General Discussion Forum

If you've ever put too much torque on a bolt and stripped the head off, pulled a drain plug and got covered in the splash of oil hitting the bottom of the oil pan, had a wrench slip off a nut and smash your knuckles tearing off some skin, then you've entered into the wonderful world of mechanics.

I myself have been tinkering with engines and drive trains, pumps and motors for as long as I care to remember.  And I always try to feed off my past experiences and the experiences of others (like all of u on this board) to make what I'm working on as good or even better then when it was new.   .


But, even with all the knowledge and experience I'm carrying around I guess I'm still gonna smash my knuckles now and then   .....or even worse.

A while back I  did a little preventive maintenance on my 4 stroke to freshener her up a bit and because I really didn't know how much time was on the engine because I bought it 2nd hand.

So I bought a weisco piston and rings and a gasket kit and went to work, and I did a little write up on it too. just for kicks.



After all I'm a mechanic. I got the knuckles to prove it.  
I've done dozens of top ends for me and my friends.  An engine rebuild is just another day at the office.

Well here is my newest mistake and one that I gotta tell u about because it hurts.
Its the type of mistake that seasoned guys aren't suppose to make. it falls under "you should have known better" and "What the he11 did you do that for??"
You see, when rookies make a mistake you zip your lip and you tell em its part of the learning curve and you'll know better next time. But when vets screw up we get out the popcorn and watch em squirm!!  

When someone rebuilds something its generally attention to detail that's going to result in a successful job. carefully looking at each part to discover wear or damage.  kinda like forensics it tells how the engine has been doing and what it will need to keep doing it well.

And attention to detail will also tell u if two parts will work together, if they will match up and be as strong as the manufacturer intended.

Ok, so back to the F'up.

As long as I can remember, the hardest part of changing a piston is prying out the little retainers that hold the wrist pin in place called "circlips". Commonly known as " Ohchit clips" because when u try to put them in they spring out and across the room never to be seen again or fall deep into the engine and make you fish them out with a magnet or pick.  
If you have never seen one they are "c" shaped little pieces of spring material. just like a little piece of wire. They fit tightly in the groove of the piston journal and won't allow the wrist pin (which connects to the crankshaft) to walk out.

Well to my surprise Yamaha and all their infinite wisdom has decided against the springy little piston pieces in favor of another type of retainer known by me as the tru-arc type. It is similar to the circlip but has circles on the end.



They can be manipulated with a special tool called  tru arc or "snap ring"  pliers. they kinda look like needle nose pliers with special tips.



Weisco on the other hand makes pistons for just about anything that has to do with internal combustion and they, to keep things simple, send they're pistons with circlips.

So as normal procedure when I started replacing my piston with the new aftermarket one I began by installing the first clip (Weisco's circlip) with the piston on the bench because its easy that way and its important to see it "seat" in the groove.








With the easy part done, the piston is put on the connecting rod and the wrist pin locks the two together and then the 2nd clip is put in to keep the pin from moving. But only this time as i was inserting the clip I bent it. And because it was now out of round I didn't trust it .

So what was I 2 do?? I could look through my tool box to see if I have any from other jobs, I could go to the local dealer and get a new clip, I could call Weisco and have them send me one.

Coulda,woulda,shoulda!!   NAAAHHHH!! I thought as I looked real hard at Yamaha's little retainers.

Heck if a company with an extraordinary record for reliable motorcycles like Yamaha can use a snap ring on their piston, then well, why not me??   Right?

WRONG!!  

Apparently, and I really should have guessed this (because of all the missing skin on my knuckles) Yamaha's clip groove, while very similar in design is not exactly like Weisco's. Its deeper and more square to accept the Tru-arc's flat steel shape. Where as weisco's groove is more rounded like the wire the clip is made from. And while the yamaha clip did "fit" into the Weisco's groove it just wasn't made 2 be there and wasn't going to handle the "wiskey" throttle i like to give it.  

Actually, in hind site I'm quite amazed at how long it did last. After all I have a least 6-7 very hard hours on the bike since I did it and most of them WFO.

Here's a little view of what happens when the wrong clip is used and decides its not happy with its new home and falls out.



The piston pin walks out of the journal and the fast spinning connecting rod becomes free to wreak havoc on anything in its way.

And unfortunately for me it did it as i was ripping off a nice jump lip in a huge sand   section at a local track.  

Let me tell u the crank didn't like being apart from the piston and let the rest of the engine know about it.  





And it was not only the cylinder, crank and piston that took the hit but the cases are toast as well.




