You are making this to easy for me. I picked up a 98 yz125 last weekend and just like yours it has two chips in the ports as well. On mine you can tell that the chips that damaged the top of the piston and head were caused by the ring catching the edge of a port and breaking off two pieces of piston from the between the ring and top of the piston, they were still stuck in the bottom of the head. They tore up the surfaces well enough, I'm going to grind the ports and replace the piston and head.
i cant wait to see this bike doen man, i recently did everything your doing to this bike to mine so its cool to see how your doing it and what your end result will be. keep em comin!
It will run for a while until the piston starts melting. Maybe get 10 -20 hours. I smoothed out mines and it ran good for about 20 rides. Then I took the exhaust off and saw the piston melting into the cylinder
Ger C I just sanded the cylinder jug smooth with red scotch Brite pad/ 320 grit. Then put a new pro x piston in and it ran good for awhile, then started to lose compression.
i know lots of guys who have done it and goten away with it. just make sure the bike warms up a decent amount before you rev it or let it go above a high idle, and make sure its warmed up fully before you put a load on the motor. and the piston shouldnt catch it or it chip.
I had a 50cc Minarelli Horz. AC moped which had some bad luck after about a thousand kms after piston change, the piston circlip went somewhat loose and the tip of it made quite severe damage to the cylinder and piston. I said **** this and sanded the cyl up with very fine wet sandpaper and installed old piston and top bearing. Over 20 kkm in total with that bike and still running like a charm. Not the same thing of course but if the groove is completely vertical and low on stroke this is OK.
I would do the same, an wildcat 700 engine i overhauled in 2000 still runs and it had damage like yours..a little work with the dremel and acid wash and a light honing it was ok.
What we’re your end results did you have any blow by that came out your exhaust like un Burnt oil my cylinder is the same ona. Vintage 90 kids Franco morini looked as similar and almost as if the same thing was done on my cylinder guess my question was do you have any bad results from this or do it run fine? Just quite of bit oil spattering out silencer or muffler until the mainedrive shaft sprocket broke On my sons bike old school Franco morini s5 engine air cooled now parts for this bike are superseded and damn near rare . Guess part of my question was did you have any blow by and unburnt oil that came out the exhaust at all?
do you think i can do like you, i have the same bike as your yz, and i got a sleeve in the heads, and she is craked between the two ports of the exhaust! The reste of the sleeve is pretty damn great!
Hi John, I have a Sym Fiddle version 1 I by a Nakaru 75cc kit to fit on,the moment I have a stand carburetor If I fit the new 75 cylinder we give me more power or I need to Chang the carburetor Whitch best 19 or 21 Nakaru carburetor tks
PLEASE RESPOND! ok, i bought a kx 250, nice bike, but the cylinder has a huge chip in it ( the previous owner blew up the piston). my uncle grinded it down like you did and said it might work. should i keep it or buy a new one. THE MAIN REASON WHY I DON'T WANT TO BUY A NEW ONE IS BECAUSE, THIS CYLINDER WAS 'PORTED' and i can't afford to buy and port a new cylinder. what should i do?
You seam to know alot about bikes, know anything about a kawasaki ke 250 1977 i just bought it the other day and rode it all over the place until today the clutch i belie went out, the cable was just lose i dont think i snapped the cable and i was able to power shift all they way back home, i dont know where to get a clutch that fits or where to really get any parts for it...any advice you got for me would be great
my bike blew up today never had a 2 stroke blow up before so just wondering if it is worse if it kicks over but has zero compression or is it worse if it doesn't kick over at all
i have 99 yz125 the cylinder is in good condition except that their is a little crack on top next to the head if i grind it out or something will it be fine..?
I have a question, my bike stopped running and i took the cylinder off. 91 CR250R. It is fairly difficult to turn stator/crank by hand, and i cannot rotate crank by pushing/pulling on piston very easily. Would this mean bad crank bearings? Not much play lifting up/down on stator... What else could cause this? Should the crank/piston be rotating very easily? Almost freely with the cylinder off?
