Thanks for the video. I thought it was widely understood to never hone a modern plated cylinder. Always good to get a reminder out there! Also old enough to have owned old school air cooled two strokes with iron liners. As mentioned in the video, the iron liner never lines up with the port castings from the factory. The air going through the transfer ports is traveling at very high velocity and the "step" from the misalignment with the iron liner is a big deal. I had a 490 that ran like crap until it had it's ports "cleaned up". After the port work, squish band work on the head and some remedial jetting, it was a crispy critter running scary arm stretching monster. Don't get me wrong, not romanticizing the old 500s, I know exactly what those evil paint shaker open class air cool things are, I'll take modern bikes, thank you 😂
Just had the OEM plating on my YZ125 cylinder become worn at 48 hours, right above the exhaust port. I went through 3 OEM pistons, each at about 15 hours when changed. Maxima 927 30:1, always allowed to warm up sufficiently before putting in hard laps (only used for MX) to avoid cold seizure. Gonna run 1 more piston on it but the new OEM cylinder just arrived 2 hours ago. Hoping to get double the hours out of this one, and might try going to like 22:1 on the premix ratio.
And I never honed it during any piston change. Just wiped it clean, sprayed some brake/carb cleaner down it, then wiped a little premix inside during reassembly.
Depending on the wear and what you mean by cleaned out the cylinder between pistons( just a towel or muriatic acid to remove piston deposited on cylinder) theres a few possibility. Leaky exhaust flange can be a culprit. Next up is pipe is full of carbon and some keeps coming loose. Pictures would definately help
dont put more oil in. Right jetting is way more important than oil. You could put 40 to 1 in there and if you had perfect jetting it would be better for the engine than 22 to 1 with shitty lean jetting
Great talk Jeff. Good to know the replating process in basic terms. My 2020 TPI just hit 300 hrs. Even if I had accurate tools to measure the cylinder I’d have no idea how to judge it. These 2stroke cylinders are like Swiss 🧀cheese! I just sent it to Millennium for replating, 1 week turn around. Cylinder should be good to go for another 300+ hrs.
Really awesome video. I’ve never rebuilt a top end as this is my first 2T. I feel if you own a 2T, you absolutely need to know how to rebuild a top end. You are my go-to for technical information on all things dirt bike Jeff. Your experience and expertise is invaluable and I thank you for sharing it and passing it along. I can’t tell you how much I appreciate it.
Hello: Nikasil is an excellent lightweight product that offer excellent heat transfer and excellent wear qualities. However, guys sometimes don't service the air filter correctly or seize the top end and that requires replating.
Helpful video, thx. I did a beta 300 top end last year. Cylinder looked good after 250 hours (generally easier riding) but I could have cleaned off some of the darker spots like your indicated. Larger "B" piston from your site seems to have worked well.
I will never use us chrome again, they messed up my cylinder and claimed that they didn't do it. The cylinder had less than 1000 miles on it when the ringing came apart and destroyed the liner. They poked a hole in the water space above the exhaust valve, and leaked coolant, couldn't have happened when the ring broke.
I deal with these on a daily basis. And what im seeing is "standard" size pistons that these companies are offering are either to big or too small for the correct clearence specs. By +/- .001 to .002. And people wonder why they have a failure shortly after a rebuild. They dont measure anything and put it together. I have boxes of pistons that are unusable that the seller or seller will not take back because they are opened. So i try to deal with only a select few sellers that will take them back. If i end up with clearence issues that are too tight i send them out to a company that does the plating and have them re hone it with their Dimond hone to get to correct clearence. All these plating companies hit that 1 number of bore spec when they plate and thats that. I have yet to see a plated cylinder be the wrong bore size. Its always spot on. Pistons, thats a whole nother story. I do about 200 topends a years. Not sure how many other shops do, but i do a good amount of topends and this is what i know. Great video!!
Hello: We are the largest Vertex dealer in the USA and we've have not had any complaints about piston sizes but most people don't have equipment to correctly measure them. If you are a legit shop or repair service, we can offer you dealer pricing and we accept returns if the product is not damaged and the box is in good shape. Apply here >>> slavensracing.com/dealer/
If I get aluminum transfer on my cylinder wall from the piston and the cylinder is salvageable (chainsaw top end), I will try to revive it with oil and sandpaper, then perhaps a light ball honing. It works great for me.
👍🆙SR, If there is an option of Nikasil and hard chrome, roughly same price. Which is better? In a normal work enviroment for a chainsaw. Come across this option when getting a extra cylinder for a 92cc saw project, I chose the Nikasil but would like 2 know for future projects. I will be doing some porting on these but nothing radical.
Thanks for your time and experience! Question, brand new 24’ 300 XC, the only run time was at the dealer and factory, when removing the cylinder head to swap with aftermarket I noticed some darker coloring streaks in the cylinder wall. .2 hours on the display, should I be concerned? Cannot feel anything with my fingernail, so I put it back together. Thanks in advance!
Thanks for the in depth explanation, I will be ordering a set of rings (dlc coated) from a reputable firm that has detailed explanations on a very fine grit Flex hone , 320 grit or more explaining that it is only for light touching of the visible cross hatch. 4stroke cylinder in quesion, so it is basically doing the function of the brush hone, is that something you would consider useful? Thank you
Hello: DLC coated rings are a waste of money and using a flex hone of any type or grit is a BAD idea. Whoever is selling that Koolaide needs shut down.
Hello: Sorry, I have no idea where you live or what's available in your country. In the USA I would send it to a replating company where they would weld the crack and replate the bore.
Thanks Jess saw all the video, you gave similar suggestions a cuple of year ago and I've changed several 250cc ktm top ends. My only debate is always to use a or b pistons
