Yet another jetting question...55/158 or BIGGER


11 replies to this topic
  • 94XR650LaJolla

Posted September 21, 2005 - 08:47 PM

#1

San Diego,CA, sea level. Mods: De-smog, Uni-Filter, I'm going to run 55/158 and a .03" shim. This is what is said to do in the carb mod article. I've noticed people running up to 58/163 at the same altitude without exhaust mods. Should I maybe go up a little?

Also, how does the shim affect things? Does it need to be changed in accordance with the jetting? I know "every bike is different", how do you tell when you need a bigger main or pilot, or when to be using a thicker shim?

Lastly, I tried running around stock without the baffle. It was too loud for me, everyone wanted to race...What's a good aftermarket baffle, if anyone makes one? I assume it would be much cheaper than a whole exhuast and do the same thing. I don't have access to a spot-welder, otherwise I'd just throw in a larger tube and make something.

I did search around quite a bit, but didn't find the answers I was looking for.

Thanks guys

  • crmc33

Posted September 22, 2005 - 03:30 AM

#2

Jetting is dependant on how much air youre pulling thru (as well as other factors) and its pretty much trial and error unless youre on the dyno. The main jet controls your mid and top end power. The shim alters the height of your needle which controls the midrange.

If you go richer and bike pulls better then youre going in the right direction. If not try leaner, tho be careful not to run it so lean you overheat or seize the the motor.

My experience is that the dyno is great to get close to the right jetting put you cant beat setting it up on the road for better real world riding, where airflow and different throttle openings are encountered.

HTH :banghead:

  • lrutt

Posted September 22, 2005 - 04:40 AM

#3

I could not go 158 or 160 on the main, just too rich. I'm at sea level as well, although in FL where it's humid. I have all the mods you do plus opend up the air box some and an IDS2. I have a 155 main and that is just right. These bikes really don't have a huge top end rush anyhow. My low and mid is great. Powers the front up in 2nd no problem. I think if I were to cam it I might go a 158, but for now it's perfect at 155.

  • goblin127

Posted September 22, 2005 - 05:01 AM

#4

that jetting worked fine for me before I put a complete exaust on. Im at about 140 feet above sea level.

  • 94XR650LaJolla

Posted September 22, 2005 - 07:37 AM

#5

Thanks guys. Add to that mod list: removed snorkel. I'm going to try the 55/158. What should I play with first, the 2-2.5 turns on the screw, then the shim or the main?

  • TREADMARKS

Posted September 22, 2005 - 09:09 AM

#6

55 pilot, 170 main and needle shimmed 50k. Sea level hell hot and humid Florida too.

01 XR650L Mods include Dave's carb mods, desmogged, snorkle removed, HotCams stage 1, big tube header (wrapped), W/B E-series straight through with turn down tip, 16/45 gearing.

I think the 170 may be a tad too much, but she pulls nice and solid right up to 100 mph. Will port the side cover next, and it should be about right.

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  • justicedone

Posted September 22, 2005 - 02:43 PM

#7

I am in SD and run 55/158 aprox oo3 shim, and about 2.3/4 turns. It runs sweet and doesnt hesitate. You have to turn up the idle when shes cold for about 2-3min then lower to correct idle. Then PIN it...he he

  • Dual_Dog

Posted September 22, 2005 - 05:32 PM

#8

San Diego,CA, sea level. Mods: De-smog, Uni-Filter, I'm going to run 55/158 and a .03" shim. This is what is said to do in the carb mod article. I've noticed people running up to 58/163 at the same altitude without exhaust mods. Should I maybe go up a little?

Same area, similar machine, same mods except I'm using an IDS2 QC slip-on. I'm using a 158 mj & a 58 pj with the ps 2.5 turns out. Runs strong with no issues.

Also, how does the shim affect things? Does it need to be changed in accordance with the jetting? I know "every bike is different", how do you tell when you need a bigger main or pilot, or when to be using a thicker shim?

Fuel delivery past 1/4 throttle as stated. 0.030" is right in the middle. You can go higher (thicker) but it's not needed with the stock compression & cam. Full exhaust systems can require richer jetting. Do a plug chop and see what the color is. White = too lean. Black = too rich. Brown = just right.

Lastly, I tried running around stock without the baffle. It was too loud for me, everyone wanted to race...What's a good aftermarket baffle, if anyone makes one? I assume it would be much cheaper than a whole exhuast and do the same thing. I don't have access to a spot-welder, otherwise I'd just throw in a larger tube and make something.

Baffle? Do you mean muffler, or are you talking about the core inside the stock muffler? I've heard of a HRC tip you can add at the end of the stock can but that's it. Slip-ons aren't too pricey and they shed some weight and provide better flow.

I did search around quite a bit, but didn't find the answers I was looking for.

Thanks guys

You should be good to go now.

  • 94XR650LaJolla

Posted September 22, 2005 - 07:30 PM

#9

Thanks guys!

By "baffle" I am referring to the restrictor that is soldered onto the very end on the exhaust opening and held on by 2 bolts, it's also a spark arrestor.

I picked up all my parts today, hopefully I'll have time to throw them on tomorrow. I'm going to throw on my air filter tonight since that takes about a minute. Then do the de-smog and make sure it's running right. Then the carb mods, that way if something's not right I know where the problem is, plus I'll get to feel the performance increase step by step which should be fun :banghead:

Hopefully, it will all go smoothly without any hickups. Thanks again.

  • XR650L_Dave

Posted September 23, 2005 - 08:17 AM

#10

The baffle/restrictor at the end of the stock XR650L muffler is not part of the spark arrestor, so you're still USFS approved if you yank it.

Dave

  • goblin127

Posted September 23, 2005 - 12:53 PM

#11

You need to do the shim and the drilling of the slide to make this work. I think that was part of your Question.

  • 94XR650LaJolla

Posted September 23, 2005 - 06:01 PM

#12

Na, I considered that all part of the "carb mod", but thanks for your input.





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