Exhaust popping

[Canadian]

Hello
Sorry have the same question posted on the wrong page,I still have to get used to the forum.
I just did some carb work on my 89 like setting the fuel mixture and sync the carbs. The lady was running rough before I did this. The carbs were out of sync and the mixture screws 6 to 8 turns out. I set the mixture to three full turns out after I carefully seated them first than synchronized the carbs ( just bought the Emgo Tester online for 97$ and it works really nice) The bike is running nice now, good response on the throttle from idle to full but when I close the throttle she is popping quiet a bit. She was not doing this before. I have a Vance & Hynes exhaust so maybe I have to go back to the old mix setting or does anyone has an other solution that I can try?

Thanks
T.

[baldy3853]

mmmm    Could be sucking air in thru the joins in the exhaust  
Baldy

[Canadian]

 
By popping I mean backfire just so that It does not lost in translation .
Cheers
Try to figure this out this week because I am planning a round trip from Houston to Las Cruces next weekend and do not want to hurt the bike.

[Flynt]

Assuming your synch is good (confirm first since popping is a great indicator for synch issues), popping can be from too rich or too lean, so you need to do some additional testing and adjustment of the pilot mixture.  Did you "blip test" after the carb synch and pilot mixture adjustment?  If not, you should get to the pilot adjustment screws again and try 1/2 turn out on all screws (guessing you may have gone in too far) followed by blip testing.  When a throttle blip gives you a drop in RPM initially, you've gone too far.  Go a full turn in from that point and go for a ride...  then report back.

BTW - others have documented this kind of testing on here somewhere.  I don't usually offer much carb advice, but am telling you why I'd do in case you're fiddling with it now.

Frank

[Flynt]

If you are having actual backfires (where you shoot flame back through the carb), my prior advice is BS...  you likely have a much bigger issue with carbs, timing, or both.

Randy?

[racerrad8]

So lets get it clarified...

You are hearing a popping in the exhaust system or from the carbs?

If you are hearing it from the exhaust, you could have air leaks, sync & tuning issues.

If it is popping back through the carbs that is usually a sign of a lean idle mixture and should only happen at warm-up.

Randy - RPM

[Canadian]

Thanks a lot
I just went on a 30 mile ride and checked the sync again in idle(1100) and at 3000 they are all nice and even.i also checked the sparks they are all four light brown . Sorry for the confusion but the popping is in the exhaust.I wonder if one of the plugs for the sync connection in the intake is leaking ,because they are really hard and after reinstall seem to be loose even with the little clamp on them but I thought when they get warm that they will settle again. Any thoughts ?

[bigbore2]

Is the popping when you de-accelerate?  Or when you accelerate?  How bout when running at a steady rpm down the road, at highway speed?

[Alf]

Ufffff!. I´ve maintained a hard and long fight with that exhaust popping

Read this

http://www.fjowners.com/index.php?topic=5130.msg44853;topicseen#msg44853

Today the exhaust popping is at minimum and only at very hard gear dowshiftting

My conclusion: change your old and sized emulsion tubes and make a careful float bowl fuel level, setting it at minimum. 42,5 European model pilot jets (mine is a 3CV)

The bike will be faster and accelerate more, and the pops will be reduced, but any tuned FJ in a way or another will pop at the exhaust more or less

Use earplugs (good solution) or  fit OE silencers again works too

I hope this helps