The fellows on this site know more about  the S40 than Suzuki does.  Be patient.

The first thing you need to consider....is that this is a big single, and it is a very primitive one that was not designed to make HP.  You can make this engine run better - you will never make it fast.  Anyone that makes big HP and speeds claims has most likely never ridden a really fast bike.  I am going to use the term "power" in this discussion as the big single really makes torque...not so much HP.  HP is torque multiplied by rpm (work) - but in this engine you will not be able to increase the rpm so you will never be able to make big HP numbers.  With engine improvements and an aggressive launch you may be the first one across the intersection.....you will never be the first one to the end of the block!

There is nothing available for larger valves and a different cylinder head.

Cylinder head mods would be the removal of some of the donut in the exhaust port, and a smoothing out of the ports.  You can't do too much to the nasty bump in the exhaust port, as that is below the valve springs and will make the area weak if you take away too much material.  Most likely the cylinder head is the limiting factor to what you can do with this bike (and the long stroke).

The stock 94 mm (652cc) piston is low compression, the piston upgrades are generally around 10.5:1 compression - but we don't know for sure as the piston was really made for the DR650 and just happens to work in the Savage if you bore the cylinder.  The Wiseco is available in 95mm (666cc) and 96mm (680cc), and the 97mm (694cc) used to be available in the Wiseco - but now the Woessner piston is the only one available.  Although the Wiseco is more known - Woessner have a very good reputation and product.  The size of the piston to choose is a personal choice and open to debate.  A big part of the performance improvement comes from the increased compression - but you will have to start using Premium fuel.  When I built my engine I chose the 95mm, as most of the time I am cruising around at partial throttle and I really don't need the extra cc's sucking air and using fuel...if I ride really carefully I can get 62 mpg.  The 95mm is the smallest you can go, and with each bigger piston you are only gaining 2% in engine size.....so the difference in piston size is not really all that significant.  All 3 piston sizes will give you a significant bump in "torque" over the stock low compression piston.

There are 3 cam grinds available for this engine.  The Stage 1 cam is the mildest, the Stage 2 cam is the wildest, and the Stage 3 cam is a cross between the other and has the mild duration of the Stage 1 cam with the increased lift of the Stage 2 cam.  None of the grinds are aggressive race cams - you can look at Lancer's page for a better description of where the cam makes power.  Once again I chose the Stage 1 cam as I do a lot of cruising and making big POWER numbers are not as important to me as the ability to cruise around on my bike all day.  The increased lift of the Stage 2 and Stage 3 cams may promote a little more wear on the cam lobes, rockers and valve guides - but Oldfeller has been running a Stage 2 cam in his bike for years and hasn't worn anything out yet.  Make sure you use an oil with 1,200 to 1,400 ppm of ZDDP to protect the cam and rockers from wear.

The stock header is about 1-1/4" diameter and is a bit restrictive - but does work OK as long as you have a non-restrictive muffler. You should not install a header that is more than 1-1/2" diameter for best performance.  The DYNA muffler works great on a stock engine - but may be a bit too restrictive once you want to make more power.  You need to avoid any muffler that does not have some form of baffle (drag pipe), as those can cause jetting problems and flat spots in the power curve.

The stock carb can run OK with engine mods, as can the stock air cleaner box.  A switch to a Mikuni round slide VM carb is proven system, and the 34mm is most likely the best choice as the idle and low speed manners are better than the larger 36mm carb.  The carb is just a bit more responsive as it does not have the vacuum operated slide and reacts almost instantly to what your throttle hand does.  However you need to learn proper throttle control.....you can't just "whack" the throttle open when you accelerate and have to "roll" the throttle on.  Instantly opening the throttle slide can cause the vacuum in the carb to drop so much that the fuel will stop being pulled into the engine.  The VM carb also doesn't have the TEV valve, and if you let the slide drop completely back closed between shifts or while you are compression braking you will get lots of backfires out the muffler.  You need to keep the throttle open just a tiny bit between shifts and while you are slowing down to keep the engine from making a lot of noise.  You can make the bike really noisy or really quiet....it all depends on what you do with your right wrist.  (You just open the throttle enough to add some fuel flow and make the noise go away).

