YZ450F Lost 2nd Gear

[M5-]

Well my 2018 YZ is done for the season. It has developed a problem staying in second gear. I can go from 1st to 3rd and its all good but it clunks and skips hard in 2nd, feels like the track is ratcheting only way harder. I suspect the shift forks are done and its popping in and out of gear. I was planning a FULL rebuild this summer but I guess that'll be happening sooner. Bottom end has 165 hours on it. Apparently this is a common Yami problem, its the first one I've blown up. I'll be riding the backup YZ which has 159 hours on it, ride that one until it blows up too.


M5

 

[Mendomotox]

I think we are just asking a little much of these machines. These bikes are designed to make 50-60hp, but only for a few seconds at a time. I've broken 2 chains, shattered a piston and witnessed a 2 year old yz450 blow up with only 120hrs on it. That's all in about 2 months riding snow bikes. We need purpose built machines for this kind of use. I love riding the snow bikes, but I think they are going to be expensive and time consuming to keep up

 

[kanedog]

I hope you find 2nd gear. Maybe try the lost and found section.

 

[Mendomotox]

M5- your on 450s right?

 

[eric82930]

Just a thought did you make sure the shift star didn't come loose? I've seen that happen a lot.

 

[kyle.B.]

Closing in on 250 hours on stock bottom and stock clutch on my 15 yz 450, on its 3rd piston.
Still running strong, planning on a full rebuild this summer.

 

[Sheetmetalfab]

Closing in on 250 hours on stock bottom and stock clutch on my 15 yz 450, on its 3rd piston.
Still running strong, planning on a full rebuild this summer.

The 14-17’s are bulletproof.

The 18+………. Not so much…….

 

[M5-]

Yes YZ450's. I haven't had a chance to look at it yet but wouldn't the shift star coming loose cause issues in all the gears not just 2nd?

M5

 

[eric82930]

When it comes loose anything strange can happen but the 2nd gear dogs are usually the most worn and need the most perfect alignment to stay all the way engaged. It's easy to check without pulling the engine out so it's worth a look before giving up the rest of the season.

 

[M5-]

So after doing some homework on the MX sites, seems that Yamaha updated all the cog gears in the trans for 2020. The 18 and 19 bikes have the crappy gears. Interestingly, the MX guys seem to all blow up 3rd gear which is their go to gear vs snowbikers favoring 2nd gear as a go to, most of the MX guys break theirs around 70 hours so I'm not feeling that bad at 165 hours. From all the pics I've seen the cogs will be worn and rounded off and the forks will be hogged out. I will rebuild it with the updated gears regardless of whether I keep it or not, I wont sell a bike that I know has issues, that's just a douche move.

M5

 

[eric82930]

Cool post some pics of the damage when you get it apart. I'm a ktm guy and have been lucky to have very few failures other than the shift start coming loose. in dozens of high mileage snow bikes only issues were my buddy's bike that was a 250sx run with No oil for 25 miles on a powder day. Everything in the trans turned blue. The other was an 11 250sx was just notchy and random missed shifts to 2nd but not bad enough to justify a tear down.