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General Category >> Rubber Side Down! >> Does cooler wheather contribute to backfiring?
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Message started by JFinol on 09/12/07 at 17:10:56

Title: Does cooler wheather contribute to backfiring?
Post by JFinol on 09/12/07 at 17:10:56

I am curious about this, since I noticed that my bike has been backfiring lately. I live in wisconsin and the temperature has dropped in a matter of days from 80 to upper 60s. I got my bike this summer and it did not used to backfire until now when started to get cold. Does this has anything to do with the backfiring or it is just coincidence?
I wanted to put a EA muffler but when I heard that backfires is produced when the pipe is change unless re-jetting is done I stop thinking about it, because I do not want to deal with it ( I do not how to do it ). But now I have the problem even I have not done anything to the bike.
What should I do? >:(
I do not want to damage the engine.

Title: Re: Does cooler wheather contribute to backfiring?
Post by bill67 on 09/12/07 at 19:04:05

yes the air is denser which your getting more air compared to gas in cold weather

Title: Re: Does cooler wheather contribute to backfiring?
Post by thumperclone on 09/12/07 at 19:39:07

here in west colorado we experince temp swings this time of year 50s in the morn hi 80s to 90 in pm..
ive modded my o6 with a 3" hardkrome slash cut, de snorkel,k&n drop in and had the stealer shop re jet,i followed "lancers quick and easy carb tune" (do search)
with a digi tach and still get some back fires but not the 155 howz. BOOM at shut off...have leaned to controll back pops with throttle ..some times a good POP wakes up the cager eatin an egg mcmuffin,on the cell phone drivin with a knee...

Title: Re: Does cooler wheather contribute to backfiring?
Post by jkhulon73 on 09/13/07 at 04:49:18

thumperclone wrote:

...the 155 howz. BOOM at shut off...

I may be a sadistic S.O.B., but I can't help smiling from ear to ear when it does that at the gas station. ;D

Title: Re: Does cooler wheather contribute to backfiring?
Post by T-Mack1 on 09/13/07 at 08:44:32

Thanks for starting this thread.

I also noticed a few pops the last few days when i had almost none since the Whtie spacer & mix screw setting. It's now 50's for the morning commute, mid 70's going home (eastren PA).

Title: Re: Does cooler wheather contribute to backfiring?
Post by Max_Morley on 09/13/07 at 09:38:05

In my experience the cooler weather and cooler pipes seems to magnify the small exhaust leaks. Mine backfires on decel when cold, but after getting warm they all go away. I checked last night and I have a couple small leaks at the adapter and muffler. Will need to address those with Fall weather coming on, but only ordered the new header gaskets yesterday. I had used up my supply and didn't ordered enough last time. FWIW as long as this is an exhaust topic. I recently blew the center baffle out of the HD-FXD muffler I had on for 7 years or so, changed the muffler to the 2nd one in the set, but never looked inside the RAASK pipe I used for a header. While I had the exhust off to change the clutch lever cam, I happened to look in the RAASK and the inner liner was partly blown away at the very top. Greg sold me a used OE pipe and I had an adapter made to go on the muffler I was using before. The sound is totally different with the stock head pipe, single wall adapter and HD muffler than it was with the old not really double wall header and no single wall connector. Much more distinctive sounding on low to med RPM run up in each gear. Louder but still OK i think. Not sure how much of the change is due to the exhaust not dumping some of the pressure pulse (and hence noise) between the heavy RAASK walls and the single wall connector not absorbing some of the noise. I know the single wall Highway Hawk Drag pipe I tired was noisy from the exhaust port on down as it was very this wall. I may try to find a foot of schedule 80 water pipe and have it bent for the adapter and try it as it is much heavier walled than the exhaust pipe. Did that years ago on a Dodge Crewcab PU and it outlasted the body on the truck. The sound is more HD like now where before I would have compared it to a Wing with aftermarket exhausts, more of a purr. Apparently the new RAASK is dirrerent, has packing between the inner and outer pipe with perforations in the inner and packed baffle. Only available in 60 mm now, old one was 50 mm OD with a much larger inner pipe the than the OE one. Still like to find another used RAASK for a header as it works great with the HD mufflers. Max

Title: Re: Does cooler wheather contribute to backfiring?
Post by serowbot on 09/13/07 at 09:48:13

Yes, cooler air will make you leaner, also less humidity will make you leaner.
Racers rejet for weather conditions, sometimes multiple times per day! What you want is a good average for your general area conditions (temp, humidity and elevation). That's why it is best to do jetting on an average day, not during a heat wave, or monsoon rain, etc..

Title: Re: Does cooler wheather contribute to backfiring?
Post by JFinol on 09/13/07 at 13:41:21

Wow, I am glad to read all this comments and advises. I can tell that I am not the only one with this boom! problem (Well, I do not if this is a problem).
Now the question is: Is my engine going to be hurt from this backfire during cold days?
Is there a forum explaining or showing how to re-jet? I would like to know how is done, and what should I use to re-jet my carb.
Thanks again ;D