'06 450F Rear Hub Broke

OK guys. I broke my hub on my '04 from having the chain too tight, so have been extra careful with my '06-to no avail. Bike has about 30 hours on it, chain was adjusted correctly, just entered the track onto a table-top, so landed a little flat as I grabbed third gear, and the rear wheel locked. My broken hub looked exactly like the last guy's I saw in here. Busted neatly all the way around, near the spoke holes. Only guess is spokes were too tight, but again, after doing this before on my '04, I'm very, very careful with rear-wheel adjustments. So I know most believed the issue was chain too tight, but I guarantee this was not the case this time. I'm beginning to think the hubs on the 450's are just a little under-engineered. Ended up with a jammed knee (very lucky), but otherwise am fine. Don't worry, I'd never trade mine in for a Honda!

Sounds like it is time for you to get a spoke torque wrench and to start leaving your chain kinda loose.

I don't use a spoke torque wrench, and I just tighten them sung. My chain is 2 finger slack and it seems perfect. Go 2 or 3 fingers under the chain @ rear slider bolt...that's about right for slack, depending on how big you're fingers are.

Sorry to hear about it man.

Were all lthe sprocket bolts still there? What amt of adjustment are you leaving in the chain slack - Barch is correct 3 fingers at the rear top chainslider.

3 fingers is on the tight side of the measurement. 2 would be way too tight.

hubs just don't explode.

Sprocket bolts were fine. After the hub came apart, some were missing, but only where the hub cracked right down the middle of them. Chain was definately not too tight. I may have to get that spoke torque wrench. I've had 19 motorcycles previous to this one and never broke a hub. Gotta believe the torque of the 450's put everything under stress.

Your sprocket bolts were loose or missing. This is what causes 90% of hub failures.

Loose spokes would actually be more likely to cause a hub failure than excessively tight ones, but in that case, the hub would have failed by pulling all or part of the spoke flange away from the rest of the hub. Here, however the force has obviously been applied at the sprocket flange, and the hub broke at the weakest point between there and the bearing pockets, which is where the hub's resistance to that force originates.

The hub is the same part number as all YZ450/426 models at least as far back as the 2000 model year, possibly farther (2000 is as far as I went), so unless there has been a change in vendors or machining that is neither apparent or reflected in the part number, I'm going to have to agree with those who are suggesting a problem with chain tension being set too tight. The force that creates is potentially many times greater than the engine is capable of delivering.

The '06 is a different chassis, and the tension curve of the chain as the swing arm moves through its travel may well be different than that of earlier models. I would either run mine a bit loose ( I tend to, anyway), or compress the suspension through its entire range to check what the minimum tension adjustment really should be.

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