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S40 Backfiring- Do I really need to fix it? (Read 319 times)
Fahad
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S40 Backfiring- Do I really need to fix it?
05/26/16 at 11:27:17
 
Hi Guys,
I just bought an S40 2005. The person I got it from also mentioned it to me while selling it but I have actually experienced it the other day while trying to slow down from 50mph in traffic.

The question is, am I causing any harm to the engine or bike if it keeps backfiring and do I need to fix it rightaway. I am really not bothered by the sound and like someone said in one of these forums, it keeps people from tailgating, so I really don't mind it.

Can I still continue riding?
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oldNslow
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Re: S40 Backfiring- Do I really need to fix it?
Reply #1 - 05/26/16 at 11:43:12
 
Quote:
Can I still continue riding?


Yes

Quote:
am I causing any harm to the engine or bike if it keeps backfiring and do I need to fix it rightaway


No. In,fact you don't need to fix it ever if it doesn't bother you and you don't want to bother.

There are things you can do to minimize it, and I'm sure folks will be along shortly with suggestions about how to do that.
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Re: S40 Backfiring- Do I really need to fix it?
Reply #2 - 05/26/16 at 11:46:13
 
If the bike is backfiring on trailing throttle (which a lot of pollution era carb bikes do), it usually means it's running lean on the idle and low end circuit.
I've seen a bunch of Savages that ran so hot they blued the head pipe all the way under the engine. Keeping in mind that the bikes use a double wall header pipe (think Thermos bottle type insulation), it means the bike is running crazy hot.
Really not a good thing for the engine. On a lot of bikes, my fix has been to unscrew the idle mixture screw 1/2 turn (often a blanking plug needs to be drilled out) and to shim the slide needle. A simple thin washer works fine, no need for a full jet kit.
The bike will be faster and more responsive, and run cooler and longer.
-Armen
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Dave
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Re: S40 Backfiring- Do I really need to fix it?
Reply #3 - 05/26/16 at 11:52:01
 
If your bike has the stock jetting - it could be running lean as Armen has suggested.  A change of jets might help your situation.

The engine backfires when you close the throttle fully while the engine is at speeds higher than idle.  The engine is trying to suck in a lot of air - but the closed throttle only allows a mall amount of fuel to flow.  The fuel/air mixture in the engine becomes so lean the spark plug cannot get the mixture to burn - but when the unburned mixture goes into the hot exhaust pipe....it ignites and makes a racket.

You can cut down on the noise by holding the throttle open just a crack....which allows a bit more fuel to flow.  If you don't let the throttle close completely shut as you shift gears - you won't get the noise between shifts.  If you hold the throttle open just a bit when slowing down....you won't get the noise (or you will get less noise).  You don't have to open the throttle far enough that the bike wants to accelerate.....just enough to make the noise go away.  It is all part of the charm of riding a big single!
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Re: S40 Backfiring- Do I really need to fix it?
Reply #4 - 05/26/16 at 12:07:02
 
Armen,
The pipe is already half blue. I was thinking about commuting to work on it which is about 20 miles on the highway, do you think I should hold off until I get it fixed?
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Re: S40 Backfiring- Do I really need to fix it?
Reply #5 - 05/26/16 at 12:11:33
 
Check for leaks at the head and muffler, those will cause backfires too.
a leak will blow the flame of a lit candle around or smoke.
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Re: S40 Backfiring- Do I really need to fix it?
Reply #6 - 05/26/16 at 12:14:01
 
A blue pipe on a Savage is not a sign of doom.  The bluing occurs when the chrome gets hot.....bikes that spend a lot of time in traffic are more prone to the bluing that bikes that are run on the highway a lot.  A lean mixture can cause the pipe to blue - but that alone is not a sign of any damaging condition.

If the bike accelerates smoothly, and does not have hesitation or bucking or flat spots when you open the throttle slowly - chances are the bike is not running so lean to cause any problems.

I wouldn't stop riding the bike just because your pipe is blue.

What elevation do you live?  Does your bike have the stock muffler and air cleaner?  How many miles are on the bike?
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Fahad
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Re: S40 Backfiring- Do I really need to fix it?
Reply #7 - 05/26/16 at 12:40:13
 
11000 miles. It has a stock muffler and it rides smooth. The other day I rode on the highway for about half hour. When I got back the pipe was hot. Is that normal?

Dave wrote on 05/26/16 at 12:14:01:
A blue pipe on a Savage is not a sign of doom.  The bluing occurs when the chrome gets hot.....bikes that spend a lot of time in traffic are more prone to the bluing that bikes that are run on the highway a lot.  A lean mixture can cause the pipe to blue - but that alone is not a sign of any damaging condition.

