Correct Jets?

[emanuel_v19]

Ok,

I getting a bit frustrated by the fact that i cannot seem to find the culprit of my exhaust popping/backfiring. Honestly, i am confused on the definition of both after reading so many threads online!

Anyway, at first i assumed it was a vacuum leak. Sprayed some Wd-40/carb cleaner and noticed significant change in RPM after i sprayed the fluid into the intake boots. Bought new intake boots, replaced and that fixed the problem. So i am happy about that. But now, its still making the same noise through the exhaust. I have not sprayed any fluid on or around the exhaust, if thats even reasonable to do, should i do this and see if there might be some leakage caused by the exhaust? Is that even possible? Im assuming maybe where they attach on the exhaust part of the engine...

Now, i took the carbs out, they looked clean but still cleaned them up a bit. I did notice something a little different on the main jet. It had a 132.5 rather than the stock 127.5. Every other jet was stock. My question is, can a rich setting cause this? Can the 132.5 cause this problem? Should i replace the 17.5 with a 20? or should i go back and install maybe a 130 instead? Ive read that both rich and lean mixtures are bad, so could it be possible the richness of the main jet is causing this? Adding to this, I am a bit perplexed after analyzing my spark plugs and seeing they are normal and no symptoms of running rich or lean are noticeable. Ill have to recheck them and compare more closely i guess.

Right now, i am thinking of buying new stock spark plugs and going with a 130 main jet and a 20 pilot. Play it a bit conservative.

I would like to mention that it has a stock air filter element.

Please help! Thank you

[smokestack]

At what throttle input is it popping? I'm not a carb expert but here's what I've gleaned in the past week. All rejet recommendations I've read say 20s for the pilots. If it's only popping at idle or below 1/4 input but the spark plugs look good under normal riding conditions, it seems like your mid-main and mains are good and the pilots are leaning the mixure at low inputs. I'd bet a dollar that replacing the pilots would fix it (but seriously, what do I know?)

Edit: here's a rough idea of when each of the jets kicks in: http://www.iwt.com.au/images/effects3.gif -- if you can figure out when it's popping, it should be easy to isolate the jet, assuming it's a jet. If you're already getting popping through the exhaust, then the headers are already hot enough to ignite starter fluid on contact

[smokestack]

Also probably better to isolate that popping issue before messing with the other jets because it seems like it's running perfectly otherwise.

[emanuel_v19]

It is popping about 1/4. Whenever I try and give it fast throttle, there is a lag built up. And whenever I throttle slow, it either starts popping or completely shuts off!

[emanuel_v19]

According to the diagram, the problem should be the pilot. As soon as I get at 1/4 or a little over that, it runs flawless. Its before the 1/4 throttle when the popping occurs.  Ill have to change the Pilot to a 20 for sure! Now, from your guys experience or knowledge, should I replace the main with a 130? or leave the 132? ahhhhh! Or maybe I can just buy the 130 since they aren't that expensive to begin with.

Ps- just wondering, I don't think I have ever seen anyone change the midrange. Should I mess with it?

Thank you!

[smokestack]

I'd think the mid-range would run richer, not leaner, after replacing the pilot since the pilot is always on. Seems like it's running fine as is.

[smokestack]

Do you have three jets or two? What year? If it's an earlier model, pre-2001 I think, you won't have a mid-main, just the pilot and main.

[emanuel_v19]

Ok hopefully once I change the pilot to a 20 it will run good.

Its a 2002 with 3 jets.

[emanuel_v19]

Update: Went with 20 pilots and 130 main and it runs great now! I will experiment with the 132.5 later to see the difference. For now ill enjoy it as it is! Thank you all.

It does have a tiny whole on the exhuast. Not sure if thats normal but ill post it here sometime. About bb gun size, perfect circle near the exhaust chrome protector..

[smokestack]

Awesome 

[lucas]

The stock exhaust has a small drain hole on the bottom to let water flow out