Try changing the throttle. Put on a slow action trials throttle. I have used this trick for newbees to a powerful bikes & those using big trail bikes in tight going e.g. ktm 525's. It takes the sting out of the need to be accurate with your right arm, yet still allows you to use full throttle with two goes on the throttle. When my missus first got on her 640 KTM I even machined out the slot on the throttle to make a slow throttle even slower. It really helped her gain confidence on the trails. LOONAL
I helped some one I work with do this to his kids KX80/100??? I just put a 1/4" sheet metal screw into the plastic housing that connects the cable to the throttle tube on the handle bar.. Take off the housing and disconnect the cable and you will see the lug that the cable goes into...When you give it throttle the lug moves toward the back of the bike, by putting in a small sheet metal screw you will limit the distance the thottle(lug) will move since the lug is now stopping short on the screw....Use a small enough screw(short) so you dont bind or hit the throttle tube. Once she gets used to the bike just remove the screw and put a dab of black silicone over the hole.. This took me about 5 minutes to do,it's very easy.... It worked pretty good for him and his kid, he took it off a few rides later and jr. was tearing it up.. He never had a issue with it fouling the plug...
My son's KDX50 has both a throttle stop screw and an exhaust limiter. All the exhause limiter is is a flatwasher between the barrel and the pipe. The washer makes the biggest diff. The aperture is about 4mm wide. I'd guess that you'd have to mess around with that size to match your 100.
Let's not get this thread kicked to penalty box. I don't think restricting the exhaust is a good idea in this case.. The KX100 has a full on expansion chamber pipe and powervalve. I'd be concerned with fouling up the powervalve mechanism with spooge if you restrict the outlet. Not to mention it'll run like crap. Just put some gear on the woman and turn her loose! She'll get the hang of it. The KX's are pretty tractable at low rpm due to the powervalve. My kid's 85 has a pipe, reeds, airbox mod, and it will get away from the average rider (short wheelbase + strong hit = loop out) but they're not insanely twitchy when stock. HEY! I have a great idea! You pull the cylinder assembly off your 100 and I'll swap you the cylinder from my kiddo's 85, they're a direct swap. That way you don't have to worry about too much power and I can misappropriate my kid's bike and ride it like a hooligan!
If you only want to lose some power for a couple of rides, open up the gap on the plug past spec. Opening it should take power off the top end. Its easy done, and easy undone.
How about restricting the intake somehow? Manufacturers have used this for years to restrict bikes. You could even put a smaller carb on it.
You bought the wrong bike, period. There is no point in trying to tame this bike- it is not a bike for a timid novice to plod around on. You would be better off giving it to your aggro 14 year old that wants to clear triples at the track, and buy your wife a CRF 230. A KX100 is a highly tuned, hard hitting two stroke. Trying to make it something else will be an exercise in frustration for you, and dissapointment for her. J
I just re-read my post, and figure that I should offer something more helpful. I think you are fighting a VERY uphill battle, but a flywheel weight will be your best bet in taming the powerband hit of the bike. I don't know if you can find one, as I suspect most 100cc riders want their bike to hit harder! 1.) I would try flywheel weight- biggest you can buy for the bike. 2.) Gear it up- the gearbox on these are tight. Widening the ratios will allow you to keep it off the pipe better. I wouldn't try messing with a potato in the exhaust, although if you wrap it in foil, you might have a tasty treat on the trail when it falls out. I would still suggest a CRF230- they are a nice bike to learn on that actually have some potential once the skills come up. Remember- this is your chance to either get her stoked for life, or turn her away scared and disappointed. J
try the G2 throttle cam. It tames even wicked 300's response. Pop in the G2 cam with the 400 or 500 Cam and it'll help out a lot.
I already answered your question at dirtrider.net:) For the record my wife really likes her KX100 as does my sister and my mom. My wife's KX100 has a 12oz flywheel weight, is jetted quite well, stock exhaust with a 5mm spacer in the header, stroked to 48mm (bought used, stroker kit was a nice surprise:)). Disconnecting the power valve and wiring it shout would really tame the top end, but that's more extream than my wife needs. Limiting the throttle would probably do very little good. Lowering the compression will lessen the low end power and if anything shift the power curve up. Increasing compression will generally move the power curve down and help with low end. Making the exhaust header longer will move the power curve down and vice versa. Lowering the exhaust port will also generally shift the power curve down. Advancing the ignition timeing will shift the power curve down a bit too. For the record, the little KX can plunk around all day at low throttle/low rpm without fouling provided the jetting is remotely close to what it should be. We went all year last season on the same (stock heat range) plug. It slowly built up carbon as it never really got hot enough to clean off. I replaced it with a one hotter plug (B8HS, normally a KX100 would take a B9ES, the "8" is hotter, the "H" is because her KX is stroked). It can even be left idling without any ill effect. My mom and I The little KX is very docile at lower rpms and with the extra flywheel weight its not too bad when at higher rpms. For the most part my wife just lugs it around and really enjoy's it. Its also super easy for her to start (ok, perhaps not as easy as a CRF230, but much easier than any of the kick start thumpers). My wife has ridden most of the typical small to mid sized thumpers and hated them. A CRF230 weighs 100lbs more than her KX, has crappy brakes, suspension and handles very poorly as a result. Some folks like them, my wife is not one of them.
