The CR250R Locks Up! A mechanic shows us why it happened
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- Опубликовано: 6 фев 2019
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Live and learn. When Scott sent the cylinder off to a company to have work done to repair the damage we found on the bike almost a year ago, it came back to us with not quite enough clearance between the cylinder wall and piston. Of course, we didn’t know this at the time. This caused the motor to lock up right after it was put under a lot of load/heat when we drag raced it for the first time. For all those that think that you can’t drag race ANY motocross/enduro/Offroad dirt bike for fear of blowing up the motor after the motor has been good and warmed up/hot first... I have some ocean front property in Arizona for sale that I’d like to talk to you about 🙂
I mean, they call them race bikes for a reason. What do you think the start of a race is like? Every desert race, motocross race, Supercross race, and endurocross race I’ve ever seen starts with what amounts to a drag race into the first turn. These bikes are designed to do this very thing. I’ve done this very maneuver hundreds of times. I’ve never owned a bike that I haven’t done this very thing over and over again for fun.
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people have told me " Dont run a 2 stroke wide open in 5th gear then let off the gas." The lack of fuel after running that rpm under load strips the cylinder of oil. When u let off she locks up. Makes sense to me.
it's true you should always give a bit of gas to lube the piston and cilinder
Always hold the clutch and rev it up. Don't engine break the shit out of 2 strokes either.
@@OGKILLa9365 What he said. Clutch and blip the throttle.
RobinMX713 on dyno its primordial to lube after a curve
yeessss this is true.....
Clearance issues typically don't take 12 hours of ride time to reveal themselves... Just sayin
MotoMatt within the first hour of ride time at the max
MotoMatt you’re right... they typically don’t. Think about the engine load difference between single track/enduro riding vs drag racing. The piston is going to expand more with greater heat. Up until this drag race, all the riding on this bike was low load/low heat. I measured .04mm piston - cylinder clearance on the failed piston and cylinder. The spec is .06mm. Uniform scuffing on front and back of piston also indicates clearance issues.
@@kevinegbert1251 Then who was the genius that sent a head off for machine work, used and new piston and didn't check clearances... Kinda engine built 101.. new work... Check bore top, middle, and bottom to make sure you are actually round, and then check piston to wall clearance... Guess some people slap stuff together.
MotoMatt I didn’t rebuild the last top end. I just took it apart, measured everything and came to my conclusion based off of measurements and scuff pattern.
Due to turnaround time and other concerns with this cylinder we opted for a brand new OEM Honda cylinder and “A” sized piston. Flushed bottom end, verified ring gaps, cleaned intake, checked squish, etc.
@@kevinegbert1251 I totally get it. I didn't mean to point the finger at you. But I feel like why they are catching so much crap over this build is they threw TON of money at a nearly 20yr old Motocross bike to try and make it like a KTM that was purpose built for tight single track. Spent 12 hours of ride time between a few guys. Complained about things thate are 100% intrinsic to a 20 year old two stroke (vibration, having to feather the clutch a bunch, on/off power), even did a video where it was only 6 seconds slower than a KTM on the same trail. Guys that ride alloy frame CR250's in the same environment kinda feel like they should sack up, get more seat time before they complain about trivial things, and label it a just a meh... Bike in the environment they tested it in with the possibility that it could actually make them better riders ...The fact things like PTW clearance were missed just reinforces the impression they threw a bike together, didn't learn the nuances of the bike, and gave it a bad review.
I love it when people say something isn’t right but continue to drop the clutch when it’s trying to stall🤦🏼♂️
Right what a dumb ass
Shut up
Not a clearance issue, this would show on four corners and show up much sooner not after all the time you have put on it. The scoring on the exhaust side shows that this was a lubrication failure. Leaking crankcase (crankseal, base gasket) , jetting, carb isolator ect. Correct the problem or it will happen again.
100% agree!
Absolutely agree. I started tuning 2T bikes in the late 1970s so have heaps of experience. I also felt that on top of what you say here, he seemed to be off the throttle a little too much for my liking - it starved the engine of lubrication.
