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Enduro Intake/Carburetion - 2 stroke Jetting, Reeds, Air Filters, etc.


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Old 12-03-2011, 10:02 PM
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Hi, all-

I am just getting my 2002 XC300 ready to ride, and wanted to run my jetting past the "experts." I bought the bike last month and spent the last few weeks sorting out some issues, but now I'm about ready to ride it in anger. A couple of spins in front of the house do not provide accurate jetting, but it does upset the neighbors a bit.

Here's my current set up-
50:1 Premium pump/Amsoil Dominator
Carb is stock, as far as I can tell. No obvious modifications to any external points or functions.
Needle- Don't know. The only markings are "CC" (maybe GG?). Nothing else indicated.
Clip- was on second from top (lean), now in middle (it's what I do to set baseline on my other bikes)
Main- 170
Pilot- 38
AS- Now at 1.5, was at .5

Any suggestions from those who ride Walker Valley, Tahuya, and Capitol Forest? I don't mind buying a handful of brass, but I do want to make sure I am going in the right direction. I don't want to make any broad generalizations or assumptions, but previous experience with this bike in my riding area is preferred. The main reason to question the current jetting is that it's a former California bike, and I think it was set up for hot weather high-country riding. The piston looked kind of lean (lots of carbon), and I want to make sure I don't melt anything my first time out.


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Old 12-03-2011, 11:40 PM
PEB PEB is offline
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I am by no means a jetting guy. However that is lean compared to what is in mione for the same areas. I think I have a 42 and a 178, which i run from sea level to 8,000' Which one is the air screw and what does it do?
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Old 12-04-2011, 01:42 AM
cascade_crawler cascade_crawler is offline
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With the cold weather around here your probably gonna want to richen it up a bit. Our carbs are different but this gives you an idea of what worked well today...42 pilot, 178 main.
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Old 12-04-2011, 02:01 AM
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Jetting is all depends on how you ride. Are you going to ride 1st gear single track well then that 38 pilot might work for you; I run a 38 in my 07.
A 170 main could be OK unless you hold it wide open for long periods. Since you opened the air screw out that means you wanted it leaner. I've been riding a few years now and I have never seen anybody seize their bikes because of a lean pilot or needle; bad jetting = bad throttle response at lower RPM and a poor idle.
A rich main jet will run like crap (spit and spudder but never clean out when pinned) at high RPM but a lean main will sound good but will toast your motor, so it is better to be rich on the main and then slowly back off just to the point where it runs clean for the area you ride at.
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Old 12-04-2011, 09:52 AM
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I plan on riding slow single track to fast fire roads, mostly second and third gear open trails. Walker Valley is closest to me (Shoreline), but my riding buddy lives near Tahuya and we go to Capitol Forest more often now. I hope to be on the trails more than last year.

Regarding the air screw, I simply opened it per the manual to start jetting. I haven't even heat cycled the engine yet in my neighborhood, hopefully later this week will provide an opportunity. Heck, maybe even today if I get the chance.

I plan on taking a "mental health day" on the 16th to Walker and really sort it out. That's two weeks away, but it's the best I could plan for.

Now, what's the easiest method to swap jets and pull needles? I have a desert tank that surrounds the carb, do I need to completely pull the tank and carb, or can I get away with pulling the tank and rotating the carb in the boots to access the float bowl? Oh, and any suggestions on float height? I never measured that, probably do that later today, too.
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Old 12-07-2011, 09:28 AM
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I warmed the bike up and gave it a couple of spins down the road. I was running really rich off idle, AS is at 2 turns out with needle at 2nd slot from top (lean), jets as listed above. Runs better, was very rich off idle before. I can not wait to give it a proper trail ride and sort it out. Also, I was able to change the needle without too much effort, the main will be a bit more trouble as the desert tank won't allow me to rotate the carb to get access to the float bowl.

Anyone have float height suggestions? I still need to measure mine, but I would rather get in there just once rather than several times.
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Old 12-20-2011, 08:05 PM
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Okay, I am absolutely frustrated right now. Cleaned the carb like it swore at my mom. Fresh gas. Fresh oil. Same result. Doggy on the bottom and just not running right. Runs "best" (relatively) at 1.5 turns on the AS with needle at leanest clip. As I have a 170 and 38, should I just go big and see if that clears it up? Should I go for the NEDJ needle, 175 main, and 40 pilot? Different ratio? Different oil? (Amsoil Dominator at ~50:1)

If anyone around the North Seattle area wants to come over, or have me come over, I am down with that. I really want to ride this bike over the holiday break, and I want it to run properly. Heck, maybe my problem is that I don't know what "running properly" is? Therefore, if someone wants to help me out, there is food/beverages/gas money in it for you.

Anything at this point will be helpful. Don't make me go back to my YZ426, did you see what that four-stroke did to Jakobi? Don't make me do it!

Phil

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Old 12-20-2011, 09:33 PM
PEB PEB is offline
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What do the reeds look like? I think you would need to pull the carb so set the float. Not a big deal, easiest if you swing the sub frame up and away by pivoting it on the upper bolts.
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Old 12-20-2011, 10:04 PM
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As above. Whats the state of the engine?? Compression? Spark plug? How many hours on the top end? Any chipped reeds? Float height? Has the head been modded at all? Squish gap?

Then variables. Elevation, temp, relative humidity,
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Old 12-20-2011, 10:36 PM
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I pulled the carb (I had to clean it, after all), float height is 19mm. Float seam not level with carb seam (closes early). Reeds were interesting. They did not seal, about a 0.030" gap from totally closed. I took them off to flip them, thinking I was so clever, but after I flipped the top one the gap was worse. So I returned it to original. I know it sounds like I'm from Planet Stupid, but shouldn't the reeds seal? But no chips or cracks.And yes, pivoting the subframe helped immensely.

As for variables, about 45F, 250' above sea level. 92% humidity. I'll check compression tomorrow. Decent sparkplug. I think stock squish (not measured).

As for top end, the seller told me that it had ~10 hours on an Eric Gorr top end. Which is a lie, unless Eric uses wrong fasteners, strips threads, loses washers, and is a general incompetent. Which he may be, but beyond that, it's a bit tired. I'll get proper numbers tomorrow.

After some deliberation, I'm thinking reeds are causing some issues. Same as 1996 YZ250, yes? Boyesen reeds, if there is any question.
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