poor performance/back firing
Posted January 07, 2002 - 11:41 AM
168 main, 48 pilot, 100 pilot air, 1 1/2 turns out. It's been 40-45 F degress and high (70-90%) humidity. My location is 500 above sea level.
I've tried different jetting (including stock) and have played with the air/fuel setting/jets, new plugs, different plug gaps, new gas all to no avail. The plugs are not rich or lean. I've talked to a lot of peolple and have read all the posts on back firing, but nothing seems to help. Has anyone experienced a sudden change in performance similar to this? Has anyone experienced electrical issues? Any advice would be appreciated.
01 WR 426
Posted January 07, 2002 - 10:31 PM
If you bought it new, then I assume the electronics are fine, but I recommend you pull the carb and go through it. I mean soak it in cleaner and blow out EVERY passage with high pressure. Seems like our bikes have real carb issues until you get it dialed in. Never hurts to know you bike's innerds.
When you solve your problem, give my a holler at my e-address as it might help me too.
BTW, took a vacation in the SeaTac area MANY years ago and caught some drag races too. They were having a drought, so it was pretty nice up that way (remember we get <9 in. rain/yr. here in ABQ.)
Posted January 08, 2002 - 02:04 AM
Posted January 08, 2002 - 03:35 AM
Posted January 08, 2002 - 05:34 AM
Thanks for the suggestions. But my bike never makes the turn for the better, warm or cold. Even after more than 10 or 15 minutes, it still runs rough and back fires. I guess what really has me stumped is that it was an over night change without any modifications to the bike, from running perfect to absolute crap. I've pulled the carb and have cleaned it out but it wouldn't hurt to do it again before it goes to the shop (which I don't want to do). But if it is electrical (CDI) I'm hoping they can find it qiuckly.
Thanks agaun for the the input ... anyone else have anything like this?
Posted January 08, 2002 - 04:05 PM
Before you take it back to the shop it is fully worth putting the jetting back to stock.
What is your 'newly' installed sparkplug telling you? is it black, white, tanned?
You make no mention of the carby needle, is that still at stock setting... Personally I think your running rich.
before you take it back to the shop you can do yourself a favor by starting from the begining again -
clean and reoil the air filter
check the sparky, replace(or reseat in your case if it's new)
return the carby to stock jetting(including air)
+ the needle, and eyeballing it's in good condition
also eyeball your float needle still exists
Kick it over and see if it works well.
I take it you haven't gone to YZ timing or added flywheel weights yet.
Posted January 08, 2002 - 05:33 PM
"You didn't happen to adjust your IDLE did you"? Well it never occured to me through all of this but Yes I Did. Bike seemed to be running a little on the Low Idle side one cool morning so I turned it up a bit. That is where it all began and that is where it all ended.
Hope this helps.
The only problem this bike has ever had is me.
WR 426 2001
Posted January 08, 2002 - 05:42 PM
Ike of Colo
Posted January 09, 2002 - 03:28 PM
Does it just pop/gurgle or really backfire like a gunshot? If it pops/gurgles-probably jetting or obstruction in carb/instake/exhaust. If it sounds like a gun shot, could be a stuck valve. You're bike is so new, though kinda doubt it's a stuck valve.
Also what needle are you running? If you're on the stock needle, I may suggest dropping the PJ to 45. Alternatively, a DVR needle might be a good choice (for WR timed) or EKP/EKN for YZ timed.
Good luck, and please let know us know what is causing the problem once you find it..
Posted January 13, 2002 - 03:31 PM
I will be calling the shop I bought it from (Florence Yamaha) and see what they say. Has anyone else heard of this or experienced this?
Posted January 14, 2002 - 07:26 AM
Have a great day!