Going through your video"s, and they are very helpful to someone like me who knows basically nothing on 2 stroke engines. Very helpful, and much appriciated. .
Hi Johnny, Thanks for the informative videos. I misplaced my manual the other day and this video came in handy as a reminder of the sequence of assembly/disassembly. One note. Your reference to the circlip positioning in the piston - you mentioned that you weren't sure about positioning. The Manual (I finally found it) states that you should NOT leave the open gap in the ring at the open gap in the piston pin slot. They depict the ring gap opposite the opening. Thought I'd pass that along.
Great videos. I'm rebuilding a 1998 CR125 from top to bottom very similarly to your bike - replacing on case half, new top end, inspecting everything etc. At the moment I'm acid washing the parts though because they all have some surface gunk that is hard to get off. Thanks for the videos though, it confirms what I already know!
I see you installed a numera, I too also like to live life dangerously. Had a few of them break the skirts off after not many hours at all. They were cast, but never going back to numera.
+David B Haha.. Yes, I do! Cheapo piston and I milled a chip out of the sleeve. All ended up okay but just feeling the piston in my hands deterred me from ever wanting another!
Just had a ProX fail on my bike. Cracked skirt, I am lucky the top edge of the piston melted near the ring first and killed my compression because that skirt was gonna let go soon and I know it would have destroyed the bottom end when it did. I am putting a Wiseco Forged Pro-Lite piston in it now, which is why I am watching this video, haha
i used regular 10w 40 once when i rebuild my 125 and it completly screwed my top end. i dont know if its just me but id use premix just to be safe. even cheap marine premix works great. but otherwise great video!!
I have heard of people soaking the piston, rings, and other parts in oil so when you do the first startup they have oil on them. Does this sound right?
Brilliant video!, very informative, thankyou! I have a 08 yz125 with a relatively new cylinder which is a B size, what piston size should i get? B aswell? And are Vertex pistons as good as OEM standard?
You actually don't have to take the bottom end apart after a circlip has fallen inside the crankshaft side of the engine, to remove the circlip pour some wd40 in the bottom end and shake the bottom end around and flip it over facing down & let all of the fluid drain out into a clean bowl or clean pan. Or you can do this instead flip the bottom end over and grab a can of maxima contact cleaner and spray it into the crankshaft side until the clip falls out into the clean bow or clean oil pan. Don't use brake cleaner or carburetor cleaner as this will ruin the oil seals and mating surface gasket where you applied a paper gasket or rtv silicone and yamabond when putting both of the cases back together.
Hey Johnnysshop, idk if ya remember when i asked you too look at my bike, it was the day i got it, and u commented sounds like a top end is needed...well guess what. You are right! it needs one and needed one when i got it. It has piston slap, so ima get it fixed soon, but for now ima drive it till it gets worse, i mean i got 130psi and it runs fine...just ya hear it adn my plugs go like crazy when u just idle. anyways how much we looking at for a new top with piston slap? the piston is 110$
Im having problems I have a bud head and I keep getting coolant coming through the head bolts replaced the o rings and and copper washers and has seemed to made it worse
lol, it's a 2stroke. There is no "timing" because there is no camshaft or overhead valves, and it accomplishes "suck,squeeze,bang,blow" in only 2 strokes instead of 4... Bask in the simplicity and beauty of the 2T engine design!
yep...jug too. idk id rather just re sleeve it...if i go new jug route ima go ahead and get a complete 2012 motor...anyways i can't afford it so re sleeve jug and a wossner piston. anyways how did ya know? that was like the day i got the bike and i never noticed it till weeks after and when i took it to the shop they said it.......then another mechanic my uncle really trusts says it. So we know now 3 people said it and we hear it now. But still how'd u know?
Hi man i watch all part of yz rebuild just great job. I have one question this week im buy used yz125 2004 the seller says piston and cylinder are replaced with new everyone seller says that :D but my question is How do I know is really new without open engine i mean some sound that i can hear or how it look outside.My english is bad i know but i try it. I'll be very grateful if you tell me for what i have to look. And again great job with yz project. greetings from Bulgaria.:)
Use premix not motor oil it will actually help not hurt it motor oil has to burn out and you will got alot of blue smoke just like when your crank seal blows.
my piston has gouges on the top all the way around in a circle, the cylinder is also not fully centered. one side is thicker than the other but it still is circular. I dont know if i should rebuild it or just throw it away. There is no scarring or scratches in the cylinder. What should i do?
