Weirdest mechanical failure or problem

motofool
Posts
248
Joined
12/19/2008
Location
Sioux City, IA US
5/11/2020 8:13am
Thought I blew up my 2005 kx250 coming off the face of a double it bogged and shut off. Thankfully I didn't crash. Bike still kicked over after got off to check over engine to find the spark plug had completely spun out of head and was still in cap dangling next to cylinder. Hasnt happened sense but i do check it more often now. Best outcome of what i thought was a bad situation. Anyones else ever had this happen?
5/11/2020 8:17am
Another one I had was on a 91 CR125, put a new Wiseco piston on the day before a race meeting, running fine all day, went to the line & the bike died, kick kick kick, it started & lasted a lap before it stopped, kicked it over, backfired, no compression. Pulled it apart & the ring stop? came out & wore a nice groove down the side of my cylinder. As it was still in its 30 day warranty, the dealer gave us a new cylinder & piston kit.
5/11/2020 8:22am
motofool wrote:
Thought I blew up my 2005 kx250 coming off the face of a double it bogged and shut off. Thankfully I didn't crash. Bike still kicked...
Thought I blew up my 2005 kx250 coming off the face of a double it bogged and shut off. Thankfully I didn't crash. Bike still kicked over after got off to check over engine to find the spark plug had completely spun out of head and was still in cap dangling next to cylinder. Hasnt happened sense but i do check it more often now. Best outcome of what i thought was a bad situation. Anyones else ever had this happen?
I have actually, I remember my dad swearing blind he tightened it up beforehand. Never happened again also.
1
mx317
Posts
5294
Joined
4/1/2008
Location
TN US
5/11/2020 8:24am
I had a 2-stroke bike that had an up pipe that crossed in front of the airbox. The pipe cracked there and was filling the airbox with exhaust fumes. It ran great when you first started it, but the longer it ran the richer it got and the more it smoked until it would shut off. I finally noticed it smoking from the crack and being pulled into the airbox. I welded the crack in the pipe and it ran fine.

Another one was a flywheel key had sheared and I didn't know it. I was kicking it trying to start it and it kicked back and started. What I didn't know is that is was running backwards and when I put it in gear and let out on the clutch, backwards it went and I fell over the bars. Fun times lol.
9

The Shop

edge60
Posts
46
Joined
5/11/2020
Location
MC
5/11/2020 8:31am
Another one I had was on a 91 CR125, put a new Wiseco piston on the day before a race meeting, running fine all day, went...
Another one I had was on a 91 CR125, put a new Wiseco piston on the day before a race meeting, running fine all day, went to the line & the bike died, kick kick kick, it started & lasted a lap before it stopped, kicked it over, backfired, no compression. Pulled it apart & the ring stop? came out & wore a nice groove down the side of my cylinder. As it was still in its 30 day warranty, the dealer gave us a new cylinder & piston kit.
I had the exact same thing on my first 125. 94 Kawasaki. We put in a new Wiseco piston the day before a race in 95. Broke it in and all was fine. I was not so lucky as my bike stalled on the face of a 4th gear wide open jump. I went full over the bars, making a front flip. Never crashed so bad. I only broke my collarbone but could have been way more bad. I told my dad when i was lying in the first aid medical post my bike blew up. The marshall who helped me said: no you just crashed, you went over the bars. But my dad checked and the kicker had no compression. Later we found out that that pin that fixs the piston ring came out and destroyed the whole cilinder. Never used a Wiseco piston again to this day.
3
spimx
Posts
1297
Joined
3/25/2019
Location
Port Isabel, TX US
5/11/2020 8:52am
The top shock bolt came out durring a race and the shock was hitting the underside of the seat. Found an m10 in my toolbox and a guy took a lugnut off his car and I got 2nd in the a class 2nd Moto. Only time I ever did that, smaller race.

