For those of you that ride in extreme elevation changes:


11 replies to this topic
  • Rot Box

Posted August 09, 2011 - 07:32 AM

#1

I went for my first ride on local single track with the WR (02 426F) a few days ago and had a lot of fun!

I think I have the jetting nailed @ 4500-5k' here in the valley however once I started heading towards a mountain peak @ 9200' the 1/4-1/2 throttle response was completely falling on its face and bogging out. I had a very difficult time keeping it going forward unless I was on the clutch or balls to the wall. I'm guessing here but it seemed like at about 7.5k feet is when it started having issues. Starts up fine, idles fine and revs out well so I'm going to drop the needle and try that for next time. I fiddled with the fuel screw and it helped a little bit but not much...

How well do your bikes deal with altitude changes like this? Assuming this is normal do you know of any tricks or tips for these situations? Do you think a dial a jet would work for bottom end as well? I don't really want to lean the jetting (pita on these bikes!) out too much because I ride it down in the valley a lot during the week. Anyway open to ideas thanks!

Andrew

  • Krannie McKranface

Posted August 09, 2011 - 07:47 AM

#2

I keep a lean needle and a rich needle in my tool box.
If I go above 6000ft, I go lean, and vice versa.

A R&D remote fuel screw is also a HUGE deal to have on the trail, as you go up in altitude. It won't solve a rich needle jet, but it will reduce it's affects....
Until you stall, and then you have to adjust it back, to get it to start easily....

  • Alizar

Posted August 09, 2011 - 10:48 AM

#3

I ride an 06 WR450, so I'm not sure how well my experience will transfer to your bike.

I have ridden mine at Moab (~4,000 ft) and up mountains in Colorado to just over 13,000 ft. without changing jetting, fuel screw, or anything. I have a 50 pilot jet (stock is 45), and a 160 main jet (stock is 165). Needle and everything else on the carb is stock.

It did not run perfectly under all those conditions, and it definately was hard to start & idle at 13,000 ft, but it was not as bad as what you describe. My typical rides are from 6,000 ft - 10,000 ft and I don't normally notice any difference.

  • Rot Box

Posted August 10, 2011 - 08:10 AM

#4

Good to hear thanks you guy's :eek:

I wish the needle was a little easier to change lol. With my desert tank it makes for a 15minute job. I bumped it down a clip position--Hopefully it helps a bit :smirk:

  • Just_a_trail_rider

Posted August 10, 2011 - 03:48 PM

#5

I jet for 6-9K feet using the JD Jet kit. I ride all the way down to 2500 feet (and lower elevations) at times.

I have the flex jet and the adjustable leak jet. A half to full turn on these will keep you running good. Both are external to the carb and are really easy to reach. I haven't change the jets and or needle in years.

  • RockyMtnScotsman

Posted August 10, 2011 - 06:27 PM

#6

I ride an 06 WR450, so I'm not sure how well my experience will transfer to your bike.

I have ridden mine at Moab (~4,000 ft) and up mountains in Colorado to just over 13,000 ft. without changing jetting, fuel screw, or anything. I have a 50 pilot jet (stock is 45), and a 160 main jet (stock is 165). Needle and everything else on the carb is stock.

It did not run perfectly under all those conditions, and it definately was hard to start & idle at 13,000 ft, but it was not as bad as what you describe. My typical rides are from 6,000 ft - 10,000 ft and I don't normally notice any difference.



Identical jetting to mine except that I have a YZ needle in my '06

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  • jcbikes

Posted August 11, 2011 - 05:37 AM

#7

My 02 WR426 is jetted for around 8,000 feet here in Colorado. I live at 5,600 feet and ride a lot around 10,000 feet and sometimes up to 12,000. Bike runs great at all elevations. When I get above 11,000, sometimes I have to increase the idle speed just a bit but that's about it. Maybe you can try to jet somewhere in the middle of the elevations where you ride. Works for me.

