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625 front sprocket size

6K views 12 replies 8 participants last post by  mxrider14 
#1 ·
So I have an 04 625 SMC and I have a 15t front sprocket (42t rear). Seems like first gear is almost unuseable. Will going up to a 16t make much difference for me? I dont want to kill the low end, but want a more useable first gear. Wadda ya think?
 
#2 ·
The from-factory sprockets in the USA's 2004 625SMC are 16-tooth front and 38-tooth rear (not absolutely positive about the rear, but pretty sure-- I can count when I get home this afternoon), so your current gearing is really pretty low (numerically high) comparatively. If you just switched to the 16-tooth front, you'd probably pick up a good bit more useability in first-- it's been recommended here numerous times to use the KTM OEM front sprocket rather than aftermarket to reduce the possibility of countershaft seal leaks.

If you typically need more flat-out speed (highways and such), you may also want to drop a tooth or 3 in the rear. But for around town and the fun stuff, just going with 16-42 should be the good ticket.

Bryan
 
#3 ·
I agree 16/42 is about the best combination I've tried ,and yeah 1st/2nd gear's are like a dump truck especially going from 3rd to 2nd fast with no slipper.
 
#4 ·
Cool thanks guys. I find its really low when streetriding. Leaving parking lots and such that has pedestrians and car movement. Real herky jerky in first, and second lugs. I will try a 16 and see how it does. Got to be better than it is!

The guy that had it before me gave me some dirt wheels and tires for it too, so apparently he had it geared for dirt. But it does make for REAL easy up first gear wheelies!
 
#5 ·
Jerking and lugging on the beeg 625 is from being in too high a gear; Big singles struggle against themselves at about 1/8 to 1/4 throttle. Alarka is very wise with 625's, but keep in mind the right gearing in NC is not always what is best in the midwest, with what roads we have vs being in paradise. I have been running 16/40 gearing for a couple years, and will top out at about 114. But for the expressway, if you must run it, (sigh)... I am gonna try a 38 on back, as the bike feels put upon to hold a sustained 70mph for more than a mile, unless you are hotdogging it. Keep in mind, tho, that many of our 625's have been tweaked; Mine has a crower cam and a 5 angle valve job, and a thinner .035 headgasket, with Leo Vince slip-ons, and makes 60.5 rwhp @ 7,600 rpm, so a true stocker will act a bit different, depending on state of tune, and esp jetting. One last thing, re jerking... Has your bike been desmogged, is the air filter cover been removed, do you have a jd jet kit installed yet? Sorry for the bit of complication, but I mean well.:clap:
 
#7 ·
Well what i mean by jerking is from being too low geared. Its just too much power in too low of a gear. Feels like it wants to jump out from under me with that gear in first. The when I go to second to smooth it out, its too high of a gear for the low speed im going.

And for me, it will never be on a road that has a higher speed limit than 50 mph. Just how it is where I live. So I have no need to go 115 mph. Which is why I chose this bike.

Only mods on mine right now is the the top of the airbox has been cut out, and the slide derestricted.It had a Pro Circuit T4 on it when I got it, but it was much too loud for me living in a condo. He gave me the stocker when I bought the bike, so I threw that on (not gutted). Running a 172 main and a 50 pilot with the needle on the 6th (from the top) position and no JD kit. Jetting feels and looks pretty good. I just ordered the parts to remove the SAS today. Found i had a pretty good leak on the left head pipe to tail connection, so I ordered a new graphite seal for that too.
 
#8 ·
Definitely go up to that 16, I'm running 16/42 and can't imagine it with a 15 tooth front...with a good yank I can get her up in 3rd while seated, can't imagine with a 15 tooth... :hmmm:
 
#9 ·
I will know next fri how well the 16/38 combo works, when I bought the bike, it had a 17 on the front, and the bike was in a marginal state of tune (bottled up stocker cans) and it seemed geared too tall, now that i've picked up 7 hp, and the carburetion is right on, with way better throttle response, it is feasable that if you were not on tight roads, a good running 625 could pull that tall gear, making first gear more practical, vs. quick shift into 2nd after moving only 20 to 30 feet.

Whatever your riding style and local roads dictate, I always say.:thumbup:
 
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