Bad Idle/Loss of Power w/o DB Killers?

So I have an 05 FZ6 and I got the carbon fiber Scorpion slip-ons installed. The bike sounds wicked mean with the decibel killer inserts removed but when riding I noticed that I may have lost some low end torque. Also the bike has an unstable idle with the dB killers removed, it bounces from 1100 all the way to about 1400rpm, sounding like it barely wants to stay running, almost sounds like a v-twin would, not smooth like a inline 4 should. It does this every time once the bike is hot at normal running temperature. But once I put the dB killers back in, the idle stabilizes almost right away and everything runs normal.

I've heard a hundred different opinions on whether or not to run the bike with the backpressure from the dB killers. Some people say it's bad for the engine while others say it does no harm at all. Does anybody actually know? I know other people run their bike all the time without the dB killers; does your bike have a weird idle like mine? Is their any way to correct the idle? Is it bad for the engine? Would a fuel controller like a Two Bros Juice Box make any difference? I just want to operate engine without dB killers safely so I won't damage anything. Thanks.

How long did you run it withoud dB killers? It takes a while for ECU to adjust to significant reduction in back-pressure.

One of the recommendations is to unplug the battery for 15 minutes to reset ECU.

You shouldn't have to get PC just to smooth out the idle. How long has it been since last TB sync? You may be overdue and putting new, much easier breathing exhaust on the bike may accentuate the symtoms.

^^ Agreed - either run it longer or disconnect the battery (pull fuse).

Are you by chance at a high elevation? I'm at ground zero (100 ft above sea level) and felt no real change on mine. RPM change you feel may be from running lean because it is breathing better.

07 and up should adapt with a ECM reset/battery disconnect.

I rode the bike everyday for about a month last summer without the dB inserts in, the idle seemed to be getting worse the more I rode it without them.

I did disconnect the battery but I just separated the negative terminal. Which fuse would you pull/where is it?

Elevation is pretty normal in Metro Detroit.

I bought the bike 2 years ago bone stock, I have no idea when the last throttle body sync was or if it ever has had one. Could that make that big of a difference? From normal idle to spudder-y?

Also since it's an 05 there is no O2 sensor for additional info to the ECU.

Is there the possibility the CAT has been removed? That might also be a factor because that eliminates a lot of back pressure.

That's right no oxygen sensor on mine.

No the stock cat is still there, I wanted to eliminate that too but it would probably make the problem worse.

mikeshungry said:

So I have an 05 FZ6 and I got the carbon fiber Scorpion slip-ons installed. The bike sounds wicked mean with the decibel killer inserts removed but when riding I noticed that I may have lost some low end torque. Also the bike has an unstable idle with the dB killers removed, it bounces from 1100 all the way to about 1400rpm, sounding like it barely wants to stay running, almost sounds like a v-twin would, not smooth like a inline 4 should. It does this every time once the bike is hot at normal running temperature. But once I put the dB killers back in, the idle stabilizes almost right away and everything runs normal.

I've heard a hundred different opinions on whether or not to run the bike with the backpressure from the dB killers. Some people say it's bad for the engine while others say it does no harm at all. Does anybody actually know? I know other people run their bike all the time without the dB killers; does your bike have a weird idle like mine? Is their any way to correct the idle? Is it bad for the engine? Would a fuel controller like a Two Bros Juice Box make any difference? I just want to operate engine without dB killers safely so I won't damage anything. Thanks.

Click to expand...

I'm trying to find the original link on the back pressure myth, but it's just that. A myth.

I rode with my two brothers exhaust with no PC3 for a week. I even and stupidly admit that I rode with no muffler and didn't notice a difference. Anyways I'm not sure that your baffles alone are the problem. Make if you do have a cat that isn't bad.

Regardless of fact or fiction it has a symptom of unsteady RPM.

I would begin with spark plug and wire inspection. Any vacuum leak on the intake side could cause this. If simply placing the DB killers back in corrects the issue, it sure makes it sound like its running too lean and its not TPS issue.

You could richen it with a CO adjustment, but I'd inspect the throttle body boots to the intake and make sure those are tight (4mm Allan Cap IIRC), also inspect all of the hoses connected to the TB for damage, leaks, punctures.

