yfz450 carb and hub problems

[Zakradu398]

Will these work just as well on a 400ex as a 450r carb?

Also, it seems my hubs always come loose and will wiggle. I always tighten them as much as possible and get the cotter pin in real tight.

[Stickman400]

I'm almost positive that someone on here has a YFZ carb. on their 400. And if you are reffering to the rear hubs then I think that is a common problem, because I tighten the hell out of my castle nuts and they still come loose and wiggle, and I use hairpin style cotter pins so the castle is not coming loose. It gets really annoying but I can't seem to get them tight enough. Only thing I can think of is to wrap teflon tape on the axle splines.

[AtvKid4Eva]

might be able to make the carb work..but id throw a 450r honda carb on there.

Make sure when you tighted the castle nut you sort of "wedge" a thick cotter pin in the hole. That will make it impossible for the nut to loosen up.

[CJM]

Impact gun on the nuts, mine dont come loose.

[2001400exrida]

The yamaha fcr carb will work.

For those of you who are suggesting the honda carb, there's different carbs depending on the year. the 04/05 honda 450 carbs are not FCR carbs, the 06+ are the FCR carb which is very similar to the yamaha FCR carb.

Either carb will work and will provide and upgrade for you!

the castle nuts have to be torqued major while on the ground. when you think you are tight and there's an opening for the cotter pin, go 1 more opening and that will hold tight. also, u can use locktite and that will help hold it on as well. impact gun doesn't give you anymore torque than you can do on your own.

[400man]

im running a yfz450 carb on mine and ive been happy with it. It revs alot quicker and feels more "snappy". but it does take a decent amount of modifications to make everything work and fit good, not really a bolt on and ride type deal. I can take some pics later if your interested.

[Zakradu398]

Originally posted by 400man
im running a yfz450 carb on mine and ive been happy with it. It revs alot quicker and feels more "snappy". but it does take a decent amount of modifications to make everything work and fit good, not really a bolt on and ride type deal. I can take some pics later if your interested.

What all did you have to modify? Pics would be cool. Also, what year carb did you use?

[powerbomb400]

I'm with CJM about using a impact gun and thick cotter pins. Mine don't come loose and I use anti seize on the splines.

[Rohr397]

Just curious, why use a Yfz carb? I had the Yfz and without the zip tie mod it was terrible. They have a delay in throttle response caused by a gap etc etc etc but the point is the Trx FCR is awesome but the Yfz FCR has that one issue. There's a video on it if you look up Yfz zip tie mod it explains why the Yfz FCR is flawed, not hard to fix but still flawed.

[Zakradu398]

Originally posted by Rohr397
Just curious, why use a Yfz carb? I had the Yfz and without the zip tie mod it was terrible. They have a delay in throttle response caused by a gap etc etc etc but the point is the Trx FCR is awesome but the Yfz FCR has that one issue. There's a video on it if you look up Yfz zip tie mod it explains why the Yfz FCR is flawed, not hard to fix but still flawed.

They seem to be 50-70$ cheaper. But i've done the zip-ty mod on an old yz250f. Thanks for the heads up though bro.

[Rohr397]

No problem just makin sure! That delay made for some scary moments at the track especially on doubles haha

[audioworks04]

The trx and the yfz both suffer from accelerator pump lag. They are almost identical so there is no reason one would and the other wouldnt. The lag can be jetted out with correct jetting along with the correct leak jet. Also companies like r&d and a few other make adjustable leak jets. Overall the fcr is a better carb than the butterfly carb of the 04-05 trx450, but they are harder to tune.

[400man]

and i think the honda 450r fcr carb is a little bigger than the yamaha carb?

[Rohr397]

Originally posted by audioworks04
The trx and the yfz both suffer from accelerator pump lag. They are almost identical so there is no reason one would and the other wouldnt. The lag can be jetted out with correct jetting along with the correct leak jet. Also companies like r&d and a few other make adjustable leak jets. Overall the fcr is a better carb than the butterfly carb of the 04-05 trx450, but they are harder to tune.

I'm not talking about the accelerator pump lag I'm talking about the delay seen at 4:40

http://www.youtube.com/watch?v=tzsBrNhX52g

[2001400exrida]

the trx450 does not have the same lag that the yamahas come with. The yamahas require a ziptie mod, the trx's don't have this issue.

the carbs are very similar so i would say get whichever one will save you a lilttle money.

[JOHNDOE83]

If you want a carb for power and performance, get the 05 450r carb, its a 42mm and gives throttle response and "overall" performance gain.

The fcr carbs are 38mm and 39mm which is good for all lowend and midrange power now stuff, and they increase throttle response slightly more then the 05 450r carb but they dont do anything for overall power gains.

However, they do perform WAY better the stock 400ex carbs.

Basically in my opinion, get the fcr if your not gonna do 426 or 440 type mods and do alot of mx'ing and trail riding.

If your building a race motor, get the 05 450r carb

[2001400exrida]

i think you are mislead johndoe

the 04/05 carbs are inferior to the 06+ trx450 carbs.

the 06+ are FCR carbs whereas the older ones are not. It's a common upgrade on the older 450's to put a newer carb on it for more power.

that being said, some XC guys prefer to run the older carb because it's got more low end response apparently.

[Zakradu398]

I actually wanted to do a 465 stroker.

[JOHNDOE83]

Originally posted by 2001400exrida
i think you are mislead johndoe

the 04/05 carbs are inferior to the 06+ trx450 carbs.

the 06+ are FCR carbs whereas the older ones are not. It's a common upgrade on the older 450's to put a newer carb on it for more power.

that being said, some XC guys prefer to run the older carb because it's got more low end response apparently.

No, Im not misled...:chinese:

It's impossible for a carb of the same size to be better for performance simply because the slide is flat instead of round.

The fuel delivery and even the jets are the same, the parts look different but they do the exact same thing as the stock 38mm carb. The flat side unlike the round slide delivers a "stab" of air instead of a even flow of air like the round slide 05 450r carb.

The size of the carb "like the 42mm" delivers mass air flow throughout the entire RPM range requiring more fuel to added through jetting to balance it out.

More air+More fuel=More HP in any engine.

If size didnt matter for overall HP and performance, people wouldnt need 44mm lectron carbs.

And explains why a edelbrock carb for the ex isnt that great if any good at all, FCR carbs are essentially tuneable, proper working, edelbrock carbs.

The only thing a flat slide carb gives you is throttle response and allows what usable power the engine has to use literally on demand, giving you the impression of more overall HP.

In theory, on a dyno the FCR might show more torque but not as much HP gain, the 42mm carb would show less torque and more HP increase.

For a big bore or stroker, I reccomend the 05 42mm 450r carb.

For a mx, xc, hairscramble or trail quad I would reccomend the FCR.