The stock air box and the drop in K&N works just fine.....the cone filters don't make the bike run any better.              

The stock clutch can handle these improvements - as long as the clutch has never been exposed to any oil with friction modifiers, and you don't apply full throttle while the engine oil is still cold and thick.  Installing stronger springs can cause the little metal piece inside the clutch housing that pushes on the clutch rod to break...it is made from some form of powdered metal and is not all that strong.

Having to run Premium fuel can be a curse not only because of the extra cost - but the rumors are that the Premium fuel sits in the tanks at the gas stations longer and can be old when you buy it.  I did a long term fuel test to see how fuel holds up, and the Premium was the first fuel to deteriorate and go through the phase separation where the ethanol settles out of the gasoline.  Also when you pull up to a pump that dispenses all 3 grades (mixer pump), the chances are that although you hit the switch for Premium - the hose will most likely be filled with Regular from the car that was in front of you....and you will be getting 1/2 gallon of Regular with your 1-1/2 gallon of Premium.

So...yes you can improve the engine pretty easily...as long as you are handy with a checkbook.  The engine will be much more responsive, able to pull higher gearing, and a bit faster.....but it will not be fast!  Mine is as fast as an 883 Sportster up to 80mph....beyond that is starts to run out of power - but I can get up over 100 given enough room.

I certainly want to wait and have Lancer comment....he is the pioneer in the Savage engine hop ups, and has most likely built the most aggressive Savage engine on the forum (REX).


One more thing I wanted to say....is that you need to have a really competent machinist do the cylinder bore.  The clearances and roundness and surface finish are really important.  A lot of shops don't bore cylinders regularly...and may not be all that good at it.

If the cylinder is bored with too much clearance you are basically starting out the a brand new worn out piston/cylinder.  The piston will rattle, you could burn oil and have low compression and a lot of piston blow by.

If the cylinder is bored too tight the piston and rings can seize in the bore when the engine is running.  This will ruin your day.....along with all the new piston/cylinder parts.

If the cylinder does not have a good cross hatch pattern, the rings may never seat properly and you can have lot of oil usage and blow by out the breather tube.

The silicone carbide treatment it a good product for long service life from the new piston and cylinder bore.

   

I chose the Savage,, low , light, enough power to get me outta trouble in traffic, not designed to carve corners like a race bike, but it Will run thru a curve grinding a peg. There's no point in having more power than the rider can Safely use. I did rejet, mod the exhaust, up to a Stage One cam, Then we were matched. If I had Lancers (I'm bad with names, might have who has done the most power mods wrong  ) bike I couldn't run it thru the Dragon as fast as he can, I'd bet. The question is, how good of a rider are you?
How fast can you run thru  a corner on a cruiser? You might find yourself very pleased with an economy rebuild, and get to riding sooner with more gas and tire money in the budget. I hope that before you decide on how it's going back together you consider Not going Full On .
I wanna say Serowbot has his cylinder treated, nitride? Sounds like a possibly intelligent thing to do...
Accurate machining is a big deal here..
Ditching weight equals immediate results.
Jacking the rear end up increases ground clearance and helps handling.
Being 60 and remembering NOT being 60,,,,
Do the compression check outlined above.
If it can be coaxed to run, if the rings have stuck, maybe, dumping diesel and Seafoam or any number of solvents in would help...


I sure hope you didn't pull the plug and let the crud that accumulates in the cavity it sits in fall in.. cuz That would mess with the compression..

In fact, This guy has a build I can only drool over. I would love to have something very similar

https://www.youtube.com/watch?v=U5Yd2BrlDDI

Tell us what You want , and someone will tell you what you hafta do to get it.
Read my posts, if I didn't have six second 0-60 times, it was real close..
And I never took the head off.

Iceman4193 wrote on 03/21/15 at 09:29:08:


No, the DYNA is fine for the stock engine, and the DYNA the muffler came from as they are not making much power.  The DYNA muffler does not have a lot of holes in the baffle and would restrict flow for a hopped up engine.

The EMGO muffler can work, and I can show you what to do to make it a lot less noisy.  The Supertrapp can work - but it is pretty loud as well and is expensive.  Some of the sport bike mufflers are very tempting to try and a little bit of welding could adapt them easily.