Performance (Motocross) mods for KX100

[MagnaTrey]

You gave me a little inspiration Hot125. :nod:

I was getting a little bored with the stock avatar. So here we go with an "artistic" pic. of one of my compression readings.. :whoa:

As far as 205psi goes, I've jetted it pretty crisp on a BR9 with pump. No advancing, or other timing tweaking other than the cylinder work where the exhaust port was widened.

Where are you at in regards to compression?

 

[hot125mod]

175 psi, but it will be a little higher now that i have the head off to put a new head gasket in. I thought I might tighten up the band a little, since I get any machine work done for free it can't hurt. This bike seems to eat head gaskets and rings like a fat kid eats cake. After I get it back together I plan on trying some ignition advance and a smaller main jet, also i just got a pc ignition not to long ago i have been itching to try. since i am using U2 I am kind if leery with the timing, but it should work out. Even if I melt a piston. this bike flies but i can get more out of it, i can beat older 250f 's on it sometimes, most of the time the kids suck at riding so thats part of it.whats really cool is that it is a true 125 mod bike no big bore or stroker, thought about a long rod but i didnt tell my engine builder in time to do it he already had the motor almost all together so I was sol on that, no biggie. :)

 

[hot125mod]

your using a flat top piston right? do you also have a spark plug spacer?

 

[hot125mod]

do you have your head and cylinder grooved, I bet you cant use o-rings with that kind of pressure is it a copper wire that you use for a head gasket, fill me in. thinking of trying it if i blow a head gasket every few hours.

 

[hot125mod]

205psi on pump fuel or not because if that is what you do then if the bike even runs your kid will be riding around with the spark plug up his ass. please tell me this is not how you run your bike.

 

[MagnaTrey]

205psi on pump fuel or not because if that is what you do then if the bike even runs your kid will be riding around with the spark plug up his ass. please tell me this is not how you run your bike.

:whoa: Wow, just got back from the track tonight, and let me check real quick....Ok, I'm back, and checkaroo, no spark plugs where the sun don't shine...

Okay, now on to your questions.
Flat,no,no,no,metal gasket. I believe that on 2003 and up on some Kawasaki models, they switched to o-ring gaskets to help create "a more positive seal", but not on the smaller KX brother'n.

I love to learn as much as I can with the best of them, but sometimes trying to apply everything one learns on these forums can lead to one; over analyzing, chasing their tail, and just plain add to ones frustration levels. I listen, look, and feel. If it's jetted correctly, not blowing rad' juice, can keep a spark plug for a month, and feels crisp, then as the Taco Bell commercial goes, I'm "good to go".

So, do I get into distillation curves, etc.? Not so much, but I get the gist, and frankly it's just not my thing. I think it's pretty cool that a lot of you guys do, but I just love to ride.

Finally, the KX112 @ 205psi is running great. I spend some dough on my gear, and traditionally I have not made it a habit of smoking my stuff prematurely over the years. About twenty five of them in all.

Speaking of smoking, here is a terrific post on crankshaft smoking by the legend himself.

http://www.dirtrider.net/forums3/showthread.php?t=62498&highlight="psi+range'

PS. I ride the bike.

 

[hot125mod]

wow your a cool dude glad to meet you :cool:
Ryan

 

[MagnaTrey]

Glad to meet you to Ryan. :cool:

Trey

 

[whenfoxforks-ruled]

Compared to a stock 100 bore and stroke,where you at? I find it odd to start with an 85.

 

[griffbones]

Many of the shops like RPM and Varner (I don't know about Eric) won't use the KX100, they all insist on starting with the KX85 cylinder, but I don't know why, port differences or something?

 

[hot125mod]

because the 100 is an 85 cylinder that is punched out. The factory doesn't re port the cylinder to gain back port height and width that is lost when it is cut.

 

[MagnaTrey]

because the 100 is an 85 cylinder that is punched out. The factory doesn't re port the cylinder to gain back port height and width that is lost when it is cut.

Exactly... :nod:

 

[hot125mod]

:cool:

 

[whenfoxforks-ruled]

Where did they make up the 2mm at?

 

[MagnaTrey]

Where did they make up the 2mm at?

I'm sorry FoxForks, I'm not sure what the question is.. Do you mean the Crank rod length?

 

[DieselTech]

Trey-

Nice to meet you! You seem to know quite a bit - I also see you have an '04 CR250R - as do I. You ride it as well, I assume. I'm curious as to your setup on that bike. Do you race MX at all, or hare scrambles or anything? What is your "day job" - related to bikes or not? I know I'm asking alot of questions, I hope that it's ok. My CR is stock, and this is my first year on it, racing Sr C class MX. I have a total of less than 14 hours on the bike (and I haven't ridden in 17 years til now, and never raced MX before). I'm not fast, but best finish of 13th out of 18th isn't to shabby I think. Too bad I broke my collarbone 7 weeks ago trailriding on my DVX400 in PA, as I've missed the entire summer series!!! I'm sooooo ready to get back on the track. I'm assuming that you are NOT some 14 yr old kid, so I'm curious as to how the whole KX112 thing came about......

