Rebuilds gone wrong

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#1
So I just got done rebuilding a bottom end on a kx250. This is the second one I've done, but I still feel like such a genius/god/hero when I do one. Sure, it's not that big of a deal, but after all the mechanical mishaps that I've been a part of it's nice to have a success. This got me thinking about mistakes I've made in my few (I'm 18) years of working on motorcycles. Putting the piston in backwards, siezing top ends after changing jetting, having chains jump due to improper adjustment, etc..... I figured all of you out there must have some stories of your own you could share about your mechanical mishaps. Oh, and don't try to lie and say it was "your friend" or "your neighbor" and not you....we'll see right through it ;)
 

Highbeam

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#2
It seems every time I put in a new truck engine I get the stupid distributor in 180 degrees off so no sparky at the right time depsite lining up the timing marks.

On the motorcycles, xr200s, I seemed to have no problem getting the timing chain a link or two off and blowing the head gasket.
 

Moto Squid

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#3
the former owner to my old snowmobile did a top end...one old piston circlip went flying but he couldn't find it and said screw it. Turns out it ended up in the crank. Lets just say I bought the thing real cheap

My favorite is this 300ex we have at work right now. The guy and his buddy did a top end but totally scewed up on cam chain tensioner position when reintalling and just jamed it in. Chain stretched, skipped a few teeth and the valves nailed the piston. That was pretty cool :laugh:

My mishaps are far less spectacular...especially now that I'm a little older.
 

gwcrim

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#4
Circlips... yeah.

I lost one down into the case on my old CR125. Had to remove the engine and shake it out.

I didn't do the 180 out but wired the distributor backwards on a 383 Mopar. Even tried to start it by pulling it. Man were my buddies pi$$ed when we figured out what was wrong.

Heh.... then there was the old 383 I rebuild and put the bearing caps on backwards..... It lasted, oh..... 5 miles maybe?

That was all when I was in high school. I quit rebuilding engines for a few years until I figured out WTF was going on.
 
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#5
An 89 yz250 is able to be assembled with first and third gear swapped. Tranny will work also. Luckily I caught it before it went back in the bike!
 

Y2Z

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#6
lol yam! luckily i have never had anything serious go wrong with rebuilding bikes. but i did spend an hour and a half trying to figure out why the rings wouldnt go on the new piston for my 89 KDX. drove out about an hour to the local kawasaki dealer and turned out i had them in upside down! i didnt know it made a difference. stupid me
 

rickyd

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#7
I was wrenching on a 650sx (jet ski) and had too do a leak down test on it.. After doing the test, went too start it and couldn't get it too fire.. Scratching my head, realized i forgot too take out the plug ant the reed cage :laugh:
 

jboomer

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#8
I raced once and was doing well until about the end of the 2nd lap (5 lap race). Every time I jumped, the bike would die so when I landed it would start the engine again, almost throwing me over the bars. I even crashed once when I hit the face of the jump, the bike died, causing me to land nose low on the face of the landing ramp. Well, after struggling through the race, I finished dead last. It was really rainy that night and the track was extremely muddy, so I didn't even bother doing a bike inspection until the next morning. Went outside and searched the bike, but couldn't find the problem. So, took the bike out of the truck and when I turned on the gas, gas started POURING out of the bike. Well, traced the fuel stream to the drain bolt on my carb. Turns out, before the race I put in a larger main jet (so the bike wouldn't get too hot) and finger tightened the drain bolt, but I guess I forgot to tighten it with a wrench. Everytime I would jump I guess the carb would raise up a few milimeters allowing the gas to drain out of that little hole on the side of the drain bolt and drain my float bowl. On the big jumps, there would be enough zero "G" to cause the bike to bog, then die.
 

splatt

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#9
Originally posted by gwcrim
Heh.... then there was the old 383 I rebuild and put the bearing caps on backwards..... It lasted, oh..... 5 miles maybe?
 

It's a wonder you got it to turn over. Most of the time it won't. I've been profesionally rebuilding car and truck engines for 12 years now and there are still those times those bonehead mistakes come up.

