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12/14/2016
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Kingston, RI, USA
I bought a 2013 300 xc a few months ago. After riding it a quite a few times Im noticing that it doesnt seem to rev out all the way almost like its hitting a limiter and falling on its face at WOT. Im coming from a 250xc and was told I shouldn't really notice a difference in how much they rev. Things I know, supposedly the bike was swapped with a 250sx cdi, bike is jetted 175 main 40 pilot at sea level (pulled them and cleaned them but neither seemed clogged_. Previous owner just did a top end 10ish hours ago and he was running 32:1 (way too rich imo). Im thinking he may have put the powervalve back wrong when he did the top end or maybe its gunked up from running too rich? Ill be pulling the right side powervalve cover off sometime this week but I was looking to get a few other opinions as well.
Thanks for the help
Thanks for the help
The 300s don't rev as high as a 250.. FYI
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Once that is done, your pipe is already removed and you should be able to feel if the powervalve is opening smooth or not.
If it is movbig smooth, maybe look at what your powervalve spring is adjusted to? Not sure if someone changed the spring pressure.
Another problem I had with my 2 stroke that helped, was repacking my silencer. When I got my bike it was really packed out and beat up. My bike felt a bit smooth once I cleaned and re packed it.
usually if a bike isn't running out as far as youd expect on top, check the PV action first
then move to jetting. If its gargling and smoking a bunch, too rich up top(needs smaller main). If it sounds like a frog and like its running out of steam, likely too lean (need larger main)
if the manual and stock jetting specs call for 60:1 and its been moved to 32:1, youll likely need a LARGER main jet since 32:1 contains less fuel per a given volume than 60:1 would.
Here ore the oem ktm part numbers for the springs:
54837072100 AUXILIARY SPRING HARD, GREEN
54837072000 AUXILIARY SPRING SOFT, RED
54637072300 AUXILIARY SPRING MID., YELLOW
Running the harder spring will cause it to not really rev out/open up as quickly as it should and could prevent it from opening at all.
Normally a fouling spark plug would be a good indication that your jetting is off or that the power valve is not opening.
Kreft Moto makes a key that replaces the square head adjuster screw making the spring preload adjustable on the fly.
A gnarly or PCII 250 pipe will kill your over rev.
Shorty silencers will too
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