just jetted XRLand still backfires


11 replies to this topic
  • babbs

Posted October 07, 2004 - 07:27 PM

#1

I know this has probably been asked many times, but here goes again. I just desmogged, jetted with the baja designs kit and removed the snorkel. It still backfires upon backing off the throttle.
When putting in the new jet, I unscrewed the knob on the bottom of the carb (the one with the tab preventing this)2 1/2 turns. I don't have a manual so I don't know if this is the one they meant, could this be meesing me up?
It runs well otherwise, the idle needed adjustment, but it seems to backfire more now than before, what gives?
Thanks. :cry:

  • sportbiker929

Posted October 09, 2004 - 11:32 AM

#2

try another 1/2 turn for now. You need a bigger pilot jet.

  • budinsac

Posted October 09, 2004 - 12:42 PM

#3

My xrl popped like crazy when I first got it. A previous owner had installed a smog block off kit and had run the vacuum hoses wrong. California bikes have 2 vacuum ports on the top front of the carb. He had both ports tee'd together and run to the air cut diaphram. This not only made the air cut system inoperative, it created and internal vacuum leak!!! Once I had the vacuum line run correctly, I had no popping. It should run from the port nearest to the throttle cables to the air cut diaphram. The other port(if you have 2) should be plugged.

Hope this helps :cry:
Bud

  • 4WheelingPlus

Posted October 09, 2004 - 06:33 PM

#4

When putting in the new jet, I unscrewed the knob on the bottom of the carb (the one with the tab preventing this)2 1/2 turns.

Did you tighten the "knob" all the way down, then turn it out 2.5 turns?

I removed mine all the way from the carb, ground off the tab, screwed it all the way back in... then back out 2.5 turns. Mine runs perfect. I've also de-smogged and removed the snorkel.

Also: Which jet did you use? #160 or #165?

Do you have an aftermarket air cleaner? Did you remove the baffle from the exhaust?

I'm no expert but I did have to play around to get the correct combo of mods to make the bike run great.

- Ron

  • babbs

Posted October 10, 2004 - 06:30 PM

#5

I added a UNI filter at the same time as desmogging, and rejetting. I went with the 160 jet, as I still have a stock exhaust. I have screwed around with the screw...1/2 in or out, and it still pops like crazy. Maybe I do have a vacuum leak, but when I desmogged, I used the 2 vacuum caps per the directions. I didn't leave any ports uncapped. Also...other than a temp guage dipstick, is there any way to tell if my bike is running too hot? it seems really hot.

Thanks

  • budinsac

Posted October 10, 2004 - 09:05 PM

#6

The air cut is designed to reduce or prevent decelaration popping. Under very high manifold vacuum (decelaration), the air cut diaphram blocks the air feed to the pilot jet, making the mixture richer.... I don't know why the smog block off kit manufacturer recommends eliminating it.... But, all it will cost you to try it is about 4-5" of vacuum hose. Again, it worked for me!!! :cry:
Bud

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  • MotoChris521

Posted October 11, 2004 - 06:25 AM

#7

You have to replace the pilot jet.(with a 52 -for stock exhaust)Stock is a 50.Did you grind off the limiting tab on the idle air screw?That needs to be out (from fully seated )2 to 3 turns.I never did get my '03 to run right with the DJ needle.I went back to the stock needle shimmed(.040")and factory Keihin jets.
Yes ,the oil temp guage is a good way to tell how hot the bike is running.Mine was up to 285-300 degrees when not jetted right.After i finally dialed it in ,it dropped to 225-250. :cry:

  • seebee

Posted October 11, 2004 - 06:49 AM

#8

You have to replace the pilot jet.(with a 52 -for stock exhaust)Stock is a 50.Did you grind off the limiting tab on the idle air screw?That needs to be out (from fully seated )2 to 3 turns.I never did get my '03 to run right with the DJ needle.I went back to the stock needle shimmed(.040")and factory Keihin jets.
Yes ,the oil temp guage is a good way to tell how hot the bike is running.Mine was up to 285-300 degrees when not jetted right.After i finally dialed it in ,it dropped to 225-250. :cry:


Ditto.

Babbs, did you drill the slide?

  • babbs

Posted October 11, 2004 - 12:14 PM

#9

I talked to the guys at XRs only, and they said a 58 pilot, might do the trick. So I ordered a 58 pilot, and a temp sensing dipstick. So I will end up with a Baja designs jet kit with 160 main, 58 pilot, uni filter, desmog, desnorkel. I am waiting on my manual to arrive before I check the other suggestions mentioned above, as I have no idea what the peices are that were mentioned.

Thanks for the advice, Babbs

  • babbs

Posted October 11, 2004 - 12:18 PM

#10

I did not drill the slide, Baja designs said the new spring made it so you wouldn't have to drill the slide. I'm waiting on the manual to check the Air Cut diaphragm.

  • roadcam

Posted October 11, 2004 - 02:49 PM

#11

I gotta go with a vacuum leak ... spray WD40 all around your carb. base and manifold, etc. while the engine is running ... if it picks up a few RPM, you'll know where the leak is ... stick with it, usually your problems will be the simplest, check your basics first ... good luck

  • XR650L_Dave

Posted October 12, 2004 - 09:07 AM

#12

drilling makes a MUCH bigger difference than changing the spring.
In the end, since I got ripped-off by the kit, I drilled and kept the weaker spring.
Throttle response is quite nice.

Dave





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