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Old 05-07-2012, 11:06 PM   #211
thump_co OP
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Location: 8532'
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Quote:
Originally Posted by wakewop View Post
Setting the idle a tad higher can get rid of the bog some.
As far as boiling over, every ktm should be running the 1.8 radiator cap. Also, make sure your coolant is just a tad over the fins on the fill side radiator. If too full, there is nowhere for the coolant to go when it heats up and expands. It goes out the overflow in that case. Unless you have a catch tank, then it recycles itself. The bikes have tiny radiators compared to how much heat they produce. They need good airflow which means going faster.
Another solution is to wire in a computer case fan (more cfm and less power draw then the oem ktm fan). Simple to do and extremely cheap. That is what saves my slow butt on my 450. Lots of info on KTMtalk about the compuer fan.
Thanks. I do have a new 1.8 cap on there, but with the lean jetting it was still boiling the bike dry. I've also added a catch tank, upgraded impeller, and have the fan kit on the way. I love my fan on the 450 as well, but don't want to slap it on this bike until I'm sure I have the jetting sorted first.

With the pilot being lean right now I have to crank the air screw so far in that I have to max out the idle just to keep it running.. and it idles very uneven. I'm hoping that bumping up to the #40 pilot will allow me to open back up the air screw enough to allow it to breath proper and get a stable idle setting. It also still occasionally dies on longer, steep downhills, so if the idle doesn't fix that I think I'll probably need to drop the float a little further as well.
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Old 05-08-2012, 04:06 PM   #212
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The impeller upgrade did very little for my hot running bike. I also fought the jetting for an entire summer. This was in a bike that had 0 problems before. I finally gave up and sent the carb to Dave Hopkins in Washington (Ktm talk guru) and had him give it the royall treatment. Full ultrasonic cleaning , jetting and a custom tapered needle. Accelerator pump all tweaked up , squirt duration, and several o rings replaced. Set float height. Basically completely serviced all parts of my carb. Had 2 cracked o rings that I did not know even existed in the carb. Cost was $ 160 and the bike ran amazing after. Temps were never again a problem. Every bit of bog was gone.
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Old 05-08-2012, 04:26 PM   #213
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Originally Posted by wakewop View Post
The impeller upgrade did very little for my hot running bike. I also fought the jetting for an entire summer..... Every bit of bog was gone.
Innnteresting.... was that on a 4-stroke or 2t? I've heard even the slightest air leak can cause these things to freak out.. but the carb on this 300 is so simple I'm not sure what else could be replaced.
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Old 05-08-2012, 07:01 PM   #214
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Originally Posted by thump_co View Post
Thanks. I do have a new 1.8 cap on there, but with the lean jetting it was still boiling the bike dry. I've also added a catch tank, upgraded impeller, and have the fan kit on the way. I love my fan on the 450 as well, but don't want to slap it on this bike until I'm sure I have the jetting sorted first.

With the pilot being lean right now I have to crank the air screw so far in that I have to max out the idle just to keep it running.. and it idles very uneven. I'm hoping that bumping up to the #40 pilot will allow me to open back up the air screw enough to allow it to breath proper and get a stable idle setting. It also still occasionally dies on longer, steep downhills, so if the idle doesn't fix that I think I'll probably need to drop the float a little further as well.

thump-I am glad you got it sorted out.
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Old 05-08-2012, 07:26 PM   #215
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Mine was a 4 stroke. Leaking oring was causing a vacuum and a lean problem.
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Old 05-08-2012, 10:46 PM   #216
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thump-I am glad you got it sorted out.
Thanks.. it's _almost_ there.. still got to get rid of the bog at the very bottom and settle the idle.. should have a #40 pilot coming in the mail tomorrow. Fingers crossed.
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Old 05-09-2012, 08:18 AM   #217
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Thump, I can hear the bog ur talkin about. Through most of that vid the lowend seems off, not just in the couple places you mentioned. To me it sounds peaky in the lower revs, like you might be lean, def not normal for a 300. The idle didn't sound right ether, is it cranked way up? I thought this can't just be me seeing this so I asked another 300 owner who watched it and agreed. These things are like tractors, I know that trail was really steep and knarly but the bike should tractor a little better then what I'm seeing in the vid.

I followed Gordy's advise when I got the 300 and put in a JD kit right away, the 38 has been spot on for everything EXCEPT high alt in the San Juans. I didn't get to fiddle with the bike enough to dial it in up there but it was RICH. I run the 38 from 4k' to mostly around 9k', I imagine that vid was higher than that. I'd think the 38 might be rich up over 10K but then I don't know the mods to the motor. I've heard the mule mods run a big pilot jet and tall gearing.
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Old 05-09-2012, 11:26 AM   #218
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Thank you for taking a look. I'm glad to hear it's not all in my head.. this being my first 300 (and 2t) I have no baseline for comparison and was starting to think it's just not going to be the ideal climbing bike for me.. which would suck because I love everything else about it.

