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Have YZ450FX , HATE wide ratio trans....YZ gear swap?

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11 hours ago, Timo2824 said:

I know the old rule of thumb is a stroker makes more torque, but I've seen Dyno shootouts with 383's with identical Cam's and heads one stroked and one a larger bore and the larger bore made more hp and torque. Plus you have a way lower piston speed which I think is better for durability.

Yes the increase in piston speed on a stroker isn’t great. 

But my experience with stroker engines is you get more low end pulling torque. Especially with a stock cam. Normally I don’t like strokers but when you look at the numbers the Yamaha is the only one that’s so oversquare. 

The dyno shoot out may have showed more torque but higher in the power band? 

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13 hours ago, Timo2824 said:

I just looked it up, the old 5 valve engine had a 39mm carb and my 19 FX has a 44mm throttle body. They can get away with more by fuel injection, but you will still make peak torque at a lower RPM with the 39mm carb. The trade-off is a lower maximum HP and less over rev. 

Note: your 500 (510) is 60 cc larger than a 450 but it's throttle body is a 42mm. Definitely designed for a lower rpm peak torque.

you can't quite directly compare the size of a TB vs an FCR carb, as the TB butterfly still restricts some airflow when at WOT while the slide doesn't (I guess the needle does a tiny bit but much less than the butterfly). I remember reading about flat track production vs race bred rules and I think they claimed it was similar to a couple mm difference... so 44 is still bigger than 39+2, but not as much as it initially appears.

12 hours ago, Timo2824 said:

I know the old rule of thumb is a stroker makes more torque, but I've seen Dyno shootouts with 383's with identical Cam's and heads one stroked and one a larger bore and the larger bore made more hp and torque. Plus you have a way lower piston speed which I think is better for durability.

If the bottom end is what limits your max RPM, with the stroker it makes sense to go for more torque because you can't rev as high. You also can't fit as big of valves, which again limits top end power.

 

I agree that they don't really inherently make any more torque. 

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9 hours ago, StevetheSnake said:

Yes the increase in piston speed on a stroker isn’t great. 

But my experience with stroker engines is you get more low end pulling torque. Especially with a stock cam. Normally I don’t like strokers but when you look at the numbers the Yamaha is the only one that’s so oversquare. 

The dyno shoot out may have showed more torque but higher in the power band? 

Apparently I remembered wrong:

Stroker max torque 464.9@4200 rpm 

Horsepower: 440@5600 rpm

Big bore max torque: 463@4300 rpm

Horsepower: 440@5400 rpm

The big difference was the bb was making 50 ftlbs more torque at 3000 rpm and 25 more horsepower. So the bb was actually better at lower rpms. Max torque and horsepower were basically identical. Also the overrev drop-off was almost identical. I would have thought the higher piston speed of the stroker would cause more parasitic loss, but it's apparently matched with the higher surface area and weight of the bigger piston.

Edited by Timo2824
Added the overrev info
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9 minutes ago, Timo2824 said:

Apparently I remembered wrong:

Stroker max torque 464.9@4200 rpm 

Horsepower: 440@5600 rpm

Big bore max torque: 463@4300 rpm

Horsepower: 440@5400 rpm

The big difference was the bb was making 50 ftlbs more torque at 3000 rpm and 25 more horsepower. So the bb was actually better at lower rpms. Max torque and horsepower were basically identical. Also the overrev drop-off was almost identical. I would have thought the higher piston speed of the stroker would cause more parasitic loss, but it's apparently matched with the higher surface area and weight of the bigger piston.

Might also be a drastically different bore to stroke ratio.

The new Yamaha is a bit crazy oversquare. 

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well, my complete 450F trans came yesterday. Hopefully today a few gaskets and one shift fork will show up and it will be 450FX engine reassembly time

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On 1/18/2019 at 9:14 AM, whipit1k said:

well, my complete 450F trans came yesterday. Hopefully today a few gaskets and one shift fork will show up and it will be 450FX engine reassembly time

Let us know how you like it! If you don’t mind my asking how much did that cost? Sounds expensive!