Seems to me that it was running lean not enough 927 bro 32:1 never would hav happened ur not riding a MX bike on a mx track and rebuilding it every race
Rory Cobleigh
yeh thats what it is...
they just blame d clearance...
even if theres a bit off d clearance but have sufficient oil it wont bug down
If you go on my channel I have a drag race of the same bike and I hold it wide open much longer. The issue here was the engine brake and the lean oil mixture he’s running.
Definitely he is running 80:1 or 100:1 he does in all his bikes that's not even close to enough oil
@@singletrackmarc819 So true my man! This guy clearly has little no experience but thinks he does.
I've constantly redlined and abused my XR400 for years and it still runs like new😂
That's a HONDA for you...... I only ride red dirt bikes.
Oh oh. I think this is turning into an oil thread.
Down the rabbit hole we go
RUN IT 32 to 1!! No! 50 to 1 is fine........... This never ends the age old debate will always go on.
I've got a 2000 KTM 200 that I've ran at 100:1 for 600 hours on Amsoil and all the internals look like brand new still.....nahhh just yanking your chain...I love a good oil thread just to see all the claims and arguing back and forth.
32:1 would have kept it cool. I have had/raced lots of cr250's and never seized. I have held them wide open for a lot longer than that. Unless that bike was not fully warmed up yet I am not buying the to tight of clearance. Clean that cylinder, put the same/new piston in it, run 32:1, make sure jetting is not to lean and run it wide open with no problems.
I run 50-1 and never had any problems. Ive got almost 300 hours on the current piston and rings.
i find that 32:1 is the best ratio for any 2 stroke. now i dont race and ride strictly recreationally, but i've never had a problem running that ratio ever. sure you may get a bit of unburnt premix out the silencer here and there, but at least you know the crankcase is getting lubrication. I never have problems with fouling plugs or excessive carbon unburnt fuel on the piston either
32:1 is what the old ester based oils used to be mixed at newer synthetic oils should be run at 50:1 or 60:1 exactly what the manufacturer recommends right on the label any richer than that is just wasteful and more likely to create more spooge.
@@robh3267 that's what has made 2 strokes last about the same as a 4 stroke. The old oils would wear pistons fast. These new synthetic oils makes the pistons last 50 times longer if not more.
@@robh3267 just read this on motosport
"Older non-power valve 2-stroke engines, air cooled bikes and ATV dune riding work best on a 32:1 ratio. Modern 2-stroke bikes call for a 60:1 ratio which veteran riders flinch at after the once popular 32:1 ratio so instead settle on 50:1 ratio along with some extra spark plugs, just in case."
i see what you're saying. the machines i ride are yamaha blasters (91 and 02) an lt 250 (87) and a yz 125 (02) the only one i really notice the splooge with is the 125 and of those 4 machines its the only power-valved one.
I have never siezed an engine in 25+ years of riding. Allways confirm your tolerances. Ive run everything on Sunoco Silver (100 octane) and Klotz castor @ 40:1, allways with a forged piston and a steel-sleeved engine. Never a hint of trouble.
I was worried at first but I'm positive I have the correct clearance! And I've ran the piss out of mine too! Good luck kyle
Haven’t watched these vids in quite some time, now I remember why
Letting off the throttle with that much ground speed would also have only left the pilot circuit to fuel the engine at high engine rpm potentially leaning it out. Thanks for the vids
One thing I have always done on my 2 strokes when riding fast is periodically pull in the clutch and open the throttle back up, with my thumb on the kill button for a couple seconds. This cools the motor some and adds a little extra lubrication.
Remember when you let off the throttle the slide closes restricting air. Air rushing through the carb is what draws gas through the jets. So chopping the throttle doesn't lean out the motor bad enough to cause seizure.
@@vdriveit I think many a dyno guy would disagree. Very interesting case. Probably a combination of things. Too lean on the main, to light on the oil ratio for wfo , then not pulling in the clutch after the run, not enough piston clearance....
I can attest to this. Had my Cr 500 tapped out on the highway, let off the throttle to make the corner and just like that it seized. Although it was a crank seize not piston.
