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Message started by metri on 05/12/07 at 18:41:25

Title: Backfire while slowing down
Post by metri on 05/12/07 at 18:41:25

I just got a savage on the road... yesterday. I have never owned a bike before and what fun it is. Now I have driven a dirtbike before and do know how to shift gears, but am by no means an experienced rider. All that being said, this is what's happening.

When I shift down to slow down or brake to slow down, I often get a backfire. I was out for maybe an hour and it must have happened 20 times. It's a bit on the disconcerting side and sure makes everyone look...

My bike is an 87 frame with a 2002 engine from a crashed bike.

Any ideas what might be causing the backfire's and is this to be expected?

Title: Re: Backfire while slowing down
Post by verslagen1 on 05/12/07 at 19:07:43

Backfires of this type are most offen caused by exhaust leaks. Had this one myself. ;D

Check the header bolts, check the slip on clamp.

Intake leaks also happen so check all the clamps. ;D

Title: Re: Backfire while slowing down
Post by georgekathe on 05/12/07 at 21:38:39

don't overtighten the header bolts - can be really easy to strip them I've heard! hopefully someone who can find their manual (don't even ask! :) ) can post on here the correct tightness for you. also as I'm sure you know, check them when the engine is dead cold.

Title: Re: Backfire while slowing down
Post by verslagen1 on 05/12/07 at 21:58:46

13-20 ft-lbs
It's been recommended to use anti seize ;D

Title: Re: Backfire while slowing down
Post by metri on 05/12/07 at 22:37:30

Thanks, I'll check that and let you know.

Title: Re: Backfire while slowing down
Post by firsts40 on 05/12/07 at 23:08:54

My 06 does it when I shut down guick doing 50 or more, but that is it. I have been told that my backfire is just the build up of gas when I shut down guick from highway speeds. If I ease off the throttle it doesn't do it, and I have just learned to live with it just like my ocassional speedo buz.

Title: Re: Backfire while slowing down
Post by courtem on 05/14/07 at 12:34:48

:) I just got a 2007 S40. It would backfire everytime I rolled the throtle to idle while driving. I pulled the brass plug from the idle mixture screw. The screw should be about 2 1/2 turns from fully seated. The one on my bike was barely 1/4 open. I opened it to 2 3/4 turns open then re-set the idle speed. The engine was more responsive but still backfired a little (mostly when ridden agressively). I increased the idle speed a little and now the backfire problem is just about non existent. I can still get a pop when riding agressively, usually at throttle roll back before entering a turn. The backfire is less violent, and my wife can not make it happen when she rides it.

Title: Re: Backfire while slowing down
Post by verslagen1 on 05/14/07 at 13:35:07

If any of you who haven't tried it, now's the time...

Lancer's simple carb tuning (or something like that)
in the tech section, and quit ur bitchn till u have. (sorry 4 being short with ya)
It's very good instructions, and you'll know a lot more after you read it. ;D

Title: Re: Backfire while slowing down
Post by tuxedo on 05/14/07 at 18:01:51

If it feels like it's chopping its way down and popping, try setting your idle higher. I just discovered that this was causing a lot of the "problems" I was having.

Title: Re: Backfire while slowing down
Post by courtem on 05/18/07 at 06:55:11

After reading Lancers Carb Tuning I ended up at 2 1/2 turns open on the mixture screw. And I think you are correct about the idle speed being a significant factor in the elimination of back-fire. My 07 seems to be running acceptably well. I find the transmission to be a little notchy especially 5th gear. I think that will smooth out with break-in. :)

Title: Re: Backfire while slowing down
Post by LANCER on 05/18/07 at 13:13:48

courtem wrote:

Turning the idle speed/rpm up a bit can help with the backfire issue, but keep in mind that doing so is sort of like a "cheater step" in the tuning process. If you need to do that ( increase idle rpm), it is a substitute for the low speed range (pilot system) being a bit on the lean side and and not getting the pilot system dialed in just right. When the pilot system is properly jetted and tuned there will be no backfiring and the idle can be set at the standard 1000-1200 rpm.

Slight, or even moderate, popping and crackling is perfectly fine on a well tuned engine. It is very common on race bikes, and not unusual with modified street bikes.
I consider it to be the sound of a successfully well tuned modified big single street bike. .. oh yea ! ;D

Title: Re: Backfire while slowing down
Post by DianeS. on 05/18/07 at 16:23:42

My savage will backfire if I decel quickly, but if I don't have to stop quickly, I can prevent it from happening.

My bike has been jetted etc., but the backfires aren't totally gone. I still get a pop on shut down. Yet, I can live with that!