  • GCannon

Posted August 11, 2011 - 07:39 AM

#8

My 02 WR426 is jetted for around 8,000 feet here in Colorado. I live at 5,600 feet and ride a lot around 10,000 feet and sometimes up to 12,000. Bike runs great at all elevations. When I get above 11,000, sometimes I have to increase the idle speed just a bit but that's about it. Maybe you can try to jet somewhere in the middle of the elevations where you ride. Works for me.


Maybe you could share your jet setup with the OP when I ride altitude I drop my main from 168 to 165 and I drop my pilot from 42 to 40 I leave my needle the same for convenience.

I then adjust my flex jet remote air screw (critical for kick start only)http://www.rockymoun...dFamilyId=22925
After a warm up ride. then i am good to go.

I am not sure what to OP's set up is but if it is running very poor as described he may need more of an adjustment that lowering the needle 1 clip.

I don't know what the situation with his Accelerator Pump (AP) is but the area he describes his problem happening could be too much squirt volume in conjunction with too much pilot jet since they are both happening at the same time he describes and he is needing a lot more air to clear the problem (wot). if during constant 1/4 throttle on a long straight the engine clears after some time (or not) may give some indication whether the pilot jet or the squirt volume need to be addressed.

  • Rot Box

Posted August 11, 2011 - 08:35 AM

#9

Thanks everyone for the ideas and sharing your experience! I forgot to mention my jetting :eek:

45p
2turns fuel screw
needle 4th clip
main 165
Airbox lid removed, stock muffler with GYTR insert, FMF power bomb header and 91 octane.

When I bought my bike it was VERY lean everywhere and ran terrible. Again it now runs very well at 5k' without hiccups or backfiring. I have my needle in the 3rd clip now and I'm going to see how that works out for tomorrows ride in similar elevation. I'm afraid once clip position isn't going to make the difference...

I don't know what the situation with his Accelerator Pump (AP) is but the area he describes his problem happening could be too much squirt volume in conjunction with too much pilot jet since they are both happening at the same time he describes and he is needing a lot more air to clear the problem (wot). if during constant 1/4 throttle on a long straight the engine clears after some time (or not) may give some indication whether the pilot jet or the squirt volume need to be addressed.


I have been dreading this ^ but thanks I think you may be onto something. Prior to me buying my WR I spent about a week tuning in the AP on a friends modified YZ426 and although I was able to get it I really don't want to do it again lol. If that's what it takes though I'll do it :smirk:

  • jcbikes

Posted August 11, 2011 - 02:42 PM

#10

Here is my jets: 152 main jet, 40 Pilot jet, Starter jet 65 (stock)
Middle clip on needle, air screw is 2 3/4 turns out.
I have done most of the mods (no yz timing) except I left on the top of the airbox which has the snorkel installed and a twinair filter. Also, I have the stock exhaust peashooter removed but packed the inside of the muffler with a tight packing of steel wool. This helped a lot to smooth out the power and to quiet it down.
Hope this helps.

The bike is dual sported (street legal) and I ride from home, 5,600 feet all the way up to 12,000 feet with no problems. Never a hickcup. Engine runs very smooth.

  • GCannon

Posted August 12, 2011 - 09:30 AM

#11

The OP should be a little careful comparing 450 jetting with 426 jetting since the 450's have a newer version FCR carb and they seem to use slightly leaner jetting that the older carb. the slightly larger engine may also have a slightly stronger vacuum signal which may account for the slightly leaner jet requirments of the 450

  • Rot Box

Posted August 12, 2011 - 09:31 PM

#12

Well guy's (thanks again everyone!) the drop in the needle just might have solved my issue. I didn't get as high up as the last ride, but I was close and I didn't get any blubber whatsoever.

We'll see what happens for now I'm keeping my fingers crossed :eek: As a side note I'm really impressed with the WR offroad lately. Coming from a strictly 2T background I'm really coming to grips with how good a 4T can be :smirk:




 
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