Just bought a 2004 xb12s and it seems like a great bike but It has a pop and cough when letting of the throttle and a lag when you get on the throttle. The stock muffler has been cut and the pipes inside have been cut and it has been slobbered together! Hacked up really! I assume this is the cause of the rough running issues. Does any one have any ideas if this might be the problem or should i be looking for other issues? Thanks in advance!
It is just a lean cough in decel, or is it actually running rough? If just a cough and pop on decel, you can tune that out using ECMSpy if it bothers you, but most people just run it. That's what happens with cheap pipe hacks on our motors tho.
Thanks for the reply! Yes! It is just the lean pop on decell and a lag when pinning the throttle. Kind of like a carbed bike with a plugged pilot jet. Otherwise the bike runs great! Hopefully I can find a stock muffler that someone has laying around so I can try that. Hopefully that clears it up! Not sure what else it could be. Any other ideas? Thanks!
Why, why, why do people leap to saying "lean" for any engine problem?
It's not a condition you can really guess at. It requires, at the very least, a plug reading. There are other exhaust tests that can be done.
In the meantime, EFI and ECM, work to deliver a relatively close to correct ratio at every pulse.
And the piston melts in, oh, about 20 minutes.
The pop and cough are natural parts of the engine design. If you feel a kick with that, there may be another problem.
The lag is a separate issue, It could be your riding style getting used to a V-twin that wants to be revved higher than other Vs, it's a pretty narrow powerband. Or, your guess about the muffler could be correct.
Decel Popping on my XB I changed my plug gap from 038 to 036 and it helped quite a bit. Blipping the throttle is also not good and make sure the little end cap is on the little air pipe on the throttle body is still on that will cause a little vacum leak and clean the throttle body if you don't have a catch can installed.
Thanks to all! I'm not sure where the little air pipe is you are referring to but there was a little metal elbow pointing up on the right side of the throttle body, (if you are sitting on the bike). It had nothing on it. I plugged it and the decel pop is 90% gone. Still a little pop but nothing to get twisted about. There is still a lag in the throttle on accel. Once you get past it the bike pulls hard! If you are at higher rpm and pin it there isn't a lag. Where do I go next? Thanks again!
(Message edited by straight-shot on July 16, 2011)
Adding to Iamarchangel's wise thoughts, it *could* simply be the so-called "dead-zone" that you're feeling. Many people have mentioned the "dead-zone" somewhere in the 4-5k range. Then hit 5k and she starts pulling like a freakin' truck! I was one of those. It's due to the EPA constraints placed on the engine.
Want an easy fix (*if* this is the problem you're referring to)? Get yourself a race ECM. Among other things, it completely removed my dead-zone and she now pulls powerfully hard throughout the band.
Ok here is an update! Went riding today and the bike ran good most of the day. I was doing like archangel said and just avoiding the lag. Temps were in the upper 80s and low 90s. Quite a bit of stop and go riding and stopping for lunch so the bike got turned on and off quite a bit. Just getting ready to head towards home and bike died pulling into a parking lot. It would start back up but ran like it was running out of gas and then die. after a few tries wouldn't even stay running. Still had 3/4 tank. tried it a few times and didn't get any better. You could hear the fuel pump when you turned the key on but sounded weaker than normal. If I cycled the key without starting the bike the pump would sound stronger each time but when I started it it would run like it was running out of gas and die. Left it sit for 45 minutes waiting for the tow truck. When the tow truck got there the bike started right up and ran like it had earlier in the day! Got it home and still runs good! Is it possibly a fuel pump or possibly a vapor lock? What are my options now? Thanks!
Very likely a clogged filter on the intake for the fuel pump, or possibly the one just after the pump. Both are pretty cheap so if you decide to pull the pump you might as well change both of them. American Sport Bike probably has them in stock.
However you pump itself may be going since it starts functioning again after it sits for a while, not a real cheap fix unless you are going to match it to an after market racing replacement, I think Walbro was mentioned in one post, Siemens also makes pumps like this.
Bike is going to dealer this Saturday. I have done all the checking I can without a ecmspy. I did find cracked rubber on the rear plug wire. Backfiring back through the throttle body Found a fuel pump for $359.00! Yeah!!!! We'll see how it goes!