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Post Info TOPIC: stock jets 2003 US model


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stock jets 2003 US model
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There was some question about stock jets on US models - for the record, I pulled the carb on my 2003 US model, which I'm pretty certain has never been touched, and the jets are in fact 137/50 (as Jarrah had opined) even though my manual says the pilot is 52.  I was told this bike was originally sold in Alaska, where it sat for many years (without draining the carb).  Don't know if the Alaska thing could mean a different carb set up from the factory, that doesn't seem likely.

I bought it this winter and have only had it out for real 4 times since.  After I cleaned the air filter and pipe I was having an idle speed problem, it seemed lean at idle and I couldn't adjust it, so cleaned the carb and it idles just fine now and starts without choke when warm (all settings are per manual, air intake, filter and pipe are still stock US).  The jets weren't super clogged but needed a cleaning.  It still doesn't purr at idle quite like it did with a gummed carb and filthy air filter, but I no longer have any gasp or drag when accelerating off idle and it seems to accelerate a little faster overall.  Maybe the bike just runs a little lean stock.  Or maybe I'm just fooling myself.  This is near sea level and at mild temperatures.  I plan to leave it as is for a while since most of my riding will be above 5000 feet (when the snow melts, that is), and being a little lean down here may work out ok up there.  I'll try some air flow mods in the mountains, maybe a new air filter.



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Thanks for the report PlumasDude thumbsup.gif.

Now the tally is (about) 6 people using 50/137 from factory. I am yet to find anyone using the #52 from factory so the manual is wrong!

I have always wondered if the US models run lean with the #137 main. It seems such a small main jet but I guess that the poor fuel quality in the US may have a lot to do with it? I personally would try lowering the jet needle clip position (towards the sharp end) out of curiosity.

Jarrah

 



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I can see that it will take some time to get this carb thing dialed in. Now that I've got it cleaned, and set needle at what I think is recommended in manual, I took it out for a few hours and the plug doesn't look bad, it doesn't seem to bog down on acceleration or miss at high RPMs, doesn't smoke or anything, but it now POPS (mini-backfires) a lot more on low-pressure deceleration (by "low pressure" I mean it doesn't pop when I downshift hard for serious engine braking, just when I let off throttle and "coast" a bit). So maybe I'm a bit rich now? That would be the needle I guess, maybe the clip is set too low. Or maybe the airflow is so restrictive its rich even with the 137? Back into the carb ... not what I had in mind for the weekend. Maybe I'll just wait a few weeks till I can run it at 6000 feet and see how it does up there first.

And the idle speed is now highly sensitive, if I set it just a little high it wants to race when warmed up so I have it set at the lowest speed I can run without stalling.

I don't know about the gas quality but I'm not using any ethanol, just US regular (whatever that may be).

Any comments on davecambo's post from a year or two ago ("quick way to adjust needle clip") about adjusting needle clip without removing the carb? Dave? I'm not much of a mechanic so anything to make this easier.

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Sounds like it is running slightly rich, adjust the needle accordingly. I would suggest to just bite the bullet and remove the carb as taking short cuts can be costly.

Just about all fuel in the US contains up to 10% ethanol (and up to 18% with some dodgy sellers), unless you buy racing fuel. Only a few states even need to label it E10 as they do in AU- http://www.fuel-testers.com/state_guide_ethanol_laws.html

http://www.ehow.com/about_5501439_epa-ethanol-regulations.html

Jarrah



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