Closing the gap on the plugs can help and if the engine has some vibes across all RPMs I'd be looking closely at the plug wires... http://www.600riders.com/forum/fz6-...tion-cure-bad-vibrations-spark-plug-caps.html

Also, if the timing chain is noisy/loose, it coupled with a poor tune will make the revs vary at idle but should be steady under load.

My bike does the same thing if I take the db killers out of the pipes. If you unhook the battery as stated in another post it will reset the ecu.

How many miles on the bike? Valves checked if over 25,000 miles?


Since I put my Scorpions on (open initially-didn't come with DB killers) the bike ran fine, nice smoth idle (1,000 RPM, low on purpose).

Ordered and put DB killers in, way too quiet, didn't make it down the driveway. I do have the stock cats on, no added PC, stock CO settings.

Yanked the DB killers. I never re-set the computer specifically for an uneven idle. To date, it idles dead smooth, if there's 50 RPMs variance at idle, that's alot....

Besides checking the above, have you ever done a throttle sync? Yamaha allows 10mm's of variance, I have mine set no more than 3mm's off at idle and at 4,000 RPM's.

I strongy suggest doing it yourself or with the help of a friend. 10mm's vs 3 mm's in variance does indeed make a difference in performance and vibrations.. A Yamaha tech may stop once he hits 10mm's as it is inside of spec's. You can buy the tool much cheaper than paying them to do it once...

With such a large variance in idle, you may try running some Seafoam in the fuel. I run at least a little in every tank and can feel the difference, without using it.

BTW, it won't hurt the engine without the DB killers (as long as the rest if the bike is stock). An aftermarket air filter can, in conjunction with any other mods, can make a difference. I can document at least 12,000 miles W/O DB killers, no loss of low end, and she "sings" when you crank the throttle..

Good luck

THERE FIXED IT!!!! NO MENTION OF YOU HERE!!! Chill!


Mine, Joe's, xxxxx all are 07 up... His is not going to fix itself. Its too lean and an unsteady idle is less favorable on the CCT.

FinalImpact said:

Mine, Joe's, Scott all are 07 up... His is not going to fix itself. Its too lean and an unsteady idle is less favorable on the CCT.

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Who said it was going to" fix itself", because I mentioned "Seafoam"?

If there's some crap in th fuel system, the "Seafoam" can only help and certainly won't hurt anything..

If you read my entire post, I suggested several things to check, we still don't know the mileage (for /if it needs a valve check/adjusment, TB sync, etc)

I think we all agree that TB sync would be a good idea. I know my FZ1 started *hunting* at one point and would hesitate a bit off the line. TB sync made it smooth as glass again.

Erci said:

I think we all agree that TB sync would be a good idea. I know my FZ1 started *hunting* at one point and would hesitate a bit off the line. TB sync made it smooth as glass again.

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IME, I don't see this fixing it. It may mask it just off idle but if there is an actual loss of power, it indicates a greater issue that the engine running lean because it is breathing better AND needs more fuel across the whole RPM. If the owner also said they heard it detonate, this would further substantiate that this engine needs / wants more fuel!

Because the sync could/would result in reducing air to fuel ratio, it will only help at idle and off idle RPM. However, as the throttle opens it will go lean again. My point; in the tuning world, the engine is asking for more fuel. The sync option only gives it less air at idle/off-idle conditions. It does not fix the underlying issue.

In the ideal world one would connect a wide band sensor, OR an exhaust temperature sensor, OR a dyno + monitoring wideband 02 as means of getting actual information. These all come at cost.

So, if the butt dyno is accurate, its *very likely* going lean across a much larger area than just at idle. Idle issues can be a nuisance but they won't burn pistons or cause detonation. Thus, richening it now would likely be the best choice and then do a TB sync.

Now the question is; what option do you have to richen it or is it easier to just install the db killers?

There's a forum member in your area (sorry can't remember who or what part of southern Michigan) who's got a TB sync tool and offered for me to come borrow it sometime (I'm in the CLE area) if I'm in the area. If you decide to re-sync and don't feel like making your own tool, I know there's a friendly one in your area.