I have a little problem... I don't know how to remove the cylinder head, beacause of all the wires, emmm like the RC valve wires, got a Honda CR125R 04.. Is it also very important to get these settings right when you put them back on?
Hey Johhny, i was puttin a top end in my bike Yz, and i noticed the wrist pin was actually hard to get out, like i had to hammer and punch it out, i was wondering if this is normal after wear of the pin, and will a new pin slide in easily?
Why dose my 2 stroke 125 dump a pretty excessive amount of oil through exhaust & pour out the muffler ❓❓ fouls plugs in 7 min of riding. Thank You in advance for info.
+Johnnysshop I'm relived to hear that's the problem. Now I put the top kit on & can't get a torque wrench in on cyl hope I have bolts pretty even. I guessed the feel of 20ft. Lbs .... Thanks for the reply !!
i know this video is rather old but this may be a stupid question but i race mostly 4 strokes, why would you need to replace just the piston head and not the rod? for example if the bike blows up, would you only need to replace the head or would you replace the whole piston, crank, rod,etc.
I bought a Yamaha yz125 2 stroke its a 2007 but the motors completely torn apart because it need a new piston and rings was wondering if you have a rebuild video or planning on one?
oh yea, i never noticed it until later, and then after being told what they sound like im like omg it is. i also stethoscope it and heard a pint sound of slap.
hi i have a cr85 what has just stoped working ive check everthing there is a spark n all clean filter n carb fuel getting throw but when u try to bump it it just sound boggy i whas thinking it could be the piston ring what does it sound like to u mate and my mates cr the piston ring went on his but it still started plz help
1 question! what year is this bike? all that I know is that my bike uses a needle bearing that is bigger then stock, did they change the size of needle bearing to a larger size is any specific year
Ian Arnold All the bolts have a specific torque setting they need to be set to, you can't just crank them down with a socket. You need a torque wrench.
Every bike I've had that I discovered had a Namura piston had problems. They are cheap and sloppy. They will break quickly. If they don't break they will lose compression very fast!! Spend the extra dollars for a quality piston. The rings are soft and equally shitty too. Wiseco, ProX, Vertex.. forged is the way to go.
I just put on my piston and everything and put my clips in and made sure they were in place but when I grab the piston I can move the piston side to side and it will slide side to side, was wondering if this is normal, thanks!
im going to replace my pistons and rings in my KX100, i heard that i need to get the engine slightly bored out for the new piston for a good seal, is this true or can i just throw the new piston in without boring it out?
hey, i want to attempt my top end rebuild my self for the first time, where would i get my head refinished and where should i order my parts? i have a 1986 yz125
i just put a new top end in my bike and broke it in properly but it fouls plugs like a mofo and the compression has gone down it also doesn't seem to have the power that it did before is there something wrong or is this normal
I've got a 1998 kx125 dripping black oil from ehaust and its smoking rich white smoke n lots of it no power hardly on bottom end but lots on top??? Any idea what's wrong...
hello. so I have a yz 125 01' and I just got a problem . water is leaking throw my exhaust and radiator cap. I'm new to this but I recently changed the water pump seals by myself. can you try to explain me what I need to do? please
+Johnnysshop thx for the answer I'm very appreciated but , I've been looking around and some more people are saying the same and it's about the head gasket but I have also some radiator overflow I mean when I start the bike the water is pumping right by the radiator cap. does it got to do with that as well?
ah i t rebuilt my 97 yz i just bought i thought it just was bored to a 167 here it was a full 167 kit but the cylinder and piston are stock bore because i just wanted to get the bike going
Johnny, I really love your videos but when are you going to get some riding videos!? Im not saying you are but its like your a rich kid thats just does them up but never rides them, get out and give them a ride for once! I really love your videos and have been a subscriber for quit a long time (on a previous account) and have only seen 1 riding video which was up the street & back.
6.20 mins in the video where you said to move the gear to make sure everything is smooth. When you move your gear the piston moves.When i move my gear it just spins freely not a thing moves, any ideas??
