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

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the huge jump is actually between second and third.

oh the irony...I start discussing transmission gear swaps and yesterday the fifth wheel gear in my FX transmission grenaded...broke the engagement dogs to bits and destroyed my right shift fork as well. I pulled the engine and split it today. no case damage...just fragged gear and smeared shift fork.I will probably put a complete moto trans in as long as it's apart...

also rich in the irony dept: I bought this Yamaha over other electric start off road race bikes because of its reputation for indestructibility .... or not

Edited by whipit1k

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Gear it down on the rear sprocket and put in the F 1-4.

Also call Hot Rods and ask them to make a stroker kit for this bike. They'll do it if there's demand.

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I actually just bought a complete 450F trans and will probably install the whole thing. I thought about keeping the granny first gear- may still do it

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32 minutes ago, StevetheSnake said:

Too lazy since I sold mine but has anybody even checked if the transmission ratios are nearly the same as a 07-11 WR450. 

according to GearingCommander, everything is identical vs 07-11 WR450 except primary drive ratio (which is fairly close: FX 2.609, WR 2.652, a bit smaller of a change than one tooth on the rear) and tire size. 

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1 hour ago, toten said:

according to GearingCommander, everything is identical vs 07-11 WR450 except primary drive ratio (which is fairly close: FX 2.609, WR 2.652, a bit smaller of a change than one tooth on the rear) and tire size. 

Well that pretty much proves the FX has a torque problem. There are no issues with pulling the 07-11 WR450 five valve gears. 

The only problem on those is when you put in both Hot cams it lost so much torque you had to ride a gear lower. 

I doubt YZ internal gear ratios are the fix. It might likely help a bit. But it is still not going to pull tall gearing well. 

It’s likely the cams hurting torque along with the bore and short stroke. The cams would be a easier fix. I know mine was a horsepower monster on top but lacked bottom. 

 

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2 hours ago, StevetheSnake said:

Well that pretty much proves the FX has a torque problem. There are no issues with pulling the 07-11 WR450 five valve gears. 

Lol...

There is nothing wrong with the FX torque, it pulls as hard or harder than any YZ I've ever owned ('02/'06/'08/'13). Of those, the '08 had the least pull down low but was a monster up high.

I have no problem off-roading with the FX wide ratio transmission, no bike will ever be perfect for every single possible scenario. First gear is too low for me in even the tightest riding (and we have some seriously tight stuff here in western Washington) so I dropped to a 48 in the back to make first gear more useable and spread the rest of the gears out even more. The FX makes more than enough power to pull the gaps, and there is a device on the left handlebar called a clutch that helps when you are between gears.

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11 minutes ago, Wiz636 said:

Lol...

There is nothing wrong with the FX torque, it pulls as hard or harder than any YZ I've ever owned ('02/'06/'08/'13). Of those, the '08 had the least pull down low but was a monster up high.

I have no problem off-roading with the FX wide ratio transmission, no bike will ever be perfect for every single possible scenario. First gear is too low for me in even the tightest riding (and we have some seriously tight stuff here in western Washington) so I dropped to a 48 in the back to make first gear more useable and spread the rest of the gears out even more. The FX makes more than enough power to pull the gaps, and there is a device on the left handlebar called a clutch that helps when you are between gears.

That is sure not what I found. I found it not to have anywhere near the torque to hold third gear on power hills. Everytime I let of for a second it would not pull third. The previous generation of WR had way more torque. 

I even tried the GYTR head and a big bore on my 16’. Still no torque to hold taller gears. I had my hand on the clutch 24/7 on that bike. 

So the people complaining (me one of them) are likely riding in different areas than you ride. 

Edited by StevetheSnake

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I definitely don't think it's a torque issue, when I first got my FX back in October I thought 2nd was too low and 3rd was too high, but since I started staying in 2nd longer before shifting to 3rd I no longer feel like the Gap is too big. 2nd feels like it's getting close to redline way before it's actually there. I think 1st has the same issue, you can go 15 mph in first but everyone wants to shift to 2nd at 5 mph.

Note: from my experience I think it's harder on gears if you're running a low rpm and really lugging the engine vs running a higher rpm and staying on top of the torque curve.

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1 hour ago, Timo2824 said:

I definitely don't think it's a torque issue, when I first got my FX back in October I thought 2nd was too low and 3rd was too high, but since I started staying in 2nd longer before shifting to 3rd I no longer feel like the Gap is too big. 2nd feels like it's getting close to redline way before it's actually there. I think 1st has the same issue, you can go 15 mph in first but everyone wants to shift to 2nd at 5 mph.