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$215 shipped/from ebay for a very nice,complete YZ450F gearset. seller parting out a 2014.

paid maybe another $100 for a few gaskets, one shift fork and new piston rings. so about 315 total.

so far it is good, though the few short test rides have been on snotty/frozen ground. we are having a crappy weather snap here in NC

Edited by whipit1k

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why not just sell the fx and buy an f?  An FX is worth more than an F.....

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11 minutes ago, Zuminazx said:

why not just sell the fx and buy an f?  An FX is worth more than an F.....

A lot of people with the FX like everything about it, Except the trans, IMO the FX valving is perfect! & I’ve ridden a lot of bikes that have Been revalved, by many tuners, none of them come close to the FX , the smooth power, the tunabilty, the lager tank, the kick stand, for some it’s perfect as is! For some the ONLY issue is the trans!  But as been said before ya can’t please everyone all the time!!

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More power is not the solution to the massive gap between second and third, though I am sure it makes it more liveable. I suspect you guys don't ride tighter stuff.

 I have about 10 hours on my FX with its complete 2014 YZ450F transmission now. This thing is perfect to me now, so nice. If I get another 16-18 450FX, and I almost certainly will, I will swap out the transmission immediately. Its a big pain , but the wide ratio is absolute garbage for the stuff I ride, and was really the only fly in the ointment with this bike. I totally love it now

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Wide ratio is garbage for the stuff I ride here too.  I ride yz' s and put 18in on and revalve suspension.  I know that fx valving is to die for.

Edited by HORSEPOWER35

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2 hours ago, user760a said:

More power is not the solution to the massive gap between second and third, though I am sure it makes it more liveable. I suspect you guys don't ride tighter stuff.

 I have about 10 hours on my FX with its complete 2014 YZ450F transmission now. This thing is perfect to me now, so nice. If I get another 16-18 450FX, and I almost certainly will, I will swap out the transmission immediately. Its a big pain , but the wide ratio is absolute garbage for the stuff I ride, and was really the only fly in the ointment with this bike. I totally love it now

Not more power more but more torque to pull a taller gear. 

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Wide ratio is garbage for the stuff I ride here too.  I ride yz' s and put 18in on and revalve suspension.  I know that fx valving is to die for.
The 16/17 valving was pretty shitty to be blunt about it.

The WR box should have been about half the difference that it was from the YZF box, except for 5th, and it would have been bang on.

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Im going to Have to go ahead and kind of disagree on the 16 valving being bad.

for what I ride, the suspension on this bike is the best I have had, I added some oil to the forks for bottoming resistance and tuned accordingly. Better than any of the Kawasaki KYB stuff I have had valved for my weight in the past, and it's just stock.  I have only seen videos of guys riding in the desert in the western US and I can tell you that type of riding has almost nothing in common with east coast type stuff, so maybe that is a factor

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is it cheaper/easier to put a YZ tranny in an FX than it is to spring/valve YZ stuff to FX specs, or is there some other FX component that makes it worth it?

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3 hours ago, toten said:

is it cheaper/easier to put a YZ tranny in an FX than it is to spring/valve YZ stuff to FX specs, or is there some other FX component that makes it worth it?

Well there are different things that would matter to someone & nothing to others, like bigger tank, 18” wheel, kick stand, map switch, all of which surly can be added to the yzf, but at additional cost, ! It’s all personal preference! 

 

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I ride some pretty tight trails, some times barely getting into 2nd from 1st. Anyone who is having issues with the gap from 2nd to 3rd isn't revving 2nd out far enough. Just keep it in 2nd and you'll be surprised how much faster you can go before it actually gets to the limiter.

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lol running up into high RPM's and approaching the limiter is NOT how you ride a 450 smoothly for a two hour race....or at all for that matter.

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