Kawasaki Concours Forum
The C10, aka Kawasaki Concours - The Original => The Bike - C10 => Topic started by: VodkaAndPickles on October 20, 2011, 09:44:46 AM
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I've been getting loud backfires out the right pipe on deceleration. Thoughts? Recently did valves, all is good. Carb settings?
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The old saying goes "check the last thing ya did" If you didn't have the backfire before the adjust than I would pull the cover a re-check them.
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A backfire in the pipe is usually a rich mixture encountering oxygen. So, like SNARF said, check those valves again and be sure you don't have a tight exhaust valve on cylinder 3 or 4. Other than that, a leak in the exhaust allowing air in might cause a backfire. Overly rich mixture, high float setting etc. will be the other end of the spectrum to look at.
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No, the backfire was there before I did the valves. One of the exhaust valves on I think 3 was tight, so I adjusted that. Still pops. Maybe it's the exhuast gasket? The rear tire was replaced a while ago so maybe the gasket got damaged at the dealer?
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No, the backfire was there before I did the valves. One of the exhaust valves on I think 3 was tight, so I adjusted that. Still pops. Maybe it's the exhuast gasket? The rear tire was replaced a while ago so maybe the gasket got damaged at the dealer?
OMG there is the problem. Gremlins run amuck at dealers. Who knows what you picked up while your bike was there. I would think if your exhaust gasket was bad you would be able to hear it going pffft...pffft...pffft...pffft...
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OMG there is the problem. Gremlins run amuck at dealers. Who knows what you picked up while your bike was there. I would think if your exhaust gasket was bad you would be able to hear it going pffft...pffft...pffft...pffft...
Yeah... It was just a tire change though...
Well I don't think I hear that sound so maybe it isn't the gasket. Maybe carb settings, which may well have been f*cked up by an imbecile of a mechanic I had the misfortune to entrust this bike to soon after I got it for a throttle cable replacement.
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Easy test, put a section of hose on your drain nipples. Open the drain and check your float height.
Dont forget to burp the air bubble out of the line.
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I've been getting loud backfires out the right pipe on deceleration. Thoughts? Recently did valves, all is good. Carb settings?
Is your air injection system working properly? It takes care of the unburnt fuel in the exhaust before the mufflers.
D.
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Is your air injection system working properly? It takes care of the unburnt fuel in the exhaust before the mufflers.
D.
Mine are blocked off, no backfiring here.
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I've been getting loud backfires out the right pipe on deceleration. Thoughts? Recently did valves, all is good. Carb settings?
I had the same start on my bike, worse when cooler weather hit. Found the rubber nipple I had on the #3 carb vacumn port had split and wasn't doing a thing. I also have all the emissions air valves removed.
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Is your air injection system working properly? It takes care of the unburnt fuel in the exhaust before the mufflers.
D.
It's blocked off.
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It's blocked off.
And there in lies the tributlations people will experience with jumping in with mods without considering the effects of multiple mods combined. the correctly functioning air injection system, coupled with an exhaust mod, will compensate. but when pieces are replaced without doing one part at a time, results like this occur. I have a feeling the only cure will be to begin leaning out the mixture a bit, and going the route of Bubba's 2 min mod now.
I would also add that the Aircut valves n carb 1 & 3 need to be looked at, likely those diaphragms are perforated and non functioning...and the pistons in there are hanging open likely allowing a more than required amount of fuel to flow during backoff of the throttle.
Couple this with a less restrictive exhaust, that has a larger volume of area for air and unburnt fuel to mix and pop off in...well, there is the equation.
Again, i will say that when the air injection and aircut valves are working correctly, backfiring does not occur...goes to show Big K actually knew what they were doing when they put the complete system into play.
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:popcorn: :popcorn:
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Someone please correct me if I'm wrong, but European GTR's didn't have the air injection system to start with? I know of many Euro C-10's running with non stock exhaust systems, mainly the Motad N-ETA, and no one's got problems with backfires.
So, in essence, with Snarf's (or similar) block off plates in place, you've effectivey got a Euro C-10 :-\.
How about checking for air leaks between the carbs and the engine block and just tighten the clips to be on the safe side?
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:popcorn: :popcorn:
Big difference between a backfire and a bike that burbles or growls loudly on cutting the throttle which is what you will often get when a bike is set up with block-off plates, free flowing exhaust and a rich fuel fixture. Which is exactly how my bike is set up. Backfiring can be caused by many variables several of which includes an overly lean mixture, exhaust leaks, valve seat issues just to name a few.
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:popcorn: :popcorn: Bubba.....Where's Bubba...?... 8) :popcorn:
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Someone please correct me if I'm wrong, but European GTR's didn't have the air injection system to start with? I know of many Euro C-10's running with non stock exhaust systems, mainly the Motad N-ETA, and no one's got problems with backfires.
So, in essence, with Snarf's (or similar) block off plates in place, you've effectivey got a Euro C-10 :-\.
How about checking for air leaks between the carbs and the engine block and just tighten the clips to be on the safe side?
I for one sure am glad that somebody brought up the GTR model bike. I was trying to figure out how to discuss this without sounding biased. I honestly do not think the plates or the exhaust cam gear are the problem. I have forgotten to tighten up my block-off plates before. The bike made a hell of a racket but still ran without issue.
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Lets deal with this fellow's USA bike, as I doubt he's riding GTR.....
1- GTR had restrictive carb tops that the spring projection moulded in did not allow as much slide opening as US models.
2-many Euro models actually had coolant pasages in the carbs to prevent freezeups.