By the way 40:1 chevron or anything with TC-W3 endorsement. ( they’re always blue) Bike will run forever and fuel never degrades.
I really like the way you edited this video Kyle.
Well done.
Wow I was so hype seeing the cr250 videos coming out Couldnt believe it when I seen this video...I don’t believe it was clearance issue I’ve seen other videos you have saying you run 80:1 or 100:1 oil ratios that cr ain’t the same as your new ktm try running 32:1 when you get it fixed that’s what I run and hold it wide open much longer then that on my cr, 80:1 just isn’t enough oil for high rpm on a race bike in my opinion
my cr 250 r is on its third piston same barrell i use 30cc for every liter and my top end is a little over lubed but without a problem is over twenty years ..The other thing i would say is these models have had a history of catching the ring on the ports my first piston ring did this and was blown out the exhaust the 2nd did it too i now only use one ring pistons .I dont use the bike now very much but i love the thing ,i have done beach races on it hare scrambles mx , enduros ,and its always good to go ... Dont let this get you down once its right it will right for ever
Honda HP2 40:1 93/104 mixed 50-50 I live in New England, so elevations vary race to race, but it's been a solid mix with zero issues.1995 CR250r my daily driver.
Read all the comments and lots of good info on predictions of the issue. I'm sure only one main cause might be hard to nail down as there sounds to be a few issues here not only one.
I have also been on the 100:1 saber kick but it never lasted long. The 50:1 to 32:1 range sure feels and sounds safer. What ever the issue is if Kyle was running 100:1 it definatly never made things better. If less oil was better why run it at all?.....because it lubricates.
As always great video Kyle and for the sake of smokers use a tad more oil 👍
Towing a bike in the desert looks so much nicer than an east coast swamp.
KHoff77 haha agreed!! It sucks on both parties the tower and the towee
No kidding I live and ride in east tn when we have to tow a bike out of the woods it's not easy up and down a bunch of ridges that are covered in wet rock and roots full of giant ruts
It might well be an overheating of the exhaust bridge, causing expansion and seize up. I noticed the piston had marks in both exhaust bridge and opposite side. Also, no lubrication holes drilled on the piston.
Let me guess, amsoil saber at 100:1. You engine braked it super hard after too, you’re always supposed to pull in the clutch after a drag.
Yup.....also I don't care what ams says I'm running 50:1
@2:55 "Somethin's happened to this" 😆 😂 😆
After a drag like that, pull in the clutch and blip the throttle on slow down. Not enough premix coating the cylinder. That piston was screaming yet when the throttle was off. Basically, that bike ran dry for a few seconds.
Why did I laugh when u said,” I think I just seized this motor” I promise I’m not a hater that was just so relatable🤣
Too much enginebraking after a dragrace like that. Maybe even to lean on the mainjet🤷♂️
wasnt it about lean mixture with d oil?
@@endurofan9854 i dont think so i run the same oil 1:80 and sometimes wide open for some time no issues till now for 80 hours
maybe it just worns slowly..
cuz there was still oil
what ive learned was mixing oil/gas more than 60:1 is not recomended for intense riding...
me i always mix by 40:1 ratio...
i let it smoke so my bike havent bog down in 2 years...
i use it daily as my service vehicle
if the track youre in have a lot of engine braking dont do the lean mixing...
80:1 ratio is for use with few engine braking...
@@endurofan9854 i dont engine brake at all
So many of my buddies locked up there old two strokes EXACTLY like this. Blast down the road, spin the engine fast, and the second they let off ( not putting oil in the cylinder) they would blow. I'm still nervous about getting a 2 stroke became of how many times I've see it
Honda two strokes are one of the most reliable bikes made. These bikes are not meant to ride at 60:1 ratio. I run mine at 36:1. I bet the bike is way lean, then your riding wide open and then immediately shut it off...pilot was prob way lean and boom there it went.
Why don't you run 32:1, easier to mix and its barely any richer.
Whiskey Throttle the throttle is more crisp with 36:1
Explain how a bike is designed for a certain mix ratio.
