2003 Savage. 6,500ft. elevation. HD Dyna exhaust, K&N cone filter, 52.5 pilot jet, 147.5 main jet. Trying to eliminate backfiring.

I changed the 145 main jet to the 147.5, installed, tuned idle screw. Still got the backfire.

I bought the 150 main jet, installed, tuned idle screw. Now it dies when I give it throttle. Help please....

When installing the 150 main jet, it never seems to fully tighten in, just keeps spinning. I also noticed that the jet can be pushed up into the carb, then it pushes itself back down, is it suppose to do this?

Thanks for any advise!!!

Kenny has it right....you have lost the washer.  The brass tube that holds the main jet is called the Needle Jet, and it has a notch that keeps it from rotating when fully inserted.  The washer under the main jet keeps the Needle jet from moving upward.

For your elevation, a 52.5 idle jet is likely too big.....and......you will never be able to jet your bike to eliminate backfiring.  You should jet your bike to run well.

Backfiring is caused when you close the throttle completely and the slide drops the needle completely down into the Needle jet....the fuel flow is closed off from everything except the idle circuit.  Making the Pilot Jet bigger can reduce some backfiring - but does that at the expense of fuel mileage and an engine that runs too rich.  A better way to cut down on the backfire is to use your throttle hand to eliminate the condition that causes the backfire.  Don't close the throttle completely as you shift gears, gently roll it off a little bit - but leave it open about 1/8th turn.  Same thing when you are decelerating....open the throttle just enough to reduce the noise - but not so much that the bike accelerates.  You can make the bike pretty civilized by just learning what to do with the throttle.....you have to be the "computer" and brains on this bike.....it is not fuel injected and a carb is very primitive in comparison.

He never said anything about a jet needle spacer mod, and how many turns is his idle screw open? that idle jet sounds way to big for 6500 feet.

I must lead a charmed life. My bike never backfires and only sometimes gives a little poof on shutdown, it doesn't do that if I give it few seconds to cool a bit.

All I did was adjust the idle and raise the needle .035" which is Mikuni's needle width. My elevation is 4000' and mostly warm. I do have the idle speed set fairly high to protect the cam but not over 1100 rpm, probably nearer 1000. Right now, in Summer, she starts without choke and is only a bit hesitant for the first half mile or so.

Norm I'm not surprised, at 4000 and above the air is thin enough that the stock jets won't be making your bike run lean .the closer to sea level you are the more you're likely to need larger jets.

Savageman wrote on 07/26/16 at 22:40:44:



Why are you selling your bike ?  Or is it a spare ?
If the jets in the JETSET are not adequate for you needs at altitude, then I can get other jets for that purpose.

Batman,
I'm one of the lucky ones. The EPA adjusted my carb for me. 4000' is probably about optimum for a lean sea level bike.

SO....LET'S GET THIS GUY IN THE BALL PARK! A 52.5 IS WAY TO LARGE FOR 6500FT GO BACKTO STOCK47.5 ? HOW MANY TURNS OPEN ?NO ANSWER! 1/2 ,IDLE JET TO BIG! 2 1/2 TO SMALL......NEEDLE JET 3 #4 WASHERS (WHY? HARLEY MUFFLER )   MAIN JET ...STOCK 145  (WITH BRASS WASHER )  NEW SPARK PLUG ,DRIVE IT! PULL PLUG BLACK ,SMALLER JET ,WHITE LARGER JET ,LIGHT TAN ,YOU GOT IT!   AIR CLEANER ? NO INFO ! STOCK ,MAY MAKE IT RUN RICH,NOT A GOOD MATCH FOR HARLEY MUFFLER ,REPLACE WITH K&N SLIDE IN OR OLDFELLER HOME MADE,(IN THE TECH SECTION) ANY DROP IN JET SIZE SHOULD BE MADE ONE STEP AT A TIME HE'S AT6500 FT BUT A RUN DOWN THE MTN. CAN BRING HIM TO 4200 FT(32mi to Salt Lake City)