Motorcycle 2 Stroke Top End Rebuild - Piston Replacement
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- เผยแพร่เมื่อ 17 มี.ค. 2008
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Learn how to rebuild the top end on your 2 stroke ATV or motorcycle. This video demonstrates how to easily replace the piston and rings on your 2 stroke engine like a RM250 or KX250. Refer to your service manual for your machine. Rocky Mountain ATV/MC carries all the parts and tools you need to completely rebuild the top end on your motorcycle. Visit our website www.rockymountainatvmc.com for a complete list of parts and accessories for your machine!
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Not sure if you have all the right tools and parts for this job? No worries, we have you covered. www.rockymountainatvmc.com/Sales/1710/Top-End-Rebuild?
Just did my first top end today after watching this video. Thanks!
+beefcake3131 *Nice Job!*
About to do my first job as well.
Dude I started tearing apart engines a year ago and im 17 now. They are a PIECE of CAKE if you pay attention, take your time, and do it right the first time. Go for it. Its a blast :)
Your reed valves control the air fuel mixture flow into the cylinder. The act as a one way valve so as your piston rises which is compressing your fuel mixture it also at the same time creates a vacuum underneath the piston which opens the reed valves and allows the fuel mixture to flow under the piston. Once the fuel on top of the piston combusts the piston creates pressure as it drops down which closes the reed valves and that fuel that was under the piston flows to the top of the piston.
You can do it. I started learning at your age. Pay close attention to the service manual. It is easier than you think!
Your 2-stroke has to have oil (premiX) mixed in the gas to lubricate the crank and piston. This oil may not burn all the way and it ends up coming out the exhaust. This is normal, but if it oozing out you are most likely running rich. You may want to look into adjusting the carburator to leaner settings. And you want to seal the pipe a little better so it isn't making a mess.
If I rebuild a top-end, i always use a new top-end gasket kit. Either Tusk or Cometic gasket kits work great. I don't use any "sealer" or silicone unless the manual requires it. It rarely ever is required.
Thank you for all of your videos. My kid and I are using this information to keep our bikes running like they should. We feel good about the 200 dollar purchase from you last week. You have great prices on top of all this good stuff. Thank you very much guys.
you are my hero. seriously been watching videos all morning and you are the only one to say put the ring gap over the centering pin made it go together so simple. thank you
You are right; we didn't because there are too many variations in the inspection and repair process. We recommend you refer to your specific service manual for this. On this particular bike (YZ250) a hone is recommended and the Wiseco rings don't have a specific up or down. Thanks for the input.
On most bikes the power valve is opened and closed by a governor that runs off the Crank's primary gear (bottom end). Usually there is linkage that connects the power valve to the governor and it needs to be disconnected for the cylinder to come off.
Thank YOU!!! You and one other YT video saved me time, money, appointment setting... and a trip to the local mechanic! :D
you don't have to on most bikes, but it makes things much easier on most bikes.
Sounds good, if you run into any questions during the rebuild be sure to let me know!
Sounds like you got it! You'll want to refer to your service manual along the way to be sure not to miss a step
That gap in the piston can range as far as where it's located but i have usually positioned the circlip with the gap up or towards the top of the piston
awsome ordered my parts on monday arrived Thursday to newzealand , mega fast shipping , really cheap prices , everythings here so satisfied with the order DEFINITELY buying from you guys again , cant wait to start on my top end now
you are refering to the powervalve breather hose. It is normal for a little exhaust to come out (not to mention a little blob of black oil after you park it). I like the v-force reeds myself.
by FAR the best video on top end rebuild on youtube.....simple, to the point, and not jumbled with a ton of other stuff from the narrarator trying to sound smarter than he is.
That is a close call! I've had that happen to me and we were lucky enough to easily get it back out but a rag is always a good idea!
Jeeze finally someone with simple videos that get to the point! Thanks RMATVMC!
make sure you have free play in the cable to ensure the slide isn't hanging up. Back off the idle adjustment on the choke (if it is a Kehin carb). Make sure you have no air leaks in the intake.