The trail in this vid is only around 7k. I had pulled the carb apart, cleaned it, and installed fresh needles and jets from the JD kit. The settings were at:
* Red needle in #4 clip (from top)
* #38 pilot
* 152 main
* air screw at 1/2 turn from full in
* idle screw maxed

I feel like the needle is pretty close to being on now, even though it's a clip or two richer than what JD said would be the norm for this altitude. Like you said, I do think the pilot/idle is still too lean, even with the #38 and the air screw so far in.. and cranking the air screw in this far makes it idle like crap and die, to the point I had to max the idle screw and even cheat with a bit of throttle cable tension.

I have a #40 & #42 pilot that should be here today. I'm hoping one of these will get the pilot circuit back into shape so I can use a normal air screw setting and hopefully stabilize the idle. Out of curiosity, how many turns (from full) do you run your idle adjustment?

The PO told me that Munn racing did a port & polish when they did the top end. I'm going to call them and see if this (plus the PC pipe) may be why I'm having to jet so much richer than the "norm".
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Old 05-09-2012, 02:06 PM   #219
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Talked to Munn.. They don't think the port/polish should have any significant effect on jetting. They said I shouldn't be needing anything larger than a #38 pilot and this sounded more like a leak somewhere. I tried what he suggested and sprayed windex all over the carb, boot and cylinder with it running to see if it affected the idle - no dice.

Mystery continues...
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Old 05-09-2012, 03:26 PM   #220
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Quote:
Originally Posted by thump_co View Post
Talked to Munn.. They don't think the port/polish should have any significant effect on jetting. They said I shouldn't be needing anything larger than a #38 pilot and this sounded more like a leak somewhere. I tried what he suggested and sprayed windex all over the carb, boot and cylinder with it running to see if it affected the idle - no dice.

Mystery continues...
It does sound like there might be an airleak from the way it's idling. The LH crankseal can let air in also and wouldn't be detected by the windex trick (btw: never heard of using windex for it) I can just relate my experience, 165 has been the biggest MJ it's ever needed and that's worked fine well over 7K', 38 is also the largest pilot I've ever needed and that was too rich over 10K'. I've found the JD jetting recommendations to be pretty close, I don't have the sheet handy but I remember going one clip position leaner than their recommendation, pretty sure it was the blue needle. I can see why there's an overheating prob, a lean condition will def make one run hot.

I'd suggest going with JD recommendation for your alt and give it a try up the street, if it's still lean and won't idle normally than I'd say there's def a leak somewhere, like I said, their recommendation is close enough that the most it should need is a slight tweak off their settings. I can tell you with the 300 you should have the torque to ride it fairly fast and never hit the pipe, I know because I hate to rev a bike allot and on the 300 when you do, stuff starts happening real fast. Much if not most of the riding I do isn't even on the pipe.
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Old 05-09-2012, 04:14 PM   #221
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Originally Posted by RideFreak View Post
The LH crankseal can let air in also and wouldn't be detected by the windex trick.
Interesting. Wow. That's a new one to file away.
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Old 05-09-2012, 04:23 PM   #222
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Interesting. Wow. That's a new one to file away.
Yeah, if the LH seal is bad they suck air from the flywheel area.
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Old 05-09-2012, 04:30 PM   #223
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Originally Posted by RideFreak View Post
The LH crankseal can let air in also and wouldn't be detected by the windex trick (btw: never heard of using windex for it)
He actually didn't say windex, he said some "alcohol based" or contact cleaner. Windex just seemed like the closest thing on my shelf that didn't include a risk of lighting myself on fire.

So the crankseal could be affecting combustion? I can't picture it exactly, but wouldn't that just create a leak in the crankcase, which is vented anyway? Wouldn't a "lean leak" have to be either between the carb and head, or the head itself?

Quote:
Originally Posted by RideFreak View Post
I'd suggest going with JD recommendation for your alt and give it a try up the street, if it's still lean and won't idle normally than I'd say there's def a leak somewhere, like I said, their recommendation is close enough that the most it should need is a slight tweak off their settings. I can tell you with the 300 you should have the torque to ride it fairly fast and never hit the pipe, I know because I hate to rev a bike allot and on the 300 when you do, stuff starts happening real fast. Much if not most of the riding I do isn't even on the pipe.
I started with the recommendations he had for 8K+ feet: #38 pilot, 152 main and #2 clip Red Needle - and was way too lean at the low end. I'm now running 2 clips richer on the needle and still lean on the 38 pilot.
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thump_co screwed with this post 05-09-2012 at 04:35 PM
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Old 05-09-2012, 04:41 PM   #224
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Quote:
Originally Posted by thump_co View Post
So the crankseal could be affecting combustion? I can't picture it exactly, but wouldn't that just create a leak in the crankcase, which is vented anyway? Wouldn't a "lean leak" have to be either between the carb and head, or the head itself?
two stroke crankcase is sealed and is used as a pressurization chamber for the fuel/air mixture
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Old 05-09-2012, 04:48 PM   #225
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Looks like your carb is set up pretty good. On that video, It looked like it could have been cold. Maybe in the
low 40's? Any how, if there is a pretty good tempurature drop, you may have needed to mess with your air/fuel, mixture screw, which is mostly for the bottom end response, ie, pilot jet. Jeff Slavens has a pretty good little video,
which explains the simple adjustment for big differences in temperatures. This is pretty much the only adjustment
I usually make to the bike. Only a few times a year. Just a suggestion. You may have seen the vid already.
Hope you can figure it out.
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