FMF pipe comparison

[Rhodester]

I have a '95 200H1 KDX that was purchased with a -30 rev pipe. Bike is equipped as follows: Ram valve, stock carb (re-jetted), turbine core 1 SA, air box cover removed, 91 octane pump gas, mxt2 @ 40:1, test rides at 2600'. The -30 had tons of power everywhere with a top end that would rev to the moon. It encouraged me to ride it like a 125 motocrosser. There is also a hit in the midrange which I smoothed out to a large degree though jetting. The pipe is great if you plan on riding the bike mostly on the mid to top end. It does work ok on the bottom, but that's not its optimal range. I purchased a Fredette Torque Ring to see how the pipe would react. It seemed to lose about 200-300 rpms on top with maybe dropping the power curve about that same amount (200-300 rpms). The change is extremely subtle. The main difference was the sound. It seemed to deepen to tone of the exhaust and produced a more 250 like sound. The suprise came when I installed the -35 pipe! I expected a major difference in power characteristics, but the change was not nearly as much as I expected. The pipe went on a perfect fit and required about 2 main jet sizes smaller. It seems just barely richer on the bottom with the same pilot and needle positions that I have been running. This pipe has power everywhere like the -30, but without the hit. It seems a little stronger on the bottom to mid range and not much of a loss on the top end. It will rev at least as far as the -30 with the torque ring. In a drag race with my son on his '97 XR250, the -30 with torque ring was close to a dead heat as far as top speed goes (I blow him away in the acceleration department). He would just barely pull ahead over a 1/2 mile at WOT. With the -35 pipe (no torque ring) I would walk away from him over the same distance. The main thing I noticed at first with the -35 is that it seemed to have a very slight resistance to rev past the point where the KIPS would open (very subtle). I went up a size on the main jet and that pretty much cured that tendency. I'm Very happy with the -35 (woods) pipe and that will be my main pipe I'll be using for foreseeable future.

 

[mnnthbx]

Thanks for the feedback.

 

[palmer69]

Thanks for the story Rhodester.

I went woods riding today with my buddy. We both have KDX 200s, his an 00 and mine a 98. He has a -35 and I'm running the stock pipe with a torque ring. We switched off today and his bike feels much crisper to me and definitely will pull mine in a drag race. Mine, with the torque ring, may make a bit more low end at very low revs.
Anyway, I'm ponying up for the -35. I'm ready...

 

[mnnthbx]

So how bout the -35 w/ the torque ring? Overkill or great bottom?

 

[Rhodester]

mnnthbx, I must say that I haven't heard of anyone using the torque ring with the -35 pipe....must be overkill. palmer69, You won't be sorry. I also was out this afternoon in the desert with my boys. My youngest is at the point of out-growing his Z50 Honda. We all had a blast and were loading up as the sun set.

 

[canyncarvr]

Please note a couple of important things.

Rhodester's comment, '..and required about 2 main jet sizes smaller..' about the -35 is telltale indeed. It says he must pay attention to jetting (why else would he know that?) and that is nothing if not a critical issue.

No amount of swapping this'n that, changing stuff around is going to do anything but confuse the issue if you don't have a handle on jetting your bike.

It's real handy to have a known issue to compare against, too. Sometimes the 'seat of your pants' method lies to you. A run against the same bike you ran against the other day (or will run against tomorrow) is a great tool for figuring out what's going on with your bike.

re: '..it seemed to have a very slight resistance to rev past the point where the KIPS would open (very subtle). I went up a size on the main jet and that pretty much cured that tendency.'

There are a whole lot of kdxer's that would do well to read that one sentence and understand what's going on!

Thanks, Rhodester! Your write-up on the pipe differences (with jetting included) is the most concise and informative single piece I've ever read.

....sez me.

 

[mnnthbx]

cc, point taken, but no one said anything about a lack of jetting.

"No amount of swapping this'n that, changing stuff around is going to do anything but confuse the issue if you don't have a handle on jetting your bike"

I thought this was a simple comparison of parts, taken into consideration that the given bike, with a given combination of parts, is correctly jetted for that specific application. If I gave the impression that I want to blindly throw parts at my bike expecting magic results, that is not the case. I was simply currious as to the possibility that the tourqe ring could enhance an proven strong woods pipe.

 

[canyncarvr]

No offense need be taken, cuz none was intended.

While it should be obvious that any performance part bolted on should have jetting changes made as required, I guarantee you that that doesn't happen 90% of the time!

'...taken into consideration that the given bike, with a given combination of parts, is correctly jetted for that specific application.'

That certainly should be true. ....but it's not. Read this board for a few years and you'll know what I'm referring to.

My point was to the casual readers of the thread that would infer changes made to rhodester's bike's performance were due to the pipes alone and not having anything to do with jetting.

If 'blindly throwing parts' is not your idea of doing things, that's great! I promise that IS the idea of too many riders.

 

[palmer69]

Great banter guys!

Well I did it today, I laid down the dough for the KG-35. I got a good price for the pipe but the O-rings cost me $11.72 each!! Guess they made a little back on the pipe price!

My bike is a '98 and was totally stock when I got it last year. After following along on this site for the past 6 mos. or so and reading all the posts on the importance of jetting etc., I started my jetting/mod journey. I've settled on a 155 main, 45 pilot, stock needle and 3rd clip position. I yanked the snorkel and drilled two one inch holes in my airbox. Stock pipe and silencer (for now!), boyesen 607s and Fredette torque ring.
I did all the mods in a day. Just slapped it all together and went for it. Not really.
I actually tried to approach it in a somewhat systematic way. Here's the order that I did the mods and the seat of the pants results:


0) STOCK - Loads up when idling around. Takes a few seconds to clear before decent throttle response is restored. Pulled good and hard in all gears on the top end. Third gear wheelies, fourth too with a little pull on the bars.

1) Drilled two one-inch dia. holes in airbox, left snorkel in-place. No real noticable difference. Maybe a bit more mid hit, but naahh... I don't know

2) Pilot change - my bike was loading up and bogging when I cracked the throttle after putting around for just a few seconds. This was largely fixed with the pilot change. More responsive off idle, required AS diddling.

3) Main jet and reeds - whoops, two mods at once, couldn't resist. Definitely more responsive off idle. Much less prone to loading when putting around. Mid and top end unchanged.

4) Torque ring - deeper exhaust note, growly, when accelerating off idle. Feels torquier down way low. Wheelies even easier in first gear. Noticably flatter at the high mid range to high end. Doesn't want to loft the front like it did before in 3rd gear.

5) Snorkel yanked - A lot louder. No noticable difference in performance.

This bike the way it is now is, in my humble opinion, a great tight woods bike. It does everything I ask of it in the tight trails. I really like it. I have lost quite a bit on the high end however.
So, now I'll add the KG-35 pipe and pull the torque ring. I'm keeping the stock silencer for now. Hopefully this will retain most if not all of the low end and fill the high end gap.