Got a sweet 2005 wr450f that I used as a daily sumo. Love the bike, but to use it to its full potential took it off-roading in the weekends. Last weekend however the chain snapped and took a piece out from the crankcase, exactly where the clutch cable connects to the block. I noticed it immidatly as there was no drive and when turned my head down to look at the sprocked i saw oil spitting out.
As I saw oil gushing out i turned off the motor, so the internals should be ok. What are my opitions now? Since there is a piece already out of the crankcase any chance of an easy plastic weld repair is out of the question?
So Im guessing I got to strip down the whole engine and replace the crankcase? However from what I've read so far, people have said i should replace both sides, or can I just change the left side that has a hole in it?
Attatched some pictures of the damages aswell.
Any help and suggestions are highly appreciated.
Greetings from the Netherlands!
05 WR450 chain slapped out a piece of crankcase, options?
Posted August 09, 2016 - 10:28 AM
Posted August 09, 2016 - 10:42 AM
might be able to have it welded, but it's thin there and you may have to restore the bearing and seal bore afterward.
Best bet is a new set of cases, but you're splitting cases either way, so guess it's time to get to it...
I may have to beef up the case protector on some of my bikes if that's all the stocker was good for. How fast were you going when this happened?
Posted August 09, 2016 - 10:52 AM
Posted August 10, 2016 - 03:18 AM
Thanks for all the replies.
I managed to source a bottom end locally for a lower price than i would just pay for the empty cases shipped from overseas. Hopefully i can just swap the top end to it and it will work. Although I have a question inregards to this. My bike is an us model and the bottom end is a eu spec one. There shouldnt be any difference right?
and bikedude, this happened going around 30kph, 2gear, with a whack of throttle, although not wide open. Surprised me aswell.
Posted August 11, 2016 - 01:52 PM
What kind of chain were you running? Did a link break, did a master link fail, did it fall off the sprocket, or what exactly?
To be honest i dont even know what chain it was, it came with the bike, but i converted it to sumo and for this i bought a new chain. For offroading i used the old one and the masterlink failed.
What kind of case saver would you guys suggest to prevent this from happening again?
Posted August 12, 2016 - 07:08 AM
Got a used bottom end today. Unfortunetly wont have time right now to work on the bike for this week.
I probably need new gaskets and what else? . And should i also change the piston if im digging in or judge when i see it?
Posted August 15, 2016 - 11:53 AM
Sorry, if its a stupid question, but why do you advise me to change the cam chain?
Also, if i decide to change the piston, how do I know which size to order?
This thread will keep going as this is the first time for me to do engine repairs as substancial as this. But we all got to learn somehow, so a bunch of questions and pictures will soon follow!
Posted August 15, 2016 - 12:41 PM
Cam chains on old bikes wear out and can skip teeth and cause major engine damage.
You would need to take your barrel to a competent machinest to determine the piston size.
If it is a stock Yamaha cylinder, there is only one size to order for piston and rings... standard. The cylinder is plated
and is not designed to be bored or receive oversized parts.
If the cylinder measures out of spec it will need to be replaced. Depending on how worn/damaged it is there is the
possibility of replating but the cost is normally pretty close to a new cylinder so I usually just go for the new one.
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