Measuring Piston Ring Gap

Quick explanation on piston rings and measuring the ring gap.

[@NorthCust]

found this video again by searching on the-workshop.net. Once again, just what I needed. Thank you :)

[@alinstaicu8780]

Greeting from.Romania!Amazing job keep.goin'!

[@ducaduke]

Hi cheers 🍻 from socal !! I have a question on my ktm it doesn’t Give me a specified range it just gives me a wear limit of 0.80 mm how do I figure out what gap it should have it in stock piston with the rings already installed

[@thedirtyworkshop]

This means they spec all their parts before sale.

[@ducaduke]

@@thedirtyworkshop so just plug and play correct?

[@teninchrichard4016]

Came to your channel via Andy

[@aterack833]

no clue where to put this but this is the video i'm watching right now so here it is, i just found out that the sudo atkinson cycle in the toyota prius and others is actually just the miller cycle, it has a name

[@davidlevy281]

Just found your channel. Terrific explanations. Why can't you measure the ring outside of the cylinder with a caliper? Thanks for the video.

[@thedirtyworkshop]

Because you'll squash the rings. This measurement is an installation measurements and calipers are not accurate

[@RyanKeane9]

I work in inspection at a manufacturing company (1938 might give you a clue) and we make these. On outspringers like these we use feelers in a ring gauge on a surface table. If in doubt, pop it on a shadowgraph. We also take a measurement in free state but this has more to do with diametrical load than anything else. Good explanation and nice video, I enjoyed it👍🏻

[@johnnyh127]

I know this video is very old, but I watch a lot of your older stuff. A lot of good info in there. I'm building (2) 2 Stroke scooter engines. One is an AC 50mm Iron Bore Honda, the other an LC 47.5mm Nikasil Minarelli. Since these are big bore kits and not factory, would I still use the manuals ring gap from the original stock engine? Or do I need to adjust it for these larger bores? Any recommendations? Thank you!

[@thedirtyworkshop]

Yes if you change the bore the gap needs to be adjusted.

[@johnnyh127]

@@thedirtyworkshop the Athena paper with one of the pistons has what I believe to be rec ring gap up to 100cc .04/.06mm. Does that sound right? Thanks again!

[@thedirtyworkshop]

You should ask Minarelli. Different cylinders and rings have different temps etc

[@paojengsmeattrading1497]

nice demo thumbs up.. what will happened if over gap?

[@thedirtyworkshop]

Sorry for the really late reply, KZbin is shite at informing me of comment. If you over gap then the compression within the cylinder will fall as the gap allows for more piston blow by (gases passing the piston and into the crankcase) in other words you power drops. How much? it depends on the size of the gap. hope this helps - matt

[@clubsnapperuk]

I believe to get the average ring gap for any cylinder is the convert the bore measurement from mm to inches and times that figure by 0.005". for instance.66mm bore = 2.59843" times by 0.005 =0.012" or 0.33mm.Do think this is a good formula?

[@thedirtyworkshop]

No. Material of the bore and rings have to come into play.

[@clubsnapperuk]

The Workshop your right. It's send a good formula for iron sleeves but not for nikasil. Factory for 66mm on nikasil cylinder is 0.20 to 0.35. Still a very fine slot.

[@paojengsmeattrading1497]

if over gap what w will happened?

[@kevinstearns4198]

put ring in from the top of cylinder say 2 inches use piston to square the ring now use a feeler gauge and check the gap.

[@mullaway5746]

might help if you did it with a bigger cylinder and a piston

[@thedirtyworkshop]

It might have - this was a long time ago now

[@maxoneill5208]

Awesome cheers

[@Eeropolvasti]

Use piston to push ring down, so you get even measurement!!!!

[@thedirtyworkshop]

I didn't have the piston at hand, thats what I was looking for.

[@Eeropolvasti]

So you missed the important part.....

[@1stMrSceptical]

Air cooled engine ring gap is 3thou per inch of bore.. Well I was when I were a lad

[@sahiel5]

what do u mean rings dosent have to move?ye they do! if they dont u het nasty vertical scar in the cylinder and u loose compresion

[@thedirtyworkshop]

What do you mean? Move or rotate?

[@sahiel5]

Pony Power - Theory rotate

[@thedirtyworkshop]

2 stroke rings don't rotate, as mentioned in the video, otherwise they will protrude into the ports and break, hence the piston ring pins.

[@kevinstearns4198]

+Pony Power some people are brain dead your right.