What’s the worst you’ve ever gotten your ass beat trying to troubleshoot a dirtbike ?

That happened on my 09' RMZ 450 while riding.  Took me more than 6 hours to figure it out though haha.

Have one going on now… My trusty 96CR250 will not fire….tried all the usual suspects last winter while down in Florida, where I keep the bike…. Didn’t have my flywheel puller, so I had to stop diagnosis…but… ran great last time I rode it….then no start condition…. Getting fuel, has spark, compression, nothing…. Removed & inspected carb, reeds, new plug, new coil as original had a frayed wire coming from coil pack. Tried push start, almost wanted to start but didn’t….Have not pulled top end yet, piston looked good through exhaust & reed opening. I brought down my spare stator & black box to try, now that I have my puller with me…I have even poured  some fuel down plug hole and still not even a pop….

Have a cr250 with what felt like a lean condition at wide open.  A brand new carb, different jets and needles, new reeds, new crank seals.  Turns out when I put the trigger wire on the coil I didn't mate the spade connector, the rubber boot was just holding them in contact. Connected it properly and problem solved after a few weeks of trying to figure it out.

I once had a front tire inner tube drive me nuts. Found a flat tire. Pumped it up. Checked valve stem. Flat again the next day. Pulled the tube and leak tested it in a bucket of water. No bubbles. Figured  it must have been the valve stem. Replaced core. Put wheel back together. Flat again in the morning. I ended up putting the tube into the tire and winding rope around the tire/tube to let the tube be constricted under pressure. The dam thing would only leak when it stretched the tube just right under pressure inside the tire.

I had a 2003 KX250 that would run flawlessly until you put a load on the engine.  A real head scratcher, went through engine, carb, electrical and had an identical donor bike for troubleshooting.  It ended up being the inner reeds on a V-force reed cage that were cracked in a non-visible location unless you removed the reeds from the cage. Sometimes it's the little things!

replacing the clutch in my 1990 cr500.  put in a pro-x basket with recluse torqdrive plates.  bike wouldn't run, either stalled or started running away as soon as you put in gear. .so replaced recluse plates with Barnett plates, same problem.  I took the clutch apart and back together at least 10 times.  turns out the pro x basket doesn't line up with the plate stack.  finally found out when took it to mechanic who had to mic down the washer/spacer to make the plates fit that pro-x basket.  I was mad so frustrated with the ordeal and lost many months of riding that bike.  it's been great ever since.  Pro-X basket buys beware if you have a cr500

Tried jetting around a lean condition on my son's KTM50SX. (auto / no clutch) It would intermittently hang at idle. Well, it became evident on a practice lap and he was coming into a corner pretty hot and I 1st though, "Man he's hauling!". Well, the idle hang enough that he couldn't hit the brakes hard enough and over the tall berm he went. Starfished flip in the air. I went running thinking, OMG, please let him be OK. He was very scared and bruised but not broken. Found a leaking mag side crank seal. Never again!!!

A meme of your NASA chimp doin’ that would be “hilarious”. 

07’ kawi 250f (I believe Suzuki was the same that year as they were the same bike..? Can’t remember the details of that deal). The pawl guide kept breaking in half. I changed it 5 times before Kawi eventually put out a recall. I probably spent the cost of the motorcycle trying to troubleshoot this $hit. I definitely gained multiple grey hairs and lost many hours of sleep 😅

I've had my share of dirt bike issues but a good one was a 1968 International Scout, my hunting truck from back in the early 90's.  I broke a spring in the Texas Hill Country hunting.  Brought it back to Houston and had a set of springs made at Cole Spring in Houston.  The place was so old they had buggie wheels and wagon wheel in one corner.  They make me a new set of springs, even added a little lift.  Installed all four, truck set higher in the left rear.  I called the company and said one spring was off.  Manager pretty much told me I was a dumb ass.  He said the guy that made those springs is best in the country and those springs were perfect.

