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Message started by rong on 02/14/15 at 21:28:27

Title: To eliminate backfiring
Post by rong on 02/14/15 at 21:28:27

I really enjoy getting information from this forum about the Savage.

Here is my question:
The S40 Savage has some normal backfiring when it comes from the factory.

Can the backfiring be eliminated by adjusting that idle-mix adjustment screw (after drilling out the brass plug) as described on the website. Or do you also have to modify the carburetor in other ways too? I'd like to eliminate the backfiring but would prefer not tampering with additional carburetor modifications other than the idle-mix screw.

Thanks,
Ron G

Title: Re: To eliminate backfiring
Post by justin_o_guy2 on 02/14/15 at 22:15:44

You got stock exhaust?
You're sure you don't have any leaks in the exhaust?
Year model will tell the smart guys what jetting is probably in it.
How many miles on it?

Title: Re: To eliminate backfiring
Post by KiwiGeek on 02/14/15 at 23:53:23

I was wondering about the backfiring myself. I have just bought my S40 and took it for it's first trip other than the ride home from the dealership. On the trip to the start point of the ride, a charity ride for the local rescue helicopter, I noticed the occasional backfire.

I made a mistake of going to the local petrol station and filled up on 95 instead of 98 and was wondering if it was more down to that or the fact that I'm going through the pre 1000k (600 mile) run in period for the engine.

Title: Re: To eliminate backfiring
Post by Kris01 on 02/14/15 at 23:59:31

The compression is low enough that you can safely run 87 octane. Any more than that and you are spending too much for absolutely no benefit.

Title: Re: To eliminate backfiring
Post by Kris01 on 02/15/15 at 00:02:24

Oh, and backfiring has nothng to do with octane. If your exhaust system is sealed up nice and tight then you need to rejet to a richer jet to help with the backfires. The engine runs lean from the factory.

There are plenty of threads here that detail how to rejet the carburetor to what it should have been from the factory. Check in the tech section.

Title: Re: To eliminate backfiring
Post by KiwiGeek on 02/15/15 at 00:30:54

I'll wait until after the dealer warrantee finishes before starting to look the rejetting, although, to be honest, I like the occasional backfire ;)

I'll do some economy runs to see if there is any real difference between the fuels type which down here are 91, 05 and 98.

Title: Re: To eliminate backfiring
Post by jcstokes on 02/15/15 at 00:46:25

You will probably be quite safe with NZ 91 octane. The Americans use a different way of calculating octane ratings. They use AKI we tend to use RON.

Title: Re: To eliminate backfiring
Post by Dave on 02/15/15 at 05:44:48

The idle fuel adjustment can have some effect on the backfire - but it will not eliminate it. When you completely close the throttle while shifting or compression braking - the slide drops down and the jet needle completely shuts off the fuel flow through the needle jet.....the only fuel going to the engine is through the idle circuit, and that is not enough to provide fuel to allow the spark plug to ignite the lean mixture. If you put really big pilot jets in you may reduce the backfiring with the overly rich mixture - but your fuel mileage will suck and the engine will be running too rich when you are cruising at low throttle settings. Jet your engine for proper running - not for backfire issues. The TEV valve is supposed to help with this backfire situation when the throttle closes - but maybe because of the E10 fuel it just does not provide for a rich enough mixture.

In order to reduce the backfiring - don't completely close the throttle when you shift or are decelerating. Hold the throttle just slightly open and the backfire will be reduced significantly. When you shift gears just slowly roll the throttle off until you have about 1/8th throttle still applied, and then shift....after a while you will get a feel for how to cut down on the noise. This is not a modern fuel injected engine...you need to learn how to adapt your riding style to suit the quirkyness of the big single with a carb.

And as others have said....make sure you don't have an air leak at the cylinder head or muffler connection. Don't over tighten the bolts at the cylinder head.....they break easily and should only be snugged up.

