Problem with FMF full system
Posted May 14, 2008 - 12:16 PM
Posted May 14, 2008 - 12:26 PM
I have a 2006 WR 450. Put on a Power Bomb header with a Q-4 exhaust. I live in Michigan so the elevation is right around sea level. This is how I re- jetted the carb. 172 main, 52 pilot, jet needle 3rd. position from the top and the fuel air screw is 1.5 turns out. Every time I get off the gas it pops like crazy out the back of the exhaust. I have taken the carb off and re-jetted 6 times to try and correct and no luck. I been on the phone with FMF every night after work trying to come up with solutions. I have had 4 other FMF systems on different bikes and quads and there has never been an issue. The funny thing is the bike starts right up, and idles perfectly. When you ride it the difference is like night and day compared to the stock system. The bike pulls harder and is a lot quicker. Just back fires and pops when you back off the gas. Any one have a problem like this? Any suggestions would be greatly appreciated.
do you have the AIS installed?
Posted May 14, 2008 - 06:12 PM
Posted May 14, 2008 - 06:14 PM
Posted May 14, 2008 - 08:57 PM
Posted May 15, 2008 - 10:53 AM
Posted May 15, 2008 - 03:53 PM
Posted May 15, 2008 - 06:35 PM
I thought that is what AIS was, just a controlled air leak.
I've left my AIS on and boy do I get a really loud POP if I hold it open for a while, then back off quik. its like the bike is angry I decided to slow down. Ka-Blamo!!!
It reminds me of the last time I went to a Champ Car race. Every time one of the drivers let off the gas for a turn, Ka-Blamo!!! it is interesting to me that you never hear that pop on TV.
Posted May 15, 2008 - 07:31 PM
Second, ensure that none of the carburetor vent lines are plugged, pinched or kinked.
Posted May 16, 2008 - 08:24 AM
These guys are taking you down the wrong road with all this air leak stuff. A really rich pilot will dump extra fuel and lead to LOUD , random popping when deccellerating -like gunfire. You'll also get rich looking plugs, and eventually hard starting not to mention all the carbon sooting.
A lean pilot will do that muffled pop pop pop nowhere near as loud as the rich backfire.
I think your pilot jet is way too rich personally.
Try a 48 and see what happens.
Look at these jet combos- Hardly anyone at sea level in NA goes above a 48. Try a more conventional jetting combo.