As recommended in the tech forum, I bought the Harley Dyna mufler, as well as Ryca adapter, and had it installed. I own a TIG welding machine, so instead of using crash gaskets, I just welded it on. Love the sound, its much deeper with a lot of off throttle popping - makes the little S40 sound like a much more serious bike.

Question is, do I really need to reject my carb? The bike seems to run great, and I really don't notice any change in performance. I think it might have started consuming more fuel, but I can't even tell for sure because I only have 320 miles on the bike so far, and I installed the exhaust just last week with around 220-250 miles.

I am pretty good with tools and somewhat mechanically inclined. I've worked on car engines before. Nothing too crazy, but I've done timing belt/water pump changes on several cars, along with other repairs, so I'm definitely capable. However, I have absolutely zero experience with carbs. I've only worked on fuel injected engines, and have no knowledge how exactly carbs work. Does the term reject imply replacing jets of the carb, or is it just the matter of fine tuning whats existing? In modern engines there are a bunch of sensors that monitor air fuel mixture and engine's performance, and you can hook up computer to monitor the data - but when adjusting the carb how do I know its running at optimal performance?

I know, I should probably RTFM.  

Depends on the year model of the bike.
Our EPA regs forced ever leaner jetting on the factory.
Odds are, your engine would be happier with a bit of tuning..

Kris01 wrote on 08/19/16 at 21:47:47:


Thank you for your help. I've just ordered the Jetsets from Lancer. I'm pretty confident I'll be able to replace the jets but how do I know what are the right jets to use for proper tune?

With your elevation - I believe the #50 or #52.5 pilot jet, a #150 main, and 3 washers is the best place to begin. (Stock air filter box, dyna muffler).

Here is an idea of how jetting should be done.

Brass Plug over idle fuel screw - remove it.

Pilot Jet - Start with this adjustment first....With the bike fully warmed up, adjust the idle fuel mixture screw to obtain the smoothest idle.  If you turn the screw in you will hear the engine slow down, as you turn it out you will hear the engine begin to run smoother/faster....and as you continue to turn it out you should be able to hear the engine begin to run a bit rough. (Do this adjustment with the idle speed set slower than normal, as it the adjustment just doesn't work if the engine idle speed is high, and put some kind of a block under the kickstand to keep the bike from leaning over too far on the side stand as the cam does not oil the right side properly when the bike is leaned over).  If you can turn the mixture screw all the way in and the bike keeps running smoothly - the pilot jet is too big.  If the idle mixture screw can be turned 3 turns out and the bike still runs smoothly - the pilot jet is too big.  The ideal pilot jet size is one that allows the smoothest running at 1.5 - 2 turns out.  (When you turn the screw in all the way to count - don't crank it in hard...just lightly touching).  Here are a couple videos that show you how to adjust the mixture screw....the Savage has a fuel screw and turning the screw in provides less fuel and a leaner mixture - turning the screw out provides more fuel and a richer mixture.

https://www.youtube.com/watch?v=YxpQjDQzX7g

https://www.youtube.com/watch?v=zm5mB3R8Ucw

Once you have that adjusted, you can turn your attention to the main jet.  Under full throttle acceleration the bike should pull hard and strong...and smoothly without any surging.  You want the smallest jet that provides strong acceleration.  It is best to find a nice long uphill section of road for these tests, and the steeper the better as it will help to keep you from going really fast.  With bike at about 50 mph in high gear, apply full throttle and the acceleration should be smooth and even.  When you slowly roll of the throttle pay attention to what the engine does - if it just briefly seems to run stronger as you close the throttle, that is a clue the jet may be too large.  Install one jet larger and see if the bike becomes smoother and pulls harder....if not, then install a size smaller and see what happens.  When putting in smaller jets you want to pay attention to the smoothness under full throttle acceleration.....if the bike starts to surge and run unevenly under full throttle - the engine is lean and a larger jet is needed.

Needle Spacer - The white spacer on the needle should be replaced with some #4 machine screw washers.  Most bike run well with 3 - some run better with just 2.  Install 3 and go for a ride, and as you accelerate slowly in each gear using only about 1/8th throttle....pay attention to the smoothness.  The engine should accelerate without any surging.  If you feel the bike accelerating unevenly, and that surging goes away when you add more throttle - remove one of the washers and try just 2.


Proper jetting requires about 5-6 different combinations to get right.  If you replace the screws on the float bowl with allen head screws, you can drop the bowl much easier and jet changes can be done in about 10 minutes.  (I am selling stainless allen head screw kits in the Marketplace for $ 16 .....or you can go to your hardware store and try to find them - they most often have the black oxide ones and they rust quickly).  

Just remember to start slow. Go 1 size up and see if performance improves. If not, go up 1 more size. I wouldn't jump up too far in 1 leap. Running too rich will actually wash oil off the cylinder walls.

If your bike doesn't surge while cruising then you may be jetted correctly already.