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YZ450FX feedback and reviews

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4 hours ago, ktm300dude said:

Hi Guys, have you guys seen Dave Simon on his site ktmhusky and how he fixed yz250fx lean out condition when at low rpms and cracking open the throttle? I have a 16 yz450fx and it has the same fuel line and injector top which is crap. But i fixed it and fixed it better than ktmhusky. The stock injector has a real tight as 90 degree bend on top of it, then 4 inches or so upstream towards the tank there is another tight as 90 bend. These bends are really bad for fuel flow, especially when riding slow or cornering slow then cracking open the throttle, there is a sudden lean condition while the fuel regathers itself, which can cause stalling out. I got an engineer to make a new straight shot injector top out of stainless steel, then i got a 8mm steel fuel line off an old car, (1990 300zx nissan fairlady) and it had almost the perfect shape bends in it to suit the yz. Its difficult to explain but the fuel line has a hose tail with a barb on one end then goes like an upside down U shape with nice curvy bends then bends again towards the side of the bike and goes out to side and bends again towards back of bike and continues for about 8 inches then has a barb and hose tail which you push stock rubber fuel line onto after cutting it in correct place and hose clamping it. I used a short piece about 2inches long of 8mm rubber fuel injection line to join the injectors new straight up 8mm tail with barb, to the upside down U shape steel fuel line. The upside down U shape steel line almost touches the bottom of the airbox, which is the worst part of this mod but its ok. I was lucky to find the fuel line from the car cos it is almost perfect, it needed a few slight tweaks and minor bends here and there but i got it real good. Steel was the only solution i could see would work because of the bends, rubber will kink, so will steel braided line if you bend it 90 degrees. The finished result is nice smooth rounded bends so the fuel can flow smoothly to the injector. I have not stalled my bike at all and can chug right down low in a higher gear then crack it open and it just hauls, its how it should be from the factory.

I would love to see pictures of you install.

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5 hours ago, ktm300dude said:

Hi Guys, have you guys seen Dave Simon on his site ktmhusky and how he fixed yz250fx lean out condition when at low rpms and cracking open the throttle? I have a 16 yz450fx and it has the same fuel line and injector top which is crap. But i fixed it and fixed it better than ktmhusky. The stock injector has a real tight as 90 degree bend on top of it, then 4 inches or so upstream towards the tank there is another tight as 90 bend. These bends are really bad for fuel flow, especially when riding slow or cornering slow then cracking open the throttle, there is a sudden lean condition while the fuel regathers itself, which can cause stalling out. I got an engineer to make a new straight shot injector top out of stainless steel, then i got a 8mm steel fuel line off an old car, (1990 300zx nissan fairlady) and it had almost the perfect shape bends in it to suit the yz. Its difficult to explain but the fuel line has a hose tail with a barb on one end then goes like an upside down U shape with nice curvy bends then bends again towards the side of the bike and goes out to side and bends again towards back of bike and continues for about 8 inches then has a barb and hose tail which you push stock rubber fuel line onto after cutting it in correct place and hose clamping it. I used a short piece about 2inches long of 8mm rubber fuel injection line to join the injectors new straight up 8mm tail with barb, to the upside down U shape steel fuel line. The upside down U shape steel line almost touches the bottom of the airbox, which is the worst part of this mod but its ok. I was lucky to find the fuel line from the car cos it is almost perfect, it needed a few slight tweaks and minor bends here and there but i got it real good. Steel was the only solution i could see would work because of the bends, rubber will kink, so will steel braided line if you bend it 90 degrees. The finished result is nice smooth rounded bends so the fuel can flow smoothly to the injector. I have not stalled my bike at all and can chug right down low in a higher gear then crack it open and it just hauls, its how it should be from the factory.

So you’re telling me that the stock fuel line can support 60+hp wfo but can’t flow enough fuel when the throttle is cracked open at low rpm?

I’m going to go out on a limb here and say it’s all in your head.

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That suggests there is a pressure drop on quick openings, so a bit of hysteresis in that valve and the pressure built behind it. That also suggests the flow rate through the middle and the corners of the fuel line is high enough to see turbulent flow.

With the ports on the injector being on the micron scale, I'm also not buying it.

Data would settle this. The butt does not.

Pressure versus throttle opening (or injector duration) with the opening rate being constant across both configurations would tell all.

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You guys need to take a look at what ktmhusky does, he has fixed ktms rubbish fuel systems with great results and watch the YZ250fx video, he has a air fuel ratio guage mounted on the bars and shows how he fixed that. Cars dont have crap sharp as bends in their fuel lines, they are all rounded swept bends for good flow, why dont cars pop stall??? I can tell my YZ is better, it would stall before, now it doesnt, thats data enough for me.

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6 hours ago, ktm300dude said:

You guys need to take a look at what ktmhusky does, he has fixed ktms rubbish fuel systems with great results and watch the YZ250fx video, he has a air fuel ratio guage mounted on the bars and shows how he fixed that. Cars dont have crap sharp as bends in their fuel lines, they are all rounded swept bends for good flow, why dont cars pop stall??? I can tell my YZ is better, it would stall before, now it doesnt, thats data enough for me.