All the bolts rattled out of the stater on my 300sx and It was still running, just ran a little dirty like a carb issue.
ehr400
Posts
2629
Joined
4/1/2008
Location
Britton, MI US
5/11/2020 9:07am
Had a rear axle break on my 2006 CRF450 during a race back in 2007. Sheared off flush at the swing arm on the fixed side. Very bizarre and low hours on the bike too. At first I was like how did my chain derail, trying to put it back on and noticed it sheared off.
2
5/11/2020 9:44am
Happened to my friend yesterday either top shock bolt came out or snapped
rongi#401
Posts
1635
Joined
6/20/2016
Location
southern, CA US
5/11/2020 9:52am
Mx4life320 wrote:
2005 I was riding a practice track at my buddies, and started hearing some clicking in the rear end. I stop to check out the bike...
2005 I was riding a practice track at my buddies, and started hearing some clicking in the rear end. I stop to check out the bike, turns out i broke the rear spring. The next day i call my dealer and tell him what i did, he says no you didnt. Im like dude, i broke a spring. He said bring it in and we will check it out. Brought it in an he was shocked. They didnt charge me for a new one which was cool.
Haha he was shocked...I get it
1
brimx153
Posts
3344
Joined
5/3/2012
Location
IE
5/11/2020 10:05am Edited Date/Time 5/11/2020 10:06am
AJ565 wrote:
On my 99 RM125 I fell over in a corner because I lost power. Thinking it was my fault I tried everything to get the bike...
On my 99 RM125 I fell over in a corner because I lost power. Thinking it was my fault I tried everything to get the bike to restart. Pulled the cylinder and found the ring locating pin popped out and ended up on top of the piston allowing the ring to turn and lose enough compression to not run. Other than some marks in the head everything was fine so I threw another piston in and got out there for the second moto.
Yamaha piston s had a big problem that one year. I ssen one where the locating pin came out and got stuck in the spark plug gap . He got away with no marks at all . Just bought a new plug . And piston .
1
5/11/2020 10:17am
Just remembered another one. I had big wheeled CR80 but this was before the manufacturers made a big wheeled bike. Over here in the UK, you went from 80cc to 100cc then on to a 125. This was in the early to mid 90’s. Only Kawasaki made a 100 but we didn’t have a Kawa dealer near us so I stayed on the 80. They did a conversation that made the forks longer, different swing arm if I remember & the bigger size wheels.

Anyway I was busting some laps out at a local practice track when all off a sudden the bike lost drive & it was making this horrible grinding noise that was coming from the back end. I thought it’d thrown a chain. Looked down & the hub had snapped on the drive side. We put it down to the fact that the hubs wasn’t man enough for the bigger size wheel.
DYE
Posts
237
Joined
2/23/2016
Location
KY US
5/11/2020 10:55am
I was racing a national enduro once and was on the last test and my bike started pinging like it was running hot. Had no idea the reason but the test was the hardest of the day, sigle track, lots of eleveation change and I thought I´d never get the bike out of there so I started riding smooth and as fast as I could in a higher gear and not charging. Got back to the pit and was telling a guy about it and he said let me check somehthing. The fuel line had kinked up somehow and it was starving for fuel....funny thing about it is it was my best test of the day compared to the rest of the class lol
sumdood
Posts
8656
Joined
3/11/2013
Location
San Clemente, CA US
Fantasy
5/11/2020 11:03am
Not a dirt bike but a funny story. I had a 78' field & stream C class motorhome. (440 Dodge motor) We were in San Felipe watching the 1000 and discovered the alternator took a shit, it was Sunday, and we were ready to get out of there. Wound up finding a local mechanic to swap one out for us, Made it home no problem. The next day I pulled into U-haul to get propane. There was a super clean A class in front of me and I pulled up in our hammered C class with Baja dirt and dust all over it, greasy hand prints on the hood etc. When I shut off the engine I heard a weird noise and a piece fell out of the engine compartment. It hit the ground spinning and took off across the parking lot. The owner of the A class had to jump out of it's way. I went and grabbed the part, it was the pulley off the alternator. Further inspection revealed that the shaft coming out of the alternator was pretty much corroded away to almost nothing, and the pulley had been welded onto what was left of the shaft with glob of weld about half the size of a pencil eraser. How it made it the whole way home was a miracle. Later when I went a bought a new alternator I paid about 70 dollars, the guy in San Felipe charged me 100 for the pos he put on there. But it did get us home haha. The look on the A class owners face and the guys at U-haul was worth every penny Laughing
7
pete24
Posts
2733
Joined
10/20/2011
Location
Marlborough, MA US
5/11/2020 11:33am
so I was winning a +25A class moto at Winchester speed park on a Cannondale and I feel something hitting my leg, and I think to myself this pos is gonna shit the bed and im wining and then I think is it gonna die on a jump and kill me, well I finish , won the moto and when I get off the track I found I had a wrench in my pocket (I was wearing baggy gear) so my weirdest mechanical failure was that I won on a CANNONDALE it finished!
5
JustMX
Posts
5239
Joined
4/1/2008
Location
TN US
5/11/2020 11:34am
If you ever shear a fly wheel key at a race you will never go without having a spare in your tool box again.