If the bike accelerates smoothly, and does not have hesitation or bucking or flat spots when you open the throttle slowly - chances are the bike is not running so lean to cause any problems.

I wouldn't stop riding the bike just because your pipe is blue.

What elevation do you live?  Does your bike have the stock muffler and air cleaner?  How many miles are on the bike?

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Re: S40 Backfiring- Do I really need to fix it?
Reply #8 - 05/26/16 at 12:46:14
 
GENTLY snug the header bolts on the head. If you feel like it's not tightening up, back one side off, clean, put a dab of antisieze on, and snug it up, same thing on the other side.

The gasket looks like a miniature clothes dryer exhaust. It's reusable and can be pulled out, the head cleaned up, header cleaned, gasket carefully pulled a little longer.
Mine was backfiring so much that the people on the ride were bothered, I was kinda embarrassed, but the fix was stop the leaks, but that didn't get it all. Made it reasonable.
The cam swap and Supertrapp muffler made rejetting necessary.

And it sounded Sooo good, snarling and growling through the downshift s.
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Re: S40 Backfiring- Do I really need to fix it?
Reply #9 - 05/26/16 at 12:53:43
 
Fahad wrote on 05/26/16 at 12:40:13:
11000 miles. It has a stock muffler and it rides smooth. The other day I rode on the highway for about half hour. When I got back the pipe was hot. Is that normal?


Absolutely!  The exhaust pipe on any motorcycle is hot.  It will melt or burn almost anything that comes in contact with it.....rainsuits, saddlebags, boot soles, polyester leisure suits!
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Re: S40 Backfiring- Do I really need to fix it?
Reply #10 - 05/26/16 at 13:26:57
 
Hey Fahad,
It takes a while before engine damage happens. If it was mine I'd do the rejet thing. As the other folks said, an exhaust leak is possible. The gasket is cheap enough, just pull the pipe and put in a new one.
When I hear of these symptoms (blue pipe, backfiring on trailing throttle) it usually means lean jetting on the low end.
Pollution tests are done only up to legal speeds. At 55 mph, the throttle isn't open much, so you are on the pilot jet, the mixture screw, and the needle taper/position/needle jet. I don't usually have to do anything with the main jets.
Enjoy your new ride  Smiley
-Armen
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Re: S40 Backfiring- Do I really need to fix it?
Reply #11 - 05/26/16 at 13:38:07
 
Well there is not doubt that the Savage (and just about every other EPA compliant motorcycle) comes jetted lean from the factory.

My Savage had a lean surge just off idle, and when attempting to ride away at low throttle settings the bike just didn't want to accelerate smoothly.  It was fixed with a #50 pilot jet, #150 main and 2 washers in place of the white spacer on the needle.  The Rescue bike had the same....and it wanted a #52.5 pilot, #150 main, and 3 washers on the needle.

My Kawasaki Super Sherpa 250 dual sport was jetted so lean that you had to sit in the driveway for more than 5 minutes warming the bike up before you could put the bike in gear and ride off....it would just stall if you made an attempt to ride it before it was fully warmed up.  The SuperSherpa forum had a cure they called the Jekyll mod.....new larger jets and an adjustment of the idle fuel screw.

My Ninja 250 also had the lean fuel mixture issue, and the forum for those bikes had the recommended jets to use.

The bike will generally run with the lean EPA jetting - but they run better with a bit richer mixture!  Thank goodness we have forum member who have worked it out....and we can still buy jets to make the bike right!
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Re: S40 Backfiring- Do I really need to fix it?
Reply #12 - 05/26/16 at 14:44:45
 
The engine and carb are the same as the first year. The jets have changed,down through the years, as the EPA has dictated more and more from the manufacture rs,
Go back and see what they were equipped with back in the day..
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Re: S40 Backfiring- Do I really need to fix it?
Reply #13 - 05/26/16 at 14:53:57
 
justin_o_guy2 wrote on 05/26/16 at 14:44:45:
The engine and carb are the same as the first year. The jets have changed,down through the years, as the EPA has dictated more and more from the manufacture rs,
Go back and see what they were equipped with back in the day..

bad advice JOG, the carbs were jetted completely different back then.
get a jet kit from lancer which has a range of jets.
go up a size progressively till you find the one that works best for you.
all locals vary, due available gas, altitude and humidity.
In the tech section there's a progressive guide.
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Re: S40 Backfiring- Do I really need to fix it?
Reply #14 - 05/26/16 at 15:17:04
 
I was not giving advice. I was pointing out that the EPA has forced change.
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