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Popping back through muffler on deceleration

1K views 30 replies 7 participants last post by  beestoys 
#1 ·
Hi guys , 07 xx with yoshi muff on her , k&n air filter . Looks like it’s got a tuner of some type under seat . Not sure when plugs changed they are a nice colour on electrode . Bike starts and runs nice but then sounds like it gets Rich and stumbles at idle , it rides fine but when throttled back starts popping back through muffler . Thinking of puttin new plugs and genuine filter in . What do you guys think ? . Any help appreciated 😊😊. Nick
 
#2 · (Edited)
Fresh gas? Some “pop” is normal. If you just bought it, install new NGK iridium’s anyway. Go back to OEM air filter. The OEM air filter is hard to find and very expensive but the hiflo is the go-to for perfect replacement! Consider losing the “tuner” as well if this doesn’t solve your problem…but I’m betting it will. I use K&N on many of my bikes…and other vehicles. They’re great…but makes most ‘birds sick…especially with the wrong “tune”…and older carbies just plain hate’em, especially when using non-OEM cans! Also, Run a good fuel-system cleaner through a full tank of fuel (like redline) as well. If it’s only “popping” under deceleration, it’s not the cct!



 
#8 · (Edited)
Yes, an 07 FI model. Should be in newer shape than my 05 with 130k kms, so probably not having age related issues yet....... I suspect the tuner is the problem. I have a 20yo K&N filter that followed me from my 02BB, so it has done 54k+130k kms and is still ok....but I have never changed the pipes.

A fuel injector cleaner treatment over 1, 2 or even 3 tanks might cure the issue as silt builds up on the intake valves (you can see it if looking down the intake manifolds).

The iridium plugs really do last 45k kms and ULP is very hard to read anyway. One issue with K&N type filters can be over oiling. This will cause rich running if the O2 sensor has been disabled.

It's bound to be a simple fix, but new plugs and a paper filter is money well spent. Do not pay for valve clearance checks until 100,000kms (ask me how I know ;) ) and all the chat about cam chain tensioners is history on late model BB's ( mine lasted to 114,000kms).

A possibility could be the FPR leaking, but it should cause bad idling and loss of power and the oil dipstick should smell of fuel. An easy check is to dislodge the vacuum hose from the FPR and see if it is wet. Unlikely, but it is 16yo.......

(y) Download the Honda workshop manual from the reference library on this forum.....it's very good to have for trouble shooting and testing.

Late thought...sounds like it has a 4-1 system? This could be an issue if not tuned in properly or if the O2 sensor is failing (if still there). That's probably why there is a piggy back tuner under the seat......so if all the simple stuff is good (battery, filter, plugs, FPR, hoses, throttle body synchro) then it might be the tuner that has quit.
 
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#12 ·
Did you happen to run a top fuel system cleaner through? Injectors might be a bit gummed-up! The redline is the best I've ever run (not snake oil, amazing shtuff if you can get it over there-chevron "Techron" is one of the better cleaners found on the shelf over here too), my bet is a good cleaning will rectify the throttle response. Keep us posted...

 
#24 ·
Ah then that's why it's sooting. They are tuned rich from the factory as a rule. It also explains the popping.
Just thought of something. Does have an 02 sensor bung in the pipe. It'll be back in the junction just before the Y split. Or just behind the rear brake Master cylinder and footpeg.
 
#26 ·
Ah the system is going to lean out per the factory AFR. That'll make it want to pop as well.
Have you tried doing a delete on the 02 sensor to see if it stops the popping.
With your setup that thing should be running lean. I suspect your driving stuff crazy with the 02 hooked up. The system is swinging the fuel table point all over.
Are you feeling a surging at around 135 klicks. While trying to hold a steady throttle?
 
#28 ·
Checking for codes will probably give you no results but it won't hurt.
You can buy a delete plug from Dynojet. Or you can bridge the heater circuit for the sensor with a 300 ohm resistor.
The system only looks for a heater voltage.
What your dealing with is a fueling issue. Pull the 02 sensor first and see if it settles down.
What was the tuner that was in there?
 
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