Note: from my experience I think it's harder on gears if you're running a low rpm and really lugging the engine vs running a higher rpm and staying on top of the torque curve.

Try riding a 06-09 YZ450 or a YZ’d WR450. More torque you don’t have to rev it up to get to the next gear. ??‍♂️

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2 hours ago, StevetheSnake said:

Try riding a 06-09 YZ450 or a YZ’d WR450. More torque you don’t have to rev it up to get to the next gear. ??‍♂️

Have you played with the tuning app? If more bottom end is what your looking for I wonder if anyone makes a reducer for the throttle body. Increasing the Venturi would make Max torque at a lower rpm, which is what some of you are looking for. These bikes are definitely built for horse power, I have the MX map loaded into both switch settings right now and in map 1 I bet it's over 50hp.

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1 hour ago, Timo2824 said:

Have you played with the tuning app? If more bottom end is what your looking for I wonder if anyone makes a reducer for the throttle body. Increasing the Venturi would make Max torque at a lower rpm, which is what some of you are looking for. These bikes are definitely built for horse power, I have the MX map loaded into both switch settings right now and in map 1 I bet it's over 50hp.

Lots of tuning. I did find a bit more torque to pull taller gears adding fuel on the bottom. 

I haven’t seen anything for a intake reducer. But I tried the GYTR head and a big bore and still no dice. Also put in the Hinson steel clutch basket. I finally gave up and sold it. I might be a bit sorry I didn’t go to see a cam expert. But we do 1,000 foot monster hill climbs combined with our riding out here in So. Cal. So I gave up and bought a 18’ 500. That was hard being a Yamaha guy. 

But I will say for fast riding where you might not need the torque the Yamaha ripped and handled very well.  I can see that engine ripping on a MX track. I wonder if they really developed the engine for MX then just stuck it in the other bikes. The KTM 450 sx seems to suffer from torque also as we have had them on our rides. One thing nice about the smaller KTM company is they made the sx and then the exc 450’s. My understanding is they say the sx might even have more hp on top than the 500 but that doesn’t hold up in our riding. The guys on sx’s suffer. 

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2 minutes ago, StevetheSnake said:

Lots of tuning. I did find a bit more torque to pull taller gears adding fuel on the bottom. 

I haven’t seen anything for a intake reducer. But I tried the GYTR head and a big bore and still no dice. Also put in the Hinson steel clutch basket. I finally gave up and sold it. I might be a bit sorry I didn’t go to see a cam expert. But we do 1,000 foot monster hill climbs combined with our riding out here in So. Cal. So I gave up and bought a 18’ 500. That was hard being a Yamaha guy. 

But I will say for fast riding where you might not need the torque the Yamaha ripped and handled very well.  I can see that engine ripping on a MX track. I wonder if they really developed the engine for MX then just stuck it in the other bikes. The KTM 450 sx seems to suffer from torque also as we have had them on our rides. One thing nice about the smaller KTM company is they made the sx and then the exc 450’s. My understanding is they say the sx might even have more hp on top than the 500 but that doesn’t hold up in our riding. The guys on sx’s suffer. 

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.

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8 minutes 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.

I do run 43.5mm tapper bored FCR’s on my 450’s. ?

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Long stroke on the 500 orange bike. 

Bore x stroke: 95.0 x 72.0 mm 

?

The YZ450fx specs. 

Bore x Stroke: 97.0mm × 60.9mm

?

The 07-11 WR450 specs. 

Bore x Stroke: 95mm x 63.4mm

?

 

The KTM 450sx specs. 

Bore x stroke: 94 x 63.4mm

Edited by StevetheSnake

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11 minutes ago, StevetheSnake said:

Long stroke on the 500 orange bike. 

Bore x stroke: 95.0 x 72.0 mm 

?

The YZ450fx specs. 

Bore x Stroke: 97.0mm × 60.9mm

?

The 07-11 WR450 specs. 

Bore x Stroke: 95mm x 63.4mm

?

IIRC, the 450 and 500 KTMs share the same bore.  the difference is longer stroke for the 500.  it might explain the 450's lack of torque.  my 450 sxf doesn't like to tractor at low revs.  lots of weird sounds, probably just chain slap... but still weird sounds.

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1 minute ago, Kallendbor said:

IIRC, the 450 and 500 KTMs share the same bore.  the difference is longer stroke for the 500.  it might explain the 450's lack of torque.  my 450 sxf doesn't like to tractor at low revs.  lots of weird sounds, probably just chain slap... but still weird sounds.

Well true but the 450sx also has a much lighter flywheel, larger ports, larger throttle body and hotter cam that the 450exc. I think the sx is more like the new backward head Yamaha  450’s. A top end monster. 

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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.

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