Joe Young if you do some
Research, ktm recommends you to run there bike at 60:1. Same with my sons 2015 ktm 65. The older Honda’s recommend running 32:1. Common sense will tell you more oil,more lube,bike runs longer between topends and depending how it is ridden possible detonation. That’s what this bike did. To lean and boom. I’d be really curious to see what the plug looked like.
@@vetracer5046 The Oil is better now than back then, I raced a 2001 CR250 for years and never had any issues with running Dominator at 50:1. The jetting is determined by the Jets, running 32:1 jetted wrong could be way lean or rich. I bet this bike was either jetted way lean or had some other issue.
Could be detonation issue. I don't know if you had the head decked for more compression. I've had issues with my Jetski motors failing that would look like lean seizures but I was just running too much compression and timing for pump gas. They would always fail WOT.
It sounds wfo 5th gear then he closed the throttle without pulling in the clutch = super lean. Super lean is high combustion temps . Just wonder how to tight the bore to piston clearance was ? .001 or .002 ?
My first instinct is to say engine braking or not enough oil etc. but judging by those pictures of the piston I would definitely agree with the mechanic that was some crazy wear pattern on the side of the piston.
Unless the main was way lean, I don't see an issue with jetting. The plug looked good and had a good oil burn on the flat surface. Also, no indication of detonation.
My machine shop showed me they drilled oil holes in the piston between the bridge of the exhaust ports if that makes sense, anyway I blew my motor twice until he did the piston drill and I’ve been riding it for 4 years without any issues, still have around 160 compression so I’ll do a top end next year
The same thing happened to my 250 crf 2007 model year while i was at fool throttle for about the same time. Is it not strange for this to happen in a four stroke liquid cooled motorbike?
What did you change on your previous rebuild?
here comes all the Mr. know it all's
I just had this problem to me on my 4 stroke!!!! The top end over revs and it stalls. Does that mean my motor seized ? I can still getbon it and ride butboncr I floor it, it will do that? Please help me
U went on engine brake at like max rpm, my heart cried
what tolerance did you have? and what piston where you running??
What was the bottom end like? Does it affect it?
Should do an info video on all things to check when rebuilding the engine .
It looked pretty cold where you were, potentially the cooling system was working too efficiently at high speed, the cold water running through the barrel but the hot piston under heavy load caused the piston to expand more than the barrel. This is exactly what happens if you dont warm up a 2 stroke properly.
I guess the work around if you are riding in extremely cold areas would be to run more clearance.
The Lectron Carb isn't helping with the lean/seize at the end of the run.
The temp may have played a part in the failure as well. When riding at temps below 40 deg F you may want to consider covering one or both radiators. A thermo rad-cap will show you your water temp. 160-210 F is fine. So drag racing= high load = high temp on piston, cold air temp = cold water=cylinder not expanding at the correct rate - totals seizure.
thats sounds very correct, happends to mine as well, i took the themo out in hot summer days which is very stupid thing to do, anyway, lessons learned in hard way.
Hey How long do those axp skid plates take to deliver to the USA?
What oil and ratio were you running?
Eric Gorr big bore kit ?? :)
Hey guys just wondering what oil were you running those bikes you need good oil
It happens. 10 hrs on my old RM and it had to have a couple bucks spent on a kit. I never took a chance.
You've got a ring catching on a port. You can see the damage plain as day. There is NO new cylinders for a cr250 anymore. If there's damage to the exhaust bridge, they won't replate it. Send it off and sleeve it. It's the best thing I did.
Good video. Took guts to post it. Lots of interesting comments below. I doubt clearance was the sole contributor. Run at 40-50:1 on your oil, jet it slightly rich, and they will run forever. That said, typical seizure on 2-strokes often occurs once you chop the throttle after a full throttle run, due to lack of fuel and lubrication when the throttle is chopped. Fuel serves a purpose when not under load, and that is to help cool parts as well as provide lubrication. When the throttle is chopped, a carb provides no fuel. This can most often result in a big end bearing seizure. Those rarely break free though, and are more expensive to fix. My 2 cents.
You could hear the detonation before she blew. Could also hear it was running lean. Not a clearance issue.
