How To Measure Dirt Bike Piston To Cylinder Wall Clearance
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- čas přidán 11. 07. 2024
- Take good care of your bike by replacing worn out pistons, keeping your bike fresh. Pistons are constantly in motion, providing power to your dirt bike. But with the wear and tear of high RPMs, they can really take a beating and eventually wear out. In this video we show you how to match your new piston to the cylinder with some simple X and Y measurements.
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#howto #pistontocylinderwallclearance - Jak na to + styl
Take the telescoping gauge. Put it in the bore tilted vertically so it is telescope out slightly and lock the gauge lightly, now roll the gauge till it's level. This is the only way to get an accurate, repeatable measurement with a telescoping bore gauge.
Thats how I do it.
As a machinist this really bothers me. He used that guage wrong. You want it in there crooked. Tighten it enough that the pins can still move but will stay in place. Then then pull it so it tilts in the opposite direction. From wall to wall it will be the smallest. And that's where the guage will stay at. And then you check that with a micrometer not a set of calipers.
Damn dude, I knew you were gonna get a beat down for the using the calipers...I got past that quick. But for informational purposes, the digital calipers are a great learning aid. Besides, I would bet a lot of people who watch this video couldn't even read a mic. Aside from all that, this video is killer informational, at least to a dummy like me. Thanks for posting, and keep up the good work. Cheers
Outstanding video!
Very very very helpful!! Thanks!
Been a mechanic for 31 years (automotive) and I've rebuilt a dozen or so bikes as a side hobby. But I got this little 80cc 2 stroke I'm looking to do a refresh on, and this video hit the bill! Do I just hone, or do I need a bore? NOW I KNOW how to check it correctly! Thanks man, this was EXACTLY the Correct information I was looking for! Thanks for the solid! Subbed. God bless you and yours my friend.
Great video
Unless your running high compression and leaded race fuel, the clearance wisco puts on the box is usually a good number, even with most air cooled motors. Getting good measurements is critical. I put a top end in an old yz125 last summer and due to a crappy hone ended up with .006 clearance midway down the bore .002 at the top. I ran it anyway since I didn't want to wait for an order of a bigger piston. It ran fine but was really noisy. A lot of skirt slap. Just rebuilt it again last week with a +.050mm piston and did a better job boring and honing, got .0025 all the way down this time. Amazing how quite it is now compared to before. There was quite a bit of aluminum on the cylinder walls on both sides. I got 15 hard hours out of it but it probably wouldn't have taken much more the skirt cracked. Just a few thousandths of an inch. Calipers are good to about .002 when trying to measure the round ends of a bore gauge and that .002 maybe .002 to much.
Hell yea Rocky mountain I don't plan on rebuilding the 2016 kx450f but those look like good useful tool I need in the shop, I told you Eli all day for energy cup that was an intense race!! Did you guys pick the gear give away winner
Thanks Chance Cheers
Great video, question: If my old honda C110 49cc specs says (Bore size is 40mm), after boring/honing the cylinder for a new .75 piston, the cylinder bore should be 40.7mm? or around there? or more. Please let me know. Thanks
Please tell me that all you guys watching this video are not gonna use digital "very near" calipers to measure a bore gauge. You might as well use a damn tape measure
Agreed. I use a micrometer.
Lol Do you still use a slide rule? My Mitutoyo digital caliper is spot on with my mics. Most amateurs don't have the touch for the proper drag required to measure accurately with mics.
@@sportscarclinic most have friction thimbles that make them idiot proof for the most part. I stopped using digi calipers a few years ago when I had started having them fail calibration. Work fails them if they are off by .002 at any point in the range. 2 starret and one Mititoyo failed by Cal. There still good but they won't let us use them. I just use my Verniers when I need a caliper. For holes between .2 and 1.5" we have Intrimikes, far better than any bore gauge on the market. By the way I still have a slide rule just for nostalgia. Do you know how to use a slide rule?
This is bloody fantastic. 🍺🍺🍺🍺🍺🍺🍺🍺🍺🍺🍺🍺🍺🍺💪💪💪💪💪💪💪💪
Do you have big bore kit for yz65cc? or even having racing cylinder head and cdi for yz65 hope you can help, thanks
Awesome
awesome
If I know my bike cylinder and piston are full stock could I just put my make model and year in a website and order that stock one.
I bought a 96 yz250, head piston and cylinder were all toast. I am looking at a cylinder sleeve since a brand new cylinder is 400+ and the sleeve is 160, a much nicer option, the sleeve bore is 69.00mm, do I buy a 69.00mm piston kit for it or the 68.50mm piston kit? (68.5mm is sold out)
I thought you shouldn't use calipers to measure the bore. You should use a micrometer..
Great thankyou , i was wondering about deckhight adjustment?
We have a great video showing how to get the correct deck height you can check out here: czcams.com/video/MbYxxp9UZpI/video.html
The bike in this video is an 85 SX but the process will be the same, you will just want the deck height tool for your specific bike.
a vernier caliper isn't going to give you an accurate number. you really should be using a micrometer. also make sure not to measure at the very top or bottom where the cylinder never sees any wear. also, your specs clearly indicate that you should be using an "A" piston but yet your using a "B" piston. It would appear your using a piston that's too big. One last thing, if your cylinder is out of spec you can have it replated at companies such as millennium or powerseal for around $200. no need to spend $600 on a new cylinder.
Just out of curiosity, how can you find out the measurements on the "a" "b" "c" "d" pistons? the measurements arent listed on the parts list. thanks.
@@Xgamer121X Google the bike and the specific piston sizes. like "what is the size of an A piston for a (*_insert bike and year here_*) "
It's a digital caliper, not a vernier caliper. Before you make such a stupid, uninformed comment, at least learn the difference.
