Need advice for more bottom end

looking to get some more low to bottom end out of my 09 yz450f. need some opinions on exhausts. i am thinking about getting the yoshimura rs-2 full exhaust found it for $420.00 shipped anyone have any experience with it?. Or would re gearing and dropping a tooth of the back be better . any help would great thanks guys

I wouldn't really Waste your money on an exhaust.

Go up one or two teeth on the rear sprocket if u can. Or look up on google this:

Type in Chad sanners eleven ten mods

then u should be able to go to their home page. They do a carb mod for like $150 and it adds 2 1/2 hp. And it takes away any bog as well. My buddy got it done on his 250f yz 2008 and it really added some low end

I wouldn't really Waste your money on an exhaust. ...

(Chad Sanners does) a carb mod for like $150 and it adds 2 1/2 hp. And it takes away any bog as well. My buddy got it done on his 250f yz 2008 and it really added some low end

First, regarding the exhaust, almost any slip-on or full system, either one, will add anywhere from 4-8 HP at around 5000-5500 on an '08 or '09 YZ450, simply because the OEM muffler is a piece of junk designed to be cute rather than functional. Even a stock '06 or '07 system will improve them considerably. Not many of them will add much significant power on top, but that's not what the OP wants, anyway.

Second, I don't know where you got the 2 1/2 HP number from, but let me say succinctly but as politely as possible, "BS". The only carb mod that would produce anything like that is boring it oversize, and that's not likely to give those kind of results without adding in port work and a compatible exhaust, anyway.

This is from Sanner's site:

FCR Carb Mod (four-strokes only)- Using the right combination of 8 mods & adjustments, this mod increases throttle response thus eliminating any bogging. Package includes mod and all parts necessary. ...
...No mention of any power increase. Probably the same thing that Zip-Ty's been doing for 3 years; modified emulsion tube and an accelerator pump tune-up. Pass. The '09 doesn't need this, and it won't accomplish what the OP wanted.

To compliment the exhaust, add a CDI unit from an '06, and if that's still not enough, buy an exhaust cam from an '06 to go with it. Adding flywheel weight will smooth out the power delivery at very low speeds and make it pull better down low, also, all with no noticeable penalty.

.....

Edited by crf450319

I have a fmf megabomb and 4.1 system on my 09 and it made a huge difference, it now feels like power is available and smoother in any rpm.

Grey, the noticeable penalty I've felt on a bike with a flywheel weight is a loss of flick-ability in the air, the bike wants to go straight and upright. Not as manuverable in the air. I agree The stock 08-09 pipe is in fact a pile of BS. However, I have seen a National pro level rider going really fast with the stock pipe on his stock 08. The 07 pipe is usable but an aftermarket system will yield more noticeably more bottom end. I went with the now defunct white brothers Aluminum pro 2 and have been greatly impressed with the improvement.

... I have seen a National pro level rider going really fast with the stock pipe on his stock 08.
The question wasn't whether or not one could go fast with the stock pipe, it was how to get more mid range power, and changing the pipe will do that.

I'm not buying the flickability thing, either. I have a 9oz GYT-R FW on mine and my son's is stock. Neither of us can tell the difference in that regard. As a percentage change in the total rotating mass of the crank, the change is very small and the effect it has is subtle.

i put a yoshie slip on and it made noticable gain. the bottem end inital throttle response

is awsome. i also just put on a gytr fly wheel weight and did not notic as much dirrerence. i would go with the exhaust. i have an 09 yz 450.

lilbob,

Did your Yoshie slip on fit right up to you 09? I have been hearing that the stock header is too big and the slip on's wont work....did you have these issues or did you bolt it right up to your stock header?

I had a Yoshimura RS-2 full system on my '08 YZ450F and it made a huge difference- more power everywhere and quicker throttle response. It's a great pipe especially at that price.

I have 2 09 yz450's.

First we changed the pipe to a DrD big improvement but we wanted more snap off the bottom. We then installed an 06 cdi. Just about right. Very happy. I then I put an Edelbrock on my 450 and when I got it tuned, it has even more overall power than the one without one.

What is the bore size of the Edelbrock?

What is the bore size of the Edelbrock?

40 mm

Edited by Gunner354

Just curious. The YZ450 responds pretty well to bigger carbs, and some will use the 41mm FCR-MX from a CRF with good results. Ron Hamp bores them even larger, I believe.

One of the guys that I race with has an Edelbrock on an XR650R, and he says it never ran so good. Of course, that was a different carb to start with.

They can be a pain to tune sometimes, and I'm personally so much more familiar with the FCR that I just don't want to bother with them, but when you get them right, they do seem to work.

-full system pipe of choice

-stage 1 hot cams(intake and exhaust)

-+2 teeth on the rear sprocket

-high comp piston

.....now that would be a nice setup!!

Just curious. The YZ450 responds pretty well to bigger carbs, and some will use the 41mm FCR-MX from a CRF with good results. Ron Hamp bores them even larger, I believe.

One of the guys that I race with has an Edelbrock on an XR650R, and he says it never ran so good. Of course, that was a different carb to start with.

They can be a pain to tune sometimes, and I'm personally so much more familiar with the FCR that I just don't want to bother with them, but when you get them right, they do seem to work.

I have ran them and tuned them on many different bikes and quads. To be honest I was going to leave the stock carb on because the jetting on the other yz

runs well everywhere but my stock carb gave me major troubles while out in Mojave so Idecided to change it out with the Edelbrock I had laying around. It was somewhat more difficult to get just right compared to my wr and yfz quad. I now understand this carb very well. One thing I found was that the acc pump was pulling in fuel all the time and effecting the tuning of the needle. I also replaced stock needle with one size leaner and all is good.

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