What was the oddest mechanical failure you've had during a race?

Second race on my brand new 89 YZ125 (the revolutionary new model with upsidedown forks and 19" rear wheel) when all of a sudden I find myself on my ass having been catapulted off the bike going wide open down a whooped out straight.
I go to pick up the bike and the rear end looked like it had colapsed. Turns out the shock had detached from the top mount and smashed into the pipe (which in turn embedded itself into the underside of the tank) and then continued on it's trajectory directly toward my ass through the seat. Luckily it didn't get that far.
The next day we were contacted by the local dealer informing us that Yamaha NZ were recalling all 89 YZ125's to do a mod on the top shock mount, however because mine had already failed, they replaced my shock, tank, pipe, and did the mod.

One time, they watered the track right before my race, and the 4th or 5th turn was a left-hander, and I was in about 3rd when I slid out and my bike laid over on its left side and my throttle got stuck... weirdest thing ever (and first time it has ever happened to me).

had a rock jam betwen the chain and sprocket on a fast 4th gear sweeper.........Bike stopped dead and pitched me.

this happend to a kid one time when I was a mechanic for him....

He insisted helping me work on the bike because he was bored (knowing he was terrible at working on bikes) so I gave hime a few no-brainers....oil chain, check air pressure, and clean the air filter and put it back in. I'm busy doing a top-end while he's farting around. I finish up and put the subframe back on, I tell him to put the air filter and seat back on. I start cleaning up and loading junk into the trailer for the race the next day. Somehow he gets distracted and disappears for awhile so I go inside to eat. Come back out and he's back with the seat back on and bike ready to go, so we load up.

Get to race next day, start the bike up in the morning to warm up and it's running funny. I make a few carb adjustments to clean it up a bit. He starts his first moto and gets about 1 lap in before the bike bogs down and dies, won't restart. I get it back to the pits, take the carb apart...nothing wrong. Take the pipe off and look at the piston..nothing wrong. checked the stator and electrical...nothing wrong. I'm baffled at this point, thinking it's something internal. We call it a day and head home. I get ready to tear the engine out and break it down. I get the seat off and notice there's no air filter! So I go and ask the rider about it. Of course he forgot! He said he had to run an errand while he was doing the work so he had covered the carb boot with a rag to prevent anything from getting sucked in. He came back and must have obvisouly not even looked and just threw the seat on. I found the rag sucked halfway down the carb boot!

Engine dies. Won't re-light plenty of compression. Gas tank has fuel. So I begin trouble shooting back in the pits plenty of compression seemed like good spark and the plug was wet. It wouldn't fire......get the bike home and begin teardown. Cylinder looks perfect when I pull the head. Next up the reeds are fine. Out the motor come for complete teardown. As I put the puller on the flywheel I notice play I give it a tug and it moves in and out a bit. Sure enough the crank journal broke off right at the bearing. There was enough friction to spin the flywheel and produce an intermitent spark but no where near the right time. How I lucked out and only wrecked a crank I will never understand.

Sitting on the starting line of a local SX race back in Colorado, started up my 97 CR125 and clicked it into gear and as soon as I opened the throttle to wait for the gate to drop, bike dies. I throw up my arm to signal the starter and he waits to drop the gate so I can get it started again. After kicking about 15 times, she fires right up, he sees this and lets the gate down, I slam the bike into gear and rocket off the line...about 5 feet. Dead. Start kicking it again, and about 20 kicks later, she comes to life. Make it another 5 feet, bike dies. Figured better pull off and figure out WTF, get back to the trailer, good spark, jetting's great, compression is top notch. I drain the fuel, put a new spark plug in, and installed a new air filter. Fired right up on the first kick. Sweet. As soon as I rev'ed it up, died. Come to find out, it was the CDI box cutting out when the bike hit a certain RPM.

Damn.

Oops

On my 87 RM 80, we kept breaking the piston skirts off. Went through 4 or 5 and finally discovered the local shop doing the work was honing the cylinders with a slight oval. After that my dad bought his own and started doing it himself.

