Sputtering and backfiring after desmog

[Mo_Corley]

Just finished getting the tank back on and did a test fire.  Had to turn the idle up a bit and my '97 valk is sputtering and backfiring.  Does it worse when applying throttle.  Would the bottom smog pieces cause that if they aren't sealed perfectly?  The gasket was a little chewed since it was factory.  I wasn't sure if the flow went in or out on those.

I made sure everything was tightened down.  Anyone have any ideas?

[Ricky-D]

Just finished getting the tank back on and did a test fire.  Had to turn the idle up a bit and my '97 valk is sputtering and backfiring.  Does it worse when applying throttle.  Would the bottom smog pieces cause that if they aren't sealed perfectly?  The gasket was a little chewed since it was factory.  I wasn't sure if the flow went in or out on those.

I made sure everything was tightened down.  Anyone have any ideas?

A de-smog will not cause any problems to occur as long as the job was done correctly, such as replacing the vacuum lines with stoppers at the intake risers.

All of the removed air lines terminate in the exhaust chamber on the downriver side of the exhaust valves and there will be no ill effect if a gasket is leaking when referencing motor behavior or running condition.

Sounds to me like you have some bad gasoline as long as it had been running ok prior to the de-smog.

Was there any other operations that you performed at that time you did the de-smog?

***

[Mo_Corley]

I capped the ports where the 2 vacuum lines were removed.  I didn't do anything else besides the desmog and my fuel should be good as its only a week old.  The bike ran fine before the desmog.  I did it hoping to get rid of my backfiring on deceleration.

The only thing I can think of is in one of the write-ups where they had to plug a tube that had 6 lines going into it from the carb bowls.  I have that on mine and didn't touch it.  But it said it should only be on CA bikes and I am pretty sure mine was not originally purchased there.

[indybobm]

I've looked at the desmog procedure. From what you are describing, you have done one of two things. You have either disrupted fuel flow or introduced a vacuum leak somewhere. The vacuum source for the fuel petcock is off of carb #6, I believe. Make sure it is connected at both ends and not kinked, or smashed anywhere. Make sure all of the spark plug wires are on correctly at both the plug and the coil and are going to the correct plug. I would bet on a vacuum leak.

[Mo_Corley]

Vacuum line to the petcock was replaced while I had the tank off and has no kinks that I can see.  I didn't touch the other 3 vacuum caps.  Maybe if the airbox tubes are not seated correctly on the intakes?  I thought I got them all on there good.

[Chiefy]

Did you remove the intakes?  And if so, you DID replace the O rings, right?

[Black Dog]

The Air Box can be a bitch...  Flashlight in hand, do your best to look up and under the carbs to be sure you have the Air Box tubes seated properly.  Also, as mentioned, be sure yer intake O-Rings are good, and seated properly.  Also, check that the vacuum caps on the other 5 carbs (as mentioned, carb 6 is fuel vacuum) didn't blow off.

If it ran right, before the job, it sounds like you have a vacuum leak.

Good Luck

[Mo_Corley]

Did not remove the intakes and the o-rings were replaced about a month ago. When I get home I'll replace the stock caps with the leftover new ones in the pack.  Maybe I bumped one good when capping off 3 or 4. And I'll double check the petcock line.  If that doesn't work, I'll check the airbox tubes at the carbs.

[Chiefy]

Well, keep it simple.  As you've mentioned, recheck all the vacuum connections.  See if the vent hose from the rear of the gas tank is pinched.  Some may say that doesn't matter, but it's not supposed to be pinched, and it's easy enough to check.   You don't have something like an external fuel filter that you may have reinstalled backwards?

[tank_post142]

try plugging the 6 line manifold. I remember reading some people experienced problems some did not with this left open.

[Patrick]

Did you use Normand's [Quexpress] desmog article in shop talk ?? If not, thats the one to use.. Something is wrong, it certainly shouldn't run like you describe..

[salty1]

Did I miss this? Have you rebuilt the petcock? 

[Warlock]

Just finished getting the tank back on and did a test fire.  Had to turn the idle up a bit and my '97 valk is sputtering and backfiring.  Does it worse when applying throttle.  Would the bottom smog pieces cause that if they aren't sealed perfectly?  The gasket was a little chewed since it was factory.  I wasn't sure if the flow went in or out on those.

I made sure everything was tightened down.  Anyone have any ideas?

