Ran the WR450 out of water!!!!
Posted August 11, 2008 - 07:58 AM
We lost the gamble and the bike died 2 miles before the gas stop.
It rolls over, so it didn't sieze.
It seems to have good compression, but with the auto decomp I'm not sure I'm getting a good feel for it.And I haven't done a true comp test yet.
It has spark and seems to have fuel too, so I ruled out any kind of overheat sensor that it might have.
There is a plastic plug in the head that faces forward just above the header that is now leaking oil onto the header. I imagine it got hot enough to melt that enough to leak. What is that plug for?
My guess is a blown head gasket or a cracked head.
I'm looking for suggestions from the hardcore yamaha 4stroke mechanics what to look for. I am very familiar with 4st bike motors, but not the 450 yamaha.
Posted August 11, 2008 - 09:03 AM
Posted August 11, 2008 - 09:17 AM
You might have gotten lucky - I'm guessing you blew a gasket.
only way to see what's what is to start tearing it down.
Posted September 10, 2008 - 04:00 AM
I cleaned the carb 3 times and still had no luck. It was just like the idle circuit was plugged or not working.
Then it accurred to me that a friend of mine had the same bike and I could swap carbs and other parts to eliminate or pin point the problem. We swapped out the carb with no difference at all. Next I was going to swap the CDI unit, then I looked at the plug cap/coil unit and thought it was easy to try. Swapped it and it ran like it was brand new! I swapped it back and forth a few times to make sure I didn't just disrupt a wire.
It's the coil for sure! It makes sense that the overheat killed the coil, seeing that it is part of the plug cap. It's too bad I took the whole top end off.
The good news is my son gets to ride Stumpjumper now.
Thanks for all of your help and suggestions.