This has been an interesting project. My take away is to keep mx bikes on the track and off-road bikes for everything else.
That sucks! Good thing you had friends and a tow rope. I imagine you were a little ways from your truck.
Saber oil .. it’s meant for your lawnmower
Well the old lawns boys were two stoke .. I guess I should have said small engines
If it seizes up that mean the Piston is stuck or the gears??
Too much engine breaking with not enough oil man
Here come all the barn mechanics knowing more about it than the real mechanic
That's a bummer man I am also a 2-stroke Rider you might want to ease off the throttle next time that way the engine gets a sufficient amount of oil to the cylinder walls
Did you wear new top end in
Next time try running maxima 927 premix at 32:1. Never had an issue.
You cant fully let off the gas after a race, you have to keep burping the throttle so the oil pump shoots oil up
Piston rings gap?
Just curious why the hell did you repeatly let of the clutch while it was abvious that there was something wrong with it??? It was about to die but before that u killed it man.
@Josh Frank he went from a just a piston to a total rebuild real fast🤦♂️
Tattoo Junk yuppppp
Guarentee if you ran 32:1 like your supposed to if would never of happened
I've ran 50-1 since 1994
yes
i agree
me im in 40:1 ir sumtyms 50:1 ratio...
but if im gonna go hotrod id use 30:1
KGB 1974
yeah real men to have ball just to spend his fortune fixing his bike cuz it wud bug down often
KGB 1974
200:1
u mean 20 liters of gas to a 100 ml oil...
thats crazy
@KGB 1974 what's your point? What's that got to do with a man. I build women's dirt bikes too. What do you want to tell them? SMH
how much did it cost for all of the repairs?
It didn't seize under the load, that would have been a nasty skid possible wreck. That is why the old time road racers always kept a finger on the clutch. It seized after the throttle was shut. Very interesting.
Ps, I used to road race rd400's.
So when the mechanic says the Piston expanded was it the actual piston or was it the piston ring didn't have a big enough end gap?
if the end of the rings had contacted, a big portion of the top of the piston would have broken off. It was the piston itself scuffing on the cylinder wall.
The rings were melted and cylinder scuffed badly from top to bottom so it was impossible to take ring end gap measurement, but the actual piston - cylinder clearance was .04mm. I measured from multiple undamaged sections of the cylinder and piston and also verified that the piston that was installed was a “B”piston. Typically, a fresh replating will be sized to an “A” piston.
@@kevinegbert1251 learning something new every day
Spencer Young me too! Never stop learning.
@@kevinegbert1251 0.04 is a little bit too much on a 250 i personaly would go with a .05 or 0.6
Is this gona be the 3rd rebuild
Where to find a cr250 cylinder
32:1 and a vertex piston or pro x
The picture is a $20 transfer gauge not a Dial Bore gauge that is used during the sizing on a hone machine. ref Sunnen
Exact same thing happened to my 2003 cr 250 at 3 hours
Clearance issue with the damage just on exhaust port side? It can't just be tight against one side. No, that's heat caused by lean carb settings and or lack of lubrication.
Lectron carb, 80 to 1 saber? (Not sure if that's what is being used on the CR) Both scare me. I don't like high rpm engine braking either. I don't think that caused the failure but it did not help.
Jason Charles front and back of piston had equal scuffing. I think he posted some pics on his Instagram/FB.
In that temperature it won't reach proper running temperature you have to block of a radiator you basically cold seized it.
Good thing you weren't out on your own, in the middle of the desert somewhere! Glad you made it home safe.
1:10 “it doesn’t feel like it’s trying to kill me” bro u ain’t riding a 2 stroke if it ain’t trying to kill ya
It’s to do with the fact that a Cr 250 doesn’t have a thermostat. So it’s the radiators and the high flow air cooling the coolant so well that the cylinder gets colder quicker and the piston is still really hot. Cold cylinder shrinking hot piston expanding. If it had a thermostat that wouldn’t have happened. Also a clearance is would have sieved within 30mins from first start.
You are doing a awesome job.
Correct piston for cylinder letter?