I would double check and make sure you've got the correct piston and ring set first. Alslo are you putting in an OE piston and ring set? I would check your piston to cylinder wall clearance (Should be anywhere from .004-.005") and then if that checks out check your ring end gap and file if needed. I would also makee sure you have installed your rings correctly and also make sure your piston isn't rotated around causing the rings to catch on a port.
It would for sure be a good upgrade especially if you are running stock reeds.
This is very helpful to someone like myself thats in the process of doing a top end for the first time. Thanks guys keep it up!!
Lee
it depends on how the cyclinder looks. A light hone is a good idea to scratch up any polished spots.
It depends on the bike, how hard it is ridden, and how well it is maintained. Refer to your service manual for manufacturer's recommendations.
Yes that is normal. even after the rings have time to seat, when kicked over slowly air can escape by through the ring end gap.
There are a lot of vompanies that make coolant specific for bikes, but I have never had a problem with regular car antifreeze. Mix it 50/50 with water and you are good to go.
It will be a little different than what's shown in this video obviously because it's a kawasaki and it's an 85. The power valve linkage will be a little different so be aware of that but as long as you follow along closely with your service manual and reference to this video you should be fine. If you have any questions feel free to call in so we can help you with it
@04CHEV - Unfortunatly you have to take the powervalve apart in order to get to that seal. That means pulling the cylinder out of the frame. I always put a new seal in whether it needs it or not when I have the top end apart. The Tusk top-end gasket kit comes with the seal.
It isn't too often you need to in my experience. My YZ 250 has never needed the rings filed down with OE rings or with Wiseco rings. You don't want it to be too tight and sieze the rings. It is always worth checking.
@FMXwwjd - We sell yamaha service manuals. check out our website.
Q1 - the powervalve is controlled by a the govener that runs off the primary gear on the crank. Yes it is connected unless you have a later model CR250 with an electronic powervalve. It is also worth cleaning while you have the bike apart.
Q2 - you need to take the wrist pin out to take the piston off. yes they come with most piston kits.
Q3- there is usually a small amout of adjustment by moving the stator. refer to your manual.
one of THE BEST videos on the internet. Thanks!
take it apart and replace the worn parts. Refer to a service manual for the right steps for your machine.
@sykal - we used a small allen wrench. you can use a small screwdriver. The goal is tp put the stess on the tool, not the powervalve.
YES PLEASE!!!! i need the powervalves replaced on mine almost on every other topend rebuild and that would be so helpful and i think a lot of people would agree. THANKS ROCKYMOUNTAINATVMC!!!
very very helpful video thank you. On the Suzuki RM 250 you have to remove the radiators which is mentioned in the video. I order all my parts on this website they do a great job !!!!
Refer to your manual for suggested replacement info. That will help, but truthfully there are many factors (engine size, how hard and often it is used, has it sucked sand or dust, etc). I change my 250 every 6 months to be on the safe side and to keep it fresh. i know some guys that go years.
This video will be a great complement to my English classes. Thank you.
you guys are great!
i got the exact same bike and now i know exactly how to do it!!!
Thank you all a lot!
RockyMountainATVMC kicks ass
Im doing my second top end rebuild today.. First was a pw80 now a rm85. Ive watched your video to help me with both haha.
Thanks - He did both Rings, but for the sake of time only one was shown. There is no small wire under the ring, not on this bike anyway. You may be thinking of a 4-stroke oil ring.
Great video, just getting a few tips before attempting first 2t piston/ring change on sons 2010 KX85.
It will be fine. just make sure your gas is mixed right. Some guys use WD-40. The point is to have a little lube to make everything assemble easy. Once it fires up, the pre-mix in the gas will lube the top end.
I am not sure what copper washer you are talking about, but yes. If it is a crush washer it is the best practice to use new.
