I’m coming up to 100 hours on my 2024 yz450 soon and just curious what everybodies thoughts are on necessary replacement parts… I’m a Vet B rider, very easy on the bike, not a revver, also am a mechanic by trade and very analytical about my bikes being maintained.
Anyways, my local cylinder head shop recommended I should do valve springs, keepers and retainers but that valves will be inspected and replaced if deemed necessary but will probably be fine. I’m also obviously going to do piston, rings gaskets etc but my main concern is the supposed weak crank or rod that Yamahas are now being known for. Is it an absolute necessary item to be replaced at my skill level? Or is that more of a pro level item to be worried about? I do have a case splitter and have the capabilities to replace the crank if necessary. And if I do go down that road does anybody know of a drop in complete crank with HD rod to minimize downtime vs sending my crank in to get rebuilt? Thanks for any help.
At 100 hours id say you've proven that you dont have one of the "weak" cranks.
I like to do a leak down test to give me an accurate indication of the overall health of the engine.
Rocky mountain sells the kits relatively inexpensive.
When doing the test you will be able to hear where the "leakage" is coming from .
Id be paying close attention to the exhaust and airbox which is going to give you feedback on how well the valves are sealing .
Then once apart you can perform the fluid test with air to actually see if and how much the valves are leaking.
If you feel like having peace of mind then send your crank to Ken Oconner or CWI.
I dont know of any "HD" crank assemblies . Prox may make one but i personally prefer an oem rebuilt crank .
I have rebuilt a few cranks since purchasing the jig from Kimmer and really enjoy that process , aside from the truing part .LOL!
If it was mine id most likely be doing a piston (measure bore of course) and cam chain and calling it good , unless of course the leak down said otherwise .
The crank is a judgement call youd have to make . You can check up/down play and measure the big end side clearance and go from there.
Good luck.
Thank you for the insight. I’m mainly just replacing the cylinder head stuff for piece of mind and it’s not very expensive. And yes, I was going to check the crank once I got the cylinder off and see how it feels. I was mainly just curious if anybody has dealt with the apparent connecting rod longetivity issue. I believe Keefer said if you’re on the faster side to get it replaced at 60 hours but i don’t know if I’m considered that yet haha. Anyways I’ll get it apart and go from there. Thanks for the help.
Sounds like the perfect time for a total overhaul crank up before it goes boom.
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