Title: Re: To eliminate backfiring
Post by Serowbot on 02/15/15 at 08:32:38

Thinking has evolved on this topic... there used to be a lot of advice on eliminating popping and afterfires with jetting,... but that is jetting for a closed throttle...
Under what conditions popping and afterfire occurs, can be used as an indicator of which way your jetting is off,... but you should jet for performance and economy, not quiet deceleration...

Unless, popping is so annoying to you that you will tolerate a bad running bike...

Decel noise is inherent to big single engines... so is a poof at shut-off (it's just unspent fuel from the last engine cycle igniting in the pipe)...
With practice you can learn to control these noises with you riding technique,... it can even be useful in traffic for alerting drivers of your position...
( ;D )...

Jet your bike to run good... not to stop good... ;)...

Title: Re: To eliminate backfiring (request clarification
Post by rong on 02/15/15 at 11:55:01

First of all, thanks for all of your responses.

So if I'm hearing correctly (especially from Dave and Serowbot), then by adjusting the idle-mix screw mixture (as has been described in the tech area of this website), some of the normal backfiring might be stopped, but not all of it? (Hope I have this correct).

I personally don't care if there is some backfiring, but just interested in finding out if changing the idle-mix flow will help.

I might also ask this: ... By changing the idle-mix mixture, will this also help save the valves from the notorious lean mixture that comes directly from the manufacturer?

Thanks,
Ron G

Title: Re: To eliminate backfiring
Post by MnSpring on 02/15/15 at 13:04:18

Not a expert on this engine, but learned a LOT from this site about it.

On my 06, When first got it, it would backfire big on shutdown.
a Little on Decel.
Found the two screws, (Header into Cyl) were loose.
Took them out, 'anti seized', them, then snugged them up.
Checked where the header clamps to the muffler,
that was also loose.
Also, opened the idle screw, a bit, (By Sound)
Idle at 800, screw out, 1/8 turn at a time, and 2-4 min listening,
idle went up, then when it went down, backed off, tell it was highest again.
Then set the Idle, (warm engine, at about 1050)
(And I always use, 'Non-Oxy' gas)

Backfire went away. When I start hearing little, 'puffts' at shutdown,
just go back to tightening those screws again.

Now, if I 'want', (and sometimes I do). It is high revs, clutch in, and as I park, hit the 'kill' switch.

Quote:

... By changing the idle-mix mixture, will this also help save the valves from the notorious lean mixture that comes directly from the manufacturer? ...

If gained, only, ONE, piece of advice/knowledge from this site.
It is Well worth it ! It was the: "This is a OLD Engine".
Even though it may be a 2015 model year.
It still is a OLD, designed engine. And it needs Zinc (ZDDP) in the oil. Something that is NOT in most oils today.

Knew that for my other 'old' ICE's. And used additives.
But, 'RED LINE', was Compatible with wet clutch.
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1344471565

Using, Rotella oil, and Redline. Will allow that engine to run Many, Many, Many miles. And, you will not, 'need', another.
(Higher amounts, perhaps first 1000 miles, then slowly lower each oil change)

Now, Just to be clear;
The words: 'need' and 'want',
Mean, Two Different Things!

Title: Re: To eliminate backfiring
Post by pgambr on 02/15/15 at 13:17:39

When my old muffler rotted out I put on a Dyna. The Dyna is great and I regret not doing it sooner. Although, I genuinely miss the that big decel "pop".

My neighbor across the street mentioned he missed it as well. He said he kinda liked know'in when I was home. [smiley=evil.gif]

Best regards,

Title: Re: To eliminate backfiring
Post by justin_o_guy2 on 02/15/15 at 13:29:31

I had a Stage One cam, Supertrapp exhaust with 14 disks, jetted carb and adjusted idle air mix.. It rumbled and growled and sounded like a free flowing well tuned engine,and it was. It roared under acceleration and growled at deceleration,, not so loud as to be embarrassing or something,, and,if I didn't Want to be loud,all that was required was ride gently. When I was near the hospital or horses I was careful with the gas and careful about how I came to a stop.