Sheared one on a 1982 cr 250.
5/11/2020 11:37am
I finished a long race and noticed this after. I can’t think of a single possible way that the spring disappeared without the pin coming out/peg...
I finished a long race and noticed this after. I can’t think of a single possible way that the spring disappeared without the pin coming out/peg falling off. Any thoughts? Obviously the cotter pin somehow came out too
This has stumped me. I've only just replaced both springs on my RM125 and those things are TIGHT. That's amazing however it happened
1
Falcon
Posts
12227
Joined
11/16/2011
Location
Menifee, CA US
5/11/2020 11:44am
I had my bike lock up on me immediately upon landing a downhill jump at Cahuilla. It was pretty high-speed and I somehow managed not to crash but instead slid all the way down the track to almost the next obstacle.
As near as I can tell, one of the chain adjuster bolts fell out, allowing the wheel to go sideways in the swingarm. The axle was broken in two, bent and wedged in the hub, sprocket twisted, etc.
Sierra Ranger
Posts
841
Joined
12/30/2018
Location
Sacramento, CA US
5/11/2020 12:01pm
One time I finished washing my new 1986 CR125 and some friends came over to check it out. I went to start it up for them and the thing would only bog and wouldn't start after I kicked for 20 minutes. They left, kind of chuckling- "great bike, man."
When I went to tear it down I found the rag I had left stuffed in the intake boot. What a dummy.
4
edge60
Posts
46
Joined
5/11/2020
Location
MC
5/11/2020 12:24pm
Some other faillures:

The rear suspension brackets cracked and broke of the chassis of my 2002 250 tm 2 stroke after landing a huge jump. Injured my both ankles.
With the same bike my dad tightened the rear axle and he could not get it tightened. Problem was that the axle was not one piece on the other side. He torned the axle out of square block. Many other problems with this bike i only rode for 2.5 months.

Losing my carburator twice. First time landing a big jump with my 1994 KX80 because of flex in the chassis. Was riding with 125cc wheels in that bike with longer swingarm and a fork that was made longer with bushes. (That one time came loose and i was all coveres with oil)
The other time was in time practice of a big race with my 2006 CR250. My dad forgot to tighten it after change the jetting.

Snapped frame of a Italjet 50cc when i was 7.

Dropped needle jet of a 1990 KX80.

Taking a holeshot in a local race and in the first turn the sparkplug somehow suddenly broke. My bike an extreme hopped up 2000 Honda cr 125 ran like shit. It sounded like a 4 stroke but i kept leading the race. After half a lap i stopped to look at the choke but is was oke. I kept going in third place and was coming closer to the 2 leaders of the race. After a couple of laps my dad had me stop the race. We quickly changed the sparkplug and i tried my bike when i re entered the race and it was ok.





5/11/2020 12:32pm
2007 RM-Z 250. Bike was a bit of a lemon, with 30 hours on it she completely seized fortunately Suzuki covered that one. Then at about 60 hours in went again, that one cost me $2500 at a local reputable dealer. I took it back to the track for the first time after that and did a gentle 1 hour break in. As soon as I went hard she seized up again. I was ready to throw it in the trash and cut my losses. My girlfriend’s dad at the time was a mechanic and he offered to take a look. It turns out that the mechanic at the dealer dropped a washer into the engine. When my exes dad took it apart he found pieces of it everywhere. The dealer paid for the parts, so I got a whole bother season out of the bike for a case of beer.
5/11/2020 1:23pm
Back in the fall of 2017 my yz250 blew the top end. Over the winter I tore the bike down to a bare frame and redid everything. Fast forward to April of 2018 I get the bike finished and fire it up for it’s first heat cycle. Ran great and everything was good to go. Went to do the second heat cycle and cruise around the yard. Made a few easy laps and the bike bogs and dies like it ran out of fuel. Hmm odd because I have plenty of fuel in it. Push it back to the garage and made sure it was getting fuel to the carb and that it had spark. Messed around and tried a bunch of different things and finally pulled the stator cover off and found my issue. I only had the magneto pick up bolts finger tight and the vibrates out LOL. Easy fix but it frustrated me for about half hour
bh
Posts
949
Joined
12/25/2016
Location
Piedmont, SC US
5/11/2020 1:38pm
Lucky noticed this after two laps. No damage. [img]https://p.vitalmx.com/photos/forums/2020/05/11/426494/s1200_20200505_131457.jpg[/img]
Lucky noticed this after two laps. No damage.