3-euro models were jetted much leaner
4- I don't believe ALL years were delivered without the air injection
5-I DO believe they were all assembled WITH the air-cut valves on body 1&4
6-Euro bikes were all delivered producing reduced H.P. from the american counterparts.
with that said, we do not know at this time HOW he negated the air injection, and he MAY have a leak, which WOULD cause this problem. Leaky carb boots do not generally create this scenario as that leak is on the inlet side, and intake and exh valves working correctly negate this from occuring. Backfiring (not burble) occurs when a rich exhaust mixture is exposed to oxygen midway or futher from there before the end of the exhaust unless there is an exhaust valve hanging open or timing issue exist. A leaky exhaust pipe gasket is NOT generally a cause, as the pipe is pressurized at this point, and usually does not "suck in air".
The air cut valves still can be dumping excessive raw gas enrichening the mixture as they were intended, and this can cause the problem as they function only on decelleration mode of the carburation cycle.
We still do not know if the exhaust is stock, or the aftermarket has a non-conducive volume (sized accordingly for the actual flow).
I'm still awaiting Bubba's thought here.... :popcorn:
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Another big cause of back fire is no more complicated than a spark plug that is not firing 100 percent of the time. This could be from a loose connection, corroded wires, defective plug boot or even a defective spark plug. You've got to start with the basics and for me it starts with a sound engine; check compression and/or cylinder leak down and work outwards from there.
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Another big cause of back fire is no more complicated than a spark plug that is not firing 100 percent of the time. This could be from a loose connection, corroded wires, defective plug boot or even a defective spark plug.
good point, I fully agree, and plugs should be inspected closely for color and function. An intermittantly firing plug will exhibit the same outcome.
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:popcorn: :popcorn: Bubba.....Where's Bubba...?... 8) :popcorn:
Bubba was camping / fishing at the beach with the family for a couple days ;D
Actually, I expect the problem lies in the carb work; maybe there's a vacuum leak, maybe the pilot screws are turned to far in... I've personally not seen problem come from the blockoff plates or the sprocket unless incorrectly installed.My 36's don't have air cut valves on them and I get backfiring on high rpm hard throttle closes. If the decel valves are ripped the bike will get horrible mileage and show rich plugs. The more normal burbling on decel can usually be controlled by opening the pilot screws abit more. steve
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Lets deal with this fellow's USA bike, as I doubt he's riding GTR.....
1- GTR had restrictive carb tops that the spring projection moulded in did not allow as much slide opening as US models.
2-many Euro models actually had coolant pasages in the carbs to prevent freezeups.
3-euro models were jetted much leaner
4- I don't believe ALL years were delivered without the air injection
5-I DO believe they were all assembled WITH the air-cut valves on body 1&4
6-Euro bikes were all delivered producing reduced H.P. from the american counterparts.
with that said, we do not know at this time HOW he negated the air injection, and he MAY have a leak, which WOULD cause this problem. Leaky carb boots do not generally create this scenario as that leak is on the inlet side, and intake and exh valves working correctly negate this from occuring. Backfiring (not burble) occurs when a rich exhaust mixture is exposed to oxygen midway or futher from there before the end of the exhaust unless there is an exhaust valve hanging open or timing issue exist. A leaky exhaust pipe gasket is NOT generally a cause, as the pipe is pressurized at this point, and usually does not "suck in air".
The air cut valves still can be dumping excessive raw gas enrichening the mixture as they were intended, and this can cause the problem as they function only on decelleration mode of the carburation cycle.
We still do not know if the exhaust is stock, or the aftermarket has a non-conducive volume (sized accordingly for the actual flow).
I'm still awaiting Bubba's thought here.... :popcorn:
MOB I don't want to debate you, rather I am unclear as to what you are saying. The reed valves are pressurized also. The way I understand it; when they open under decel ngative air pressure sucks fresh air from the airbox. I don't understand how raw gas could be entering the exhaust from here. So unless he has gas in his airbox I don't see that happening. If he does have gas in his airbox I would be willing to bet that's his problem.You know a heck of a lot more about these bikes than I do, that's why I am asking for further explanation. If an overly rich combination of fuel and air are in the exhaust wouldn't it have to be coming from before the exhaust?
I do have one off topic question. My 86 has reed valves, my keys are stamped GTR. Was that just a first gen thing?
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My comment about raw fuel was directed towards the aircut valves on carb 1 & 4, not the reed valves...totally different animal. The aircut valves enrich a lean condition during decel.
My 86 keys were marked GTR also, and it was a Cali bike, I don't know if they all were marked like that. My 88 ones were marked Kawasaki.
to add to what steve related to, I'm also running 36mm Ninja carbs (without aircut valves) on COGZilla, with the reeds still in place, and a set of SuperTrapp Ninja mufflers (zero restriction, and loud), and that bike is just radically loud and obnoxious on decel, you can hear it coming for miles.....doesn't backfire, but it pops and growls a lot. ;D
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MOB, my bad; I misinterpreted 'aircut valves'. Yes very different animal. I was sorta surprised that you made those statements, now that we are on the same page; your comments make sense.
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yeah, "Aircut Valve" is, to me, a poorly chosen name. The valves don't cut air as far as i can determine; they actually blend more air into the pilot circuit. The diaphram is pulled by high vacuum to allow more air to the pilot circuitry. steve
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yeah, "Aircut Valve" is, to me, a poorly chosen name. The valves don't cut air as far as i can determine; they actually blend more air into the pilot circuit. The diaphram is pulled by high vacuum to allow more air to the pilot circuitry. steve
agreed, but the result of its "actuation" is adding fuel above that which is normally supplied with throttle shut down and slide dropped. ;)