Well, I am sure there is no exhaust leak and that the carb is clean. I have an older carb lying around that I got on eBay to experiment with (and for spare parts in case I messed something up). I can take a look at that spring and see if I can modify it. Would cutting a coil or two off of it be the way to go, assuming that spring is the same as the one on my bike?

What's odd about the 55 jet on a stock bike?

I had gone out to 3 turns on the idle mix screw with the stock pilot jet and I was still getting a lot of backfiring. Now, with the 55 jet, the idle mix screw is about 1 1/4 turns out. Unfortunately, still backfiring. Tried the 55 jet when it turned out the TEV was fine. Going up on the jet was an attempt to increase the richness of the mix to stop the backfiring, since I couldn't go out any further on the idle mix screw and make any difference.

I'll try tinkering with it a bit more, but 1 1/4 turns seemed to give the best idle speed today (at about 45 degrees outside, sea level).

Have people here been successful at eliminating backfiring on this bike with stock air box and exhaust?

Controlling it, getting it down to what an engine like this is really gonna do,, solving air leaks, getting the jetting right, its no longer obnoxious,, now, it growls & snarls as I downshift,, but it no longer is an embarrassment, it doesnt sound like a gun at every shift,, & the spittin & snarlin as it slows can be controlled, I just dont, cuz I LIKe It

The Big One was gettin the header pipe snugged up in the jug, I Think,., I pretty much hadda richen it up, cuz I put the Supertrapp on, w/ 14 disks, but, I cant remember what jets I used.Adjusted the Idle Air mix & I sanded the spacer down a bit on the needle. K&N drop in air filter.,

Before I did all that I went riding with 3 others.. None of them appreciated my bike,, it was just an embarrassing bunch of noise,,KInda helped me wanna work on it..

You can add disks to the supertrapp to let it breathe better, but it will lean it out, so you need to rejet.

for stock jetting 6 to 8 disks are required.

after you fix the air leaks, and tune it properly, all you'll get is grumble pops on decel, much like a jake brake on a truck.

DavidOfMA wrote on 11/24/12 at 16:58:18:


What's odd is that a stock engine with stock exhaust just does not need need more than the 52.5 pilot.  I have a 2006 with stock engine and header with just a muffler change, and it is a pretty open muffler.  I have the 52.5 pilot set at 2 3/4 turns out and it is nearly backfire free.  I had no backfires at all initially but the exhaust has since loosened a bit from the quick install I did so I need to go back and tighten it up.  Point is that the 52.5 is just about all it needs.  It is borderline but it is darn close.  A stock engine with stock muffler will not move as much air and so will not need as much fuel.  Since your stocker is still backfiring then there is another issue that is affecting the engine and making it backfire.
Typically, an air leak in the head/header and/or the header/muffler connections is the other cause of backfiring.
You said you were adjusting the pilot screw to reduce the backfire.  That is a secondary but desirable effect of the tuning process.  When you are tuning the pilot screw your goal is to achieve the best (highest) rpm when the COMPLETELY WARMED UP engine is idling.  When you find that point, if you turn the screw either left or right the rpm will decrease.  Then you know you have found the best setting.  With that setting, adding no more than maybe a quarter turn for a dash of extra fuel to help that last little bit for any backfire left over.  At this point you should be at least 95% backfire free, with only a rare shot...if not totally free.
I would not expect a stock engine with stock exhaust to go beyond 2 turns out on a 52.5 pilot.
With your situation where you have a 55 pilot and still experiencing backfire, there is an air leak somewhere.  I would bet your exhaust is messing with you or perhaps there may be an air leak between carb, mounting flange & head as well.
 

affect it's function and mess with your jetting and tuning efforts.


Mess with being the mildest of terms applicable..yea, I totally forgot to include that part..A clean & properly functioning carb is just something I figure folks have, & I need to rethink that,, its just not always so..
I gotta get in mine & have a look at the jets, but I Think Im gonna do that after I do the Raptured petcock,my stocker is gonna go meet God, in the air,,