How to Measure Piston to Cylinder Clearance

[@slickricktheruler]

Thank you for always providing the YT community with useful information.

[@slaverace1]

Our pleasure!

[@slaverace1]

First of all the B is only a VERY tiny amount (.0004") larger than an A. You can easily use it in any cylinder with 25 hours or more.

[@Sensei948]

140psi good compresion 372 xp oe ?

[@ryanstewart1521]

I just put a Vertex B piston from Mr. slavens at 60 hrs in my 300 xc-w tbi and wow what a difference. Great informative vid. Thankyou Jeff

[@jw9384]

I don't have a bike but found your video on piston to cylinder clearance because I'm rebuilding my car... you should make some automobile repair videos you seem to be very knowledgeable and have a good speaking voice

[@TheOfficialKC]

Thanks. There is also a C piston for my bike (again another .0004" step). Since I have well over 100 hours I should probably pick that when I rebuild.

[@anthonylutz8419]

Hi Jeff watching you video and all those tools shown all works well. Using the feeler gauge has to have more feel but same with micrometer you need to know how to use it properly. Bore gauge are still the best easy to read but not knowing how to feel your mic you would get a difft. reading. My parents used feeler gauge for over 30 years,starting in the forties and survive measuring bores with feeler gauge during the war and some of those jeeps my parents bored where never even honed, but work in those condition.

[@slaverace1]

Loading the ring gap video now.

[@Ggordonhorseballs]

I am unsure how anybody could give a thumbs down to that. Having grown up with steel sleeved cylinders, I needed some more info on chrome bores so I turned to Jeff Slavens and the guy who does my boring. The tutorial I got from both was nearly identical in every respect except that the machinist has developed the "feel" Jeff Slavens referred to. Thanks for the post.

[@MEANMUGRACING]

great review, I went to Wyotech and learned so much, but there that saying the more you know the more no you don't know. lol

[@markskvr9279]

So glad i watched this

[@RSGang]

I have a question

[@denelvo]

You ended up not talking about ring gap

[@mirandabri834]

I'm gonna ask a really dumb question here but its because i bought a motorcycle recently and the guy gave me an extra engine with the bike; it was his dad's bike and he had passed away and so the extra engine he sold it with the bike. So, What if there's no lip on a 4 stroke motorcycle engine? (Its the extra engine). I was checking it the other day and it doesn't feel like there's any lip. But I can tell that the cross hatching is barely visible..... Depending on which way your looking at it and i have an untrained eye. Also a side note is that the heads that came with it looks as though they've been used very little. However they were already taken off the main. Any help would be greatly appreciated. Thanks

[@HugieMaceachern]

If u had any lip the coating would be worn off would it not?

[@slaverace1]

Sorry, no. IF you can feel a lip, the cylinder bore Nikasil coating needs replated.

[@strattuner]

piston to bore clearance on a two stroke is critical due expansion rates,and difference of air cooled and water cooled,i bored hundreds of them,and honed using recommended grit,and dropping piston thru cylinder or air cooled,if it slips thru under its own weight it fine,if it hangs it is not correct,continue honing,on water cooled machines as manufacturer specs,grocery getter automobiles,all clearance at 2.5 to .003 ,racing engines are as manufacturer suggests,i like your video,i watched to see your mics,to be honest and you definitely know your stuff-automobile breakin is minimum of 750 miles any less and you will do another teardown for nothing

[@TheOfficialKC]

Feeling for a lip definitely sounds like a good method to know the life of your engine. But if there are multiple piston sizes, how do you pick which one to go with? Do you hone cylinders before putting in a new piston?

[@kevinstearns4198]

you should to break the glaze for the new rings to seat use a ball hone.

[@ghostp7919]

can i use a new 57mm cylinder, head an piston kit instad of going an getting a 45mm set ? my bike is a honda mtx 50 r with a 80 cc engine in it piston is 45mm ? need to get a new top end.

[@lombardozarateiii6920]

At the moment i dnt know if i should try to get one off of the chrome exchange, send it to Pennsylvania for replating or buying a new cylinder? I dnt even know if i need to do any of these things to be honest this is my first bike ever.

[@TheOfficialKC]

That's good to know, thanks.

[@zeus-io3hn]

excellent video Jeff. does adding friction modifier and 5000miles of oil change in a 4stroke help to extend the life of the cylinder?

[@schfiftyfive9680]

Friction modifiers in wet clutches are bad. Just use normal oil. I like Rotella 15W40 diesel oil. If you putz at 60 on the highway all day, you could probably go 10k. If you rip it as hard as you can on a technical trail, 500 would push it.

[@fredc8618]

are most 2 stroke cylinder nykasil plated? mine looks like an somewhat oxidized aluminum color do you know if it is 2003rm250..i didnt hone and installed new piston alread? ...oops??

