Sudden bog with near stall?

I have a 2008 WRX with all the usual modifications EXUP, AIS, Flapper mod, FMF PP, Yoshi RS2. I have a friend with the same bike just stock and we both have a similar problem. Without warning at many diffrent speeds and in many diffrent gears the bike will all of a sudden act as if it is running out of gas or even fouling a plug (much like a two stroke feels when fouling a plug). As the bike quickly bogs to a near stop I can give it throttle or not with no result, then as quickly as it started power returns (taken generally about five to ten seconds). At first I thought maybe when I was riding aggresively or riding wheelies the fuel pump sucked in air but then it happend to me when just on a lesure commute so now im stumped. The only thing I can add; although im not sure, it seems to do it right around a half tank. Also it only does it once every tank but it does happen every tank. Help?

Wow....so what are the odds?

You and a friend both have the same issue. An issue that happens to be very uncommon.

You are riding a highly modded bike, and your friend's is 100% bone stock.

Same exact problem though?

If your friend's bike is a 2008 I'd question if it's a fuel pump thing showing up in a weird fashion.

If you and your friend frequent the same gas station I'd be suspect of the gas you're getting. Are you using 91 or higher octane?


There's a electrical connection near/behind radiator that sometimes gets loose and causes bike to do strange things if its connecting and disconnecting at times, but what are the odds both of you have that issue show up at the same time?

How old are your batteries? Ever changed the spark plug?

Have you both done any mods to the kickstand switch?

Do you notice anything happening with electrical system when this happens? Is bike losing electrical power?

Anything you can think of that might be a common denominator between you and your buddy's bike and this problem?

Like using the same gas station and the same gas pump every time it happens?

Something is really odd here, and since your buddy has a 100% stock bike, as Yamaha shipped it, and he's having the same issue my first thought goes to you both have gotten bad gas from the same gas station.

Hopefully it's not a fuel pump problem.

On the modified bike... I'm going to say it's the FMF settings. What is it set at?

Arkmage wrote:

On the modified bike... I'm going to say it's the FMF settings. What is it set at?

But how does that explain the same issue with the stock bike?

if the stock bike was not in the picture I'd think the same thing too....but....

Same problem or not, I would diagnose the separately. There are a number of things that can cause this kind of problem and it may just be coincidence that the other bike is having the same symptoms.

What he describes is exactly like my experience with the FMF bug. Checking the setting is one thing that can be marked off the list that is a known and common issue.

My next stop would be to pull the plug and check for a broken insulator, oily insulator (leaking valve cover gasket can cause shorts between plug wire and cylinder head) , or a damaged plug wire.

I agree.... probably best to look at each bike separate.
Would be a very bizarre coincidence though.

Agreed.

The fact it will only do it once a fill-up is also a strange coincidence. That can't possibly be a legitimate symptom in my book.

Arkmage wrote:

Agreed.

The fact it will only do it once a fill-up is also a strange coincidence. That can't possibly be a legitimate symptom in my book.

Which leads me to think gas from same gas station...but even that is freaky if it only happens once per tank full.


Really like to hear more about what exactly is going on.

After riding my friends bike all morning I do not believe we share the same problems( I think he was just complaining about the stock gearing; since he has a hard time keeping the RPM's up). However mine still exist. I use 91 octane only; from many diffrent stations, and my settings for the FMF PP are GR 1, Yel 2, RD .5, GR-BL 1, YEL-BL 1, RD-BL 1
Thanks for all the suggestions, I'll be checking all those this morning.

click me <-- clicky

And me too <-- clicky

would it be bad form to say "i told ya so"?

:)

Arkmage wrote:

would it be bad form to say "i told ya so"?

:)

Nah....I shall grovel like a dog....

well i have a ais and the flapper still on, the baffle out of the pipe with the end cap on taller gearing and it bogs when i leave stop signs i thought it was cuz i put too tall of gearing on, could i be wrong?

Crazy M wrote:

well i have a ais and the flapper still on, the baffle out of the pipe with the end cap on taller gearing and it bogs when i leave stop signs i thought it was cuz i put too tall of gearing on, could i be wrong?

When you say "baffle" do you mean spark arrestor?

If I'm reading your signature right do you have 15/43 gearing on your X?

Are you sure you're getting a bog, and it's not just that you have geared it to be the weakest, limpest, tallest geared X I've ever heard of?


I did not think it was possible to get a 15 tooth front on an X.


Can you post some pictures of that? A good closeup of front sprocket and chain? You must be damn close to having the chain rubbing on the case. Scary close.


I'm guessing gearing is your problem.

(geared like that - riding your bike can't be any fun at all)

WRX17 wrote:

After riding my friends bike all morning I do not believe we share the same problems( I think he was just complaining about the stock gearing; since he has a hard time keeping the RPM's up). However mine still exist. I use 91 octane only; from many diffrent stations, and my settings for the FMF PP are GR 1, Yel 2, RD .5, GR-BL 1, YEL-BL 1, RD-BL 1
Thanks for all the suggestions, I'll be checking all those this morning.

Quote :

Hello,

The Yellow/Blue mode needs to be set to 7. The yellow is just turning on too soon for the light roll on and making the bike overly rich.



Thanks,

Matt Stoxen

Tech/R&D

Dobeck Performance

ya sorry that was my type-o its a 14, and the spark arrestor i removed, i like to put the biggest i can on the front so the chain has less chance of breaking. with that info changed does that help?

Crazy M wrote:

ya sorry that was my type-o its a 14, and the spark arrestor i removed, i like to put the biggest i can on the front so the chain has less chance of breaking. with that info changed does that help?

Your chain will not break with a 13 tooth or even 12 tooth sprocket on front.

well throwing on a 1 on the front is like thaking off 3 on the rear. its just a thing my dad likes doing to all our race bikes so i thought it would work on my X

Yes - but if you're at 14/42 (according to your signature lines) your gearing is outright shitty for any kind of fun street riding.

You want to add to the rear - not take it off the rear.

Might be great for long distance slabbing - but for sporting or hooliganism....it's awful.

motokid wrote:

- but for sporting or hooliganism....it's awful.

horses for courses

long distance slabbing at 55 mph maybe. My bike couldn't maintain pace with traffic with the stock gears... just didn't have enough power.

Now I can cruise at 80. The vibrations suck something fierce, but at least I can do it.

oh dame.....well i geuss im gonna have to throw a pipe on

On my last three rides I have had the bike do the same thing. Happened twice on long hill climbs, 2nd gear at just around half throttle. Just flatlined and lost all power for a couple seconds then right back to where it was. Once I was going along but in 4th gear at half throttle cruising on the road. This weekend I should have time to play with the programmer. I have enough hours on the bike now since all my mods to know what the changes feel like (if that makes sense) when I play with the FMF PP settings. 

For those with a bit more knowledge of these bikes.... Is it possible that there maybe a dead spot in the TP sensor if it seems to happen at the half throttle spot? Or is it just his programmer with a bad transition between two set parameters? Maybe too far apart as the cycle moves out of one and into another?