 5 channels out of a possible 7 or whatever) and my dad would come in and start screaming “you’re gonna break the TV!”
This from the guy whose idea of TV repair was to hit the side of it until the channel came in clear… LOL… oh the good ole days… thanks for the trip down memory lane
Or switching that old black and white set on, having time to walk across the room before the sound ramped in, then sit down before the picture appeared.....
Remember the tube testers in drug stores ?
Yeah… waiting for the vacuum tubes to warm up… those were the days
Yeah… I understand the “hipster” kids in the SF area who are into hifi are paying big money for some of those old RCA vacuum tubes… raiding ancient TV repair shops and the like… apparently some of them are worth *hundreds* of dollars (?!)
Mullard, Phillips, Telefunken, etc. Even certain vintage manufacture for the same tube, or certain cuts of LP's in certain facilities of the same music.
If they say they can hear it, who am I to argue.
Grin… giggle… you’re speaking my language. THIS is a man who knows his tubes. I’ll admit I’m running *real* NOs KT88 Genalex tubes in my hifi right now. NOT the fake ones they’re making in China right now. I’ve got mullard 12AX7’s in my tweed champ… don’t get me started talking about tubes!!
How did we go from vacuum testing to vacuum tubes... I'd post a pic of my vacuum tube tester to try steer things back on to testing... but that would be flawed logic, & this is far nicer to look at...
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