Popping After De-smog

[Bob D]

My bike acted like it was starving for fuel, so I took the tank off to check my OEM petcock to make sure nothing was clogged or obstructing the screen filter. I pulled the petcock from the tank and everything looked clean. I reinstalled it, filled it with a few gallons of gas to check the petcock operation. Turned to "on" position and no fuel came out. Then added vacuum to the port and fuel flowed so I'm pretty sure it's operating correctly.

Since I had the tank off, I decided to install the Redeye de-smog kit I bought a few years ago. I took my time and followed the directions in the kit and also watched the youtube video by posted by Samuel Clark several times while doing the de-smog.

However, now I'm getting some popping from exhaust that wasn't there before. I checked all the header nuts and they are tight. I took my time putting the airbox back in and all the tubes and bands around the intake manifold are in the right position and tight. I checked the tightness of the plugs that came with the Redeye kit that install on the bottom of the motor and they are tight. I checked the fuel line that connects to the petcock and it is not kinked. All the vacuum caps on the intake manifolds are fine.

What did is miss?

     

[Chrisj CMA]

It’s possible to introduce an exhaust leak when re installing the exhaust. While the engine is cold, start the engine. Have someone gently rev it while you feel around each header connection and see if you catch a breeze

[Bob D]

Okey doke...I'll giver a try. I also ordered some new exhaust gaskets just in case before Honda discontinues them!

[Mooskee]

There is a vacuum leak somewhere or an exhaust gasket leak. Did you put the lines back on the air box? You would have needed to plug the one for the PAIR valves. There is also the drool tube and the box behind the key switch. Those aren't as likely to cause backfiring. Recheck all the clamps. If you had the air box off, check that the tubes on the air horns aren't folded over. It is hard to tell because of the clamps.

Check the intake O-rings. Are they all installed. Are they sealing. You can use a starting fluid test to help find the leak.

[Avanti]

Make sure while trouble shooting an exhaust leak that you do not over tighten the exhaust studs, they will brake.

[Bob D]

All the lines are hooked up to the airbox and I triple checked to ensure the intake tubes were fully seated on the carbs and the clamps were tight. I didn't disturb the intake manifolds at all so I don't think the o rings were compomised. I'll post again after I install the new exhaust gaskets see if that was the cure. Thanks for the replies!

[rug_burn]

   If the popping is on deceleration, you probably have a leak in those small tubes going to the nipples on the intake tubes;  those caps also leak sometimes.

 Sounds like you didn't take off the airbox, or actually: the air filter box.  (I don't blame you)

  I don't know what year your bike is, but the o-rings between the head and the intake tubes get rock hard after about 20 years, and are relatively easy to replace.   If you use a non-metric .103 cross section (IIRC) o-ring, they seal better because they slightly overfill the o-ring space.

[Bob D]

My exhaust gaskets came in so I will replace them first to see if that cures the popping. What do you recommend to put on the copper gaskets to hold them in place in the head while I install the header?

[Chrisj CMA]

My exhaust gaskets came in so I will replace them first to see if that cures the popping. What do you recommend to put on the copper gaskets to hold them in place in the head while I install the header?

I just squeeze them a tiny bit so they aren’t perfectly round and then stuff them in and they hold themselves in. Just a tiny bit. Tiny

[mello dude]

My exhaust gaskets came in so I will replace them first to see if that cures the popping. What do you recommend to put on the copper gaskets to hold them in place in the head while I install the header?

Having done this job with new exhaust gaskets..
- I put a bit of grease on them to get them to stick in place...
- Torque down slowly... Ease up on each of the 6 nuts to get to a final....(each side)
- I ended up using a torque wrench to nail down 9 ft-lbs, going by mechanics feel wasnt gettting it.
- It takes several ride cool down and recheck cycles to stabilize the torque setting... compressing the exhaust gasket.....
- I had a nut come off during a ride.. pop pop...

I'm all ears if someone has suggestions..

[Bob D]

New exhaust gaskets installed, still a bit of popping. Do the carbs need to adjusted after a de-smog? Everything I've read said they don't. I didn't fool with the intake manifolds so I think the o-rings are good unless by way of coincidence I've got one failing now.

[98valk]

New exhaust gaskets installed, still a bit of popping. Do the carbs need to adjusted after a de-smog? Everything I've read said they don't. I didn't fool with the intake manifolds so I think the o-rings are good unless by way of coincidence I've got one failing now.

All IC engines pop on decel aka off throttle when the engine goes lean, a sealed EPA exhaust keeps then noise quiet.

u can have lean popping or rich popping, if your idle mixture screws are not adjusted correctly.

see example #2 and adjust the idle mixture screws so the end of the plug thread is peppered with carbon. due to today's unleaded gas the porcelain can't be read.
https://fboignition.com/articles/sparkplugreading

[Paladin528]

I gave a 1/4 turn out on the pilot screws and that solved the popping issue after a desmog.

[Bob D]

Thank you! A pilot screw adjustment is in the works....