So off both rear springs came.  Both the exact height.  Put them back on, same thing, still high in the left rear.  I was traveling a lot with my job back then, figured I work on it when I got back in town.  Later that week when I got back in town my wife asked me to change a light bulb.  I went out in the garage to grab my 6 foot leaning against my Scout.  Ladder is stuck like chuck.  The ladder was stuck under the metal rain gutter over the side window.  My floor jack was still under my truck.  I jacked it up, pulled out my ladder and my truck set level.  Every time I would jack up and lower my truck that ladder would slide under that metal rain gutter.

I called the guy back at the spring place to tell what I did.  He didn't even bother to listen to me, he just hung up.    

Well since I stole that pic from you, I'll think I will try and mock that up! hahaha

I believe older 2 strokes are fully capable of running backward in the wrong circumstances, with or without a reverse wound stator.

I once picked up a Kx500 that came without a carburetor.  It may have been missing reeds too.  I can't remember. This was around 1985.

I wanted to see if it ran before putting money into it, so I poured a bit of pre-mix into the intake or cylinder, then kicked it over.  This is something I've done plenty of times when diagnosing a bike that won't start.

It sputtered a bit, then started.  When I let the clutch out, the bike moved backward!

It only ran for a few seconds of course, but it surprised the heck out of me!

My 2006 YZ250 that was less than a year old had been running great and was looking forward to another race weekend. At the track, the bike would start ok and run ok at lower revs but once on the gas hard it would blubber around like it was suddenly having jetting issues.  Couldn't race it that way so headed home and spent several days trying to find the issue and came up with nothing.  Super frustrated, I ended up calling up Tim Shepard who owns the shop I had bought if from as Tim has been racing YZ since the beginning of time.  After telling him everything I had done, first thing he tells me is to replace the spark plug cap as he'd seen them go bad before.  Sure enough, replaced the rubber spark plug and was running great again.  

Back in the day, my grand father had a car dealership and took any and everything in on trade. He had a slew of 70s model Japanese bikes in an old barn. They hadn’t been touched in years.  He had passed and my uncle said you can ride whatever you boys want if you can get it running. Mind you there was no google and no one with a clue helping us. 
Long story short we were trying to get a 1976 Honda Elsinore 250 running. One way or another, don’t recall the exact details, we managed to catch it on fire. We got the fire extinguished and eventually got the bike running. Wish I still had it and all the other bikes they got sold off. 

This is the exact reason I’ve been into motorcycle my whole life. 

2015 YZ250. The bike started intermittently running like it had a rag in the airbox. I tried all the easy things first. The air filter was clean. Cleaned and inspected the carb and the reeds, mixed fresh fuel. No luck. Then I started replacing things with parts from another YZ like the stator and the carb. Still no luck. Sometimes it would run good for an hour and all of a sudden would start running like it couldn't clear out, like the choke was on only worse. I knew it wasn't the carb as this was a completely different one. Started to think maybe a mouse family had moved into my exhaust and the nest would occasionally block the flow, so I blasted it out but found nothing. Put it back together and started it and it was running like crap again. shut it down and re started it and went to do a test run down the driveway and it went BACKWARDS!!   Somehow the engine must have backfired upon starting and was now running in reverse!   My buddy Poacher (P27 Offroad) said to try replacing the spark plug cap, and I still can't believe it but that turned out to be the issue.  

Another one, this was more costly. 1987, Southwick National, my home race. I'd done well the year before so I was really looking forward to this. Was riding well and leading the points in NESC heading into the day. Blew up my race bike in practice (KX250). Did the fire drill and put the motor from my practice bike in for qualifying. We did qualifying motos in those days, not timed laps. Was leading my qualifier and blew motor number two. Got the thing back to the pits which is a pain in the ass at southwick pushing up a sandy hill in all directions. My mechanic started fire drill number two while I went to see if I could borrow a motor from Kurt McCann (Midtown Kawasaki). He was incredibly helpful as I didn't even ride for his shop, gave me a motor and some fuel he had on hand thinking I'd forgotten to mix my own. So out into the LCQ I went, got a terrible start but had gotten into a qualifying position when motor number 3! went.  At the end of it all we discovered a radiator cap spring had gone weak and was allowing all the coolant to escape as soon as the bike got hot. All I can say is thank god we weren't racing four strokes back then!