Awesome tip on towing a bike back , that’s broke down
At least now I understand why a two stroke has to be ridden warm before you ride it hard and now I understand why I always see scratches on the inside of the cylinder
Same shit happened to me the other day when I was hauling ass on a fire road. Same exact situation. How much did you pay to fix it?
jus happened to my brand new bike😭
That old thing was laying a whoopin on that new ktm till it gave out.... wait till u slap a new cylinder and piston in that bad boi.... add some reeds and run it richer than u do those new ktms
Just because you have been riding all day doesn’t mean you can rule out Cold seize. At 40 degrees with one radiator taped off my tx300 only runs around 160 to 165. Temperature Much lower than that under hard acceleration can cause cold seize
I think that is longest time I have seen Kyle on the main jet since the 250f drag races.....of course they were on the injector.
Bummer , but opens up the great debate. Looks way to lean on the main to me. Very clean spark plug, too perfect for me. Leave them grey.
I'm sorry but it wasn't the piston clearance. It was bad ring gap. The rings expanded to the point the ends touched inside the ring groves of the piston and had nowhere else to go but into the cylinder wall. Which burned(wore out) the rings on one side. Which is why the piston is scraped up from not being centered any more.
The bike ran and performed fine in normal trail conditions because the rings didn't get hot enough to expand enough to close up the RING GAP.
Also the ride forgot he was riding a carb'd 2 stroke and not a TPI 2 stroke. Honest mistake forgetting how long you can't hold it wide open without letting off or hitting the kill switch every 5 seconds.
With the evidence I seen. Yes tolerance to tight Lue more an likely way too lean to get more power. That's crazy running race gas I would go no less than 36:1 ratio. They were probably running around 50:1 or more.
On a some what fresh top end
He runs most of his bikes with amsoil saber at 80:1 or 100:1
No exhaust Bridge Reliefs drilled in the piston! Exhaust bridge expanded enough to seize the piston only front and back, that why the wear was only of the front and back not 4 corners like a typical expansion seizure
That was brutal.
What oil to gas ratio were you running?
200:1
thomas williams 😂😂😂
You need more oil in your fuel also chamfer the piston skirt must remember if your revving it hard you need more oil nothing less than 25: 1
I vote for the 300 kit, why not you already have like 20k into it LOL
I will take it
That is to bad I will take it as is. :)
Ouch... just after a race...
Also I own a cr250, and the gears are much longer. You are shifting so quickly.
I didn't read through previous, BUT, if it's an OE cylinder, it's Nic, & clearance shouldn't be an issue at all. Poor jetting, poor fuel/pre-ignition, inadequate oil, wrong/junk oil, air leak, overly hot coolant/clogged radiator fins ... Lots of things it COULD be. Not overly tight clearance if it's a stock or properly remanufactured cylinder.
When he Said the piston expanded it blow my mind😂 they allways expend when they get warm, either you got wrong size piston or not the right oil mixture in you fuel.
He`d been riding it for over 3 hours too lol, as if its going to expand any more due to a little race than it already would have in thhe 3 hours
codenamenel yes exactly! Thats Why you have diffrent size piston so it can expand the right amount according to the cylinder when it gets hot. You need to messure the cylinder so you get the right play. Not just put one in.
Are you saying that a piston expands to the same point whether you’re riding single track or riding sand dunes or drag racing holding it wide?
Kevin Egbert No im not saying that, im saying you have a tolerance piston/cylinder that you need to respect when changing piston or this Will happend. If you have the wrong size piston to the cylinder What happends is that when it gets to hot and can expend any more then somthing has to give.
This is Why there are A,B,C Pistons to the same bike. It all depends on the condition of the cylinder.
Eddie Davidsson 100% agree. The cylinder and piston that came off measured .02mm too tight. That’s a lot when your talking C-P clearance. I don’t know what the full story is on the previous rebuild (not done by MotoXperts) but it looks like Millenium plated it and sized it down to cylinder A spec of 66.40 and the piston that was installed was a 66.36.
Can’t imagine why that happened 🤔
I've never seen someone get pulled home like that