I literally just bought an '05 YZ125 last week that I'm currently rebuilding the top end because the previous owner put a new piston in backwards. It caused the piston ring gap to be incorrectly clocked so that it goes over the exhaust port, which immediately made it snag the port's edge and get the ring all mangled up as well as take some chunks of cylinder wall and piston out. Nothing too too bad, I'm dropping the cylinder and new ProX piston I just got in the mail today off tomorrow at Langcourt for replating.
So maintained and not raced it should be good after like 2-3 years? I've also heard that if you dont change them for a while it can damage other things. Thanks for the reply.
Going through your video"s, and they are very helpful to someone like me who knows basically nothing on 2 stroke engines. Very helpful, and much appriciated. .
Thank you so much for watching!
Hi Johnny, Thanks for the informative videos.
I misplaced my manual the other day and this video came in handy as a reminder of the sequence of assembly/disassembly.
One note. Your reference to the circlip positioning in the piston - you mentioned that you weren't sure about positioning.
The Manual (I finally found it) states that you should NOT leave the open gap in the ring at the open gap in the piston pin slot. They depict the ring gap opposite the opening.
Thought I'd pass that along.
Great videos. I'm rebuilding a 1998 CR125 from top to bottom very similarly to your bike - replacing on case half, new top end, inspecting everything etc. At the moment I'm acid washing the parts though because they all have some surface gunk that is hard to get off. Thanks for the videos though, it confirms what I already know!
I see you installed a numera, I too also like to live life dangerously. Had a few of them break the skirts off after not many hours at all. They were cast, but never going back to numera.
+David B Haha.. Yes, I do! Cheapo piston and I milled a chip out of the sleeve. All ended up okay but just feeling the piston in my hands deterred me from ever wanting another!
you really should use oil during assembly
johnny thank you for posting more vids of the yz i like how u get into detail with the bikes thanks again
yea before the rebuild she rocked.. she still goes now but it acts like its bogging or somthing. it wont rev out like it did before.
@ 4000rpm you only really need to hone the cylinder if your putting new rings in b/c it helps them seat better
finally! a decent informative video. thanks.
Thanks!
Excellent video, very informative and helped me out a great deal. Thanks for uploading it.
lucky me, i just put the drill bit in from the back of the hub and it spun right out.
now I just need to wait for the new bolts
Tip don't ever buy namura cause they will shatter and fall in your bottom end and make it to were you gotta have a full rebuild
i cant wait to see it running!
Just had a ProX fail on my bike. Cracked skirt, I am lucky the top edge of the piston melted near the ring first and killed my compression because that skirt was gonna let go soon and I know it would have destroyed the bottom end when it did.
I am putting a Wiseco Forged Pro-Lite piston in it now, which is why I am watching this video, haha
same thing happened to my 03 cr it was the bottom end crank bearings i dont do engine work so parts and labor were like $600
i used regular 10w 40 once when i rebuild my 125 and it completly screwed my top end. i dont know if its just me but id use premix just to be safe. even cheap marine premix works great. but otherwise great video!!
I have heard of people soaking the piston, rings, and other parts in oil so when you do the first startup they have oil on them. Does this sound right?
Brilliant video!, very informative, thankyou! I have a 08 yz125 with a relatively new cylinder which is a B size, what piston size should i get? B aswell? And are Vertex pistons as good as OEM standard?
Oli Clothier b
You actually don't have to take the bottom end apart after a circlip has fallen inside the crankshaft side of the engine, to remove the circlip pour some wd40 in the bottom end and shake the bottom end around and flip it over facing down & let all of the fluid drain out into a clean bowl or clean pan. Or you can do this instead flip the bottom end over and grab a can of maxima contact cleaner and spray it into the crankshaft side until the clip falls out into the clean bow or clean oil pan. Don't use brake cleaner or carburetor cleaner as this will ruin the oil seals and mating surface gasket where you applied a paper gasket or rtv silicone and yamabond when putting both of the cases back together.
but i swear those pins are pains. the hardest part of fixing dirt bikes. the simplest thing
Thanks I got one there very nice but haven't put it in yet
you did a excellent job on the video...thanks
Thanks for watching!
You didn't mention the chamfer on the ends if the ring those chamfers have to face up and the points down. That's very important
Thanks just got one but haven't put it in yet!
