Maybew I missed it, BUt Rowboat asked What is your Idle Like,,
& Stated, If its slow & lopey like, it'll cook yer cam,, & It will,, Gotta keep that idle up around 1,000..

You will not be able to eliminate backfiring until you get a bike with fuel injection......your Savage is going to backfire sometimes when you shift or go down a hill, or slow down.  The backfiring is a result of having a primitive carb on the big single.

I have a Fuel Ratio monitor temporarily on my motorcycle, and I can see when the engine is running rich, or correct, or lean.  When I am cruising along at a steady speed and roll off the throttle - the fuel flow to the engine is cut drastically and the engine goes waaaaay lean - so lean that the spark plug will not ignite the mixture that goes into the cylinder and unburned fuel goes into the exhaust pipe.  Then when I  open the throttle and the mixture again burns, the flame going out the header pipe ignites the unburned fuel in the exhaust system and "BANG".  Our carb has a TEV valve that is supposed to sense the large engine vacuum and allow additional fuel to flow through the carb - but it does not stop all the backfiring.

If you start to richen the carb mixture up to eliminate or reduce the backfire you might help things a bit - but if you richen too much the engine will not run well as it will be too rich when cruising or accelerating.

You can adjust your riding style to reduce the backfire by shifting between gears quickly - and do not completely close the throttle while shifting.  You don't have to shift as if you were in a drag race - just don't be lazy about it and hustle through the clutching and shifting so you can get the throttle open again before too much unburned fuel gets into the exhaust system.

 

Thanks for the analysis. I ride as you describe and don't get backfiring when I shift. With the 55 pilot jet, I get almost no backfiring when I roll off the throttle at a turn or when stopping, but now it stalls at idle when the engine is cold and even slightly choked. I can start and run without the choke with the idle mix screw almost all the way in, but I assume I'll have problems running too rich when it warms up here in the spring, and I'll have no room to lean it out. Maybe this is a problem that can't be solved, just worked around, as you suggest. It does seem like a 53.75 jet would put the idle mix screw right where I want it, though, and let me find a better compromise between cold engine idling and backfiring.

Dave wrote on 12/04/12 at 13:39:43:


Does raising the needle make the mixture richer throughout the entire throttle range? I vaguely remember doing something like that 35 years ago, on a Yamaha 2-stroke that was running hot but can't recall what throttle range it affected.

So, that could improve mid-range performance (say, accelerating to pass)?