 

Steve
 

Yogurt

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#10
Once after installing a brand new wiseco piston and top-end in my 00 CR125, I started it up and ran it at idle, then after about 1 minute it blew up and died. Oh crap I thought! I immediately tore it all back down, and realized it sucked the circlip right out, and ran it up and down the cylinder walls real nicely. I put the circlip in all the way, but I forgot to turn the circlip so the end wouldn't be sticking up in the groove. So I had to send my cylinder out to US Chrome to have it replated, cuz it had deep gouges in the walls. I took the whole motor out, and flushed out the lower end with parts cleaner, and tipped it upside down to get the circlip pieces out. Then I had to buy another top-end kit. That was one expesive top-end job I did. I really hate doing things twice.
 

Danman

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#11
Were is Moo Cow when you need him (anyone remember that name) :) I wouldn't know any stories as I've never done anything boneheaded thing while working on a bike :confused:
 

jmics19067

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#12
Just not enough web space to list mine but my all time favorite is

while trying to figure out why a bike won't start I always check for spark, You know, remove the spark plug , lay it against the head turn it over, get a new plug, put it in the cap lay it against the head turn engine over, good spark , install plug kick till blue in the face and realized I didn't put the plug cap back on the plug.
 
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#13
Oh man, I've done that SSOO many times! I hate that, I feel like beating myself up for beeing a dumb@$$ !
 

gwcrim

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#14
Oh here's another one.....

I had a partner on a Bonneville Salt Flats speed racer. He supplied me with a 100" Sporster engine in which he had invested many, many thousands of dollars. I had to install the primary drive. But I'd never done one before. After struggling with a pile of parts and the repair book, I got it all bolted together. We first fired the engine on Friday and left from Ohio on Saturday for dyno tuning in Denver with Aaron Wilson.

After several dyno pulls, we pull the clutch cover to for an inspection and it's overflowing with oil! So we pull the primary drain plug and the magnet is FULL of stuff. I about poohed in my pants.:uh:

We pulled the cover an upon inspection....... I had left out a spacer that fits between the front sprocket/alternator cover and the crank shaft. This allowed engine oil to fill the primary. This also allowed the crank to have an in/out movement of about 1/8". This destroyed the stator and the alternator magnets. Again, I about poohed my pants.:uh:

We pillaged a spacer from a Buell donor bike in Aaron's shop, cleaned up the mess, and reassembled. The bike eventually dyno'd about 150 HP. A bit lower than what we expected but at least it was alive. We managed to get the bike to 167 and set two records. Come to find out the pistons & cylinders were scored as well.

Eventually got the bike to go 180 with a good top end.

Oh and then we're at the Flats and the cable that activated the remote petcock got pinched. The result was that it might shut at any inopportune moment. So there I am buzzing along at speed with one hand on the throttle and the other holding the petcock open. Good thing it was on the left side. Again, I about poohed my pants. ;)
 
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#15
My first 4 stroke bike, KLR 250, was hard to start when I bought it. I had to push it all the time. got worse and worse till no vroom vroom. Started tinkering and found the valves were not closing. I discovered the tapet adjusters and just turned em out untill the valves would hold gas in the intake and exhaust ports. Feeler guages? Sure! if she lets me I will! I put it all back together and felt like a hero when the bike started. Ran the bike out in the field with a big smile, then, the most gut wrecnching mechanical sound I ever herd as the nut on the tapet I forgot to adjust got into the timing chain and caused it to break shattering the valve cover and bending the crank among other things ..... No more KLR :( .
I spent 4.5 hours installing a new set of front leaf springs in a truck wich was a good time for the job. Some one esle had taken the springs out to get the measurements. I put the new ones in and go to drive the truck out, turn left out of the bay, then right,,,, the wheel dose not turn right more than 1/4 way! Back the truck back in and start looking it over, takes me aoubt 10 mins to relize they had an offset center pin and I put them in backwards! The 4.5 hour job went to 6 hours. Dohhhhh!
Oh another good one, Had a flat on my bike as a youth, so I fixed it and rode it to school the next day. On the way home to show off to all the kids I yank a big ole wheelie on the way out the lot, how surprised I am to see my front wheel keep going, forks come down, hit the pavment, I go over the bars in a heap. It hurt, but I was so embarassed. I looked up and OMG! No one had seen it! I hobbled over to the bike and collected the front wheel and hobbled around the corner to agonise in pain :p .
Other than that, just dumb stuff like putting your front wheel on with the disc on the wrong side :)