FinalImpact said:

IME, I don't see this fixing it. It may mask it just off idle but if there is an actual loss of power, it indicates a greater issue that the engine running lean because it is breathing better AND needs more fuel across the whole RPM. If the owner also said they heard it detonate, this would further substantiate that this engine needs / wants more fuel!

Because the sync could/would result in reducing air to fuel ratio, it will only help at idle and off idle RPM. However, as the throttle opens it will go lean again. My point; in the tuning world, the engine is asking for more fuel. The sync option only gives it less air at idle/off-idle conditions. It does not fix the underlying issue.

In the ideal world one would connect a wide band sensor, OR an exhaust temperature sensor, OR a dyno + monitoring wideband 02 as means of getting actual information. These all come at cost.

So, if the butt dyno is accurate, its *very likely* going lean across a much larger area than just at idle. Idle issues can be a nuisance but they won't burn pistons or cause detonation. Thus, richening it now would likely be the best choice and then do a TB sync.

Now the question is; what option do you have to richen it or is it easier to just install the db killers?

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A TB sync leans out the engine???? Are you friggin kidding me???

His issues are at idle, (see below note re CO settings)...

It evens up the vacuum being pulled by each cylinder so their all pulling the same amount of air and fuel (if there's no issues with the fuel stystem) and each cylinder is working the same. A TB sync has NOTHING to do causing it to run lean, PERIOD...


Have you inquired into checking the spark plugs for their condition???

He NEVER mentioned a loss of power, there was no mention of detonation, a whole lot of "IF's" in your post.

If the spark plugs looked lean at idle (and they may be), one option NOT presented is richening up the CO settings or at least checking them. That would easily richen up the bottom end, IF, it was indeed lean...

Leaving No options but to replace the DB killers is ludicrous..

Slow down and read... read it again. Simmer and think but not too much. Cause that aint what i said!

FinalImpact said:

Slow down and read... read it again. Simmer and think but not too much. Cause that aint what i said!

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That's EXACTLY what you posted..

Its HIGHLIGHTED IN bold :" reducing air to fuel ratio, it will only help at idle and off idle RPM. However, as the throttle opens it will go lean again"


:spank:

FinalImpact said:

THERE FIXED IT!!!! NO MENTION OF YOU HERE!!! Chill!


Mine, Joe's, xxxxx all are 07 up... His is not going to fix itself. Its too lean and an unsteady idle is less favorable on the CCT.

Click to expand...

You need to chill...

Check my below post, my name is already there, which You, as an administrator, (I don't believe) CANNOT CHANGE.

I do own an 07, and I don't have any issues with anyone mentioning that or my name.

Its false / incorrect information being distributed I have a problem with. Stating, a TB sync leans out an engine is flat wrong... :spank:

The issue could very well be a lean condition on the bottom end. Bumping the CO #'s up some, will RICHEN the mixture, especially on the bottom end and could, very likely, (if it is indeed lean) fix the problem..

**BTW, because you may disagree on how something should be addressed / fixed, it DOES NOT mean its wrong and IMO, should NOT be discounted... (IE, output sprocket shaft seal removal ((in a recent thread))-indeed worked, against your recommendation). I also posted, at your request, MORE than one instance of 73 ft lbs (which you insinuated didn't happen) torque on the rear sprocket hub is too high and strips the stud/hub, pretty much calling me on it. Once those three threads were posted, they were ignored, WTF??? If it doesn't meet what you say, just ignore it?? I'm still waiting for you to put 73 ft lbs on those studs, we need a good write up on Heli coils, thread inserts, etc.

That's fine..

I could go on, but there's no reason to, point made.
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Back to the original thread, hopefully with some input on actually fixing it..

(1) check spark plug condition
(2) check CO settings (there's numerous threads on getting to them on the US version bikes) and adjust if necessary.

Look, we can only diagnose what is stated in the OP. I don't know about y'all, but it's hard to fix something that is miles away with no video.

I want a video of the bike before and after the Db killers are removed because I feel that making it worse by removing a little bit of restriction isn't the real issue here. I'm no yamaha tech that's just my .02

Really banking off a little bit of info. Does your bike throw any codes? Does it pull foward while in neutral? But as suggested before check your plugs. Many a time have I had one idle like crap but runs fine can be a symptom of bad plugs requires no special tools to check.