This sucks. I just bought my S40 six weeks ago and now I read about this problem. The backfire doesn't really bother me, it's kinda cool actually. But if it's damaging the engine, that's not good. I was actually trying to make it happen so that I could demonstate at the dealer. If I give it a quick rev while stopped and hit the kill switch...BOOM!

 

I recently converted a 2004 Savage into a Ryca cafe racer. The bike was extremely lean once the intake and exhaust were opened up. The bike backfired, misfired, and generally would not pull cleanly. I up sized the pilot and main jet which helped a little, but the performance just wasn't there. I installed the Dynojet jet kit in the bike. What a change, it really helped. The bike pulls cleanly from idle up to full RPM. The backfiring stopped and the exhaust note sounds much crisper. Well worth the money. I live at 2500 feet, I used the next to largest main jet and set the needle on the forth notch down.

 

Afterfire. Backfire in the mechanical sense is coughing out of the carburetor. Afterfire as you are talking about is coughing (or explosions or bangs) out of the muffler. This is not the fault of the manufacturer. It is because the Federal government (IE EPA) requires the manufacturer to set the engine up to be as lean as possible in the carburetor fuel/air mixture. The afterfire does not hurt the engine, but the over lean mixture does. There is a fix for it. It involves removal of the carburetor to change the jetting and move the slide needle. Then you either drill the muffler or change it out for another freer flowing muffler, and drill a couple of additional holes in your air box to increase airflow. Doing this fattens up the air/fuel mixture and eliminates the afterfire explosion. It also gives you even more power as well as letting the engine run significantly cooler (up to 50the degrees). Suzuki would do all of this themselves if they could. But the EPA sets the rules and the manufacturer's have to live by that. So if you want to yell (or send mail) at anyone over this issue then write or call your Senator's and Congressmen. Fill the EPA's mailboxes and telephone message centers. But make the changes, you'll have a cooler engine, more power and even better fuel mileage, without creating more emmisions for those that live in area's where you have to put your motorcycle through emissions testing.

 

I just bought an 08 s40 and im looking for a louder exhaust. any suggestions?

 

Inexpensive version that works very well for a stock engine is a Harley Dyna muffler.
Their stock muffler flows the exhaust well and sounds very good without being too loud.
A rejet/tune of the carb is needed and will yield smooth running and good power.
There are Dyna's all over; tons on ebay for as low as $20 each or even for a pair of them, + shp of course.
Check HD shops too, many buyers of Dyna's and Sportsters have the mufflers removed before they even take delivery and most HD dealers have piles of them in the back of the shop.

Want louder ? Best bet is a Supertrapp. They can be adjust for sound and power by adding or removing muffler discs, then jet/tune to suit the muffler.
Price direct from Supertrapp and other motocycle suppliers is about $250.
If you go to JEGS auto parts supply online you can usually find Supertrapps made to autos that will work for almost half the price. Yea, really ... it's called merchandizing.
Charge bikers more for the same product. Yep.

 

I just bought an S40 2006 450 miles. It has sat for min 3 years with gas in it. I swapped it for premium.

It attempts to start but just turns down and stops after a second. Going through troubleshooting steps I opened the rotor alternator cover and what seemed to be an oil/gas mixture came pouring out. After starting it with this cover open it ran until I increased throttle. Why would this be the only time I got it to run? It does not do that anymore. I added oil and hoped just emptying that would work. Why was all that in there? Is oil supposed to be in there to begin with?

Opened the carb and cleaned the floats and all superficial components. Do I need to open the carb up more and clean each individual part? What else may prevent this from maintaining idle? Seems to almost start better with less choke. I can't tell what else I know about it that would be helpful.

Please help, just got it on the road anticipating it running already!
Thanks!
Steve

 

Hello guys, I have a suzuki savage LS650 2000' with the 4 speed transmission, do you know if the 2005+ models transmission are compatible to mine? so i can put the 5th gear?? thanks!

 

ok so let me tell you what I got going on- I have an 1986 Savage. Totally stock as far as I can tell, other than I know the previous owner knocked out the baffle in the stock muffler. I currently have on order, a k&n type cone filter for the bike, I do plan on changing the exhaust to a super trapp that I already own or something like the HD Dyna muffler....but in the future. From the research I've already done, it seems I currently have a 155 main jet. The pilot is like a 47.5 or something and will need to be increased from what you and others have said. I do 99 percent of my driving on the freeway commuting to work at about 75mph. I already have plans on doing the chain conversion to change the final drive ratios. I'm looking for further direction on where to go with jetting this thing correctly. Everything I read on other blogs talk about 152.5 main jet and 55 pilot jet like those are the magic numbers. Is this true for even my bike set up (and to be, with the modifications done) and current main jet? Please help I am honestly a little lost in the "tuning" area of expertise. I am however a very competent mechanic. Thanks so much in advance
-Mikey