30 thoughts on “How To Accurately Measure a Piston

  1. Smashing 🙂

    I bought a digital caliper from my local aldi store, £8 (about $12 and 70cents us), its been so handy for quick checks.

    Its not perfect but for 8 pounds i dont expect it to be lol.

  2. The Proper way is to measure it in top, center and bottom. Thrust and Pin sides. But, The tool you use, Is a micrometer, and T gauges.

  3. Dony, can you let us know how that Italian made piston works out for you? I've used one in the past along w/ a new cylinder and it just didn't hold pressure as well as the OEM. I had about 100 psi compression after the rebuild.

  4. Any way you could make a video on how to change the killswitch for a Husqvarna 36 chainsaw?…or maybe even recommended one? I can't seem to find anything and I'm clueless.

  5. Hi Donnyboy;I need to pick your brain.My friend has a vintage Johnson Iron Horse 4 cycle engine.I found a head gasket and cylinder gasket for it on Ebay,but he needs a set of rings for it as well.Hope you can point me in the right direction for the rings.Like your channel watch all your vids.

  6. Hi Donny. I need to ask a question about a repair I am attempting. I have a Poulan Pro chainsaw that the recoil starter is very hard to pull. With the spark plug removed, everything works smoothly and turns very easily. Everything seems to be in working order but the saw will not start.

  7. Avoid the plastic bodied ones which are the cheapest & least accurate. It's "You get what you pay for" but depending on the quality & accuracy you need, using something not top of the line could be ok. I think the best brands are: Starrett, Brown & Sharp, Mitutoyo, Mahr. You can't go wring with any of these name brands. I do know most people don't want to spend a few hundred on a pair of calipers. I have a Carrera, model #CP9808 they cost $40, Good enough for what I do with them.

  8. Correct…but for comparison reasons(std vs oversize), calipers will be close enough unless you are boring/honing to size. Also, based on piston design, it's important to measure at a specific point on a piston to get the correct bore diameter. Check with the manufacturer for the proper point. Many pistons taper…smaller at the ring lands, wider at the skirt(bottom).

  9. With a dial bore gauge so you can easily detect taper / bell mouthing. If one can't afford a dial bore gage telescoping gauges will work if you practice and develop a feel for how to use them. No way should one use a dial or digital caliper on a cylinder bore.

  10. I also disliked this video simply because using a digital caliper or a dial caliper is the wrong tool to use for measuring the OD of a piston or cylinder bore. Nothing against the person who made the video who seems very nice.

  11. You're wrong. For selecting std or oversize, which is what the OP did, it's perfectly acceptable to use a dial caliper. He's not boring/honing a cylinder to size otherwise, you'd be correct.

  12. Dial Caliper is ok to measure the OD, I was a machinist for many years, but I do have Mics, If I feel the caliper is off. One cylinder, small engine, a caliper is just fine. If it was the bore that would be different, I used to make go no go gauges running a cnc, saved a lot of time and when you place the piston in the bore, you know if there is any slop…. Nuff said. 🙂

  13. I'm a machinist of 40 yrs and this well intentioned, very knowledgeable guy is just checking that the piston is in the ballpark, not one or two standard over-sizes. I hope he inspected the bore for scoring but for any other work what's a small garage/home/ shop supposed to do if the piston is manufactured wrong?Plus aren't some of these cylinders chrome plated or nikasiled? Around the house I have a 6" Harbor Freight plastic caliper, it was under $20 I trust for 2 or 3 thou. Good work

  14. If you know the piston sizes are correct and are selecting off the shelf rather than measuring then that looks fine, I often use calipers to check something is "somewhere close"
    To Accurately Measure a Piston I'd use a micrometer to check OD then a dial gauge, V block and height comparator stand to check for out of round.

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