Hey Johnnysshop, idk if ya remember when i asked you too look at my bike, it was the day i got it, and u commented sounds like a top end is needed...well guess what. You are right! it needs one and needed one when i got it. It has piston slap, so ima get it fixed soon, but for now ima drive it till it gets worse, i mean i got 130psi and it runs fine...just ya hear it adn my plugs go like crazy when u just idle. anyways how much we looking at for a new top with piston slap? the piston is 110$
Im having problems I have a bud head and I keep getting coolant coming through the head bolts replaced the o rings and and copper washers and has seemed to made it worse
Did you replace the head gasket also?
lol, it's a 2stroke. There is no "timing" because there is no camshaft or overhead valves, and it accomplishes "suck,squeeze,bang,blow" in only 2 strokes instead of 4...
Bask in the simplicity and beauty of the 2T engine design!
yep...jug too. idk id rather just re sleeve it...if i go new jug route ima go ahead and get a complete 2012 motor...anyways i can't afford it so re sleeve jug and a wossner piston. anyways how did ya know? that was like the day i got the bike and i never noticed it till weeks after and when i took it to the shop they said it.......then another mechanic my uncle really trusts says it. So we know now 3 people said it and we hear it now. But still how'd u know?
did you hown the cylinder becuase I was just wonder if this is nessesary to do before putting a new piston in.
Hi man i watch all part of yz rebuild just great job. I have one question this week im buy used yz125 2004 the seller says piston and cylinder are replaced with new everyone seller says that :D but my question is How do I know is really new without open engine i mean some sound that i can hear or how it look outside.My english is bad i know but i try it. I'll be very grateful if you tell me for what i have to look. And again great job with yz project. greetings from Bulgaria.:)
Thanks for watching, I appreciate it! No way to easily tell without opening it up. If it has good compression and a good idle, you should be good.
okay thank you very much for reply +1 sub from me :)
Thank you!
by power valve do you mean reeds? he shouldnt have touch them but ill take alook at it when i get some time.
will you be upgrading the plastics, bars, cales etc?
@tommysantos I had one in my bike and it worked great! Some say not to use them but I've never had a problem with them
when putting the piston back in the bore, does it have to be at a certain stroke for timing? like top dead center or intake stroke, etc
Very good video!!!
Thank you!
ah ok, this bolt is tight in there, will it come out easy? how far do i drill into it?
Use premix not motor oil it will actually help not hurt it motor oil has to burn out and you will got alot of blue smoke just like when your crank seal blows.
Great tutorial many thanks.
I have an 01 YZ125 the spark plug hole looks like its an brass insert it's leaking from around the hole any thoughts.? It looks freshly rebuilt
my piston has gouges on the top all the way around in a circle, the cylinder is also not fully centered. one side is thicker than the other but it still is circular. I dont know if i should rebuild it or just throw it away. There is no scarring or scratches in the cylinder. What should i do?
Can you post full video of this piston change why'll engine is on bike ?
If I do another build I will do so.
I have a little problem... I don't know how to remove the cylinder head, beacause of all the wires, emmm like the RC valve wires, got a Honda CR125R 04.. Is it also very important to get these settings right when you put them back on?
i would do it your self i did mine at 10 took 30 min to get every thing out and a bout an hour or so for everything to get put back together
What about the piston ring end gap?
oh also, i broke a bolt in my clutch hub. will I be able to use a bolt extractor on it or should i just drill it out and heli coil it.
what happens if the piston has no window on the intake side and the connecting rod is 2 millimeters smaller
and do you have to buy a new needle bearing?
My inner cylinder oring is to big but the putter fit perfect any ideas?
Are all yz 125 cylinders the same from 2005 up ?
Hey Johhny, i was puttin a top end in my bike Yz, and i noticed the wrist pin was actually hard to get out, like i had to hammer and punch it out, i was wondering if this is normal after wear of the pin, and will a new pin slide in easily?
do you have to re hone the jug when just putting in new rings
Why dose my 2 stroke 125 dump a pretty excessive amount of oil through exhaust & pour out the muffler ❓❓ fouls plugs in 7 min of riding. Thank You in advance for info.
Thanks William Jones , I was hoping that's all it was. I purchased a top kit but didn't install yet.