@Rm125MX14 - make sure there are no burs in the piston where the circlip groove is cut. Make sure you have the correct wrist pin.
by changing out the jets in your carb. There are several things that can affect jetting. The altitude, temperature, and bike modifications are the biggest factors. Based on those factors, jetting is different for everyone. It is important you following the directions in your owners manual for jetting recommendations.
Sorry but I really don't want to give torque specs because each machine differs. This video's purpose is to give people the overall idea on how to change the top end. Please refer to the manual specific to your machine for torque specs. Thanks!!
Yeah i would try and find another socket and make that work if you can't get to it with a wrench. You may have to remove a couple other parts to make more room to access the top of the cylinder head
Yeah i will usually let the motor warm up and then completely cool off a couple times but it's best to refer to your service manual for proper break in procedures
@iGuey83one - check our website. We have a wiseco piston kit for $98.99 and a Tusk gasket kit for $14.99. Assuming your cylinder is in good shape, that is all you need.
Of course there are differences since this video was done on a YZ250, but the basic procedure is very similar. Refer to your manual for the differences.
You can buy a special bit that will attach to your torque wrench. Or you can torq the others, put your wrench on the torqued ones and try to tighten it a tiny bit more. Once you have a feel for how tight that is with a wrench, tighten the one you can't get too with the wrench. You should be able to get it fairly close. You will be fine.
@02rm250rider - it depends on what piston you have. You are better off getting a whole new piston kit. Check out our website. We have wiseco and Pro-x kits. Check out our Primary Drive brand chain and sprockets for the best value you will find anywhere.
One of the best instructional videos that I've seen...Thanks!
That is totally normal and OK. That hose is a breather hose for the powervalve. it prevents air pressure from building up behind the valve and allows it to open quickly. Black oil (gunk) will drip out of it no matter what. It isn't a bad thing, it is how it is.
Because there are so many piston and ring companies that do different things you should always refer to their instructions. In general if there is a # or letter it goes up.
If your cylinder has wear spots it is a good idea to hone.
I would have to agree that your water leaking into the transmission. Most likey it is your water pump seal. I would replace that and see if that solves the problem.
thank u so much worked great. removing the nut by locking two worked a treat thanks
The piston differs on the intake and exhaust side so it has to go in correctly or it won't work right and could cause problems. The rings have to line up on the pins so the don't move and catch a port.
Nice job with the video. I Always enjoy the good deals online, just bought some accessories yesterday for my 06 Crf250r. Wish you could upload a rebuild on a 08 crf250r so I can confidently jump into my rebuild.
I recomend pulling it apart; then making the evaluation on the parts you need.
AMAZING INSTRUCTIONAL!!!!! Im about to replace the rings on my Yz 125 1991 so i am glad to see how to do it next time this time my uncles friend is gonna do it!
@shonomercyy12 - It is a Swivel Exhaust Spring. We sell them for $2.49 on our site.
+Rocky mountain
Ok thanks for the fast repply and tips! Your right. Actually i just ordered a top end. Don't wanna gamble.
Frederic Jordan Sweet! Better safe than sorry :). Thanks for the comments.
Perfect! Glad you got it figured out!
Yes. It will be available soon. thanks!
It depends on how the cross-hatch scratches look. If there are polished spots in the cylinder, then honing is a good idea. refer to your manual.
I usually refer to the manual. But you can get the info from Wiseco Pistons website as well. Your 98 has a 68mm bore.
just want to say thank you for your help ,i did it by myself and everything came out fine ,my bike start right up after the 3er kick ,id have like to had a bigger ring so the gap was smaller and the compression would have be better ,but it'll be netx time if is possible to get the bigger ring (04 kx 125)
if you are running the stock size piston you will rarely run into ring end-gap problems, but it is always worth checking. you run into tight fits with over size pistons more often. Both Pro-x and wiseco are great kits.
Some 2-Stroke pistons are designed with 2 compression rings and others will only use 1 ring. The reason for this is less drag between the piston and the cylinder. The pistons that use 2 rings are going to last a little longer than the pistons with 1 ring but you'll find that most little bikes will only use 1 compression ring.
