Is programmer needed if I only do the flapper mod?

I just bought a used stock 2008 wr250r. I've been reading on these forums for a while about the flapper mod. I plan on keeping the stock exhaust as it's quieter than the after market pipes. The flapper has me puzzled as I can't figure out why one would plug up the intake on a FI engine. It seams common sense to take it out but I don't want to screw up my bike by running it too lean. It sounds from other posts that the bike runs lean even in it's stock condition. Should I do the flapper mod if I plan on keeping the stock exhaust? Do I need to add a programmer along with this mod, assuming the flapper mod is a good idea?

Thanks in advance. The bike is amazing and I look forward to making it even better.

I'm sure some riders have eliminated the flapper without adding a programmer and swear they're as happy as a clam at high tide.

In my opinion, the bike needs a fuel programmer straight off the showroom floor for the very same reason the bike comes with a flapper:
EPA regulations basically cut power and throttle response.

Why would you plug-up the intake on any motorcycle?, not just FI ones.
The reason for the flapper is to pass another EPA regulation for intake noise.
Nobody from Yamaha Motor Corp. is telling us that, but that's my guess.

Is there any recommendation for what programmer works best for this bike?

Most go with the FMF Power Programmer.

What about this "CO" / diagnostic mode on the stock bike that apparently let's you add fuel to the mix. I'm just now researching this, so I don't know what I don't know.

The Co mode is awesome for the UK bikes cause they have an O2 sensor, unlike NA models. I've farted around with mine anyway, and it just smoothed out the throttle a tad. Nothing really major.

ive done teh flapper without the programmer.

i figure at my altitude the more air is not gonna cause a lean situation with just that, but thats just a random guess dont know for sure.


Programmer is deffinataly on the list, the long makes my checking account cringe, list.

I would say deffinataly take the AIS shit off, i am still amazed how much it smoothed things out without that one there!

I did the flapper mod, dremeled out the top and removed the bottom of snorkel, and removed the spark arrester screen and from the stock exhaust. After doing this I noticed a flat spot about mid throttle so I added a 3.3K resistor in series with the temp sensor. It seems to have fixed the flat spot. To be honest I’m not sure if it was worth it, I noticed an improvement in power, but not much.

The general cry from the masses says the wr250r/x comes from Yamaha running mildly lean. As you increase the ability of the bike to breath you increase the lean condition. Opening the front end, airbox and flapper mods, you get leaner. Then, if you open up the exhaust end you go even farther down that lean path.

So the masses say if you go too lean you risk damage to engine.

The wr250r/x platform has been around now for 4 model years heading into 5th year.
I’ve been a member of this forum, supermotojunkie, advrider, and Thumpertalk for a few years and never once have I seen a report from anyone about a blown or damaged engine from running in too lean conditions due to flapper, AIS, or exhaust modifications.

Does that mean it can’t or won’t happen to somebody? No.

But I think it’s safe to say Yamaha has built a very stable and bullet-proof engine. If you just do the flapper you’re probably not in danger of anything going horribly wrong. If you do the flapper and AIS you’re probably safe too.

I did that very same thing. Flapper and AIS mods with no programmer and stock exhaust.
I ran it that way for a few months without issues.

The exhaust side is probably the larger determining factor for “needing” the efi programmer. The stock unit is pretty restrictive.

It’s a call you have to make on your own.

I’d say you’re safe in doing the flapper mod and AIS removal with no programmer as long as you haven’t changed anything on the exhaust side of the engine.

Only one guy’s opinion though.