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General Category >> Rubber Side Down! >> New muffler causing major backfires!
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Message started by S40Man on 07/18/08 at 07:42:34

Title: New muffler causing major backfires!
Post by S40Man on 07/18/08 at 07:42:34

Like a lot of us I just had to upgrade my muffler. The stock one is just too quiet for me. I bought one of those HD Dyna conversion kits for my S40. The installation was pretty simple and it sounds great but it backfires really bad. I checked for leaks but can't find any. It sounds and smells like it's running too rich. Has anyone gone through this? If so, what did you do to make it stop back firing?

Title: Re: New muffler causing major backfires!
Post by verslagen1 on 07/18/08 at 08:32:22

when and how does it backfire?
at shut down
gear shifts
engine braking
is it a poof or a pop or a KAPOW? :o

backfires are usually cause it's lean or exhaust leak.

I got a supertrapp that's so tight... (how tight is it) it refuses to backfire even when the idle screw is completely closed off. On shut down I get a little poof, on engine braking I get a nice gurgle and an ocasional pop on upshift. 8-)

Title: Re: New muffler causing major backfires!
Post by flcruzr on 07/18/08 at 08:53:54

I'm new to Savages/S40 and I keep reading about the HD Dyna mufflers. It seems that they add a nice sound to the bike but where do you get these kits from? I'm interested in adding a better sounding muffler and would like to know where to get one from? Thanks!

Title: Re: New muffler causing major backfires!
Post by S40Man on 07/18/08 at 09:12:16

I got mine off Ebay. The sound difference is night and day. My bike finally sounds like a real bike. As far as the back fire sound it sounds like a lound POP!! Every time I lay off the throttle or decelarate. At first it was fun to scare little children in the neighborhood with the loud backfire but now it's just annoying.

Title: Re: New muffler causing major backfires!
Post by verslagen1 on 07/18/08 at 09:36:31

When ever my stock muff popped it was a loose header, check that.

If tight, adjust your idle mixture richer, 1/8 turn CCW. ;D

Title: Re: New muffler causing major backfires!
Post by odvelasc on 07/18/08 at 11:59:39

maybe someone mentioned this already. Have you tried rejetting? I used a stage one dyno jet kit. Fixed my leak and put the 146 main jet it. Presto, sometimes a pop on shut down, the rare crack on upshift.

Title: Re: New muffler causing major backfires!
Post by SimonTuffGuy on 07/18/08 at 12:06:03

Any pics of the install? I've got a Dyna sitting in my basement awaiting install... :)

Title: Re: New muffler causing major backfires!
Post by S40Man on 07/18/08 at 14:13:10

That was my next step. I see a lot of different "High Performance" jets out there. Some say Stage (or Level) I, II, III. What does that mean and what should I get?

Title: Re: New muffler causing major backfires!
Post by LANCER on 07/18/08 at 14:51:30

the fella selling those jet sets starts with a small jet for stage 1 and then goes up to the next larger main jet for stage 2, then larger jet for stage 3.

If you know exactly what size jet you need then it may be ok, but in most cases when you go through the jetting & tuning process you do not know exactly where you will end up. Depending on the air filter/intake used and which muffler you have, and where you live, even each engine is slightly different, all that affects what each specific engine will need jetting wise.
Point is, you don't know what you will need until you get there. That is why I think it is necessary to have several main jets when the process is begun.

Title: Re: New muffler causing major backfires!
Post by Sandy Koocanusa on 07/18/08 at 15:02:39

Lancer, regarding the "where you live" portion of your post...

I realize it isn't an exact science, but take a guess at how much change in altitude is needed to start noticing a difference in how the bike runs. 500 feet? 5000 feet? I'm planning a trip this weekend that could take me from altitudes of 1500 feet to 7000 feet. Just wondering what effect this will have on the bike. I'm already running rich and can't seem to cure the problem. I'm afraid if I get way up in the mountains, I may have to pull over and put in a smaller pilot jet. That would be a pain.

Title: Re: New muffler causing major backfires!
Post by S40Man on 07/18/08 at 15:04:28

OK. Thanks for the info. I'll start with a Stage I jet and go from there. I'll let you know how it goes.

Title: Re: New muffler causing major backfires!
Post by S40Man on 07/18/08 at 15:17:50

One last question. Where exactly is the idle mixture located?

Title: Re: New muffler causing major backfires!
Post by Sandy Koocanusa on 07/18/08 at 15:27:22

See photo in this thread:

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1216348401

Title: Re: New muffler causing major backfires!
Post by Max_Morley on 07/18/08 at 15:38:26

On topic, I'd vote for an air leak at the head to head pipe or head pipe to muffler as this allows air (with 20.8 % oxygen usually) in the system and burn rapidly (very rapidly) any fuel left there from the closed throttle or shut off ignition. On altitude re-jet ? I've run mine from sea level to over a 9000 ft pass and it is set for 1200 ft which is the altitude where we live. It ran a little lean in Seattle area and I'm sure rich over the pass, but just kept on thumpin' in the snow in July. Years ago when I went to Auto Tech school in Klamath Falls OR, we used the 5000 ft altitude there as the cut point to rejet, we did many cars in the Tune-Up class using a chassis dyno to verify we didn't go too lean, this was before the days of Emission controls except for a PCV valve. Modern stuff, cars truck and now bikes with Fuel injection and O2 sensors check the barometric pressure on start up and at specified RPM, throttle setting, & load, check it again to use a different look up table in the computer to correct the A/F ratio on the fly. The O2 sensor(s) fine tune it from there like the scales of justice, out of balance lean add a little more injector on time, a little rich cut them back by a couple ms (milla-seconds) always varying so little you cannot feel it in the operation of the rig, but observable with a DVOM on the O2 sensor, GMM (graphing Multimeter), or scanner. Max

Title: Re: New muffler causing major backfires!
Post by Sandy Koocanusa on 07/18/08 at 15:41:55

Good to know. Thanks, Max.

Title: Re: New muffler causing major backfires!
Post by LANCER on 07/18/08 at 19:37:41

555352504D4B50513F0 wrote:

The basic rule of thumb for altitude changes is that for every 3-4000' of change there should be a 1 jets size change to compensate. That does not mean that the engine will not run adequately, and some are more forgiving than others, but that is the guide.
If you ARE running rich now then you should consider getting the jetting sorted out before going higher where the thinner air will richen the mix for you even more.

Title: Re: New muffler causing major backfires!
Post by sidny4 on 07/24/08 at 12:43:42

I have a bit of a leak between the header and muffler, what's the best way to get rid of that? I have a strip from a pop can in there now and that's about all I can fit in there.

Title: Re: New muffler causing major backfires!
Post by Robertomoe on 07/24/08 at 12:50:20

my aluminum can practically melted. my stock muffler had exhaust wrap between the header and muffler.

Title: Re: New muffler causing major backfires!
Post by Max_Morley on 07/24/08 at 12:59:13

In my experience the answer is to have a muffler shop make you an adapter to connect whatever muffler you have to the Savage head pipe. You can either use the stock sleeve gasket that goes between the muffler and pipe or clamp directly to the head pipe w/o the sleeve gasket using a different size clamp. Take both pieces into a shop and they usually have a cut off pice of 1 -3/4 pipe about 6-7" long laying around they can swedge one end to fit the muffler if needed, shrink the other end to fit the header w/o gasket or swedge it to fit the gasket and put a slight bend in it so the exhaust doesn't blast the rear brake bracket. I've paid both $10 and $20 for them depends on the shop and if the they are cycle friendly. Max