Well, it's been done for years, it's called chamfering...They (I) do it every time they sleeve or bore a cylinder...And or port and polish...Maybe a bit more than what would be done for a new bore or sleeve, but, much better than leaving the chips there.....
I recently bought the Athena kit for this exact bike I was wondering the gaskets to connect the cylinder to the bottom end they gave me three of them a thin plastic one a rubber one and that like a paper one do they all go on and what order do they go on
Measuring the squish when the piston is top dead center would tell you the distance from the top of the piston head to the squish band on the head, depending on if your using pump fuel or race fuel and your particular engines geometry would help you select which gasket/gaskets to use. By adding thicker/thinner gaskets or more than one changes the distance between the top of the piston and the cylinder head (the squish band). This allows you to tune your compression ratio. Correct me if I'm wrong please anyone.
lol what? measuring the ring gap by itself inside the cylinder doesnt do a thing? unless you plan to use it......i mean..how do you know the last person had it gaped right?
I enjoy watching your videos, but the "porting" job you did with the dremel was a terrible idea. I think that YZ has an AL bore with a Yamaha specific ceramic coating (I may be wrong) and it acts just like nikasil, when something like that happens it will continue to chip off, and usually all it takes is a few hours of the ring(s)/piston moving across it to destroy the bore. But, I'm a pessimist, and usually do it correctly the first time, so take what i say what I say with a grain of salt.
I think not a good idea grinding more off the port,wouldn't it be safer to use like JB weld to fill in the space and smoothin out the rough spot in the port?
love your videos mate but that's not a cylinder head, that's the cylinder/barrel/jug whatever, the cylinder head bolts to the top. i'm sure you already know this but it just bothers me when you call it that lol
Johnnysshop how much do u think it would cost me to rebuild a kx125 because I have been having problems losing power fowling plugs and rolling some smoke I'm pretty sure that is the top end is it best to do the bottom end while in the motor, or try to get a different bike if so can u just throw a estimated price...thanks
That's the cylinder. Not head.
Alex Laplante yeah that’s what I was thinking 😂
You are making this to easy for me. I picked up a 98 yz125 last weekend and just like yours it has two chips in the ports as well. On mine you can tell that the chips that damaged the top of the piston and head were caused by the ring catching the edge of a port and breaking off two pieces of piston from the between the ring and top of the piston, they were still stuck in the bottom of the head. They tore up the surfaces well enough, I'm going to grind the ports and replace the piston and head.
Thanks for the video, good to see someone trying to make it work instead of just throwing the cylinder out.
Thanks! Yeah, I still wouldn't recommend for someone that rides often/races..
i cant wait to see this bike doen man, i recently did everything your doing to this bike to mine so its cool to see how your doing it and what your end result will be. keep em comin!
Yeah, I completely understand. I just completely rebuilt an '87 RM125. Good luck with the YZ.
It will run for a while until the piston starts melting. Maybe get 10 -20 hours. I smoothed out mines and it ran good for about 20 rides. Then I took the exhaust off and saw the piston melting into the cylinder
Sorry, I don't understand English very well.
So you did a new nikasil for your cylinder and it doesn't work. Was it like a waste of time?.
Ger C I just sanded the cylinder jug smooth with red scotch Brite pad/ 320 grit. Then put a new pro x piston in and it ran good for awhile, then started to lose compression.
i know lots of guys who have done it and goten away with it. just make sure the bike warms up a decent amount before you rev it or let it go above a high idle, and make sure its warmed up fully before you put a load on the motor. and the piston shouldnt catch it or it chip.
Howd it turn out? I'm thinking of doing this to my 125. Did it chip
I did the same thing to a polaris 800 it ended terribly, good luck that nickasil is tough but brittle. props on a good vid
The new owner said it's been fine. I was kinda surprised really.