@@sportscarclinic it still isn't as accurate as a micrometer. What are the chances that's it's exactly 72 mm?
@@331moto Agreed.
Can I put a crf 250 bore and valves on a crf 100 I don’t think so but if there’s any possible way without replacing the engine let me know Thanks
No sorry. there is no way to but the top end of a crf250 on a crf100. The engines and their top ends were not designed to be swappable with each other. If that even was possible, you would practically need to replace the crank shaft, bearings, clutch, etc.. to be able to handle the huge power increase.
Where can I find the table with the specs shown at 3:59 for a 300 te Husqvarna from 2015 (EU). The owner guide doesn't show these information
Unfortunately we don't sell service manuals for your bike and they can be a little tricky to find for some Husqvarna's. But what you'll be looking for is a repair/service manual for the TE300. Your best bet is to search some forums and see where other's are able to find one.
i have a artic cat and need a new piston but i don't know what size it is , i have looked everywhere on the bike for info but there isn't any. so do i measure the cylinder and piston to determine what cc size the piston is?
Measure what he shows you to measure in the video and order the right size based on the instructions he gave
Dude Use a micrometer.
my cylinder is 96.02 from kawasaki 450 now i buy piston size 95.97 ????
Were gonna need cylinder crosshatches also for lubrication
Were do ii found that telescopic tool?
Telescoping gauge sets can be found online or at your local tool store, like The Home Depot or Harbor Freight.
@@rmatvmc the harbor freight bore gauges are actually not to bad, almost as repeatable as my old brown and sharpes just please try and find a micrometer off eBay or something, calipers ain't gonna cut it if you need to measure the bore gauge, you can use them to measure the piston if you have a good pair but measuring the bore gauge with them is next to impossible to get a repeatable measurement due to the limited footprint of the gauge.
Bad measurements you should use a micrometer instead of a calliper it is way more precisely
Ummm
clearance = (bore diameter-piston diameter)/2
This piston was still in spec
How do I get a piston that is 87.478 diameter of the piston ? the exact number .
You can enter your machines make and model on our website to see all the different pistons available and many manufacturers will have different size options. If you can't find that exact size piston, you may need to have your cylinder bored.
How to check clearance on a 4 stroke bike would be nice and the difference between a chrome bore and a sleeved steel bore! What can you really get away with b4 replacing the cylinder, having it bored or rechromed? Not everyone can spend thousands of dollars on a top end rebuild every year! And a 2 stroke bike if your replacing the cylinder and piston wouldn't it be wise to rebuild the crankshaft with a new rod kit? I've never had to tear down and replace a top end in a 2 stroke motor as much as people say it should be done! I've put hundreds of hours on a 2 stroke YZ250 and never had any problems! Putting a brand new piston in with out rebuilding the crank is absurdly why run any risk at all! If the top end needs done so does the bottom end! I'd really like to know on a 4 stroke motocross bike the chrome bore how much wear is to much!
Yal should sell the measurement tools. I don’t have a dial bore gauge or micrometer and don’t want to order some cheap tool off amazon.
Yes you must use a micrometer, also the shown method for sampling using telescoping gauges is incorrect and will not give a consistent accurate sizing. Measuring the gauge with the micrometer also requires a specific method. Ask a Machinist!
Lol Do you still use a slide rule? My Mitutoyo digital caliper is spot on with my mics. Anyway, most amateurs don't have the touch for the proper drag required to measure accurately with mics. One in every crowd.
why piston wear ? I thought it is not rubbing agains the wall of the cylider because of the ring.. In the video piston was out of spec
Pistons are under an extreme amount of pressure and it is normal for the piston skirt to come into contact with the wall of the cylinder so some wear is normal, especially on high performance engines.
When do you know you need to bore the cylinder?
Usually any damage that is deep enough that you can feel or that honing won't remove. There are many things to look for but we have a great video showing how to inspect a cylinder, including some examples of cylinder damage that warrants boring. You can check out that video here: czcams.com/video/InfPn0MtOPY/video.html
Thank you that video was really helpful also! I have another question, if your measurements differ slightly, do you use the smallest measurement to check against the manual and for the piston clearance check?
Wouldn’t be easier to just get the same piston that was on it before
The cylinder walls may have become worn and compressed, making it wider. So you may need a slightly larger replacement piston than the old one.
NO. unless you like piston knock 🤦♂️
Due to how informative this video was for me I would say this video alone will bring a lot of business to RM
Vernier caliper should be more precise
nope.
he used bore gauge to measure the cylinder and used the Vernier caliper to measure the bore gauge.
the bore gauge has round ends to fit into the curvature of the cylinder wall.
the vernier caliper has square edges and will not fit the curvature of the cylinder side wall.
however, he used the bore gauge wrong. and a micrometer is the best thing to use to measure a bore gauge with
Egckspecialy
Jk love you chance
My old puch has like 1mm of "clearance"
You will not get an accurate measurement with a snap gauge. You really need to use an actual bore gauge. The issue is that is an expensive tool. I just take my cylinder to a local machine shop and pay them a few bucks to measure it for me.
Of course you can get an accurate measurement with a snap gauge, but you have to practice a bit and develop a "feel" for it. I would use a micrometer, not calipers.
Agreed. These dimensions are so tight they need better accuracy than us weekend warriors can get with telescoping inside gauges and micrometers. The video even shows the mechanic getting two different measurements. This is why I just use Starrett shim stock in the cylinder and run the piston through.
Wrong answer. Snap gauges and mics are preferred by every excellent machinist I've met. Bore gauges go out of calibration. They're utility is in being quick to get a rough measurement while boring and honing. The final is done with a snap gauge and mic.