Re-tune/flash necessary with full exhaust upgrade?

[Rebel73_imp]

I've got my eye on the Moriwaki black 4-2 exhaust. Does the bike need to be re-tuned?

I mean, I intend to do the Guhl flash anyway, but I want to do that AFTER so I don't have to flash all over again.

[Olyrider]

I installed the full Yosh system last week. Worried about the same thing. Bike actually runs much better! But I am still doing the re-flash. And before that, the K & N filter. And...since Guhl doesn't have any maps for a 2013 Standard with the mods I have made, I am having my PC V dyno-tuned to get more low-end grunt. Guhl is wonderful, but he can't map a bike that he doesn't have. He can, though, change the factory settings to the RPM settings Honda gave bikes in other countries.

[Inline4_imp]

You know, I was worried about the same issues as you. I recently upgraded from a Yoshimura RS3 slip-on canister to a full Nojima 4-into-1 exhaust.
The bike had no issues with the Yoshi performance-wise, BUT I found it ran a tad rich. I could stick my finger in the exhaust outlet on the Yoshi and there was always a little black soot there. No biggie but I knew it wasn't quite right.
Since I've added the full Nojima, the bike runs crisper and cleaner..........
I have about 700 miles since the change and no soot what so ever...
Even though the exhaust note is a bit more subtle with the Nojima, the bike absolutely SCREAMS when you push it to the mid/upper rpm range, especially under load.
I do want to get a PCV or whatever its called and perhaps a reflash if needed just to get optimum horsepower from the engine, but as she is right now, I couldn't be happier nor could I smile any wider when I run it hard through the gears.

[Rebel73_imp]

Thanks for your feedback, guys. Good to know.

[Yeahoo Whoyah_imp]

"BUT I found it ran a tad rich"
That's counter to what I'd expect, seems like it would run lean after installing aftermarket exhaust.

[Siggy Javotnik_imp]

"BUT I found it ran a tad rich"
That's counter to what I'd expect, seems like it would run lean after installing aftermarket exhaust.

I had the same thought -- freeing up the exhaust would be expected to lead to a possible lean condition. However, as a fellow Yosh pipe owner, I don't think the can makes a huge difference to the air-fuel ratio. I like the Yosh because it SOUNDS so sweet -- not obnoxious, but just...right.

[HikerToo_imp]

Maybe without the Cat, it allows more unburnt fuel through, therefore the illusion it is running richer......maybe just more un-burnt fuel makes it out?

[Siggy Javotnik_imp]

Maybe without the Cat, it allows more unburnt fuel through, therefore the illusion it is running richer......maybe just more un-burnt fuel makes it out?

Not a bad idea -- but the Yosh slip-on he had / I have leaves the cat intact. OTOH, if he in fact had a rich condition (which would have been unrelated to the Yosh can), removing the cat and installing a full aftermarket exhaust would lean things out a bit and could fix it. But...a stock CB1100 runs lean for emissions purposes. I used to have black carbon deposits on my exhaust if I had been taking short trips or short shifting on my '75 KE125 -- maybe that explains the carbon build-up on his Yosh?

[Inline4_imp]

No short trips or short-shifting here!
Yea, I've been baffled (sorry, bad pun ) by this too.
I have no idea why the CB seemed to be running rich with the canister. It just goes against natural thinking. Like I said, I had no issues with the Yoshi performance-wise, although I never put it on a dyno. Loved the sound, even more so than I do with the Nojima at least until I run it hard through the gears.

[Siggy Javotnik_imp]

No short trips or short-shifting here!
Yea, I've been baffled (sorry, bad pun ) by this too.
I have no idea why the CB seemed to be running rich with the canister. It just goes against natural thinking. Like I said, I had no issues with the Yoshi performance-wise, although I never put it on a dyno. Loved the sound, even more so than I do with the Nojima at least until I run it hard through the gears.

Ha!!!