exhaust popping while down shifting..

I am very happy to say that my 1981 KZ1000 runs excellent and has an ungodly amount of power :woohoo: My previous thread was about my clutch not engaging. This issue fixed itself. Thanks for informing me about how the clutch isn't necessary when upshifting.. my driving is way smoother now. Today, me and my dad did some brake work. We bled the brakes both calipers on the front have nice clean fluid in them and the back works great as well. This being a bigger and way heavier bike than my last, i down shift quite alot more than i used to have to. Today i went on my first real ride with this bike to go and get some gas. My last bike didn't have an air filter the first 3 months i owned it and it ran fine. I figured i would stay off of dusty or dirt roads to avoid sucking in junk as best as i could. When i shift into a lower gear and the Rpms suddenly rise and then start to slowly drop as i roll along, my exhaust makes popping noises like my GS300 did when i replaced the mufflers with straight pipes and they were wide open. Could this be due to not having an air filter installed? I want to make sure that im not over heating my engine. I don't want to burn a hole in any of the pistons after all the work i did trying to get it to run.. After the ride i took it on, it still ran fine and everything is still okay with it. Should i wait till i get an air filter before i go on another ride?

Thanks guys,
KT

yes get an air filter,if nothing else to keep the bad stuff out! :laugh:

The purpose of the air box on this bike is to prevent exactly this problem. install an air box and filter, connect the two vacuum lines to it from the carbs like the stock bike is,and it will stop doing it.

Popping during deceleration indicates a lean condition but might be well enough left alone.

Have you done a sparkplug check?(sometimes called a plug chop). Bring along the tools to pull the sparkplugs, and find a nice long road where you can get some speed(say 65), pull in the clutch while turning the run/stop switch to off.

Coast to the side of the road and let the engine cool for a while, then remove the sparkplugs, noting what color the center insulator is.

White is too lean,Black too rich, and light tan, about right.

In addition to what everyone else said, if your bike has the clean air injection system on the valve cover, and it's not functioning properly, it can cause large backfires through the exhaust.

im got just the place to do that plug chop thing. My dad's bike is gonna need that too.. For the clean air injection system, are you talking about the reed valves? its that hose on the two caps on the valve cover right? I know that there is supposed to be a switch there of some sort or a T connector that combines the two hoses the connect them to the airbox.. mine just has a hose that runs from one cap to the other.. I still have to adjust the mixture screws. I think my bike is running to lean. The carbs have a hard time catching up when you rev it. It only bogs at idle thankfully. While riding, its great. The only odd thing is the popping, which personally i think sounds cool.. is there a chance that i could burn a hole in one of the pistons if i do that plug chop test? I haven't gone over even 45 on the thing..., but ill fix that:D

Also, i have an airbox installed and set up like the stock bike, just no filter or that cover and snorkel..

loudhvx wrote:

In addition to what everyone else said, if your bike has the clean air injection system on the valve cover, and it's not functioning properly, it can cause large backfires through the exhaust.

BINGO!

That's the most likely problem. If you have the clean air valve still installed and not controlled by a properly connected vacuum line, it will pop like crazy on deceleration.

Block off plates are available at www.kzzone.com and at www.tpoparts.com They sell a kit with the plates, screws,vinyl plugs and instructions for kit # TPOHRSMOG

I am not sure exactly what carburetors you have, but my 650 has Mikuni BS32 CV carbs. I have recently learned by experimentation, that the bike runs terrible - I mean it may make only 10 horsepower while poping, stumbling, backfiring, etc. - All because I had removed the round top cover to the air box. This is the piece that screws onto the top of the air box and holds the filter in position. It has the "snorkel" that sticks down inside the filter.

Apparently the carbs need the slight restriction to run well. I replaced the cover / snorkel piece, and the bike runs great. I recommend getting one.

Sounds like you have the air injection disabled with a hose connecting one side to the other. That should work fine, but make sure there are no leaks, and the ports that originally had vac hoses to the air system should be capped off.