+Mike Remvidas I agree, new rings.
+Johnnysshop I'm relived to hear that's the problem. Now I put the top kit on & can't get a torque wrench in on cyl hope I have bolts pretty even. I guessed the feel of 20ft. Lbs .... Thanks for the reply !!
+Mike Remvidas Awesome!
are the piston circlips really easy to instal on Namura pistons because I just ordered a namure for my 250 sx.
any specific brand? ive ordered a snap-on drill bit/ extractor set from my shop teacher.
THX!! You helped me a LOT :)
i know this video is rather old but this may be a stupid question but i race mostly 4 strokes, why would you need to replace just the piston head and not the rod? for example if the bike blows up, would you only need to replace the head or would you replace the whole piston, crank, rod,etc.
Depends on what damage is done. Usually the rods on a 2 stroke are ok unless a bearing goes. Typically the piston and rings are just shot.
How hard is it to to put a engine in the frame
I bought a Yamaha yz125 2 stroke its a 2007 but the motors completely torn apart because it need a new piston and rings was wondering if you have a rebuild video or planning on one?
There are a lot of them on my channel, the 98 isn't a huge difference in the 07
ended up havening to replace the crank so i just took it to a bike shop so i didnt have to split it and put it back together
mycookysdude Ahh. How much did they charge ya?
oh yea, i never noticed it until later, and then after being told what they sound like im like omg it is. i also stethoscope it and heard a pint sound of slap.
Hi, how much would it cost for new piston rings installing at a shop at about 60$/hr. I have a 01 yz 125
hey, i wanted toknow if that piston worked good?because im rebuilding a 2000 yz 125 and might get the same piston thanks
hi i have a cr85 what has just stoped working ive check everthing there is a spark n all clean filter n carb fuel getting throw but when u try to bump it it just sound boggy i whas thinking it could be the piston ring what does it sound like to u mate and my mates cr the piston ring went on his but it still started plz help
hey i had someone rebuilt my top end and now it runs but it doesn't feel like it has any power. i stopped riding it but idk what to do with it.
sorted it mate rong spark plug was in the bike but still a oryt spark sso got a diffrent spark plug cheers anyway
should i buy the namura or original piston?? thanks :)
1 question! what year is this bike? all that I know is that my bike uses a needle bearing that is bigger then stock, did they change the size of needle bearing to a larger size is any specific year
+clayton roche OEM gasket and did you torque the bolts down to spec?
***** What do you mean? What does torque down to spec mean?
Ian Arnold All the bolts have a specific torque setting they need to be set to, you can't just crank them down with a socket. You need a torque wrench.
Also, what size should the gap be in the ring?
ok thanks what do you recommend
Every bike I've had that I discovered had a Namura piston had problems. They are cheap and sloppy. They will break quickly. If they don't break they will lose compression very fast!! Spend the extra dollars for a quality piston. The rings are soft and equally shitty too. Wiseco, ProX, Vertex.. forged is the way to go.
Yeah, I don't recommend them and this was basically to build the bike as cheap as possible. I told the new owner to replace ASAP.
namura pistons are forged.
Where did you order your replacement piston from?
whats the torquing on the cylinder head?
I just put on my piston and everything and put my clips in and made sure they were in place but when I grab the piston I can move the piston side to side and it will slide side to side, was wondering if this is normal, thanks!
Side to side is fine, up and down is bad.
Johnnysshop Thanks, yea I just did my bottom end and just got my replated cylinder.
im going to replace my pistons and rings in my KX100, i heard that i need to get the engine slightly bored out for the new piston for a good seal, is this true or can i just throw the new piston in without boring it out?
and also i got my yz with out the rubber for the powervalve where can i find it?
hey, i want to attempt my top end rebuild my self for the first time, where would i get my head refinished and where should i order my parts?
i have a 1986 yz125
Awesome video thanks, i have a 2003 yz 125 that i am trying to peace together, would you have a clutch cove that would fit a 03 you want to sale?
Wish I did but I have zero parts :(
Thanks anyway
so the arrow always points to the front of the bike?
how often piston have to change on this bike?
i just put a new top end in my bike and broke it in properly but it fouls plugs like a mofo and the compression has gone down it also doesn't seem to have the power that it did before is there something wrong or is this normal
I've got a 1998 kx125 dripping black oil from ehaust and its smoking rich white smoke n lots of it no power hardly on bottom end but lots on top??? Any idea what's wrong...
