[nogard]

I've been nervous to post this for quite awhile, but I talked with a mechanically inclined co worker today about the recent issue on my bike. Ever sense I put the Staggered pipes on my bike, in 2nd and sometimes 3rd gear the engine will cut almost all power for a breef instant. I'm talking before you can count to 1 second it's back and working great. It only happens if i'm in 2nd/3rd and reaching a bit higher in the tachometer. I really didn't change my shifting style with the new bike, and i'm not reaching the max RPM for that gear as I can give it more and it's fine. It only happens randomly, and the coworker stated that it's due to the pipes and I need a Tuner.

This makes sense to me, as most members on the forums do not run with the Staggereds, and they seem a big bigger than the Swepts. Does this seem correct to you guys/gals? The bike runs as smooth as can be in 1st, 4th, and 5th gear(and about 100% all gears ok if i cruise at normal speeds. Only happens when i'm giving it a bit prolonging a shift just a bit)

 

[jmules]

I have the exact same issue with mine, maybe not for 1 second, but there def is a hesitation in the upper RPM's when holding it. I'm assuming it's a tune issue and am not that overly concerned with it.

 

[nogard]

Fantastic!! I'd love to hear from anyone else having the same problem with these pipes. I think they are just a bigger pipe, so we actually probably do need a Tuner? I was never too concerned with it, but it's def a really quick cut out of no power.

 

[saclean]

Yes Nogard, it sounds like the exhaust gas's are now backing up pand allowing the O2 sencor enough feedback to adjust the injectors correctly. It is only a guess on my part, but when fule injection first came out on cars (back in the day) i ran a datsun (now thats old) with an open exhaust for two days and it did the same thing, when i connected the exhaust back up problem solved. I tore the exhaust off losing controll over a curve, my bad. 8)

 

[kcl-labrat]

no issue here but i have the cobra auto tuner and intake aswell

 

[johnboy]

It is a back pressure issue. If you were to pack your baffles with some muffler stuffing you will find the problem will disappear. A tuner will take care of the issue also.

 

[nogard]

It is a back pressure issue. If you were to pack your baffles with some muffler stuffing you will find the problem will disappear. A tuner will take care of the issue also.

Is the back pressure the cotton around the baffles? Not really sure what that is. It's not a huge concern, but I feel that more people should be aware that this happens with the Vance and Hines. It seems to not be happening with Cobras?

 

[SmokenJoe]

Start the bike and DON'T touch the throttle! Then put on your helmet or whatever to let it warm for a min. or two. Fuel injected motors need to sense the conditions so they can adjust. That was a problem I had on my VTX and Mech. said don't hit throttle after starting.
Might help here in this condition also.

 

[jmules]

Start the bike and DON'T touch the throttle! Then put on your helmet or whatever to let it warm for a min. or two. Fuel injected motors need to sense the conditions so they can adjust. That was a problem I had on my VTX and Mech. said don't hit throttle after starting.
Might help here in this condition also.

I'm going to try that out tonight and report back.

 

[johnboy]

It is a back pressure issue. If you were to pack your baffles with some muffler stuffing you will find the problem will disappear. A tuner will take care of the issue also.

Is the back pressure the cotton around the baffles? Not really sure what that is. It's not a huge concern, but I feel that more people should be aware that this happens with the Vance and Hines. It seems to not be happening with Cobras?

That is not cotton. It's a high temp fiberglass used in mufflers. That area is an expansion chamber. the place you have to plug up so to speak is further inboard where the exhaust comes through the holes in the smaller diameter pipe. You have to wrap those holes with a high temp ss stel wool or muffler packing to reduce the exhaust flow. This will reduce the two flat spots you have. The stock ECU's cnnot compensate for the new pipes. I did this until I got my fuel controller and it eliminated the flat spots.

 

[jmules]

So I tried that let the engine run without touching the throttle thing a few times. It seemed to work the first time, then never again. FYI.

 

[strykertony]

Idk know what it is. But i had the aame issue with cobra swepts. Everyone told me to get an intake and fuel programmer so i did. It still does it. 35 in 2nd gear is when it happens most often. Ive adjusted my shift timing but it still happens. Ive read alot on this issue but have found no exact reason as to why it does it.

 

[BillyD66]

Ahhh the dreaded flat-spot. I thought that was a thing of the past with carburetors only... Always had those on friends boats which made skiing that much harder.

Could be back pressure related and the OEM ECU is limited by our wonderful government so it probably can only correct for a much narrower band of variances verses the aftermarket stuff.

I also think you removed and re-installed the baffles and had some problems with the fiberglass stuff coming off during that etc. Maybe they are off by just enough to cause the ECU to hiccup sometimes.
As a stop gap measure you could try one of the minor AC mods and get a little more air in there but then again that could make it worse as well. Without a dyno session or a fuel controller you'd just be guessing. With winter coming sounds like a great spring project and now you know what to ask for at Xmas time ;D

A stutter isn't so bad as some of the guys on the Raider forum talk about their bikes dying for no reason and then starting right back up. Hate to have that issue...

 

[middleagecrisis]

It is an issue that even a tuner won't fix. Look up the "OFFICIAL Cobra powerpro" thread.

 

[sfcmcgan]

Hmmm... The stutter will occur between 13-16--rpm.... the tuner will not help this issue. I have the cobra autotune. I do not believe it is a backpressure issue, since it really on does it in 2nd gear. I think it may be an O2 issue... hasa anyone who has done the O2 mod had this issue?

 

[11Stryker]

Hmmm... The stutter will occur between 13-16--rpm.... the tuner will not help this issue. I have the cobra autotune. I do not believe it is a backpressure issue, since it really on does it in 2nd gear. I think it may be an O2 issue... hasa anyone who has done the O2 mod had this issue?

I did before I did the O2 mod. I had autotune also and Cobra Slip-on and Powerflo before I did the O2 mod. No problems now.

 

[sfcmcgan]

Hmmm... The stutter will occur between 13-16--rpm.... the tuner will not help this issue. I have the cobra autotune. I do not believe it is a backpressure issue, since it really on does it in 2nd gear. I think it may be an O2 issue... hasa anyone who has done the O2 mod had this issue?

I did before I did the O2 mod. I had autotune also and Cobra Slip-on and Powerflo before I did the O2 mod. No problems now.

Roger that... I might do the Mod this weekend....

 

[middleagecrisis]

I did the O2 mod but it didn't help. :-[