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Stephen Daudelin 05-12-2013 08:51 AM

Backfiring On Front Cylinder
HELP!!!! My 2006 950 Adventure is backfiring on the front cylinder! It was running fine when I put it away for the winter and now this. I took the carbs off and sprayed carb cleaner in them, changed the very dirty spark plugs, put it back together. When it started, it was running great for a few minutes with full compression coming out of both exhausts. Then it started popping and backfiring again on the front cylinder. You can see flames in the carb. Any ideas what it could be and what should I check????<?xml:namespace prefix = "o" ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>
Is it the valves?? An air leak?? Or what??:baldy<o:p></o:p>

Katoom72 05-12-2013 09:02 AM

Excessive lean condition? Check airleaks and fuel

DirtyADV 05-12-2013 09:10 AM

Only time I have had flames come back up the carb one of the choke cables was not seated fully.


skianreid 05-12-2013 09:34 PM

Check to see if the O2 screw in the pipe fell out.

Two Moto Kiwis 05-13-2013 09:31 AM

Maybe the coil is breaking down, is it heat related?

Other thing to check is spark plug to make sure no losse carbon found its way back into the gap post cleaning?

The only other obvious may be check the top of the coil connections to make sure they are not loose.

v303x 05-13-2013 11:56 AM

Clogged pilot jet? Take the pilots off and use a strand of copper from a piece of cable to clean it. Spray them with carb cleaner and blow them dry with compressed air.

Better yet get new ones.



Racer111v 05-13-2013 05:08 PM

I had the same problem with my new to me bike. The threaded tip of the spark was corroded (rusted) where it connects into the coil. The temperary fix was to clean up the end with some sandpaper and cover it with some dielectric grease. Then I bought new plugs and a used coil off Ebay. Of course I did all the carb stuff before I pulled the plugs.:cry

Stephen Daudelin 05-13-2013 06:55 PM

Thanks Gents!

I currently have new plugs, I've cleaned the carbs and jets.
Where is the O2 screw? It only occurs once it's warmed up. It runs fine when cold. It's certainly running lean.

Stephen Daudelin 05-13-2013 06:59 PM

It's only got 20,000kms on it too.

Goss 05-13-2013 07:12 PM

If the plug thing does not turn out to be the issue you need to pull the jets out of the carbs and clean them. This has happened to me a number of times over the years and I pull all of them and clean them while I have the carbs off.

Orangecicle 05-13-2013 07:13 PM

I would bet that you have a vacuum leak on the front cylinder. Maybe a cracked boot. Maybe you didn't get the carb all the way into the boot. Maybe you have a vacuum line that is loose. I had this for many days and just couldn't figure out what was wrong, and then I found that one of the vacuum plugs I'd put on was blown off. That causes a super lean condition on one cylinder, and it will backfire into that one carb all day long. I'd put money on a vacuum leak.

Two Moto Kiwis 05-13-2013 07:36 PM

You can buy a new tube of vacuum but make sure it is black :rofl

norsesweger (Tobi) had an issue with a cracked manifold boot per Orangecicle but that is a fair way in so simple stuff first.

ICERIDER 05-14-2013 11:25 PM

I had this on my 950. Twas a coil. Fine when cold, then missfire comes as it gets hot. Swap them around and see if it moves to the other cyl.

Stephen Daudelin 05-15-2013 07:10 PM

Thanks for all your help Gents! I will try to see if I have an air leak first. One thing I forgot to mention was that I installed new Leo Vince pipes two years ago. It ran fine until now with this issue.

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