125 SX jetting and power-valve questions

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#1
I trail ride a 98 125 SX. The jetting seems to be very good(no spooge, pulls real clean), but it has the NOZI needle and am thinking about switching to a single-taper. I was wondering what the effect on the delivery of the power will be, and which needle to start with. Also, how do I change the opening of the power-valve on my bike. If so, what change is recommended, if any. BTW, I run 93 octane with MC1 50:1, and the NOZI needle is in the 2nd clip, pilot is a 45, main (I believe) is a 185. Thanks for your help.
Dave
 

marcusgunby

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#2
I can only give you the specs for a 2000 KTM and it has a very slightly different engine to yours but give the R1468J needle a try in the 3rd clip position.I would start with a 190 main to be safe.The needle is a Kawasaki 125 98 part.The powervalve can be altered by removing the large chrome nut under the exhaust and turning the threaded part(with the 2 flats on).Turn it one turn in(or out) and see how it responds.I run all 125s at 32:1 BTW.
 
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#3
Thanks, marcus, I was hoping you would reply as I have seen you give info. on 125's befoere. In fact, in one of your older posts, you mentioned having to loosen an 8mm bolt to move the power valve. Is this true? I see that you run 32:1, do you track ride? My riding is strictly off-road and I actually spend little time wringing the engine out. MC1 is also recommended only to be mixed at 50:1, should I switch oils?

Dave
 

marcusgunby

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#4
Yes sorry i do think you have to loosen the 8mm bolt first.Its been a while since ive touched a KTM-you may know i have a CR now.I do race only so maybe 32:1 would be too much if your having good results with your oil i would stick with it.Its a hassle changing oils and ratios so i wouldnt do it unless yours burns dirty.
 

fuzz

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#5
i don't beleive the exhaust valve is adjustable for opening on that
model.
its only adjustable for height at rest
 

marcusgunby

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#6
You are right fuzz it is adjustable on the height at rest but on a dyno ive seen it altered and you can get a straight trade in power by adjusting it, lower it gave 1hp more low end and lost 1hp on the top.
 
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#7
I would like to try adjusting it, I'll take that trade-off for the type of riding I do. How much should I try turning it, and am I turning it clockwise? Thanks for all your help.

Dave
 

marcusgunby

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#8
im sorry its quite a complicated set up to remember which way lowers the flap but as long as you count how far you go, you can always go back to std.I would only turn it 1.5turns max from std as it may cause the flap to get too close to the piston(although this is unlikely as i set mine really low once to try it out-didnt open under full throttle and no top end-but it picked up real good out of corners)