 

Regarding KTMandHusky.com:

I've seen his stuff, and I think a lot of it is snake oil. Did you know that after you pay him $75 for a straight fuel rail to replace the 90 degree stock rail, you can turn around and pay him $65 for a 90 degree fuel tank fitting to replace the stock straight fuel tank fitting? That's not even a joke. Look at his site:

https://www.ktmandhusky.com/90-degree-fuel-fitting-for-all-tank

I also start to lose some respect for his products when he markets everything he makes as offering huge increases. Here's a quote from his website:

"Fuel rail systems for the 2 stroke TPI bikes are almost available. Huge increase in power and response."

Good grief! If only KTM had talked to this guy during their 10+ years of two stroke fuel injection development, those bikes could have so much more power and response!

He's good at marketing and making good money from it.

Regarding the YZ450FX Fuel Requirements:

The max fuel requirement for a 450 making 60hp is around 12oz (350cc) per minute. You can get a feel for how little fuel this is by turning on your kitchen faucet and letting it fill up a measuring cup in the right amount of time. 12oz (350cc) every minute. That's enough to support 60hp wide open. Your stock fuel line could probably flow that much just by gravity. But remember, it's not a gravity feed. It's highly pressurized, which means it's almost a fire hose compared to the actual fuel requirements.

The fuel requirement at low RPM when you crack the throttle is nothing more than a small trickle through that line. But it's not trickling, the line is completely full of pressurized fuel. Because of this, there is next to no velocity to create restriction. Straight or bent, the fuel doesn't care when it's barely moving through the line.

Regarding Cars and Popstalling:

You're right that cars don't pop stall. But they have multiple cylinders, heavy rotating assemblies, heavy flywheels, etc. Fuel line geometry isn't even on the radar.

 

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ktm300dude,

I just wanted to follow up by saying that while I don’t agree with the original diagnosis, it sounds like the fuel line you created is pretty neat.

That’s awesome you decided to do it yourself rather than pay someone else for their product. I respect that mindset.

Can you post pictures? I think we’d all like to see how it turned out.

In the end, all that really matters is if you’re happy with your bike. Happy riding!

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Thanks Fly Low, i appreciatte your knowledge and feedback. The fuel system is buried under the tank and airbox and a bit of a pain to take it all off, i shouldve taken photos while she was in bits, if i feel keen il take it to bits again and get some pics.

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Looked at the FX and compared to the WR. MR Braap def has good insight on this subject. I ended up going with the WR for a really silly reason. It has a kick start so I can ditch the battery. I rode the FX and WR and would say the big difference is that the FX is a little more track ready.

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All I can say is I almost went to the dark side and was looking into the Husky/KTM 500 exc but when it came down to it I don’t need a street legal bike and I stuck with Yamaha and got the 450fx I’m happy as hell with it’s fast as F#%K Suspension feels almost the same as my $1000 TBT racing suspension on my 06 yz450 . I have a few friends I work with in the Stunt/film industry world and they race pro level BAJA 1000 and do test rides on all the off road bikes and there input was Yamaha has the best everything but it really boils down to what color you like Blue , Red , orange, yellow, green .. . . . Even though Kawasaki stoped make the KLR450 many moons ago and Suzuki doesn’t call the RMX450z a competition bike there not the worst but not the best .

If you like 450FX get the Yamaha you won’t be disappointed 

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14 hours ago, ktm300dude said:

You guys need to take a look at what ktmhusky does, he has fixed ktms rubbish fuel systems with great results and watch the YZ250fx video, he has a air fuel ratio guage mounted on the bars and shows how he fixed that. Cars dont have crap sharp as bends in their fuel lines, they are all rounded swept bends for good flow, why dont cars pop stall??? I can tell my YZ is better, it would stall before, now it doesnt, thats data enough for me.

I really hate to tell you this but all that stuff is garbage. We don’t use fuel rails or other nonsense. He has not fixed KTMS. They run lean because they are street legal and it’s the stock ECU that makes that happen. The Vortex ECU or James Dean piggyback controller fixes that. Please don’t believe his nonsense! 

Here is my bike without a fuel rail. 

 

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1 hour ago, 450crazy said:

Where are you riding at in that video?

That is the famous Snake Pit. Here’s another one. Still no fuel rail. 

 

Edited by stevethe
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Hi Guys, i took my yz450fx apart again to get these photos to show you all my install of the steel fuel line and stainless straight top on my injector.

2[1].jpg

3[1].jpg

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On 2/1/2018 at 5:01 PM, stevethe said:

I really hate to tell you this but all that stuff is garbage. We don’t use fuel rails or other nonsense. He has not fixed KTMS. They run lean because they are street legal and it’s the stock ECU that makes that happen. The Vortex ECU or James Dean piggyback controller fixes that. Please don’t believe his nonsense! 

Here is my bike without a fuel rail. 

 

hilarious, people all around the world are looking for ways to spend money and "fix" their bikes.

all the money in the world wont get them up those hills hahahaha

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Not so sure about that. Some dude last weekend was offering us money to ride his bike up sections for him.

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