change in sound after exhaust backfire

a week ago i purchased a second xj (1983 seca police) to use while my other one is off the road to mod and build, was running great up until yesterday when i stalled it when stuck in a bad traffic jam (it happens to the best of us) wyen trying to start it back up it let off a very loud exhaust backfire from the r/h side tail pipe and then fired up and ive noticed my bike now sounds slightly different to how it was before the "big bang" my biggest concern is what this could be it still seems to be running fine just sounding different but as its the first time ive had to deal with this situation and given how sounds can easily indicate something isnt how it should be im not sure if its just the baffle going bad as a result of the exhaust backfire or if its something serious.

 

While it was trying and failing to start it likely put a large volume of unburned gasoline fumes into the exhaust. When it did finally fire, or when it got a good spark, it ignited those fumes and you got the big bang. The 40-ish exhaust baffles in these bikes are pretty rusty in the best of cases so that explosion in there likely opened up the baffles in the cannister under the middle of the bike. As long as the outside of it is intact it will be fine. I had a CX500 years ago that did something similar when it wanted new spark plugs. You might want to take a look at your plugs and consider new ones.

 

Oh yes. Welcome to the forum and congrats on your new to you XJ. Have fun, be safe and enjoy!

 

ill be testing the plugs today and replacing them if needed

 

Agree with Fuller 56 what you might try is to remove the muffler from the collector, and see is pieces fall out from the baffle. If so you might have to either find another muffler(s) or an aftermarket set.

 

thanks for the tip, will do this after i get off work today i have already done the old "screwdriver stethoscope" trick on the engine after checking the plugs were all good and there were no out of place noises in the engine itself. ive been thinking of changing out the exhausts anyway so if the baffle is busted it gives me an excuse to do it

 

upon inspection i discovered an old patch job on one of the openings wherebthe header pipesbconnect to the collector that is now leaking, looks like the exhaust backfire was enough to break apart whatever heat resistant material it had been "redneck repaired with". time to look for either a new collector box or an aftermarket exhaust system

 

Oh, that is going to be fun to find. Be aware not all collector/cross over units are the same. They are a bit model specific and are getting harder and harder to find in good condition. Between being exposed to the road debris off the front tire, being made from less than optimal materials, being cooked by exhaust heat every time out and being 40-ish years old most out there look a lot like yours. Good luck in your search.

 

You could try to find one at a breakers yard is one option . The other is a MAC exhaust system they are not cheap around 500 $ US not sure what shipping to NZ would be. I had this system on my Seca at one time was a nice set up . I sold it to a guy I did some work for his Maxim .

 

Can you get Marving exhaust in NZ?