 

[whenfoxforks-ruled]

2mm longer rod,is there a plate somewhere?

 

[150rguy]

Not to be rude or anything but, is there a reason you put so much money and time into this bike? Im sure it was not cheap. Do you like race it in the 125 class?

 

[hot125mod]

diesels rock so why is it that they make so much more torque than horsepower? diesel tech I bet you know. Please enlighten me

 

[MagnaTrey]

Trey-

Nice to meet you! You seem to know quite a bit - I also see you have an '04 CR250R - as do I. You ride it as well, I assume. I'm curious as to your setup on that bike. Do you race MX at all, or hare scrambles or anything? What is your "day job" - related to bikes or not? I know I'm asking alot of questions, I hope that it's ok. My CR is stock, and this is my first year on it, racing Sr C class MX. I have a total of less than 14 hours on the bike (and I haven't ridden in 17 years til now, and never raced MX before). I'm not fast, but best finish of 13th out of 18th isn't to shabby I think. Too bad I broke my collarbone 7 weeks ago trailriding on my DVX400 in PA, as I've missed the entire summer series!!! I'm sooooo ready to get back on the track. I'm assuming that you are NOT some 14 yr old kid, so I'm curious as to how the whole KX112 thing came about......

Hi DT. Wow, I'm sorry to hear about your Collar Bone. Over the years I've been lucky not to have broken that particular bone.. ::knocking on wood::
Was there a non-union, or mal-union situation? I hope everything is going well with it..
I think 13th out of 18th is pretty awesome considering how much seat time you have had, wow....How long before you get back on?

In regards to some of your questions, "It was the spring of 1922, and I was born the son of a poor dirt farmer"….

Just kidding, but I did grow up kind of poor though, and I'm in my mid thirty's, and already gray. ::sigh::

I started racing when I was about nine, until I was about 15 or so, but continued to trail ride until I was about 18, and then stopped altogether until about two years ago. Boxing and weightlifting became my next "obsession" in my teen years and early adulthood. I do not race anymore, but I do frequent a couple local outdoor tracks and arenacross that have open riding time.

As far as my motorcycle knowledge base, I grew up poor, so I was the classic privateer. I tuned it, and either fixed it, or I went home. No fatherly types growing up, so I had to take on the chin and just do whatever I had to do to make it happen. Of course I asked a lot of questions and the other racers at my local tracks were just awesome. They helped whenever they were able, and (even if they were a competitor they would offer me spare parts), in conjunction with them, a long time wrench at my local bike shop, kind of took me under his wing and taught me a lot. I'll always be grateful to the people who took the time to help, kind of like a lot of people on this site. :cool:

I do ride the CR, and it's been one of my favorite bikes of all time. I have a PC pipe and FMF Turbo 2 sparky, plus some of the standard wares; Renthal bars, twin-air, etc. Nothing fancy.

As far as my employment situation, I own a financial services company. My long time girl friend talked me into quitting my prior position of overseeing and directing a micro-electronics manufacturing firm here in the Northwest to help her launch our financial business; however, my background and schooling is in Micro-electronics. For example; designing and building the circuitry for pacemakers, implantable defibrillator's, OEM logic analyzers for missile defense systems, etc.

I get asked a lot about the KX a lot.

If you look, I also own a XR100. That is my 16 step daughters’ bike.
Long story short; I was looking to buy a bike for my daughter, during my flipping through the ads, I came across this 2006 KX100 for almost nothing. It was a STEAL. So, the family I bought the KX100 from was tripping over the piles of money in their living room when I showed up, and they had more toys they knew what to do with. They bought the KX for their son, and sonny boy didn't like it after two rides, family sold KX at a two thousand dollar loss. Trey buys for daughter on the spot, Trey takes home to daughter with a huge grin on his face, daughter next day wants slower. Grin disappears.

Naturally, I had to throw a leg over to see what all the fuss was about, and whoa, the thing had a little pep stock. So…, now I start to think, “sure, no prob’, I can sell for a profit”, or, (and this is were my engineering background kicks in because I'm thinking, power to weight ratios, and limited momentum loss, etc.) Hmmm, “I think I'll just keep it and hop it up a bit”. And one thing led to another, and *poof*, I’ve dumped some cash into this thing.