Well, one good thing is that because it happened so fast it didn't lock up my rear wheel and my jump landing was smooth, even the flag guy next to the jump thought I just stalled it.
And I guess I'm lucky it didn't happen 12 miles into the woods like I was last week with about 10 other bikes. So  there are some silver linings in my story even though a lot of u should be mostly done with your popcorn and I can see a couple of you out their with you're fingers in the shape of an "L" on your foreheads.    

man that sucks. my nuckles have been quite a colorful array of bruises, scratches and cuts as well haha. i actually didnt have trouble with my circlips? they installed smoothly and quickly. do you have an estimate as to how much this ones gonna cost?? ~pat  
PEACE GUYS ITS BEEN A BLAST!!!!! ~patrick

Im watching a set of cases on ebay and I already have a spare connecting rod. IDK may i'll get an Athena 290 kit.  i gotta think about it but i'll let u know.  

nice. snap those cases up! i waited 6 months to get a set of cases for my bike. anohter thing that irks me me is when im working over a pan of oil and i drop my allen wrenches in `pat  
PEACE GUYS ITS BEEN A BLAST!!!!! ~patrick

Great post ML ! LMAO. And good info.
And where i live gotta love the wife coming out to tell me she can hear me cussing up a storm and the naoubres will not like it after a good knuckle hit.
I'v done more damage throwing wrenches then riding lol. Love the pain of a adjustable sliping off in the morning!    
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Ruff!

yzwoods:
Great post ML ! LMAO. And good info.
And where i live gotta love the wife coming out to tell me she can hear me cussing up a storm and the naoubres will not like it after a good knuckle hit.
I'v done more damage throwing wrenches then riding lol. Love the pain of a adjustable sliping off in the morning!  

Ha!! I should have mentioned that!!

CLASSIC!!

Wrench throwing for distance should be an Olympic Event!!    

I prefer Doritos over popcorn. I think I am more amazed at how well written and put together your story is. Anyway, that blows, atleast you have a spare bike to ride in the meantime.

No kiddin, It would take me forever, to write and put pics together like that. Not to mention being booted off every 20 min.s. Nice job ML!

Time to ask Santa for the 09 250F.  
====================

Nobody's gonna hurt anybody. We're gonna be like little Fonzies here. And what's Fonzie like? Come on what's Fonzie like?

LMAO. And if it's cold out....
I'v found that a good wrench throw needs cold weather 1st, Then the standerd ***
But with meaning. And it only counts if it bounces off the wall and hits your car creating even more damage then the initial pain, Having to leave the garage before you freak out after seeing what you did.
THATS GOLD BABY! Michile Felps Who ????  
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Ruff!

chud:
I prefer Doritos over popcorn. I think I am more amazed at how well written and put together your story is. Anyway, that blows, atleast you have a spare bike to ride in the meantime.

No kiddin, It would take me forever, to write and put pics together like that. Not to mention being booted off every 20 min.s. Nice job ML!

Time to ask Santa for the 09 250F.

Thanks Chud.    I've been drooling all over Pins pics of his new ride.   Are u listening Santa??  

Woods I took out a windshield on my truck one chucken a wrench. Hit the wall and came right back like a boomerang!!  

OUCH!  Man, don't know what to say!  
Dave H 2006 YZ250
(2008 YZ 125 son)

DLHamblin:
OUCH!  Man, don't know what to say!

Say you'll lend me the money to fix it. LOL   JK  

how about trying to get carb bowl screws out and have the screwdriver slip and go into the palm of your holding hand...or evern better a drill slippig off an liece of steel your drilling and going through your hand (that one hurt only way out was reversing the drill)...yours sucks man lesson learned the hard way...whats going on around here lately....this then a cracked case from washing to soon holy crap...  

yz4me:
how about trying to get carb bowl screws out and have the screwdriver slip and go into the palm of your holding hand...or evern better a drill slippig off an liece of steel your drilling and going through your hand (that one hurt only way out was reversing the drill)...yours sucks man lesson learned the hard way...whats going on around here lately....this then a cracked case from washing to soon holy crap...

A drill bit in the hand does not sound like fun.    

atkkid250:
nice. snap those cases up! i waited 6 months to get a set of cases for my bike. anohter thing that irks me me is when im working over a pan of oil and i drop my allen wrenches in `pat

i put a bid in on the cases. We'll c what happens.  

I wanted to bump my own thread and ask if any of u would choose to rebuild an older 4 stroke this badly damaged or just part it out. Keep in mind that Yamaha has left this engine relatively unchanged to date. I already know what I'm going to do, but I was just looking for other opinions.