The other "failure" was the 90 or 91 RM 80 stator cover was plastic and would warp allowing water in and causing a stator failure. Took us a while to figure that out but I got some seriously sweet machined aluminum covers later that season. I remember at Loretta's it was of of the guys from R&D and Suzuki came to look at our bikes and Rudy (I think) bought an extra cover (we had 2 extras made just in case) from us to start making them for their bikes. I think Suzuki went with an aluminum cover the following year.

This happened during the first lap of my first of four motos.

Back in 1996 I had a mechanic do a set of fork seals for me. Well he forgot to out the circlip inside of the forks (the circlip that holds the forks in place) and the forks dropped out on me. Not good. Side note, I was winning my first 125 Beg moto, I was a little bummed.

In 1981 I was on my 3 month old KX250 at Pepperell. I felt great in the 1st 250 Novice moto, but finished 8th or 9th.
Got a wicked holeshot in the 2nd moto and while braking for the 2nd turn the bike just died on me and I rolled off to the side of the track and watched everyone go by. I coundnt get it restarted.
It ended up being a bad kill button - I changed it and never had that type of problem again.
A couple of months later at Central Village my lower shock mount broke right off the frame during practice. Looked like a bad weld caused it to fail.

I LOVE reading all these stories. Don't know if I've ev er read every post in a 2-page thread before

I've had the odd loose bit fall off here and there but one time I was racing a 3 hr off-road race near Austin. About an hr into it I started getting really tired (oh and this was one of my first times racing a 250 so I figured it was just from getting used to the big KX). Well, the bike was bucking me the whole race, and it was a mix of sand and clay so lots of whoops and square edge bumps.

After the race I felt like I was gonna die and puked before I could take my helmet off. Then when i get home and put the bike on the stand I notice the rear tire is higher off the ground than normal. I look at the shock and both the bolt holding it to the frame AND the one holding it onto the linkage had come out. The one with the linkage had bent and basically locked the whole rear end together. I did 2 hrs of off-road with no friggin rear shock!


Oh and then there's the time when i thought I could figure out how to service the forks on my YZ myself. Bought the parts I needed and took them apart, put them back together, torqued everything down and went riding. Then I started hearing a clicking noise in the front end off of the jumps so I pulled off and thought maybe it was a rock stuck somewhere or something. Then I look at my bike and notice both tires are touching the ground while on the stand Yeah, my forks had like 17 inches of travel or something and I don't know how they didn't just come apart on me in mid air Immediately sent them out to PC for a full service. So much for saving money right?

87' was either 125 or 250 novice @ ponca. lost my seat shortly after 2nd lap while having about 5 second lead. held on for win, stood up rest of the race. ;P thanked my dad for leaving my seat bolts back at the camper. Was some talent in that class for being novice. Mike Brown.....Jeremy McGrath....who woulda thunk? lol.

Sheared a flywheel key one time on an '83 cr 480.

That crap will drive you crazy.

had a piston crack on my 05 KX250. bike stutered a bit on the take off of a double but then the power came back, i won that Moto and was affraid to find out what happened till after i won the 2nd Moto. pulled the Boyesen Rad Valve out and saw the skirt of the piston was all jagged. didn't DNF but it's the wierdest failure i had. only DNF's were from fried clutches in the mud. had a few from Human Mechanical error as well ;-)

Spit Crank seal in my 93' CR 125 while railing a berm and locked up the crank hard. Fell over into a massive mud puddle.

I once had the ceramic part of my spark plug get blown off. Another time I got a rear flat....from an animal bone that was still inside the tire !!!!!!!!!!