BTW, I’m 5’5” 170lbs if I don’t watch my weight, but I’m 145 if I keep it trim, with a 29” inseam. See, the KX makes me watch my girlish figure; because I can’t ride it if I eat like a horse and get comfortable (read FAT). I also mountain bike as much as I can, so that helps as well.

The KX100 the way it sits now, can trash my YZ125 pretty much in any situation. In a super tight track situation with a lot of turns, IE: Arena Cross the KX100 runs from almost any bike surprisingly enough, because it’s the turns where I gain the most time; however, as the track gets larger, like an outdoor track, or more technical, like a Supercross track where you have a large jump right after a turn, the KX is still, and will always be at a disadvantage.

But here are some pro’s though:
1. It’s much cheaper to maintain. Me likey 30.00 dollar tires, etc.
2. It’s much lighter, and I can ride much longer on the trails.
3. It surprises other people out on the trail and track.
4. It’s a fun conversation starter.
5. It taste good on toast..


Well, you DT now know more about me than my G’friend of 8 years.. :laugh:
I’m glad to have met you.

~Trey

 

[MagnaTrey]

Not to be rude or anything but, is there a reason you put so much money and time into this bike? Im sure it was not cheap. Do you like race it in the 125 class?

Hi 150guy,

This bike came to fruition merely out of chance. That coupled with my physical stature, and the overall potential of the bike, made for a fun project that really turned out to be an absolute hoot to ride. :laugh:

 

[MagnaTrey]

2mm longer rod,is there a plate somewhere?

That's a negative.The crank manufacturer, "HOT RODS", just makes a crank rod that is longer by that much. :)

 

[hot125mod]

trey you are a pretty funny guy like the pros of the 112 it is a good conversation starter and it tastes good on toast. THAT IS FUNNY!!! :nod:

 

[DieselTech]

diesels rock so why is it that they make so much more torque than horsepower? diesel tech I bet you know. Please enlighten me

Well, a few reasons for more torque:

1)Diesel fuel has more energy than gasoline (also why they get better mileage)
2)Diesels have better combustion events, as they are usually direct-injection
3)Diesels have higher compression (usually 18:1 or higher, compared to 9:1 for the typical gas engine, though a "high-compression" gas engine may be as high as 14:1)
4)Most diesels are turbocharged (older diesels used to be 2-strokes and had to be supercharged or they wouldn't even run)

Also, the horsepower is less even with high torque simply due to the fact that diesels don't rev as high - most small diesels can go to about 4,000 rpm or so, but big diesels only hit half that. Keep in mind that HP=torque x rpm (in simplified form - there is an actual formula that's a little more complicated than that, but it escapes me right now). So, a diesel with 600 lb/ft of torque at 1,500 rpm will have less horsepower than a gasser with 400 lb/ft at 4,500 rpm. The diesel has more torque though, and therefore is better for pulling.

Hope that helps.......

I was really hoping Nissan was going to build a 3/4 ton diesel truck, but I've heard they have changed their minds (I own a '05 Titan w/5.6L gas engine - 305HP stock). I'd buy a new Powerstroke F250 if it wasn't for the $50k price tag! :yikes:


Trey-

Thanks for the response. So we are the same age then. I kinda figured that you must be a smaller guy if you were riding the KX. Cool project, for sure. Did you have good luck with re-jetting your CR? How about gearing - is it stock? My biggest issue with the bike right now is the lack of low-end response - but I knew that was an issue when I got the bike. I'm trying to decide on mods for next year. So far the bike is stock except for the FASST Flex bars I put on it w/oversize mounts. The collarbone was just a midshaft break - no big deal really. Seems to be healing ok. Not sure when I'll be ready to ride - I see the Doc next week, and hope to ride next weekend if I get the "blessing". I'm happy with my performance on the track so far - my biggest problem is being out of shape I think. I really need to exercise. Not that I'm a slouch - I'm 5'10" & 170lbs, but I need to work on my cardio for sure - arm pump gets me rather quickly as well. I need to ride more, but it's so hard to find a place to ride - everbody complains nowadays. The closest track is 1 hr away and $20 to practice, so that gets expensive quickly. I've got 3 acres, but can't ride on it - too many complaints!!! Oh well........ :|

 

[MagnaTrey]

I'm glad your CB break wasn't too bad DT. I've personally seen some nasty ones that have made me cringe a bit. :whoa:

I've always done pretty ok in the jetting department, so no problems there. Stock 13-48 final.

If you are having an issue with bottom end responsiveness, and you think you have your jetting in line, try a Vforce3 reed block for next seasons modification list?

I can totally relate to the $20.00 to practice. It seems like I drop a c-note every time I take the girl up to the practice track. :yikes:

Regarding the complaints on your land, you could always switch to a thumper. :p bwwahahaha