Shock on my kawi started to do the same thing. Luckily I caught it.
1
5/11/2020 2:20pm
Early 90s. Came over a good sized double the bike started acting funny as a landed and died. I kicked and kicked. Nothing. Pushed it all the way back to the pits. It was a hike. Told my dad, that damn thing seized up or something. Just died on me.

My dad said bullshit. spun off the gas cap and said your out of gas!! My dad was always wanting to put too much gas in my bike. More than needed to be in it. I had told him there was plenty of gas in it, when he tried to put gas in it. He told me, :your grandpa ran out of gas racing boats one time.....He only did it once. Moral of the story, when your dad is gassing up your bike, just let him put the gas in it.
1
RCF
Posts
548
Joined
4/1/2008
Location
PA US
5/11/2020 2:56pm
my kid ran hour during a Hare Scramble with his chain like this.

OldYZRider1
Posts
848
Joined
7/10/2009
Location
Bushnell, IL US
5/11/2020 3:11pm
In 1980 I was racing my new YZ250 that I'd placed a Magura straight pull throttle on. I also did some woods riding and liked how it tucked the cable in right next to the bars. It worked by using a bevel gearset to pull the cable, kind of a neat deal I thought. I was at a track that had a drop into a large ravine with an uphill back out. At the top there was a sharp corner. It was on the first lap and I'd gotten a decent start but ahead of the drop into the ravine was a small jump with a corner. I was coming up on the guy in front of me quickly and he slowed for the corner quicker than I expected so I shut the throttle right ahead of the jump. Well this dropped the front end down and I endo'd over the bars front of a whole slew of riders. I got ran over (had knobbie marks on my JT pants that I could never get out) but got up and drug my bike to the side of the track and got going again. I dropped into the ravine and started up the hill, WOT of course, and when I closed the throttle at the top it just stayed wide open. I went flying off the track, scattering a few spectators and threw the bike on the ground. Picked it up again and tried to sort out the issue. No pinching of the cable when turning the bars; cable looked like it was in the top of the carb right but when I went to restart it went WOT again. I pushed it back to the pits and ended up opening the top plastic cover of the Magura throttle. Apparently in my first crash the cover opened up slightly and let in a small dirt clog which then locked the gears, hence the throttle, wide open. The cover only had one screw that held it on (in the center) so apparently it had rotated open during the first crash, scooped up the dirt clog and then re-seated itself. There was only one rather small dirt clod inside but it was enough. I removed the clod and spun the throttle around on the bars so the cover wasn't on the top side any more thinking it might stop that from happening again.

I still have the bike and the Magura unit on it. I haven't ridden the bike for probably ten years now but that throttle unit was still working fine last time it was used. Its held up well for being a plastic unit.

I think of this race these days as my "Brandon" moment Smile .
2
GODZILLA
Posts
900
Joined
3/3/2018
Location
FR
5/11/2020 3:27pm
Anybody into speleology?
Blink


RCF
Posts
548
Joined
4/1/2008
Location
PA US
5/11/2020 3:51pm Edited Date/Time 5/11/2020 3:56pm
GODZILLA wrote:
Anybody into speleology? :blink: [img]https://p.vitalmx.com/photos/forums/2020/05/11/426571/s1200_s1200_915_C2_BD1_0_CD3_41_E1_AF98_AFB0_A314_CA7_B.jpg[/img]
Anybody into speleology?
Blink


Yes I am

photos on next page because I have big thumbs
RCF
Posts
548
Joined
4/1/2008
Location
PA US
5/11/2020 3:54pm


1

Post a reply to: Weirdest mechanical failure or problem

The Latest