2003 at lorrettas lynns in the stock 450B class. It was one of the worst mud races I ever raced. I slid out around the sweeper nothing serious. This was prolly around half way and I god a little pin whole in the plastic Y pices that routs the radiator hoses. And two or three laps later it had all pissed out of that pin whole and I DNFED the moto. I rode for Honda of houston back then and I went over there and dropped the bike off. The honda guys told us they had never seen something happen to that little y piece ever. It was just a crazy fluke thing. I was running fifth so I was bummed lol

Mike,
Had that happen on an old DOT 250cc my dad & I bought. Seller started it up, ran it for a few seconds and shut it down.
We got bike home, started it and ran for about 1 minute before it cut out , again crank was in two halves with flywheel attached.

Another time I was half a lap from winning Cheshire Centre Championship in 1980 at hatherton hall Cheshire, when I hit a bump wrong and landed in a stream beside track. Maico engine sucked it a ton of water and hydrauliced up, seizing ring to piston , so no compression.
Pushing bike back to pits I had time to reflect on lost opportunity, missing championship by just a couple of points!

I would say, Dry rod caused by a cadistrophic condom failure. Resulting in chaffing and gooey balls. Oh and my daughter.

'94 KX125 at Lake Whitney. Crashed out in the first turn (common occurence for me). Picked up the bike and noticed tranny oil all over the ground. Got it back to the pits and noticed a hole the size of a nickle in my primary case. Get it home to tear it down and turns out the screw on the clutch basket came loose and shot through the casing! A new clutch basket with Red Loctite and some JB Weld.....good as new.

94 KX250 at Greenville. On my way to winning my first Expert Class after a rare holeshot, land off a small double and rear end bottoms out and stays there. Turns out the bottom shock bolt sheared in two.

mine is a body mechanical, not bike mechanical.

got sick and shit myself when i rode the 80expert class in the desert while leading. the nasty feeling in my pants made me so nauseous i threw up all over myself. a couple miles later, the smell inside my helmet caused me to throw up again.

i won the race (only Overall i've ever won in the desert) by over 5 minutes, like a Boss.

another time i burned up my clutch in my 125 and couldn't make it up the finish to take the checkers, would have won. i tried to push it but it was a big finish table top and there was no way. mark me up for a DNF.

That rag I left in my Airbox got me at the starting line......wait that's a "user" failure.

I came up short on a triple at a supercross and ripped the rear shock linkage out of the frame on my 92 CR250R. I didn't know it immediately and kept on truckin to the next jump into a whoop section. I had suspension initially, but it was because the shock shaft was bending in half as everything wadded up. By the 3rd whoop the bike was stuck bottomed out with the rear caliper against the silencer. Had to weld new tabs on the frame after that...and rebuild the shock.

The seat fell off on my husky 250f at the end of the start straight.

And the gear changer fell off leaving me stuck in 3rd gear.

My cr134 seized up after the 2 stroke we used wasnt up to scratch, died as soon as i landed a big table, 1-2 seconds earlier and it would have been a very very big crash.

Sons YZ85 sucked the brass guide for the needle in the carb throught the reeds and into the cylinder leaving a huge gouge and blown crank seals. Dont ask me how it did it because it is installed from the bowl side. I spent months and numerous forums to try to fix after a complete rebuild why the motor would not run when someone else told me to look for the brass needle guide. This is how I found it and the motor or carb was not taken apart prior to the malfunction.

My WR250XX sat in the garge for several months, started it up, seemed fine, ran good. Then started the process to get it ready to ride changed oil, plug etc, went to do the airbox and it was full of dogfood............flucking mice. Cleaned it out and it runs fine.

Any ever forget to secure the rear brake arm on old drum brakes?

Dude, crying from laughing so hard.

First moto I had my throttle return cable fray on my RMZ450 and it hung up at 1/4 throttle. Wasn't a big deal to finish the moto but I was afraid it might stick wide open. Nobody had a spare. Had to DNS the second moto. Later found out I could have just removed it since it has a spring return anyway. I'm told a lot of pros don't even run the return cable so there's less drag on the throttle. Dunno if that's true.

I had a drain plug fall out on my YZ250f.

Ran it almost four laps with no oil. Took it apart and eveything was fine.

Replaced the clutch plates and threw some more Torco oil in and never had a problem after that.

Always run Torco now,, for that reason.