Motorcycle Repair: rejetting, honda shadow spirit, stock air intake

Question
I have a 2003 Honda Shadow Spirit 750.  I recently put new slip on mufflers and tested it out for a few miles.  There was some slight popping on downshift and decceleration.  I checked my plugs and they seem to be getting a little white, but i'm not very mechanical.  Will it be obvious between the running too lean white or the just right brown color the plugs should be?  If I need to rejet the carb what is a good installation $$quote$$ from a mechanic?  I really don't want to get hosed on bringing it to a shop and paying out my rear.  Any info would be greatly appreciated.

thank you  

Answer
Hi Dennis,

Any changes to the stock air intake, carburetion, or exhaust requires some tuning to correct air-fuel mixtures. If one of the three components is altered or changed, the other componets need tuned, altered, or changed, too.

Q:  "...Will it be obvious between the running too lean white or the just right brown color the plugs should be?"

A:  The backfiring indicates the A/F mix is leaning out on deceleration. This is normal with such modifications and is reflected on the appearance of the plugs. The appearance of the plugs may or may not vary much. Learn more about reading plugs at "www.ngk.com" Click the " Plug 4-1-1" link and navigate the menus. Tuning should improve the backfiring, though may not eliminate it totally.

Tuning carbs is time consuming and usually requires removal of the carbs numerous times correcting the mixtures. Most shops avoid such work due to the time required to perform such work. It's test and tune work.

You can get the mix close scientifically (math) or by jet-kits, but additional tuning will still be necessary to dial the mix in. Per the Clean Air Act, tuning carbs is illegal other than minute pilot screw adjustments. Some shops will not perform such work.

Engineers designed the stock engine and components to work well under a variety of elements and conditions. They do a wonderful job.

We change the components with aftermarket parts and expect the same reliability and performance engineers have provided us. Often the case, we detune performance in trade of a cool sounding exhaust.

Respectfully,
Mark Shively