Rejet and lost top end power -


13 replies to this topic
  • klmmicro

Posted October 05, 2005 - 07:06 PM

#1

Quick question -

I rejetted my XRL's carb today and I love what it has done to the bottom end of the curve! It is like a new bike. I puttered around town for a while and it was nice to be able to accelerate smoothly.

The question is regarding when I hit the freeway. Though the bike pulls great at low speeds, it has lost some of the top end pull it had. There was a definate drop in power and response once I hit about 75 by the speedo. Any ideas?

  • justicedone

Posted October 05, 2005 - 07:25 PM

#2

Did you drill out the slide and shim the needle? That may be the problem if not. 55/158 jets?

  • klmmicro

Posted October 05, 2005 - 07:48 PM

#3

I shimmed the needle per the instructions, but did not drill anything. I will probably pull it apart again this weekend and drill it. The jet is a 160 (Dyna) as is the needle and spring. The guys at BD's said it should be about perfect.

It will lift the wheel now...I just need to keep it upright while going down the hills :banghead:

  • bsukalski

Posted October 05, 2005 - 08:25 PM

#4

I installed the DJ kit a while back in my L, and had the same issue! Given I am at 5000', but the response was similar to yours. Then I got bored one night, and decided to take out the DJ kit and try Daves mods...and bingo, power at highway speeds returned!!

It sucks that we spend so much for the DJ kit (BUT, I got to use the DJ spring and washer for the stock needle), when there is such a cheap mod right under our noses. I guess I wanted to find out for myself, though :banghead:

Good luck!

  • goblin127

Posted October 05, 2005 - 08:26 PM

#5

You should drill the slide. As far as top end you should have not lost any thing. Grind the tab on the air fuel mix screw and set at 2.5 turns out and try it again.

  • GIANTac1

Posted October 05, 2005 - 08:41 PM

#6

Removing the smog equipment, the snork and adding a new air filter(uni/k&n) should also help. An aftermarket exhaust is also a solid mod. You should feel a substantial power gain after all is said and done. :banghead: But remember it is just a "L" model, right B-dub! :banghead:

  • ghoti

Posted October 06, 2005 - 04:46 AM

#7

Quick question -

I rejetted my XRL's carb today and I love what it has done to the bottom end of the curve! It is like a new bike. I puttered around town for a while and it was nice to be able to accelerate smoothly.

The question is regarding when I hit the freeway. Though the bike pulls great at low speeds, it has lost some of the top end pull it had. There was a definate drop in power and response once I hit about 75 by the speedo. Any ideas?


What else have you done? Air filter, snorkle, exhaust baffle? If you just re-jetted without an air filter that may be your problem.

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  • klmmicro

Posted October 06, 2005 - 05:06 AM

#8

I have the smog removed. The fuel mixture screw is at 2.5 turns. Still running stock exhaust (I like the stealth) and filter. I am going to pick up a Uni this afternoon. The bike is noticably cooler and there is a definate difference down low.

As for not loosing top end, that is what I thought too. It is the part I can't figure out. The drilling would increase throttle response, but not make a difference in the curve I would think. I could be wrong and I am going to do it. I will probably try Dave's mods soon as well.

  • Dual_Dog

Posted October 06, 2005 - 07:29 AM

#9

The pilot screw has nothing to do with WOT performance. It's only for fine tuning the idle circuit.

Drilling the slide does not increase top end speed, it only increases the responsiveness of the vacuum piston. Faster movement = better performance and less potential for bogging.

From what you're describing, the motor is probably leaning out. Upsize the main jet to a (Keihin) 158 or 160. Shimming the (stock) needle also helps, if you still have it...

  • klmmicro

Posted October 06, 2005 - 07:51 AM

#10

I have the stock needle (not in the bike) and I am running a 160 jet in there now. It does feel like it is leaning out on the top end, though the bike is running A LOT cooler, so I sort of wonder.

After reading the page in "Dave's Mods", I think i will try that direction. At least working on this carb is easy!

  • acb0173

Posted October 06, 2005 - 08:10 AM

#11

Didn't I read somewhere in another jetting related post that the DynoJet #160 was NOT the same as the Keihin #160? I think it was Dave and he might have suggested that the DJ #165 would be a closer match to the Kehin #160.

  • klmmicro

Posted October 06, 2005 - 08:20 AM

#12

In that case I will try the 165 out. I figure it cannot hurt anything and it included in the kit.

  • ghoti

Posted October 06, 2005 - 09:31 AM

#13

The DJ 160 is smaller than the Keihien 160. I've heard the taper on the DJ needle is not good, the stock one works better. I've had my carb apart a bunch of times just messing around and always come back to "Daves recommendations. Go figure. Get the Uni filter and go from there.

  • arrowhead

Posted October 07, 2005 - 04:16 AM

#14

Here is what has worked for me. I used the DJ spring, the DJ 160, and I used the washer from DJ to shim the stock needle. Air screw 2 1/4 turns out. Removed the air snorkel. Also using the stock exhaust. It's just about perfect at 2600 ft.





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