2 great, inexpensive mods

Braahp

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#1
I have a 01 200. Been doing the usual mods along the way......FMF torque pipe & 12T sprocket. All money well spent. But I can't say enough about setting your sag correctly. I rode for many months in stock form and the decided to set it to spec. WOW! what a difference in handling that simple adjustment made. And FREE. Then a couple of weeks ago decideed to add a FMF Power Core II. Had been using just stock arrestor with the pipe. After reading and hearing others I didn't expect much of a gain whatsoever. WOW! What a difference it makes. Maybe its just me but it really made my bike come alive! Definately worth the money. I am feeling a BIG power increase. Just thought I would share my experiences of these two inexpensive but amazing mods. RIppppppp..........
 

dhoward

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#2
Maybe it's just me, but I didn't see that big an improvement over the stock silencer. Saves a little weight though. I like the stealthy sound of the stock silencer, in fact, I'm going to put it back on!
Braahp!
;)
 

Mikeb

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#3
I agree with DHoward on this one. I took the FMF Turbine Core II sliencer off this weekend and put the stocker back on and the difference was almost un-noticeable. I rode both woods and MX track and really didnt notice a difference in performance at all . IMHO The money you spend on a silencer would be MUCH better spent elsewhere ( suspension, porting etc ... )
 

Braahp

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#4
Just like I always heard...no gains. But maybe the free flowing Power Core II is the difference...I don't know but it sure made a big gain on my bike. A little raspier but still very quite compared to other MX bikes.
 
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#5
I have an FMF Powercore silencer and an FMF ISDE silencer(the forerunner of the Turbine Core) for my bike. The ISDE silencer is not much different than the stock silencer powerwise, but the Powercore silencer makes a distinct improvement in throttle response, and the bike revs a little higher as well. And the noise level is still quieter than most MX bikes with stock silencers. I think the Power Core is a little easier to jet cleanly than the ISDE, as well. I can't seem to make it run quite as clean down real low with the ISDE.
 
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#6
are you saying if I just add a Gnarly pipe I would notice a power increase,
and leave my stock silencer on..:think :think
 
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#7
Originally posted by SOMISSONE
are you saying if I just add a Gnarly pipe I would notice a power increase,
and leave my stock silencer on..:think :think
If you still have the stock pipe on, yes, you will be shocked at the performance increase just adding a decent pipe will give you, especially if you take the time to jet properly for the pipe. If your jetting is still stock, you aren't even getting all the performance that is available from the stock pipe.
 
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#9
I went ahead and put a pipe on mine without rejetting (I may get to that this winter, if I find time). You will feel a big difference immediately, jetted or not. But they are right, rejetting will help, too. There's a section on it on justkdx.dirtrider.net.
 
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#10
How did you set the sag on it. My bike sits like it has a body kit, and side flares on it :scream: . I need it higherd so I wont be cramped so much when riding. thanks
 

TexKDX

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#11
Fleshwound, setting the sag will have no impact on the seat/peg relationship. Fixing the cramped feeling will come thru bar bods. I think there is a note on this on cDave's tech tips on justkdx. Taller/flatter seat foam may help too.

Mikeb, maybe we need to set up a web cam and do real time video jetting changes! It is amazing how many people are fearful of this operation. Heck, it is easier to do this on the KDX than change the oil! Humm, perhaps they aren't doing that either ;).
 
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#13
Certainly seems to be a matter of opinion (what oil do YOU think is best??), but I put off getting an aftermarket S/A due to reports here saying, 'No big deal'.

My PC S/A made a large difference in my bike. Big improvment over stock.

But..you say 'Power Core II'..which is different from a 'Turbine Core II'. The first is an 'S', the second is an 'S/A'..the keyword here being ARRESTOR.

MikeB said he took his TURBINE core off in favor of the stock unit. So he had an apple, you have an orange.


You aren't running a Power Core in the woods, are you? If you are, please don't ever come 'roun here!! :eek:

A side note: Free sag (amount bike sags under it's own weight) of more than an inch or so is indicative of a too stiff spring. Free sag of less than 1" indicates a too soft spring.

btw..race sag (you on the bike with all your 'stuff') is normally around 4". That drop measured from where the bike sits with the rear suspension topped out (lifted enough to remove free sag).
 
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#14
I am a newbie to the forum and trying to figure out this sag issue. It seems as if i am not understanding something or what you said is backwards.
What i got out of it was the sag is the difference between the height w/ suspension at full extension and the height with the weight of the bike on the suspension. If I am right i would think a stiffer spring would give you less sag as it exerts more force therefore keeping the suspension closer to fully extended. Clarification Please
 

TexKDX

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#15
Matt -

First off, what do you weigh, and what year is your KDX?

The reason two (really three) sag measurements are taken is to determine if you have the right spring rate for your weight. Say for example you ignored static sag and just look at race sag. You'd be measuring how much your (dressed in gear) weight compressed the rear suspension, relative to the amount the bike unladen compressed the suspension. If it were say 4.5 inches, you would add preload until it came up to just 3.5 inches to have the correct "race sag".

With this method, we can't tell if the spring rate is OK. See, as you add preload the static sag (amount the bike-only compresses the susp) is reduced. If you added so much preload to get the race sag to 3.5 inches that the static sag went to zero, the suspension topped out from the spring, then we would conclude that you need a stiffer spring.

So, to set your sag, here is what you do (assuming '95-'01 KDX and you weigh between 160 and 190 with all your gear and helmet on).

1) Put all your gear on.
2) Have a friend over to help.
3) put the bike up on a stand, and measure from the axle nut to say a mark on one of the number panels. Write this number down as "A".
4) Take the bike off the stand, then "top" the suspension out and let it back down. Take the measurement as in step 3. Write this number down as "B".
5) Push down on the seat, let the seat rebound back up. Take a measurement as in step 3. Write this number down as "C".
6) Get on the bike (all your gear and helmet on) and sit fairly close to the tank. balance the bike so all your weight is on the bike, none on a foot, and have your friend take the measurement as in step 3. Write this number down as "D".

OK, now that we have the numbers, let's do the cipherin' and gazintas.

1) Add B and C together, then divide the result by 2. Call this result E. Now, subtract E from A. The result is your STATIC SAG. It should be between 1/2 and 1 inch.

Formula: (B+C)/2=E
Formula: A-E = Static Sag


2) Subtract D from E. The result will be your RACE SAG. It should be between 3 and 4 inches.

Formula: D-E = Race Sag.

Look at your RACE SAG to determine if you are going to make an adjustment. If it is less than 3 inches (and if it is in the stock position it will be) then remove a full turn of preload and start over. If over 4, then add a turn of preload.

The preload on the KDX is changed by turning the two big rings on the shock body. I use a long punch and a hammer to loosen the top ring then turn the bottom ring. Be sure and put an index mark on one of the flats of the bottom ring so you know when you have made a full turn.

Ideally try to get your KDX at 3 and 1/4 to 3 and 1/2 inches of preload. After you get it there, then re-check your static sag as described in steps 4 and 5, then cipherin' step 1. If you are still in that 1/2 to 1 inch range your spring rate is OK for your weight.

Now the bad news: even after you get the sag set on your KDX, the bike's suspension will still be out of balance (assuming you are the correct weight for the rear spring). The rear spring rate will be higher than the front. TO fix this, you can do one of two things:

1) replace the fork springs with stiffer springs
2) dial back in about 1/2" more race sag

I did #2 on my XR250 and it worked much better than with the "correct" race sag. I then went back and put in the stiffer springs and dialed on 2 more turns of preload on the back and she handles GREAT now.

Does this help, Matt?