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So this happened....

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A couple hours into an XC race my bike suddenly stalls, quite abruptly. I thought it felt unusual but Im out in the middle of nowhere so I try and kick it back over and the kick starter feels about 3x harder to kick than normal. Shiza.

 

I figure it must be hot seized, or a crank bearing is partially seized. Check the rad fluid and it was quite low, I figure I poured close to a litre of my camelback water into it before it was at normal level.  :thinking:  I only had the rad steam over once very briefly earlier in the race right before a faster section where I was able to get airflow through the rads. Not sure what happened to my fluid levels at this point, must be a slow leak I need to track down. 

 

About 30 mins later I was able to kick over the bike and it was running but didn't like to idle. I end up letting it cool down some more. Kick starter pressure started feeling normal. I end up limping the bike back to the truck as its making a pretty bad metallic clanging sound from the engine :shocked: . Didn't really have much choice but to ride it out unfortunately.

 

Got a chance to tear it apart part-ways and this is what I found. 

 

IMG_2182_zps3f515cad.jpg

 

IMG_2194_zpsefa8cc29.jpg

 

IMG_2183_zpsa7254111.jpg

 

 

As you can see, the outermost 3-4 threads are gone completely on the crank side, and the inner most two that the bolt grips are damaged. A very strange kind of failure I haven't encountered before I rebuilt this bottom end about 30 hours ago (Weisco crank), used a torque wrench and blue loctite on this bolt (as well as all other important bolts). The bolt walked itself partially out and was no longer driving the waterpump, surprisingly the drive gear kept in contact with the clutch basket gear though. The bolt head was spinning against the side case, which prevented it from coming out completely. 

 

 

Looks like I get to do another bottom end and spend more money not riding. I haven't removed the cylinder yet to see what shape its in after partially seizing, but looking through the exhaust port doesn't show any major damage.

 

Any point in contacting Weisco about this? Anybody seen this failure before?

 

 

Edited by 5Lgreenback

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yep I seen it. ......on my bike !!!!!!!

Rebuilt my 01 yz 250 using a wiseco crank back in november last year. Bolt came out in july this year. Couldn't find any reason why, got a new bolt and done it up. done the same thing 2 rides later. I have put a dial indicator on it and only had 1 thou run out. Mine didn't seize. Got some super strength loctite, have put it back together again. riding this weekend. Going to ride then pull the cover off and see if it has come lose. if it has I'll be pulling the wiseco crank and putting a oem back in

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Sounds like you've been lucky enough to not have it destroy the threads in your crank. Even with a new bolt it looks like Id only get 3 threads to tighten it into, which would probably strip out if torqued to spec. 

 

Looks like a new crank, primary drive, waterpump gear/shaft, bolt so far, and a weld on the side case as in looks like it created a small crack where the bolt was rubbing.

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Sounds like you've been lucky enough to not have it destroy the threads in your crank. Even with a new bolt it looks like Id only get 3 threads to tighten it into, which would probably strip out if torqued to spec.

Looks like a new crank, primary drive, waterpump gear/shaft, bolt so far, and a weld on the side case as in looks like it created a small crack where the bolt was rubbing.

Why all the new gears? Unless I'm missing something from the picture?

Get a new bolt and a new crank, new seal on the right side too. Then on the right side cover jb weld the crack. I crunched a little groove in mine and just jb welded it

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Why all the new gears? Unless I'm missing something from the picture?

Get a new bolt and a new crank, new seal on the right side too. Then on the right side cover jb weld the crack. I crunched a little groove in mine and just jb welded it

 

The gov. drive gear is showing slight damage on the teeth thats hard to see in the pic. The water pump and gov. gears are pretty chewed up. Enough that quite a bit of metal needs to be cleaned out of the engine. And the Primary drive is showing some damage/wear, it may still be runnable but might as well replace it if Im going through the effort. 

 

As for the JB weld, I may do that but figured getting a quick tig weld would be more permanent. 

Edited by 5Lgreenback
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When mine went it stuffed one of the gears and put a hole in the case and put a shit load of alloy through the gearbox/clutch, but didn't seize.

 

 I filled my gearbox with with diesel a few times and flushed as much out as possable.

 

 Got the case welded up

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I had something similar happen.  One thing I did to make it all work, was clean out the old loctite from the threads of bolt and crank, clean with carb cleaner to degrease, and bolt it up.  That was a couple of decades ago.  give it a try.  Loctite loves clean dry, hates wet or oil.

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Yeah OEM bottom end will be going in (still waiting on parts). New bolt for the drive gears and will make sure its clean and may use the permanent loctite on this one. Although with the new hardware and OEM crank the blue loctite should suffice. 

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