@herse88 - There are a million philosophies on this. i suggest reading the manual. I personally just let the bike warm up and cool down a few times by letting it idle and by putting it around. just go easy on it the first 1/2 hour or so.
@tm450r - Most likely it is your pipe rattling. I would pull it off, make sure the O-ring is OK and then use high temp silicone to install it. that will take the vibration out of the pipe.
You need to look a t a parts diagram. There is a small spacer that sits on the outside of the arm (between the arm and the clip).
It depends on the bike you have. Refer to your owner's manual to be sure. most bikes have a drain bolt on the water pump cover. remove it, then remove the radiator cap to allow air to enter. it will shoot right out so be prepared.
Refer to the instructions that came with the wiseco. On most the wiseco 2-storkes i have done, they are the same and there is no right way up or down. Make sure the end gap is tested as instructed by the wiseco instructions. If the gap is to tight, the rings can expand when hot and cuase them to seize in your cylinder.
hey mate, that is a very great video and very educational i wouldnt have a clue how to change a piston/ring unless i took it to to the shop until i saw that the manuals just confuse me to much thanks alot
Removing the carb is much easier with the subframe off, and removing the subframe is easy. That is why we did it that way.
- I wish I had time too, but i don't. Also, i don't have an 03 cr125. I sugest purchasing a service manual for the bike. They walk you through that stuff.
Hey thanks! We will keep posting more for you.
@UnitFmX11 - chambers around the barrel. If it went into where the piston is, it would go out the exhaust pipe.
Exactly what we did in the video. Grab the circlip with some small needle nosed pliers and stick one end in the groove and then twist the circlip to get it into the groove. We show this again in our Yamaha Top End Rebuild if you wanted to check that out. Just be sure you've got a rag or something just in case you accidentally drop the circlip
@Yamahayz2502t - refer to the inspection guide line in the manual. If there are obvious scratches or wear then you need to. if it looks good you may need to measure the bore and the piston (refer to manual). The rings should be changed every so many hours regardless (refer to manual).
@tyhudson989 - it depends on the bike and person doing it. This bike can be done in an hour or so.
Very nice video. You explain everything very well and not too fast!
Corrosion on the studs is a common thing. Just clean them the best you can and put anti-seize or oil on them for reassembly.
You are well within the limit. it will be perfect.
I really liked your video I watched like 10 to 15 videos and yours was the best so far thanks
@worldSkater31Snephew - yes it is possible to put the piston in backwards and have it still run. It depends on the bike - some may run better than others, but I doubt any would run real well. With it in backwards, there is a good chance of getting the ring end hung up on a port, wich will break the ring and cause other damage.
@kriegdouch - I have done that before too. Luckily, I retreved the clip with a magnet. I make sure to put a rag underneith now!
@WHiPZEEE - I would suspect the studs are just sticking. Look between the centimeter gap you have and make sure nothing else is keeping it down. Then, use a rubber mallet to gently tap it up. It is common for the studs to stick in the cylinder a bit. Good luck.
If you are talking about it coming out the powervalve breather hose, then it is normal. More than normal may be coming out if your bike is running rich or not being ridden very hard.
@mikepasek - you don't want to wait until it is obvious. i would refer to the manual to see how often. If the clutch starts to slip, then that is a good sign it is about done for.
@honda1296 - I am not certain what thing you are talking about, but I think you are refering to the holder. we just used an allen wrench. Yamaha puts this there so you don't put stress on the powervalve when you remove or tighten the bolt.
Looking at the OEM Schematic it looks like it might use circlips to hold it in but i would recommend investing in a service manual to finish the job.
@RM250D8rzr - you don't need to unless it is damaged or worn out of spec. Refer to your manual for specs. If it just has a light glaze, you can hone it. We sell hones on our website as well.
Thanks. We are glad it is helpful and appreciate your business.