I had a 50cc Minarelli Horz. AC moped which had some bad luck after about a thousand kms after piston change, the piston circlip went somewhat loose and the tip of it made quite severe damage to the cylinder and piston. I said **** this and sanded the cyl up with very fine wet sandpaper and installed old piston and top bearing. Over 20 kkm in total with that bike and still running like a charm. Not the same thing of course but if the groove is completely vertical and low on stroke this is OK.
the 1996-2001 Yamaha YZ125's are the best motocross bikes ever made
They are nice bikes for sure!
How bout the 2002? I just purchased one
Make sure you take out and clean the power valves so your sure there's no metal shavings or dust to fall back in the cylinder
I would do the same, an wildcat 700 engine i overhauled in 2000 still runs and it had damage like yours..a little work with the dremel and acid wash and a light honing it was ok.
Good to hear!
What we’re your end results did you have any blow by that came out your exhaust like un Burnt oil my cylinder is the same ona. Vintage 90 kids Franco morini looked as similar and almost as if the same thing was done on my cylinder guess my question was do you have any bad results from this or do it run fine? Just quite of bit oil spattering out silencer or muffler until the mainedrive shaft sprocket broke On my sons bike old school Franco morini s5 engine air cooled now parts for this bike are superseded and damn near rare . Guess part of my question was did you have any blow by and unburnt oil that came out the exhaust at all?
Doing a top end on my kx125 and the cylinder looks great but how can I check if my cylinder still has the correct bore ?
+mason mills with a cylinder bore gauge. There's plenty of videos on how to do it, just search for cylinder bore gauge :D
+mason mills Bore gauge
Make sure theres no metal chips in the ports. What destroyed the piston before might still be in there...
Ya if u go through all the trouble of rebuilding, get a good piston. I recommend wiseco ive seen them last years and years
Agreed. This build was a pure budget build.
do you think i can do like you, i have the same bike as your yz, and i got a sleeve in the heads, and she is craked between the two ports of the exhaust! The reste of the sleeve is pretty damn great!
i love to see when you post new vids!
need more videos. love it!!!
Hi John, I have a Sym Fiddle version 1 I by a Nakaru 75cc kit to fit on,the moment I have a stand carburetor If I fit the new 75 cylinder we give me more power or I need to Chang the carburetor Whitch best 19 or 21 Nakaru carburetor tks
PLEASE RESPOND! ok, i bought a kx 250, nice bike, but the cylinder has a huge chip in it ( the previous owner blew up the piston). my uncle grinded it down like you did and said it might work. should i keep it or buy a new one. THE MAIN REASON WHY I DON'T WANT TO BUY A NEW ONE IS BECAUSE, THIS CYLINDER WAS 'PORTED' and i can't afford to buy and port a new cylinder. what should i do?
You seam to know alot about bikes, know anything about a kawasaki ke 250 1977 i just bought it the other day and rode it all over the place until today the clutch i belie went out, the cable was just lose i dont think i snapped the cable and i was able to power shift all they way back home, i dont know where to get a clutch that fits or where to really get any parts for it...any advice you got for me would be great
my bike blew up today never had a 2 stroke blow up before so just wondering if it is worse if it kicks over but has zero compression or is it worse if it doesn't kick over at all
i have 99 yz125 the cylinder is in good condition except that their is a little crack on top next to the head if i grind it out or something will it be fine..?
I gotts resleave my 79 RE125 bout would love get replacement bock ,to keep it as ordinal ect.
I'd keep an eye out on eBay, it can be your best friend!
I'm not 100% sure :(
I have a question, my bike stopped running and i took the cylinder off. 91 CR250R. It is fairly difficult to turn stator/crank by hand, and i cannot rotate crank by pushing/pulling on piston very easily. Would this mean bad crank bearings? Not much play lifting up/down on stator... What else could cause this?
Should the crank/piston be rotating very easily? Almost freely with the cylinder off?
How good are those namura pistons??
Bottom of the line. They work but I'm not sure for how long!
what are the cross hatchets from, are they good, bad? neither?
did the bike run before you put the the new piston in?
do you still have it and if so does it run good ?
