Hi Desert Jetting



6 replies to this topic
  • tma

Posted February 26, 2003 - 11:37 AM

#1

Anyone have any jetting recommendations for an uncorked '02 XR650R (typical Honda uncork package w/ the HRC baffle) for riding in the Red Mountain, CA area - not sure of altitude.

Rode last weekend at Stoddard OHV (off Hodge Rd) with a 172 and the clip in the 3rd position... Ran OK but I'd like crisper throttle responce.

Thx in advance for help.

Tom

  • qadsan

Posted February 26, 2003 - 12:50 PM

#2

I believe the Peak of Red Mountain is 9874 ft, so if you're mostly going to be riding at 5,000 to 9,000 foot level, then you may want to try a 165 or 168 main jet. You may also want to try 65s pilot jet for better low end throttle performance. You'll also likely have to adjust the fuel screw to get the most out of it.

When you go back to riding at Stodard by the Slash X off Hodge Rd, then go back to the 172 main and 68s pilot as it should be in the ballpark for that area. If your throttle response doesn't seem good with this setup, then try adjusting the fuel screw, which should help to crispen things up a bit.

  • tma

Posted February 26, 2003 - 12:58 PM

#3

Thanks for the feedback. I'll give it a try. How do you like the Edelbrock carb? Is the improvement drastic?

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  • needsprayer

Posted February 26, 2003 - 01:11 PM

#4

I ride in high desert, southern AZ @ 4800'
Main: 170
Hop Up Needle Position: 3rd clip
Pilot: Stock

If I was going to 6000-7000' I would try a 165 (Like Qadsan says)
Just make sure you change back to a larger main jet when you go down to sea level or you will be lean and may cause engine damage.

Also, put on a good set of tires on for traction (rocks, sand, hard pack)

  • qadsan

Posted February 26, 2003 - 02:57 PM

#5

How do you like the Edelbrock carb? Is the improvement drastic?



I like the Edelbrock carb and would gladly buy it again. I'm the person who has to take care of a half dozen or so bikes when we go out riding, so I'm the one rejetting them when we ride at different elevations. I never have to touch my Edelbrock because it features dual vent altitude compensation to maintain the same air/fuel ratio from sea level to 10K feet, so its one less bike for me to play with. I have not tested that feature to the extremes, but it works for my typical applications from around 2000 to 7000 feet. Performance is also very good. I've been used to open class 2 strokes most of my life except for a few 4 strokes I've had in the 70's such as a XR75, XR80, TT500, so the off idle throttle response from the XR650R wasn't as exciting to me no matter how I jetted or tuned the stock carb and that's one of the reasons I went with the pumper. It's just like in the 60's & 70's when most muscle cars came with pumper carbs. They'd run without the accelerator pump, but they just didn't have good crisp off idle performance and that's where the pumper carb helps out because it manually pumps in the fuel needed at lower RPM with the twist of your wrist as opposed to waiting for enough of an already lagging vacuum signal to suck in sufficient fuel from the jet. So yes, there's a very significant improvement in off idle performance with a pumper carb if that's what you're looking for. Also, the Edelbrock has an internal fuel cell and anti-slosh plate that prevents the bike from flooding even if you take a spill. The bike can actually run sideways and while nobody is going to do that, its a good demo of how well the fuel supply system works because the stock carb would have stopped delivering and started pouring fuel out the vent lines. Also, my bike usually starts the first kick when hot, cold or when dumped with this carb and while my bike started fairly well with the stock carb, it would not have started in 1 or 2 kicks if it was dumped. This carb is also easier for me to tune when compared to a jetted carb should I need to make changes because the Edelbrock doesn't have jets. You do most of the tuning by turning a dial on top of the carb, which raises or lower a precision back-cut needle and you don't need to take the carb apart to do this.

Last time I went riding I was going down a narrow twisty packed sand wash in 2nd close to WOT and sometimes in 3rd. It was like riding in a channel about 1 foot deep and maybe 4 to 6 foot wide with scrub on both sides, so you couldn't really see the surrounding terrain except for what was in front of you and there were many blind corners along the way. All of a sudden I was presented with a washed out squared edge channel in front of me around the corner just as I let off the throttle, so I gave my bike a handful of throttle and powered through it with my front wheel up. The throttle response was right there for me to do this where as the stock carb may have fallen flat for a brief moment and perhaps I would have crashed because of this. I'm sure a talented rider would have used some trick body english to get through this without any problems, but I was glad to have that extra edge to help me out.

Later that day there was a long section of nasty whoops that were beating me up badly to the point where I was having a hard time staying on the bike due to exhaustion, pain, etc. There were a few bikes and quads in our group on this ride and while I felt pressed to keep up, I just couldn't and began to slow down from 3rd to 2nd and was planning to pull over and rest. Again, all of a sudden there was a large uneven nasty rock at the base of this irregularly spaced whoop and there was no avoiding it, so I quickly gave my bike a handful of throttle and powered through it. I hit the top side of the rock and my handlebars jerked hard for a brief moment, but I truly believe my Scotts stabilizer saved me from going down along with the quicker throttle response from the Edelbrock. If my throttle response wasn't there while I was slowing down, then perhaps my front tire would have gone deeper into the whoop to hit that rock harder and I may have been thrown from the bike. One of the quads hit that same rock and trashed one of its front wheels, which made the ride back to camp real fun. Another bike hit that rock and the rider was thrown without any serious injury, but I don't remember if there was any damage to the bike other than bent handlebars. If I wasn't slowing down at the time, I probably would have sailed right over this rock without any incidence, but its times like these where I'm glad I spent the money on the carb and stabilizer as I sometimes need all the help I can get.

You don't need a pumper carb or steering stabilizer to win races or to have a great time on your bike because it already runs good enough for most people and or racers, but it does make the experience more enjoyable in my opinion and I'd gladly buy these products again.

  • billmunson

Posted February 27, 2003 - 05:10 PM

#6

Red mountain on 395 before Johannasburg is 5000 ft. at peak (you can't get there) but city is 3200. Jet the same as Stoddard. I go down a size on my Xr600 only when i go to the Sierra's.

  • qadsan

Posted February 27, 2003 - 05:34 PM

#7

Red mountain on 395 before Johannasburg is 5000 ft. at peak


Hmmm....I should have realized there's more than one Red Mountain (good point) :). The Red Mountain I was thinking about was in Fresno county.

Red Mouintain in Fresno - 9874 ft summit
http://geonames.usgs...tab=Y&id=265295





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