My bike is an 01 with 5600 miles,  aftermarket fishtail exhaust from PO, white spacer mod with two #4 washers.   As far as I know all jets are original.  

Idle mixture is set to 3 turns out, using Lancers directions - the idle never slowed as I turned it out so I stopped at three turns. I had the carb cleaned at the dealer in June soon after buying the bike. The petc*ck needs replaced, I was having stalling issues and smelled gas in the vacuum line. I am running it on PRI now, with the vacuum line closed off.

I have always had backfiring when shutting down, sharp drop in throttle and sometimes when shifting as a added throttle.  I have accepted this as signs it was too lean and planned to order a jet kit from Lancer when they are available again. the header pipe had blueing and some gold color to it.

Then Friday I took my first extended ride,  150 miles on the slab each way at 70 -80 mph.  as an aside, I need to look into a seat mod also  Yesterday morning I noticed that my exhaust had turned gold/brown, which I have read is a sign of running rich.

I am confused and not sure what to do.  Is running the bike on PRI a problem?  I have an ebay petc*ck to replace the current one, but I didn't think that would be a big deal if I waited till riding season is done.  I noticed mileage has dropped from 55-60 to 50 or so.  but when I do this, I would like to get the carb tuned correctly, but really don't know which way to go with it.
Any suggestions?

Running on prime is not a problem,...  gas feeds the carb by gravity, the same as on and reserve.  The vac line simply opens the passage to the carb, it doesn't draw the gas,....(until it starts leaking, like yours, at which time it draws gas to the wrong place).  Be sure you block that line at both the carb and the petcock.
Cruising at 70 - 80 mph will reduce your mileage.  At that speed you are past the pilot circuit and into the needle/main.  Cruising at 50 to 60mph makes a big difference.
Pipe discoloration is an indication of heat, not necessarily lean, cruising 70 -80 mph will make heat.  So will running lean, or overly rich, or at high altitude, or in stop and go traffic.  
A good indicator of overall jetting is the weather...if popping/backfiring increases on humid days, or at higher elevation, that indicates rich....less popping on those days indicates lean.
To test the main jet, accelerate from 30 or 40 mph, in 4th or 5th gear at full throttle for several seconds, then reduce throttle by about 1/8,...if power increases for a second, you are lean on the main jet.  Go up one jet size and test again.

Arh!,..arh!,...arh!,.......good one!

I'm running too fat.

Hey all.

I'm also confused with my bike.  I have Lancer's filter, replaced the main with a 150, and have a harley exhaust installed.  I also have I think 3 of Lancer's little washers in - looked like about half of the original spacer.

If I start with the idle screw all the way in, it sounds pretty good.  As I turn it out, about 1.5 turns the engine slows down.  This seems to tell me that I'm not too lean?  (Making it more rich doesn't sound as good?)

But I backfire on deceleration.  By turning the screw about maybe 1.25 out I got rid of shutdown backfire.  And my pipe is quickly bluing.

Huh?  Confused.

Thanks for any and all help!

Marek

Marek wrote on 09/29/08 at 12:19:20:


Longmont, CO,  that's up there,  mile high zone.    I can't remember if high altitude makes it leaner or richer.   If it makes it leaner than you  may want to go with a 152.5 main.  

For the Idle mixture,  You should get a pop on deceleration every once and a while.  If you make the idle mix too rich you will affect you MPG since it has influence thru about 1/4 throttle.  

T. M.

High altitude=thinner air=less oxygen=less fuel needed for the proper fuel air mix=need smaller main jet to lean the mix...more washers on needle to lean the mix...adjust pilot air adjusting screw (turn in) to lean &/or go to smaller pilot jet to lean the mix

The chrome exhaust pipe neither knows nor cares whether the mixture is rich or lean. All it knows is whether it gets hot. If it gets hot enough, it will start to discolor. The hotter it gets, the more it will discolor. The original Suzuki pipe is a double-wall pipe. Think of it as a pipe within a pipe. The inner (non-chromed) one carries the exhaust, and gets hot. The outer one is "insulated" by the space between them and cooled by the airflow, so it isn't supposed to discolor.

A incorrect air/fuel mixture burns more slowly in the cylinder. A rich mixture (too much fuel) doesn't burn all its fuel because there isn't enough air to complete the combustion. The extra fuel evaporates due to the heat, but doesn't burn. Its evaporation absorbs some heat, so the combustion temperature is lower.  Byproducts include unburned fuel, possible black smoke, sooty exhaust pipe, and sooty spark plug. A lean mixture (not enough fuel) doesn't burn all its air. There is no excess fuel to absorb heat. The slower burn causes the exhaust gas to be hotter (because the burn isn't as complete) when the exhaust valve opens. This hotter gas causes exhaust valve temperatures to rise, and makes for a hotter exhaust manifold (or pipe, on the Savage).

It is quite possible, even usual, for a carbureted engine to be very lean at idle and low speed, because that's where the EPA tests. That same engine may be "spot on" or even go rich at high power settings. So as odd as it sounds, it is possible for your bike to be both "too lean" and "too rich" depending on where in the throttle range it is running.

Awesome explanation Charon.  I've been wondering why lean = hotter engine.

I think I know enough now to attack.  Thanks guys!

M