Sounds like you could have a few issues. New rings, new silencer packing, power valve cleaning and so on.
no ring end gap?
How do you stop the head gasket to not pinch ? (I’m working on a 99rm80)
You could use some gasket sealer with the gasket.
hello. so I have a yz 125 01' and I just got a problem . water is leaking throw my exhaust and radiator cap. I'm new to this but I recently changed the water pump seals by myself. can you try to explain me what I need to do? please
+Nelson Francisco Sounds like the seals may not be good or a bad head gasket if you are getting water in the exhaust.
+Johnnysshop thx for the answer I'm very appreciated but , I've been looking around and some more people are saying the same and it's about the head gasket but I have also some radiator overflow I mean when I start the bike the water is pumping right by the radiator cap. does it got to do with that as well?
+Nelson Francisco Yep, sounds about right.
How do you hold the engine on the bench while torquing the fasteners?
Just with my hands..
for the clips is there a certain way they should face? like the piston ring has a certain spot
wait just kept watching and saw you say something about this
Yes, each manual should tell you. Basically you want them to be opposite of one another though.
Piston clips should have the opening at 12:00 or 6:00 to prevent them from compressing and popping out.
what about pro-x??
no affense but no bueno on the namuria pistons had 2 self distruct on me before i went to wiesco
I don't doubt it. This was a strict budget build to get the bike going.
ah i t rebuilt my 97 yz i just bought i thought it just was bored to a 167 here it was a full 167 kit but the cylinder and piston are stock bore because i just wanted to get the bike going
Johnny, I really love your videos but when are you going to get some riding videos!? Im not saying you are but its like your a rich kid thats just does them up but never rides them, get out and give them a ride for once! I really love your videos and have been a subscriber for quit a long time (on a previous account) and have only seen 1 riding video which was up the street & back.
what is the torch specs for the head?
What are the torque specs for the cylinder and the head for an 04 yz125? I don't have a manuel.
Should be around 22 ft/lbs
how many ft/lbs for the cylinder head nuts?
I just put a new piston rings and gaskets on my top end of my rm250 and it is now leaking coolant out of the cylinder cap help plz
Sounds like you didnt torque the bolts down to spec.
I cannot get the head back over my piston the piston has 2 ring and it won't go on any tips so frustrating
Not a lot of tips other than taking your time. They do make a piston compression sleeve just for this job. I think they run about $25.
yo I got blow through on my new piston. I changed piston rings gaskets. not sure how this happened.
Cylinder worn by chance? Do you have a single ring?
what is the diameter of the clip 12mm or 14mm ?
6.20 mins in the video where you said to move the gear to make sure everything is smooth. When you move your gear the piston moves.When i move my gear it just spins freely not a thing moves, any ideas??
Sprocket i meant
its in neutrual
derrick medley
Thanks haha first time having a dirtbike and i got to put the whole thing together, so i was following all of johhnys videos
doestoutking
I clicked it into a gear and its certainly not moving smooth i have to press on the piston and gear to get movement??
doestoutking With the cylinder off how does it move? You could have a bad crank bearing.
Vengan a ver como lo hacemos, los argentinos sin dinero ni sin repuestos originales!
what would happen if you put the piston in the wrong way would it evan run?
I literally just bought an '05 YZ125 last week that I'm currently rebuilding the top end because the previous owner put a new piston in backwards. It caused the piston ring gap to be incorrectly clocked so that it goes over the exhaust port, which immediately made it snag the port's edge and get the ring all mangled up as well as take some chunks of cylinder wall and piston out. Nothing too too bad, I'm dropping the cylinder and new ProX piston I just got in the mail today off tomorrow at Langcourt for replating.
Phillip Bass chb148 gives some good insight.
how often do I need to put a new piston and rings on my 01 yz 125? like years hours or what.
+Josh Myers Just depends. Rule of thumb used to be 30 hours but it depends on how hard you ride, oil, etc..
So maintained and not raced it should be good after like 2-3 years? I've also heard that if you dont change them for a while it can damage other things. Thanks for the reply.
+Josh Myers Yeah and change the oil often.
Josh Myers