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Help with Tempa Flow and jetting on '02 800

2K views 10 replies 6 participants last post by  Portage1 
#1 ·
I've been reading good reviews on Holtzman tempaflow and given how sensitive the '02 800's are anyway I thought I'd give it a try, plus increased fuel mileage couldn't hurt. My main jets are 500's which specs say is for -10F to +10F and are OEM. The tempaflow needs jetting for -20F range which would require 540'on my sled. For those with experience, should I change or stay with the 500's? I ride from sea level up to 1000 ft. most of the time.
 
#3 ·
I ended up at 500's and needles in #3.5 - but that was with SLP single and airbox mod, so not directly comparable
 
#5 ·
FYI.On my stock 2002 XC800 I would run 460s (w/o Tempaflow)all the way down to 0 degrees with no problem. Years ago in an old Snowtech magazine article,Rich Daly at Dynoport dynoed a 02 800XC and had to jet down from 500 to 460 to make any power.With 460s still was safe.
 
#6 ·
Hmm, interesting. Thanks for the input. I would agree w/you if power was my main concern, it isn't. I'm not a WOT type of a rider, but I am looking for a smooth operation with wide ranging temps where I live - 0 one day and 35 the next which makes this upgrade kind of a no-brain'er.
 
#7 · (Edited)
I agree, 460 is as fat as I would go on an '02 xc800. The big problem is 2 things with that airbox. 1) the front plate pops open and will run even fatter. Put a screw in the top corner, cut the tabs off about 3/8" so the carb stops bumping it and opening it up. 2) the 2 horns inside are too close to the bottom, so it increases the vacuum and that is why they have such fat stock jets. Cut the horns off at the plastic collar, 1/2" up from the bottom (like the 2003 airbox horns are). The plastic plate gets bowed down bad from all that vacuum.
I ran a tempaflow on my 2002, then my 2005, both with 450 mains and it was way to fat. I later gutted it on the 2005 xc 800, and ran 430's, again too fat. I have now put that airbox and tempaflow on my wifes 2005 xc 700 since I sold the 800 twins. It still needs to be leaned more than the 430's with gutted box.
 
#8 ·
the front plate pops open and will run even fatter. Put a screw in the top corner, cut the tabs off about 3/8" so the carb stops bumping it and opening it up. 2) the 2 horns inside are too close to the bottom, so it increases the vacuum and that is why they have such fat stock jets. Cut the horns off at the plastic collar, 1/2" up from the bottom (like the 2003 airbox horns are). The plastic plate gets bowed down bad from all that vacuum.


Interesting. I've read allot that the air box doesn't work the best on this year. wish you had a pic that shows what you mean. why not just remove the shelf and horns altogether? I'm mechanically inclined, I just want to make sure I understand exactly what your saying...what tabs are you referring to? I thought if additional air was introduced it would cause a lean condition, much like if the carb boots were cracked?
 
#10 · (Edited)
1) why not just remove the shelf and horns altogether?
2) what tabs are you referring to?
3) I thought if additional air was introduced it would cause a lean condition
1) you can, just need to rejet much leaner and that also has a small effect on needle too, not just main jet.
2) the 2 tabs on the front airbox plate. Push them down and the plate moves into airbox for removal, to access the carbs.
Unlocking by themselve, causes a pressure leak, that makes it run (much) richer!
3) Ivar nailed that explaining vent tubes. Not about more or less air. It is what the pressure change is doing to the fuel flow in carb bowls.
I do believe gutted or partly gutted flows more air, so more power, but only if jetted right. Stock vs just cutting those 2 horns off 1/2" needs 2 sizes less main jet. Fully gutted about 4 less on main jets. My son was running 410 mj in a 2003 xc700, with SLP pipe, RKtek head, and a gutted box at -10 deg F. I went up 1 size to be "safe", just a false sense of security. Any low octane or poor fuel will detonate, causing a burn down, even with fat OEM jetting.
 
#9 ·
as the carbs are vented to the airbox, below the shelf, removing the shelf + horns (often referring to as gutting the box) reduces the vacuum fed to the float bowls making the sled run richer.
Gutting causes a little more intake noise.

Also , local conditions play a role - the jetting need2snow runs would be too lean for where I live.

Another reason for big mains on the 02 is the lean needles used compared to 01 and 03 XC's. This makes for nice fuel economy when cruising in the midrange though - bone stock my old 02 got 14-15 on hardpack - that better than all my newer sleds can do.
 
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