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Daz_426_02

2006 YZ450 Frame seems thinner than the rest ??

10 posts in this topic

Is it just me or dose the new ali frame look a lot thinner than all the other 450's? If you look at the new Kawasaki frame and even the Suzuki frames they are exactly the same looking as the Honda frames, which are quite wide and strong looking. That design of frame has been on the Honda's for quite a few years now as well....

Yamaha have got their own design which is great but its strange that their frame is so much thinner.

Anyone have any ideas or comments on this?

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Look at the frame in the pictures. The frame is build like the 250 frame, with the holes on the inside. A complicated AL construction. The yellow, red and green frame is a welded tube and a different construction. Then it is also a question of the complete frame stiffness. I´m really sure that the Honda frame don´t really need the stringer under the engine for the stiffness. It is more a question of the security of the engine. Yamaha is all the time talking about their great flexing frames and the results of feeling for the rider.

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Knowing Yamaha , the frame has been through all kinds of finite stress analysis and failure effects mode testing before is was ever put on a bike not to mention having guys like Reed, Ferry and Villumien (sp) ride the snot out of them.

I would trust it just fine ....... but I'm old and waaaaaaay slow.

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The Honda is a hollow box section with thin wall material. The Yamaha uses solid forgings and extrusions to form a perimeter similar to a Kaw steel frame. Yamahas frame allows you much better access to things like the carb. They are two completely different animals.

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This is not by a long shot the first spar frame Yamaha has built. I'm certain that the decision to use spars with more horizontal section and less vertical the "the others" was carefully made, and that it's going to work.

What I think is interesting is this: It's still a dry sump engine, but there's no external tank. At least, that's what I see. If you look at the detail of the engine, you see what looks like a dipstick in front of the cylinder, above the front mount bolt. Note that the front of the engine visible between the cradle tubes is much bulkier than the current one. That's the oil tank, built into the engine, way down low. What is it they say....? "Brilliant!"

Oh yeah, and a 5 speed, too!

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What I think is interesting is this: It's still a dry sump engine, but there's no external tank. That's the oil tank, built into the engine, way down low. What is it they say....? "Brilliant!"

The oil tank has moved from the frame to the area between the frame in front of the motor (same place glide plates normally mount)

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If I'm right, it's going to really be tough to explain the oiling system to some people. It looks to me as if the engine is still a dry sump, but now the oil tank is a part of the engine, so people are going to start thinking it's wet.

Remember what distinguishes the two; wet sumps have one pump that picks up the oil from the sump, a low spot in the crankcase, supplies it to the lube points, after which it drains back to the sump and starts over. A dry sump has two pumps and an oil reservoir somewhere besides the actual crankcase. The oil comes from the reservoir to the feed pump to the lube points and drains to the crankcase floor, but then the scavenge pump removes it from the sump, keeping it "dry", and returns it to the reservoir.

If you look at the new 250F, you'll see the oil tank in front of the engine, but still a separate part. The 450 keeps the oil reservoir in the same place as the 250F, but integrates it into the engine, or at least that's how it looks to me. But if it's in the engine, why bother making it a dry sump? Because by doing so, you can have a reasonably large quantity of oil instead of choosing between building a bulky sump under the engine, which would either reduce ground clearance or require the engine to sit higher in the frame, and the piddling 700cc of oil the CRF has.

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