Thank you all for your great suggestions, so many things to try. I'll have to read through all of this a few times to get my bearings. BikePilot; cheers for your other posts , I have monitoring the other forums and am encouraged by the overall positive feedback from others who have bought and modified the KX 100 for their wives. You have it right, this bike could be turned into a KDX 100 of sorts. So far she is very impressed with the light weight and ergos(installed Protaper contour ATV race). We'll be going to a wide open flat field today to let her slowly get aquainted with roll -on and power curve. Will have the Steahly 12oz (8 & 10oz also available)shipped asap. I wonder if threre is a pipe available to increase bottom and mid (like a woods KDX FMF). Again, great input from you all, I'll keep you posted on successes and (god forbid) disasters
I raced a KX100 a couple years ago- it was the most fun I've ever had on pavement. I also tought the GF to ride MX on it, so it's definitely doable. The pipe you're looking for is the FMF Gnarly. You're really going to want to raise the gearing to deaden the hit. Go with that and the flywheel weight and you'll be money. remember to decrease the size of the front sprocket as she gets faster. People who start on 2-strokes and stick with them end up faster that 4-stroke riders as a general rule.
The best pipe out there for botom end that I know of is the stocker. Most all the aftermarket ones seem to give a mid and or mid-top boost without really chaning low end at all - the result is a bit harder hit. My wife's bike came with a bills pipe which definatly made the bike hit harder than stock. I ordered a stocker off e-bay and mounted that - noticeable improvement. I did stick a ~5mm spacer in the cylinder head to effectivly lengthen the header which should give more low end. I really couldn't tell a big difference either way, but I left it in for good measure I advanced the ignition timeing on her bike a little which did make a noticeable improvement in the low end power. I can't stress proper jetting enough, it makes all the difference. The worst is a bike that loads up becuase it will feel slow and blubery till it clears out then it will take off and could catch a new rider off guard. Also, nothing seems to disapoint new riders than fouling plugs and being told its their fault for not riding fast enough. Hogwash, a properly jetted bike doesn't foul (oil/fuel foul anyway). Admitedly, after many many hours of really slow riding you will get some carbon build up if you retain the stock heat range plug and eventually it could be enough to carbon foul, but this would take a very long time. I think the ideal would be the CRF250 Junior that Service honda makes (CRF250X motor in a CR85 expert frame), but I don't have that kind of cash. In my experence, most can happily learn on a small bore two stroke. I do know one woman who started out on small thumpers and never could happily transistion to two strokes despite being quite good rider. She is now an excelent rider, has competed in many enduros and such, but is relagaited to small, under performaing trail bikes becuase she just can't get used to a two stroke (she was AMA D-7 HS champ till my sister started racing). "KDX100" is exactly what I was after with my wife's bike. Its even got a KDX200 headlight mounted up for good meausre (no coil to power it yet though, but at least it looks the part). Last time I checked they don't make the FMF gnarly for any of the small bore bikes - things could have changed though. I'm not at all sure going to taller gearing is a good idea. I've found the oposite to be much more helpful for my wife (we tried both). With a bit lower gearing she finds it much easier to start out without stalling, especially in technical situations, like getting going on a rocky up-hill. She can always short shift regardless of gearing. This is just what works for us, experences may vary
All good stuff! I drilled and tapped (M6/1.00) the bottom of the throttle housing as per KX250KEV's (TT forum)suggestion, and installed a BR9EIX instead of the stock plug and so far no fouling. The stop keeps it just under the hit when loaded but requires a lot of short shifting and clutch feathering which is not a bad thing for her to practice anyway. So far so good. Other mods to come.... Cheers
Well I got my Steahly 12oz fww and installed it pronto, after seizing the piston with a piece of rope in the cylinder head while trying to torque the fww bolt, don't ask Anyway, with the throttle stop, 12oz fww and the needle dropped a spot, bike is SWEEEEEEEEEET! Much more manageable now, I could lug it around in 3rd in my tiny driveway super easy w/ a wee bit of clutch. Still getting some sooty plug, even with the hotter BR9EIX and lower needle. I guess I'll have to carry extras until she is willing and ready to let the little KX sing a little. I have to add though, that when I had a go earlier myself to see the powercurve(bike stock), wheel up in 4th! just like that...wow. Very nice and did I mention it weighs 149.5 lbs, I am 210!
When my kids were less aggressive I ran their bikes on Amsoil 100:1 premix oil. Keeps things nice and clean and never had a lubrication failure. When they wicked it up we moved to 50:1 which worked very well also. Under extreme loads the Amsoil engineers advised a thicker ratio but it sounds like it would serve you well at 100:1. Good luck, Jim.
I'd recomend a 8 series plug next time around. I know the factory plug is some weird thing that doesn't go by the normal plug numbers, but most folks run a 9 for MX racing. Its really a bit cold for slow stuff, not terrible, but it will slowly build up carbon - at least ours did. Still, my wife got nearly a year out of it (then it fouled with my dad on the bike - pure happenstance as he was riding it a bit harder than she normally does). I put an 8 in it when that 9 fouled and its doing great. I see no problem with a leaner oil mix, but would question its utility. As we have several pingers in the house I run them all on the same thing - usually MX2T or Yamalube 2R at 32-40:1 depending on conditions. An impact gun is a lazy man's alternative to rope Oh, one more tip, keep and eye on silencer packing, the tend to get grungy pretty quickly which leads to really obnoxious noise levels and somewhat worsend running.