Exhaust Question

I searched the forum but couldnt find exactly what i wanted to know so i figured i would ask it here. Does an aftermarket slipon exhaust for the wr have a negative effect on the low end torque? i was maybe considering getting one not doing the full mods (airbox, ais etc.) but before i got one i was wondering if it affected the bottom end because i dont want to lose that. also how are the hmf systems? i have read some on them and they seem good and they are cheaper than the fmf. thanks sam

The following is just my semi-educated opinion, so take it with a grain of salt:

I believe that if you were to just put on an aftermarket muffler with no other modifications, you may in fact lose some bottom end power with this bike. I say that because you'd be getting rid of the EXUP in the stock muffler, which is meant to produce more low-end grunt (or so they say). I have no numbers to prove this, but it makes some sense to me.

Now, when you open up the intake and then reprogram the fuel map, you get very noticeable gains across the RPM range. A fully opened up bike (intake and exhaust) has way more bottom end grunt than a stock bike, and I'd be willing to bet that it has more bottom end than a bike with just an aftermarket muffler.

The intake mods are free. Getting rid of the EXUP is almost free (with the resistor mod). Getting rid of the AIS is very cheap (block-off plate from Krabil). The only expensive part is the programmer.

If I were you, I'd first drop the money on the programmer and then do all the free mods. Then, when you have more cash, get the exhaust to really bring the WR to life.

I'll let you know wednesday. I did the AIS and airbox flapper mod and noticed more low-end torque.

Wednesday, a FMF fuel programmer comes in along with the FMF megabomb header, and PowerCore slip-on. I intend on taking it for a spin with just the header swapped, just the slip-on, then both and comparing the power.

very interesting... my ultimate plan is to get the 290 big bore kit from athena and use the programmer that comes with that because i dont want to mess with any aftermarket programmers. once i do that i may look at getting a pipe and doing the airbox mods. i just dont want to buy an fmf programmer or anything because it is just another thing that can go wrong, and it sounds like it is rather tough to get the numbers right. i appreciate the input though, it seems there are many different opinions on this topic.

I'll let you know on the HMF exhaust. I ordered the competition one last week so it should be in the next couple weeks.

sounds good yz.

A slip on on any engine will decrease bottom end. Period

What is that statement based on?

2goose wrote:

A slip on on any engine will decrease bottom end. Period

Does anyone have the new HMF Trimax exhaust yet?

Farmer17 wrote:

i just dont want to buy an fmf programmer or anything because it is just another thing that can go wrong, and it sounds like it is rather tough to get the numbers right. i appreciate the input though, it seems there are many different opinions on this topic.

After cruising this forum for over a year, supermotojunkie, and thumpertalk and advrider I've not heard many, if any, complaints about efi programmers going "wrong" or being that difficult to "get right".

Unless you are the kind of guy that has to fiddle with things endlessly most are units you can simply set once and forget.

As for low end - look at gearing. The stock wr250 gearing sucks ballz in my opinion.

If you think your stock wr250 has good low end grunt now you should really enjoy a simple gearing change.

2goose wrote:

A slip on on any engine will decrease bottom end. Period

Wanna know how I know you don't have any idea what you're talking about?

Farmer17 wrote:

i just dont want to buy an fmf programmer or anything because it is just another thing that can go wrong, and it sounds like it is rather tough to get the numbers right. i appreciate the input though, it seems there are many different opinions on this topic.

go wrong? so running a pipe without one and having a lean, ill-running bike is rite???

a programmer with the pre-programmed settings in conjunction with a pipe makes a world of difference. i love my bike after these mods... not so much b4

Because it's pretty clear he doesn't?

Krabill wrote:

2goose wrote:

A slip on on any engine will decrease bottom end. Period

Wanna know how I know you don't have any idea what you're talking about?

kjharn wrote:

I'll let you know wednesday. I did the AIS and airbox flapper mod and noticed more low-end torque.

Wednesday, a FMF fuel programmer comes in along with the FMF megabomb header, and PowerCore slip-on. I intend on taking it for a spin with just the header swapped, just the slip-on, then both and comparing the power.

Put the Power Commander and the Powercore on today, and have noticed more pull throughout the rpm range already. I can pull the front wheel up on accident now. Will take video tomorrow, then do a comparison after installing the Megabomb header. Should be interesting.

i wouldnt think the header would make that much difference would it?

According to FMF, the header increases HP by up to 3 hp. We'll see though. Header should be here Monday, will provide a follow-up on Tuesday.

Specifically, the Megabomb has a huge expansion chamber, increasing airflow. The theory behind it makes sense, and my friends that have the header swear by it, although on different (carbeurated) bikes.

Sorry - but there is no fvcking way the header alone adds 3 hp to a bike that comes in stock at around 27 or 28hp.

A more than 10% increase from header alone??? I think not.

I would love to be proven wrong though.

It'll take some before and after dyno runs to convince me.

motokid wrote:

Sorry - but there is no fvcking way the header alone adds 3 hp to a bike that comes in stock at around 27 or 28hp.

A more than 10% increase from header alone??? I think not.

I would love to be proven wrong though.

It'll take some before and after dyno runs to convince me.

Don't shoot the messenger.

Unfortunately I don't have a dyno at my disposal. For me I'll be judging it from how easy the front end pops up. Previously it was easiest to do it in second at 30 mph, now it has enough pull to do it at 23ish in second. No clutch. Primitive, but it works

Somebody ran it on a dyno a long time ago checking the changes of each mod and adding just the power bomb header at the end added an additional 1.5 hp if I remember right. Yeah, it's half of what FMF says it adds, but an additional 1.5 hp to a 27 hp bike ain't all that bad.

Krabill wrote:

Somebody ran it on a dyno a long time ago checking the changes of each mod and adding just the power bomb header at the end added an additional 1.5 hp if I remember right. Yeah, it's half of what FMF says it adds, but an additional 1.5 hp to a 27 hp bike ain't all that bad.

Has anyone done a dyno with the Megabomb? People say it adds even more than the Powerbomb, but I've never seen official numbers.

I carried the wireless leash (pager) this week (24 x 7), and I'm getting shift premium for working this weekend. Time to 'exhaust' that extra earned pay!

I'm going to get an FMF Q4 and Megabomb. fmfracing wants US$ 360 + 275
Anybody recently find a better deal?

Powerbomb- http://www.motorcycle-superstore.com/2/10/214/6492/24169/PITEM/FMF-PowerBomb-Stainless-Steel-Header-2009-Yamaha-WR250X-Parts.aspx
$179.99

Q4- http://www.motorcycle-superstore.com/2/10/214/6903/23616/PITEM/FMF-Q4-Slip-On-Exhaust-2008-Yamaha-WR250R-Parts.aspx
$323.99

Thanks kjharn! The price you listed for the header seemed really good, until I realized I had written Powerbomb instead of Megabomb which I want. I corrected my mistake.

Q4 = $309
Megabomb = $192
Power Programmer = $197


this is where I got mine, I believe they are the best deal out there.

http://www.oemcycle.com/Item/product/3024/PU/1821-0581/Yamaha_WR250F_07-10

Still, $247.99- http://www.motorcycle-superstore.com/2/10/214/28725/24169/PITEM/FMF-Megabomb-Stainless-Steel-Header-2009-Yamaha-WR250X-Parts.aspx

Anything for a fellow WR rider.