Can I run exhaust without fuel/engine management?

I bought a graves full exhaust system, and wanted to run it right away.

Do i need to put a power commander or something to run the EFI properly?

Will the bike start and run?
Yes.
Will it run as well as it could?
No.

I've tried it both ways and throttle response is a lot better with a fuel programmer.

WR250X wrote:

I bought a graves full exhaust system, and wanted to run it right away.

Do i need to put a power commander or something to run the EFI properly?

It will run, probably with decreased low end performance, but it will be fine. Now, if you go messing with the intake, that's where you'll have to have a programmer to avoid damaging your engine. Increased airflow into the engine will lean out the mixture and therefore burn much hotter. This must be adjusted to avoid burning a hole in your piston!

Enjoy the Graves! I love mine!

Edit: Of course, once you open up the intake, in addition to avoiding an over-lean fuel/air mixture, you'll want to install a programmer to fully realize the potential of the mods you have done. I have a PC-V with autotune. Can't believe the improvement I've seen across the entire rev range. Do it!

graves full system, yes i would get a power commander. You'll be ok to fire it up and listen to it, but i wouldnt rec. riding it much.

The question should be....why would you want to?

Why spend almost $1000 on a full Graves system then NOT get some kind of programmer?

Have you done the free stuff to open up the intake side of things?

Weird!

I did the flapper mod, air injection mod and installed a FMF powercore 4 and the bike runs better than ever! It was a pretty cool day though, maybe it would be a different story on a hot day.

zone47 wrote:

Weird!

I did the flapper mod, air injection mod and installed a FMF powercore 4 and the bike runs better than ever! It was a pretty cool day though, maybe it would be a different story on a hot day.

Sure, it will run great until it grenades! Checked your plug lately? You should get a programmer before it's too late.

It's a fact. A too-lean condition is very bad for your engine.

Conventional wisdom, and just about every single post I've ever seen on the subject at multiple forums says if you open up both ends of the wr you are asking for a fucked up engine and big bucks to fix it.


It's not worth finding out on your own is it?

The bike supposedly comes lean from the factory to start. Not too lean, but lean.

By letting more air in, and allowing more to escape, you are risking pushing that too lean envelope.

It's you money, and your bike, but I would not run mine like that.

Dang dude. Why cuss at the guy?

What are you, a girl scout?

I didn't cuss at the dude. Thicker skin people....thicker skin.
You ride a motorcycle for cryin out loud.

There's women here. Show some respect bro!

motokid wrote:

What are you, a girl scout?

I didn't cuss at the dude. Thicker skin people....thicker skin.
You ride a motorcycle for cryin out loud.

thanks for the laugh . thats funny .. dont give wolfy any ideas though .. next thing you know we'll see some new pics

YZEtc wrote:

Will the bike start and run?
Yes.
Will it run as well as it could?
No.

motokid wrote:

The question should be....why would you want to?

Why spend almost $1000 on a full Graves system then NOT get some kind of programmer?

Werd. +1

Hey Motokid, How come everybody whats to give you shit ?

I give 'em an easy target. Lobbing some soft ones across the plate for 'em to hit out of the park.

If it makes their day, that's cool.

Glad to be of service.

You must ride your bike a lot to have your head on that good.

motokid wrote:

.....if you open up both ends of the wr you are asking for a fucked up engine and big bucks to fix it.

Not trying to pick a fight but I'd like to see some proof of this with a WR250R/X. Like someone who has actually damaged their motor buy not having a programmer.

No fight picked.

You'll notice I said it's basically all I've ever heard. I'm more than willing to let somebody else discover if it's really true or not.

motokid wrote:

Conventional wisdom, and just about every single post I've ever seen on the subject at multiple forums says if you open up both ends of the wr you are asking for a fucked up engine and big bucks to fix it.


It's not worth finding out on your own is it?

The bike supposedly comes lean from the factory to start. Not too lean, but lean.

By letting more air in, and allowing more to escape, you are risking pushing that too lean envelope.

It's your money, and your bike, but I would not run mine like that.

Hertz wrote:

motokid wrote:

.....if you open up both ends of the wr you are asking for a fucked up engine and big bucks to fix it.

Not trying to pick a fight but I'd like to see some proof of this with a WR250R/X. Like someone who has actually damaged their motor buy not having a programmer.

You don't have to wait until the engine takes a dump to find out if disaster is in your near future. Just remove the plug and check the color.

I have the unfortunate honor of having burned holes in three pistons in my life by running an engine to lean. No, I have never done it on a wr250x because I am now 71 years old and have shed some, but not all, of my insanity!

Just my opinion.. I highly doubt that you are going to hole a piston from doing a mod to the airbox and a pipe. Even if they come from the factory lean.. If this was the case you would not be able ride the bike in cold weather. This requires significantly more fuel than warm weather. An engine is just an air pump. You can run that throttle body in the open air if you like. It is only going to take in as much air as the cam spec is going to allow.
So what can a lean mixture do.. It will cause detonation. Horrible not really short term. no worse than struggling to push the bike in the wind at full throttle. I would not ride it long term or in the cold weather just from the detonation issue but it is again... my opinion.. the fuel injection system on the bike has a wider range than its given credit for.. My comments have nothing to do with performance. It will be bad for sure.

usgpru27 wrote:

Just my opinion.. I highly doubt that you are going to hole a piston from doing a mod to the airbox and a pipe. Even if they come from the factory lean.. If this was the case you would not be able ride the bike in cold weather. This requires significantly more fuel than warm weather. An engine is just an air pump. You can run that throttle body in the open air if you like. It is only going to take in as much air as the cam spec is going to allow.
So what can a lean mixture do.. It will cause detonation. Horrible not really short term. no worse than struggling to push the bike in the wind at full throttle. I would not ride it long term or in the cold weather just from the detonation issue but it is again... my opinion.. the fuel injection system on the bike has a wider range than its given credit for.. My comments have nothing to do with performance. It will be bad for sure.

Is it worth the risk of pushing things to the limit? Or possibly over the limit?

Just asking? Not condemning or accusing.

For sure its not a good practice.. I do however think its not some sort of time bomb.. I mainly run GP road race 125 and 250 2 strokes. Yes apples and oranges but the lean issue is the same for both. You spend all your time trying to figure out the absolute leanest jetting from pilot through the main jet system. Unlike a 4 stroke lean is fast on a 2 stroke. All engines detonate constantly it is to what level is the issue. To answer your question Yes its not really worth it but it will not blow up. One other advantage of FI is that its a very stable supply. Even tho its lean its a consistent and stable lean.. Carbs have a less precise delivery as its based on engine vacuum controlling fuel delivery not electronics.

So summary.. He can take it out and try out his new pipe and have put a smile on his face.. And get a programmer as soon as he can.

Its his call as to if its worth it or not..

One addition... BuilderBob.. Your advise is dead on.. but I would make the determination with a new plug to get a fresh reading and I would do it in a worse case in cool weather.

I think comparing a true GP 2 stroke, to a full production street legal 4 stroke, is beyond apples and oranges.
Maybe more like apples to pork tenderloin.

But I hear what you are saying.

I have seen a handful of threads where guys have dyno tuned their wr's....and I think the vast majority of them
always had to richen the mixture across all the rev ranges to get best performance.

I've never heard of anyone seizing a wr. So perhaps the "fear-mongering" around adding a EFI unit is a bit overblown.

I'd still rather err on the side of caution and not risk my bike to discover where the fine line stops, and where damage begins.