Loud ass pop after heavy acceleration or revving

Hello everyone. As you all know i have a 1981 KZ1000LTD that i have been happily riding for the summer. Still runs like a monster. Has tons of power(front end comes up no problem:D ). Anyway, i have found that sometimes when i drop down a gear and really give it the guns, after i let off the throttle or im in between gears with the clutch pulled in and off the throttle, There will be a big pop, almost a backfire, or there will be like a really sharp hissing noise for a split second. It only does it out of the pipes coming from cylinders 1 and 2. And also sometimes, after the bike is warmed up and im at a stop, when i take off it spits or coughs ones from the back side of the carbs from the air intake and almost kills the bike. But it rarely ever does that. Heres a video of the bike popping. I couldnt get it to pop like it does sometimes but this may give you guys an idea of whats going on.



That my Triumphant bastard of a bike:)


Enjoy and any help would be appreciated,
KT

If not already done, would assure valve clearances are within specs, and that ignition timing is spot on, including advancer function (not sticking or maybe needs clean and lube), using timing light.

Could also test rev with choke slightly applied to help determine whether enriching mixture might reduce popping on decel. Could also experiment by enrichening pilot circuit.

Side-located pilot air screws turn in to enrich.

Bottom-located pilot mixture screws turn out to enrich.

Good Fortune!

Anyone else notice Tim;'s face when he spun the tire on the way back to the camera.... :woohoo: :laugh:

As mentioned in the clip, didn't hear the loud pop but as described, needle running lean if popping on decelerations...

Outside of what Patton mentioned...
Carb sync and insure no leak in the manifolds as well...

When running, hold at 65mph... She stutter as if running out of gas, surging a little, erratic rpm hum?
Same scenario, let go of the throttle and let her snap back, pops?

If so on either of the two then running a tad lean, first try needle clip position for richer setting or change needle.

Are you experiencing this in hotter vs colder weather?

I noticed it looks like you live in an appartment complex area. Do you have a garage or covered shelter for it? If it's kept out in the rain or damp weather,the electrical system could have crusty connections,the wires/coils could be arcing out/crossfiring.How old are the plugs?While you are doing your winter rehab,take appart the harness and clean all the connectors and reassemble with a good quality di-electric grease and use a zip tie to hold the connector together.Use the di-e grease on the spark plug boots too,obviously.Pull off the headlight and check all those connectins too.

sounds like a loose header.

Headers go loose at the head all the time. that pop could be cold air getting to the hot exhaust as it comes out of the engine.

Let the bike cool and tighten up the header. Maybe replace the gaskets. It's a easy place to start and even if that's not it, it's good to tighten everything up anyway.

I LOVE this Kid

Tim,

Popping on deceleration is generally caused by a lean condition as was mentioned.

The single most common cause on those particular bikes is a vacuum line either not connected or leaking.

All vacuum ports are located on the carburetors on J motor Kawasaki's with carburetors.

You'll have a vacuum line going to the petcock from one of the vacuum ports on the carburetors.

If the pollution system is still on the bike and hooked up like the factory had it, you will have a vacuum line from 2 feed points leading to a T fitting. From there, a single line runs to the air cut valve above the valve cover.

The 2 feed points were #1 & #4 vacuum ports on those carburetors.

The vacuum line going to the petcock could be hooked to either #2 or #3 carburetor. Which ever one it's NOT hooked to will have a cap covering the vacuum port on the carb.

Those 4 vacuum ports on the carbs are where you would hook up guages to synchronize the carbs.

Most generally one of those vacuum lines is either disconnected or has a crack in the hose.

If the air cut valve isn't working, the bike will pop on deceleration.

Also, if you have missing gaskets or your gaskets are shot where the mufflers connect to the header pipes, that can also cause backfire on deceleration. Oliver is right on the money with his call

I notice your bike doesn't idle too bad so I don't think you have any disconnected vacuum lines but you might have a cracked one.

It did sound to me like the exhaust gaskets where the pipes connect to the mufflers were not in the best condition.

PS.... GET YOUR HELMET ON!!!

OMG!! when i took everything apart for the first (and halfassed) paint job, i found that the muffler from cylinders 1 and 2 was all wiggly. On muffler from cylinders 2 and 4, it was completely solid. More investigation showed that there was a HUGE crack in the weld that connects the muffler the the headers. There is no gasket there, just a weld. I think ill just fix it when i put it away for the summer and do all the work to it. New paint, Check valves, New header gaskets, check cylinder walls, oil ignition advancer, check timing, check all of the electrical and everything else. Honestly, i was planning on doing some work on the jetting, air intake, and exhaust anyway. I was going to straight pipe it and get pods. That left side
exhaust system is in good shape except for that weld. That same header/muffler pipe is crappy on my dad's bike. So ill swap that exhaust with him after the welding is done to seal up the crack. My right side pipe was ruined by battery acid before i got the bike. So ill have both the crappy exhaust systems. Im going to grind off the mufflers and wrap the pipes and maybe get some kewl looking exhaust tips for them:) And dont worry guys, i always where a helmet when i go on rides with my dad. Ill try and get in the habbit of wearing one when i go to check the mail and stuff too:) Thanks for all the ideas. im still going to check out that choke idea to richen things up. If the popping gets less bad, ill know that i might have to get the carbs tuned as well.

Once again THANK YOU GUYS!!!
KT

Also, my emissions control is completely gone. just a rubber hose going from one reedvalve to the other on top of the valve cover. No switch or anything. I just went out to my bike and started it. I put my hand under the exhaust. On both sides, theres a perfect hole right on the muffler. I checked my dad's bike and theres a perfect hole on both sides right on the same place. I think thats supposed to be there. I ran my hand around the pipe coming from cylinders one and two and discovered a full on leak just gushing out exhaust. That is not there on the other pipe. Also, i pulled the choke out ever so slightly, not even to half choke and ran it for a while. The popping went away completely at idle but it still pops when you rev it. Everything should be as it should after this winter. It just a slightly lean mixture and a bad exhaust leak. Thanks guys and stay tuned for my progress videos in the project forum when the snow starts to blow around:D

"PS.... GET YOUR HELMET ON!!! ".... :laugh:

And cut your damn hair as well boy.... :laugh: :laugh: :laugh:

Old Man Rock wrote:

"PS.... GET YOUR HELMET ON!!! ".... :laugh:

And cut your damn hair as well boy.... :laugh: :laugh: :laugh:

Daddy Rock has spoken

Tim,

Keep at it young man. You're doing excellent

Larry C

Man, I haven't spoken up in quite a while, but I'm just crackin up at you old farts that grew up in the seventies on these old bikes, tellin this young dude to get a hair cut. LOL! At least he pulls his pants up where they're supposed to be.