+nick39691 I sold it a few years back so I'm not sure :(
Well, it's been done for years, it's called chamfering...They (I) do it every time they sleeve or bore a cylinder...And or port and polish...Maybe a bit more than what would be done for a new bore or sleeve, but, much better than leaving the chips there.....
+Mike G True, I still don't like it because I'm not a pro :)
I try to kick start but nothing happens its not locked but I found 1 piston ring off inside any suggestions
I recently bought the Athena kit for this exact bike I was wondering the gaskets to connect the cylinder to the bottom end they gave me three of them a thin plastic one a rubber one and that like a paper one do they all go on and what order do they go on
+James Crabtree Hmm.. I dunno. The stock only uses one..
It comes with a green fabric one one see through plastic one and one thick rubber gasket I don't know what you're supposed to use
+James Crabtree I would get ahold of them, you may need to use all three..
Measuring the squish when the piston is top dead center would tell you the distance from the top of the piston head to the squish band on the head, depending on if your using pump fuel or race fuel and your particular engines geometry would help you select which gasket/gaskets to use. By adding thicker/thinner gaskets or more than one changes the distance between the top of the piston and the cylinder head (the squish band). This allows you to tune your compression ratio. Correct me if I'm wrong please anyone.
will a new head fit on my 86 yz125, say for example a 2003 head?
I have a rm85 and inside my cylinder is great but I have a small gouge on the wall of my cylinder. can I ride like that?
Or how can I fix it?
+jaxson trickey I wouldn't. If you plan on riding much, I'd get it re-plated.
ok great thanks
I have a rm 85 and cylinder has no chips just scratches and piston just has scratches...can I just replace the rings and be ok?
Yeah but you may want to hone it a little just to be safe.
did it work
lol what? measuring the ring gap by itself inside the cylinder doesnt do a thing? unless you plan to use it......i mean..how do you know the last person had it gaped right?
I enjoy watching your videos, but the "porting" job you did with the dremel was a terrible idea. I think that YZ has an AL bore with a Yamaha specific ceramic coating (I may be wrong) and it acts just like nikasil, when something like that happens it will continue to chip off, and usually all it takes is a few hours of the ring(s)/piston moving across it to destroy the bore. But, I'm a pessimist, and usually do it correctly the first time, so take what i say what I say with a grain of salt.
I was wondering, I bought a 02 yz 125 and I was wondering if I could do a motor swap with a 02-05 yz 250 engine? will it just slip in?
MAFIAxHITTMAN lol. No
I think not a good idea grinding more off the port,wouldn't it be safer to use like JB weld to fill in the space and smoothin out the rough spot in the port?
Just bought a new cylinder for my 01 yz125 for 250 on ebay
Please inform me of how long it lasts.
love your videos mate but that's not a cylinder head, that's the cylinder/barrel/jug whatever, the cylinder head bolts to the top. i'm sure you already know this but it just bothers me when you call it that lol
did it work?
+coreysteady Yeah, seemed fine.
@@Johnnysshop how about today? Do you still recommend it?
Will I loose compression if 1 piston ring breaks?
yes
how has it held up
I sold it awhile back but it was still good. I wouldn't trust it for the long haul though..
Ghetto man. Haha! As always thanks for the videos... looking forward to see how it works out for you.
Thanks
that is NOT THE HEAD. that is the CYLINDER BARREL
How did it do
Ended up being fine. Sold the bike and I believe the owner is still running on it.
Johnnysshop how much do u think it would cost me to rebuild a kx125 because I have been having problems losing power fowling plugs and rolling some smoke I'm pretty sure that is the top end is it best to do the bottom end while in the motor, or try to get a different bike if so can u just throw a estimated price...thanks
that's not the head.................
I have 2 stroke 250
not tryin to be a jerk but thats the jug buddy
cullen9017 yeah that’s the nickname for the cylinder
I would not do this just send it to millenium technologies for less than 200 bucks. And that's the jug not the head
And i think i don't wanna know it haha
Hmmmmmmmmmmm. Sent to
Millennium and not this shit