I have some horror stories about an '08 F150. That was the most unreliable "hunk of junk" I've ever owned lol. It was my second 4.6 and enough to drive me away from ever purchasing a Ford product again 🤣. The most egregious of that truck was a randomly bent exhaust valve that only intermittently caused a miss. I spent MONTHS trying to figure it out because it would only misfire intermittently. I bought that truck before leaving for college from a "buy here pay here" lot, and ultimately learned not to buy vehicles from those places.

My age is showing.  I was a Jr in high school.  My mother bought me a brand new 1973 Suzuki TM 250.  It never ran clean from the day I got it. The shop made it clear they were jetted wrong and Suzuki was coming up correct jets, which they never did.   We tried every jet we could find back then.  As I recall the main jet size we needed we couldn’t get.  We even tried to solder the main jet and re drill it.  That didn’t work, solder wouldn’t hold.  At near wide open it ran sorta clean but still as hard as it hit, was a pain in the ass to ride.  Trying to kick start that I’ll jetted bike was an experience, would kick back and dang near throw ya over the bars,  We spent hours playing with that carburetor.  Just a bunch of us dumb kids trying to race I guess.

I made a few races but it was a handful to get around the track.  Seems like I had it 6, 8 mo.  I finally gave up and drove the 90 miles from Ada, Oklahoma to Oklahoma City and traded it for a CZ.  I got really good trade in.  Those TM Suzukis had horrible suspension, but they were crazy fast.  River races were really popular in Oklahoma back then. River racers liked the TM’s cause they were fast and would haul ass down the South Canadian river bottom.

Brad Lackey wrote a really good article about how Suzuki scrapped the TM program and fired all the engineers.  If there was ever an MX bike from HELL it was a TM 250 Suzuki.  I actually think the transfer ports were so mismatched to the cylinder porting it just wasn’t right.  Some of the older guys got theirs to run right.  I was just a kid back then and didn’t have good sense lol.  

Purging showa tc47 cartridges too much. I believe the manual says to compress the rod all the way in to purge, which is what I did several times. The cartridge will extend all the way and seem normal, then after a couple rides your forks will get soft and the headshake will almost kill you. 

Then you disassemble the forks to find the cartridges “leaked”, so you replace floating piston seals and after bleeding it seems good to go. Same issue after a couple rides then you replace the rod seals and all seems well… nope. 

a poster on here tells me not to bottom the rod out when purging. So I only compress them within a half inch from bottoming and all has been well ever since.

The funny part is I have several sets of 47s that don’t have this issue. 

Oh, and measuring sag almost straight up like an Austrian bike on a 3rd gen cr250 will take away 8-10mm of sag on your measurement. So my “105mm” was actually 96-98mm. That only took a couple years of riding a death trap in the desert to figure out. 

Funny about the 73 TM 250. I had one also. It was my first real MX bike. Those were automatic oilers. Your right the jetting wasn't great. Of course the Suzuki shop said to run Golden Spectro. So I did. Well I guess they mixed too much oil with the auto oiling system. I was going full tilt in 3rd gear and the rear wheel locked up on it. It broke the chain and broke a gear in the tranny. My dad and I disconnected the oiler and started mixing the gas. Back then they said to run the ration at 30:1. We did and it still ran blubbery. About that time (74 or so) Bel-Ray came out with their MC1. Some guy at a race told me to run that at 50:1. I thought how can an engine get lubricated only using that ratio but I bought a bottle and tried it. It worked great. Bike ran much better and I never had an engine failure. I ran that on all my 2 strokes after that. But yes that bike was super fast and hard to ride as all of it's power was very high in the rpm. You better be ready when it kicked in. I won a lot with that bike though. 

After that TM250 I bought a 76 RM250. One of the best bikes I ever owned. One day it wouldn't start. I played around with it and finally I buddy had a 77 RM250 so we swapped the cdi from his to mine and it did the same thing. I got frustrated and didn't understand what was going on. I had an older guy that had a small shop I was asking him about it. He said "did you check your spark plug" nd I said "I put a brand new one in" He said "that's your problem". "Go back and put an old back in and I bet she will start". Sure enough put the old spark plug back in and it fired right up. Brand new plug was bad. Never thought that could happen, it was brand new. Lesrned my lesson on that one.

