I know this question has been answered a million times probably. I looked around the board and could't get a definite answer.

My Jardine is driving me nuts!! Constant backfiring, popping. The bike is only 3 months old and it sounds like a clunker. The dealer told me they don't make jets for the bike but I know some of you here have gotten it working. I'm not familiar with the white spacer mod and jetting. My dealer is good but my brother in law fixes race cars and bikes. I'm probably going to bring it to him so he can put the bike on a dyna after jetting.

I need to know the jets to get for the jardine muffler and if I have to do the white spacer mod. Or anything else.

Thanks so much everyone. If this continues though I'm going to slap on the stock muffler again.  :'(

Are you sure you have a good seal at the muff to header pipe junction ? Just changing to a different muffler should not do everything that you're describing, nor do I believe that jetting is going to cure it.

I have no experience w/ changing mufflers, but I sure have read enough about exhaust leaks causing all kind of backfiring problems.
And I've also read enough about hacking carbs for no reason, and to the point of not having the foggiest idea how to then fix it.

Added,....
I did the white spacer mod,.....only after having a specific reason for doing so, which was a very lean condition in the low to midrange...light load throttle position. And to verify the problem, I found it to run much better w/ the choke out one notch.
Happy to say the spacer mod fixed this problem perfectly. I have 2 friends, same bike, same year, who did not need this mod.

Agree about checking for the exhaust leaks first, they can cause havoc!!!

Next, any bike shop should carry jets for our Mikuni carbs. Having the correct ones in stock might be another story. Should only cost about $3-$6 each.

Here's the assortment of jets I purchased when rejetting my carb. Stock was 145/52.5 - I ended up using 147.5/55 with a cone filter and 36" Fishtail (only minor baffling, almost straight thru).

I just installed a jardine muffler and K&N filter on mine this week,I used a dyno-jet kit in my carb.I installed the muffler first and took it out for a ride around the block,it popped and after fired like crazy.the next day I got the air filter and carb kit.The carb kit really helped get the engine in tune to the new muffler,what I liked about the kit was the adjustable clip points on the needle which let's you adjust it without having to sand the white spacer down.what I didn't like was the lack of pilot jets in the kit.the bike is running great now with the new set up,throttle response is great and the engine just seems to have come alive,went from this quiet sewing machine sounding "excuse me" bike to a loud obnoxious "get the hell outta my way" raging beast.