[@markskvr9279]

Dont hone a 2stroke bro it damages the coating on the cylinder

[@sawbach8971]

Does it make sense to switch to a forged piston if your cast one gap is getting wide but not quite where you would wanna pay to resurface?

[@slaverace1]

Bores never wear evenly and instead of a straight bore you end up with an egg shaped bore so installing a forged piston is not a good plan.

[@sawbach8971]

@@slaverace1 ok. Thanks for the reply! Love your channel!

[@neiljohnson9686]

Errrrmmm it’s kind of important where you measure the bore right ? And the piston… the piston will be smaller around up top than at the skirt. Assuming the cylinder is not tapered you will show the highest clearance up high and the lowest down low. So when checking to see if you’re in spec ….it would be the piston an inch above the skirt at a 90 degree angle to the pin and then the bore an inch down in from the top

[@slaverace1]

Neil: If it's a new cylinder, you can measure it anywhere in the bore. If it has a lot of miles, the bore should be measured several places and the bore will be largest half way down the bore. The word tapered has been used often about cylinder bores but actually does NOT apply because they do not become tapered (smaller at the top than at the bottom). Cylinders become egg shaped (larger in the middle) and tight on both ends, not really tapered. Not all pistons are measured an inch up on the skirt. You can check with the manufacturer or measure it to find where the largest diameter is located.

[@neiljohnson9686]

And I’ve never seen a lip in my life . I’ve had 20 or so bikes of all vintages, 4 strokes , 2 strokes, some that were heavily worn out with low compression and never ever a lip

[@slaverace1]

Neil: Maybe your glasses need updated. ALL high mileage engines get a lip at the top.

[@Tatorhead1234]

so how much do the tolerances vary between forged and cast piston? which do companies usually use? cast or forged?

[@kevinstearns4198]

wiseco comes with the clearences

[@theyamahammer]

Hey Jeff I have a 2003 KTM 250 exc. The cylinder is deeply scared. Would you recommend LA sleeve or just get a new cylinder? Also piston should I go forged or cast? Thanks for the informative video's.

[@kevinstearns4198]

resleeve it u have 4 bores on it. just keep ur air filter clean as fuk.

[@stevenlamphear1945]

Cool (and expensive) tools. It is easy to do a quick check by using sound. Insert piston into cylinder at bottom of stroke where most of the wear occurs, and wiggle it. If it rattles it is too loose. You want the gap to be somewhere between a blonde's and a redheads' hair.

[@scdevon]

The amount of money people waste buying small engine special tools is amazing. That's all I'm going to say before I end up offending people who spend heaps of money on special tools.

[@daveryan9338]

Haha........i love red heads! I think my Banshee Pistons will work better leaning towards red heads gap! Lol.....

[@wernersunkel]

wow very good tip

[@jimbryant7422]

Very informative (to me anyway) Where do you buy those measuring devices?

[@markskvr9279]

Ebay lol👌🏻🤣

[@windoes98se]

i know feeler gauges are not accurate to use but if you can fit a .020 feeler between the bore and cylinder you know the clearance is way too big

[@yeahwerepthesamesmartech7113]

I heard on my 2002 Honda Crf450r that you are able to have between 0.020-0.045mm

[@dh1270]

I know this is an older video. But, 150 hours of use? I ride single track moderate pace trails and replace at every 40 hours. Is this overkill. There's so much conflicting info out there.

[@slaverace1]

Yes, 40 hours is overkill.

[@slaverace1]

NEVER hone a Nikasil coated cylinders. I'll load a video today about cylinder care.

[@donkarstedt1637]

Why??? They hone just as well as an iron liner... How do you think they are originally finished???

[@donkarstedt1637]

Oh yeah, you need the right stones...

[@slaverace1]

See above. Use the B.

[@bernhard8540]

I hope this reaches you I have rebuilt a lot of 4 stroke engines but I recently purchased a 99 husqvarna cr250 and I ordered a .060 over piston for it and the instructions say clearance should be .025 ? But that seemed like a lot to me?? Thank you for your time. P.s. namura double ring piston is what I purchased..

[@lombardozarateiii6920]

Can i send you a picture of my cylinder and piston. I would gladly appreciate your thoughts? Its to a 1998 kx125.

[@slaverace1]

Send it to [e-mail]

[@dirtrider88]

you failed to mention the method you use to measure two stroke pistons.

[@kevinstearns4198]

you can use calipers. micrometer.

[@pedrorodriguez2778]

HOW DO YOU MEASURE A 4 STROKE ON A HONDA TMX 155CC LET ME KNOW

[@dorianmccarthy7602]

should we ask our own questions? then say obviously? stall more, patronize more, feel insecure more.

[@kevinstearns4198]

do a compression test before you tear it down.

[@slaverace1]

I don't.

[@oo0Spyder0oo]

compression test will only let you know if the rings or valves are worn.