Be willing to bet you have a air box tube not on correctly. Very easy to do. The clamp will still fit on, but most times it will pinch on the inner side. Been there done it. Best way is to remove the clamps one at a time to check them. Sometimes easier to look from other side with a flashlight.
David

[Mo_Corley]

Well, got home and checked the airbox.  Number six wasn't on right so I coreected it getting excited thinking that was the problem.  No change after starting it.  Replaced the rest of the caps on the intakes (except for number 2, I dropped the damn thing in between the block and timing belt cover and it was my last one) and held my finger over the number 2 intake vacuum port, still no change.

Its an intermittent pop or spit and gets worse when raising from idle.  I am wishing I had just left it alone and dealt with the deceleration pop...

[Chiefy]

Well, keep it simple since you didn't have the problem before the desmog.  Someone here cracked the casing when the pounded in one of the freeze plugs.  But it seems a crack large enough to cause issues would be easy to see, still..........  

Any chance the spark plug cables got connected to the wrong plugs?  Any chance some bolt/screw wasn't tightened down?  Was an intake a little loose from when you replaced the O rings a few weeks ago, and you disturbed it doing the desmog?  Did you drop the exhaust manifold to get at one of the bottom tubes?  If so, did you put in new gaskets and properly tighten it?     Take a look at/replace the gasket(s) you said looked chewed up.

Keep plugging, you'll find it.

Added using edit:

Did you look at the vac line from # 6 to the petcock?  I know you replaced it, but did you look for kinks or splits at the nipples?  You did have a big hole left, (and you plugged it) in the bottom of the airbox when you desmogged, right?

[Warlock]

Well, got home and checked the airbox.  Number six wasn't on right so I coreected it getting excited thinking that was the problem.  No change after starting it.  Replaced the rest of the caps on the intakes (except for number 2, I dropped the damn thing in between the block and timing belt cover and it was my last one) and held my finger over the number 2 intake vacuum port, still no change.

Its an intermittent pop or spit and gets worse when raising from idle.  I am wishing I had just left it alone and dealt with the deceleration pop...

Have been de-smogging Valkyrie for several years. Have run across a couple that was way out of sank. Once I re-sanked them they ran fine. Have you done yours yet?
David

[Mo_Corley]

I did plug the airbox hole.  Didn't touch the carbs.  I didn't think I would have to mess with the carbs on this mod.

I did use 9/16 freeze plugs and put them in there pretty deep.  If they deformed too much, would that do it?  I will pull off the petcock line and mess with it tonight after work.

[tank_post142]

freeze plugs just block off open exhaust ports. if one leaked or popped out you would just be loud.

[Mo_Corley]

Good.  Well, if the petcock line doesn't do it I have no idea.  I double-checked the one coil I removed on the left side under the tank so I could ratchet down the airbox.  I compared it to the others and it looks like I put the wires back right.  I didn't disconnect the plug wires from it.

Should I order new gaskets and blockoff plates for the underside of the block?  I just kept the factory gasket on, cut and pinched off the metal tube, filled it, and put it on the next day.

Do you normally have to mess with the carbs after doing this mod?  I really wouldn't have done it if so.

[Ricky-D]

"Do you normally have to mess with the carbs after doing this mod?  I really wouldn't have done it if so."

No, what you did should not have had any affect on how the motor runs.

The problem lays elsewhere.

A carburetor synchronization would be one positive thing to do in trying to solve the problem.

***

[salty1]

After a desmog your bound to change air-fuel dynamics. I desmoged mine and it took a "synch" job before she ran wonderful again.    I was also fighting a decel pop and the desmog effort helped significantly. Another half turn on the pilots srews (3 turns out) pretty much got the rest of the decel pop. Hang in there man!

[Chillerman]

I capped the ports where the 2 vacuum lines were removed.  I didn't do anything else besides the desmog and my fuel should be good as its only a week old.  The bike ran fine before the desmog.  I did it hoping to get rid of my backfiring on deceleration.

The only thing I can think of is in one of the write-ups where they had to plug a tube that had 6 lines going into it from the carb bowls.  I have that on mine and didn't touch it.  But it said it should only be on CA bikes and I am pretty sure mine was not originally purchased there.

Check under the frame near the rear of the bike to see if you have a black cannister. If you do it is a California bike and you have other steps to take for desmog. I have a CA bike and ran into a few issues during and after desmog.