Two big ones:

78 CR250. Rebuilt the engine including transmission. Gear shafts turned over fine until I snugged the case bolts. Backed them off, turned fine. Snugged again, wouldn’t turn. Must’ve assembled the trans wrong. Disassembled. Nope. Reassembled. Same. Repeat 3-5x. Finally realized the blind bearing on the main shaft hadn’t fully seated by the tiniest of margins…problem solved.

Early 70’s TS (or RM, don’t remember)…rebuilt, reassembled…wouldn’t shift. Repeat several times. Finally realized there was supposed to be a spring-loaded ball in the drain plug that served as the shift ratchet…that was gone. New drain plug with said ball/spring…problem solved.

For sale; 71 TM 400 To much bike for me. Injury forces sale. Best offer! 🤕

First bottom end me and my brother did we didn't know you had to have some resistance on the output shaft when rolling the motor over by hand to go up and down through gears or it just half shifts into second, split the cases twice before we learned that lol.

Had a Husqvarna 511 SM bike that had the tank under the seat, and the filler at the rear , would run for 12 mins and then stop. 

Pinched breather hose, and the bike would quit over the same tabletop , after the same amount of laps.   Push back and it would fire up.  It had a one way valve in line , but the pipe was pinched 6 inches under the seat. 

Fun Cycle Suzuki in Ada, Oklahoma talked me into the Golden Spectro too !  To this day I don’t think I’ve ever been on a two stroke that hit like that dang TM 250 did.  

I ran golden spectro in my CZ too.  Then I guess most of us switched to Bel-Ray.  Fun times back then.  But we did stupid sh……t back then too!

Rebuilt a 96 CR80 last year. Started and ran like garbage then backfired like a mofo, so bad it imploded the reeds and sent a chunk through the carb and into the airbox boot. Several hours later I realized I hand set bolts on the pick up coil on the flywheel. So that was fun.  

I’m a year into fixing low compression on my 04 KX125. 

Had a 79 Maico 450 that was a couple of weeks old when the circlip came off the clutch. Luckily it didn’t destroy anything else but trying to get it back together was a PIA. The Maico clutch didn’t have traditional springs like Japanese bikes had, it had a stack on concave washers that had to be in the proper stack to work correctly. I never did get the stack right and ended up driving an hour to a dealer to get it back right. 

So my buddy’s an engineer at Honda on the ATV side. He buys a brand new 2018 CRF450 on a Friday, rides all weekend, and absolutely loves it. Sunday night he washes it, hits the magic button for a quick start just to hear it purr, then parks it.

Next weekend we meet at the track and the thing won’t start. Dead as hell. He spends the whole damn day screwing with it …. battery, fuel, spark, you name it. Every now and then it’ll sputter for a second just to piss him off, then die again.

Monday he drags it into work. Still no luck. Tuesday, pure coincidence the head engine  engineer for the 2018 CRF450  happens to be in Ohio and decides to check it out. 6 days later now there’s a whole damn group of Honda engineers standing around this bike like it’s a space shuttle. Parts and tools are getting overnighted from Japan. Everyone’s scratching their heads. Two weeks go by. Nothing. This bike is a hot topic in the Honda world ! 
Finally, during a break in the chaos, some intern decides to drop a scope down the spark plug hole  and finds a perfectly balled-up yellow microfiber towel sitting right on top of the piston.

Turns out my buddy shoved the towel in the intake boot when he washed it and forgot. 

Two weeks. Half of Honda’s engineering department. Overnight parts from Japan. All because of a shop rag.

Moral of the story: before you blame the ECU, check for stupid.

Top end rebuild on my 21 150sx. There's a 2 piece cylinder head with an o ring.  The o ring was missing. Dropped on the filthy garage floor. I didn't realize it. So I had rad fluid coming out of the exhaust manifold after putting it together. I pulled it apart 3 times that day. Finally called my cousin. He told me about the o ring. Sure as shit there it is in a pile of dirt on the garage floor!

I was unaware honda had electric start in 09