[Mo_Corley]

I will check for that as soon as I get home.  I have been thinking about it all day and still am stumped. I am going to put the old vacuum line on and try that. I did the bolt with silicon adhesive on the airbox hole. There were two other tubes for the box that I am sure were supposed to go back on. Where exactly would the black box be?  Right behind the bottom of the engine block?

[Mo_Corley]

Put old vacuum line on and inspected every inch of the airbox tubes.  Checked the center airbox line and realized it goes into a T fitting with another line from behind the ignition and then goes into a capped off line.  I am guessing that it would otherwise connect to the CA canister if my bike had one.  Made sure the coil I had removed was bolted up tight.

Is it possible that doing the desmog made my bike run leaner and that is what is doing it?  I'll hold the rpms in between 2k and 3k and it spits every second or so.  Not a loud pop, but a spit.  It never did this before desmogging.  I don't want to have to take it somewhere to get the carbs synchronized because that would really put a strain on the bank account right now and I don't have the tools to do it myself.   

[ricoman]

Put old vacuum line on and inspected every inch of the airbox tubes.  Checked the center airbox line and realized it goes into a T fitting with another line from behind the ignition and then goes into a capped off line.  I am guessing that it would otherwise connect to the CA canister if my bike had one.  Made sure the coil I had removed was bolted up tight.

Is it possible that doing the desmog made my bike run leaner and that is what is doing it?  I'll hold the rpms in between 2k and 3k and it spits every second or so.  Not a loud pop, but a spit.  It never did this before desmogging.  I don't want to have to take it somewhere to get the carbs synchronized because that would really put a strain on the bank account right now and I don't have the tools to do it myself.   

the desmog by and of itself will not make the bike run leaner
the spitting is likely a slow jet minor clog, break out the seafoam or techron, add to gas and ride a while staying in the rpm range where the spitting occurs.
Next step would be to retrace every move you made through the desmog process (even if you have already done that). Something you did or did not do has brought out the problem. It is not/was not caused by removing the plumbing.

[Chiefy]

Put old vacuum line on and inspected every inch of the airbox tubes.  Checked the center airbox line and realized it goes into a T fitting with another line from behind the ignition and then goes into a capped off line.  I am guessing that it would otherwise connect to the CA canister if my bike had one.  Made sure the coil I had removed was bolted up tight.

Is it possible that doing the desmog made my bike run leaner and that is what is doing it?  I'll hold the rpms in between 2k and 3k and it spits every second or so.  Not a loud pop, but a spit.  It never did this before desmogging.  I don't want to have to take it somewhere to get the carbs synchronized because that would really put a strain on the bank account right now and I don't have the tools to do it myself.   

Where are you located?  Maybe if a member is nearby, and has time he can provide an extra set of eyes.

I can't see how a correctly done desmog would cause a lean situation.  Have you ridden it?  What does it do when you roll on/off hard?

[Mo_Corley]

I plan on taking it on a test drive here in a little bit to see how it acts under load.  I am located in southwest Missouri outside of Joplin.

If it still doesn't act right, I guess I will undo the airbox and start that over.  Maybe a tube got twisted funny or something.  I am glad to keep hearing that it isn't the desmog.  It is probably something little and stupid.

[Mo_Corley]

Well, some good news.  Driving around it acts fine until I let off the throttle.  Then I have decel popping again.  I think its about the same if not a little worse than before.  Everything is good when I yank the throttle.  Would it act like this if I have a clogged idle jet?  Maybe I got a little dirt in one of the carbs when messing with the airbox.  Wouldn't it run worse when accelerating if I had a leak somewhere?

I am thinking of driving it to work today unless anyone else sees a problem with running it.

[ricoman]

Well, some good news.  Driving around it acts fine until I let off the throttle.  Then I have decel popping again.  I think its about the same if not a little worse than before.  Everything is good when I yank the throttle.  Would it act like this if I have a clogged idle jet?  Maybe I got a little dirt in one of the carbs when messing with the airbox.  Wouldn't it run worse when accelerating if I had a leak somewhere?

I am thinking of driving it to work today unless anyone else sees a problem with running it.

Drive it-spend time between 2300 and 3000 rpm-that's where you'll notice a slow jet problem if you have one. Seafoam/techron won't hurt, try some.
Popping is likely an air leak. Re-check desmog caps and tighten intake tubes on both ends.
Ride it and smile.

[Mo_Corley]

So it could still be an airbox tube?  I am starting to hate that thing...   The only desmog part that could be leaking is the two underside ports.  If that could cause a pop, I could order some gaskets and maybe make some blockoff plates.  I reused the factory ones including the gaskets.  I am starting to wish I had kept the leftover sheetmetal from my Jeep's fender chop I did

But I am definitely feeling better about the whole thing.  I want to thank everyone for the help and confidence through this ordeal 

[ricoman]

So it could still be an airbox tube?  I am starting to hate that thing...   The only desmog part that could be leaking is the two underside ports.  If that could cause a pop, I could order some gaskets and maybe make some blockoff plates.  I reused the factory ones including the gaskets.  I am starting to wish I had kept the leftover sheetmetal from my Jeep's fender chop I did

But I am definitely feeling better about the whole thing.  I want to thank everyone for the help and confidence through this ordeal 

more likely a cap where you plugged after removing tubes, or a leak in the intake tubes. The leak will be a problem in the intake, not into the airbox.

[Ricky-D]

Well, some good news.  Driving around it acts fine until I let off the throttle.  Then I have decel popping again.  I think its about the same if not a little worse than before.  Everything is good when I yank the throttle.  Would it act like this if I have a clogged idle jet?  Maybe I got a little dirt in one of the carbs when messing with the airbox.  Wouldn't it run worse when accelerating if I had a leak somewhere?

I am thinking of driving it to work today unless anyone else sees a problem with running it.

What about the exhaust system?  Is it changed or modified?  This can cause popping.

***

[Mo_Corley]

Its got the cobra 6 into 6.  Haven't touched the exhaust since I bought it in June.

[hubcapsc]

So it could still be an airbox tube?  I am starting to hate that thing...   The only desmog part that could be leaking is the two underside ports.  If that could cause a pop, I could order some gaskets and maybe make some blockoff plates.  I reused the factory ones including the gaskets.  I am starting to wish I had kept the leftover sheetmetal from my Jeep's fender chop I did

I dremeled my desmogplates out of some aluminum from Lowes and made the
gasket with gasket material from NAPA...



-Mike

[Ricky-D]

Its got the cobra 6 into 6.  Haven't touched the exhaust since I bought it in June.

Seeing you have this (6/6), I would say that you will have some deceleration popping which is a characteristic of straight pipes.

Baffles will attenuate the popping to some degree.

***

[Chiefy]

Its got the cobra 6 into 6.  Haven't touched the exhaust since I bought it in June.

I have Two brothers 6 into 2 exhaust.  I get some put-put, or a very little popping when I roll off.  Certainly not backfiring.  It's not bad, so I don't feel like enriching 6 carbs to see if it's slightly lean.  It was there before my desmog, and it was unchanged by the desmog.  If you're still concerned about it,  and you have a video camera, record what it's doing and post it here.  We should be able to tell from what's going on if it's something to be concerned about.

[Mo_Corley]

Rode it to work today and it ran just fine. It's only when raising the throttle in neutral or decelerating that it pops.  I will try and make some blockoff plates on Saturday. Do I need to get an actual gasket or do you think a high-temp RTV would be ok?  Because if so, I will put a thin bead under the top caps.  After putting the freeze plugs in, I cut the tubing off the caps and shaved them down closer to the o-ring so it would look nicer. I just put them in so the holes are facing away from view.

[hubcapsc]

After putting the freeze plugs in, I cut the tubing off the caps and shaved them down closer to the o-ring so it would look nicer.

I cut the tubing off my top caps, filled them with epoxy, and put them back in with the holes facing to the back.

But no freeze plugs.

I used the "holder-downers" for the top caps that are already there. I had to bend one or more
of the "holder-downers" to get it to really hold the cap in tight and leak-free...

-Mike

[Ricky-D]

Rode it to work today and it ran just fine. It's only when raising the throttle in neutral or decelerating that it pops.  I will try and make some blockoff plates on Saturday. Do I need to get an actual gasket or do you think a high-temp RTV would be ok?  Because if so, I will put a thin bead under the top caps.  After putting the freeze plugs in, I cut the tubing off the caps and shaved them down closer to the o-ring so it would look nicer. I just put them in so the holes are facing away from view.

There was a recent thread that discussed this particular problem and the consensus was that it is a normal occurrence when the motor is free turning.

I feel you are worrying too much about the the plates, etc.  This stuff has no influence on how the motor runs, and you could actually leave the plates and freeze plugs (or whatever) off with no ill effects.

***

[tank_post142]

the plates and plugs are blocking exhaust ports. not fresh air ports.