KX100/KDX200 Hybrid

[deviot]

Hi Guys,

22 year old aussie here looking at building a hybrid but with a twist and using a KX100 as the base.

The reason for KX100 is that I have one already and love the size and weight. I'm 5"6' and 65kg so while I can and have ridden full size bikes I still prefer the lower seat height and 30kg less for the single track trails. Reason for idea of conversion is I want more low down power and to be able to curise when the trails open up easier. Was thinking of a KX125/250 but think the KDX200 is a much better choice for the (hopefully will!) ultimate woods bike for a shorter/lighter person like me!

My research so far!
Will need a new engine cradle, possible custom air box, work out something for the boot and general chopping and welding (like brackets for radiators). I have the ability and equipment to weld but will be looking at outsource things like the engine cradle if I don't think my skills will be up for it.

Here (http://www.thumpertalk.com/topic/997004 ... beginning/) is a KX100/KX125 project half way and things look to fit ok.

Measurements:
2001 KX100:
Rear Mount: 100mm
Rear Mount to Inside Frame (Sprocket Side): 47.5mm
Outside Sprocket to Rear Mount: 28.5mm
Outside Sprocket to Inside Frame: 19mm
Sprocket Width: 6mm
Rear Mount Bolt: 11mm

Rough:
Rear Mount to Front Mount: 245mm
Rear Mount to Bottom Mount: 170mm
Rear Mount to Top Mount: 310mm
Bottom Mount to Top Spark Plug (inc Lead): 300mm

2002 KDX200 (found this off the net):
Rear Mount: 94mm
Swingarm Width: 100.6mm
Rear Mount Bolt: 15mm

Would be great to get any more measurements.

So for the rear mount I will need:
Bush equal to 6mm thick (can be one or two to align front sprocket) 11mm inner diameter, appox 20mm outer diameter.
Sleeve inner diameter 11mm, outer diameter 15mm, 94mm long.

Drive setup:
DID 428VX X-Ring (7,420lbs)
Rear 428 Sprocket: http://www.jtsprockets.com/catalogue/model/1287
Front 428 Sprocket: http://sharkshifter.com/zc/index.php?ma ... ts_id=1270

Worked out to get the same ratio as stock but with the smaller KX100 wheels will need to have 16/52 which is good because it's available off the shelf :P

I'm currently looking for a parts to start.
Found a spare KX100 frame ($270 AUD) so I can start while still riding my KX100, I will swap parts over as things get closer to the end. Next part is the KDX200 stuff. Was originally looking at '95+ because I was told it's the better bike but as I don't need the 'main' better part (frame) how much worse is the '89 to '94 motor? Worth waiting for a cheap '95+? Just cause I found a complete '94 which only needs new magneto key and coil for $650 AUD (which is cheap for AUS).

Feel free to let me know what you think or any problems you think i'll run into.

Devon

[deviot]

Been looking into the '89-'94 motors and it seems the higher running exhaust will just cause me more problems so think I will hold off and wait for a later model parts bike. The hunt continues!

[hadfield4wd]

Been looking into the '89-'94 motors and it seems the higher running exhaust will just cause me more problems so think I will hold off and wait for a later model parts bike. The hunt continues!

What do you mean by higher running exhaust? Physically in theframe higher? Making fitment difficult?

[sarrant]

Warning, Butt-pulled hearsay commencing now:

From what I've read on other forums, KX80/100s are the toughest expert-mini to stick a full size engine in (Perimeter frame and lots of bodywork). From what I understand, the RM has the most frame room(and is the best handling to boot) and may just need lower cradle modification/stretching.

The KX may require really significant mod (as in both top tube and cradle modification, at that point, all bets are off on fitting any of your bodywork, and you've basically put together your own frame.

Another issue to think about is cooling. Not much in the way of radiator space on the mini.

[deviot]

Been looking into the '89-'94 motors and it seems the higher running exhaust will just cause me more problems so think I will hold off and wait for a later model parts bike. The hunt continues!

What do you mean by higher running exhaust? Physically in theframe higher? Making fitment difficult?

As in the expansion chambers bends wont fit very well.
'94:
http://i261.photobucket.com/albums/ii62 ... 200023.jpg

'95:
http://i33.photobucket.com/albums/d62/s ... ike003.jpg

KX100 with KX125 motor:
http://i1156.photobucket.com/albums/p56 ... rks003.jpg
As you can see the plastics will already need to be trimmed with a pipe that runs 'lower' or should i say closer to the motor case? Think the early pipes will cause more problems also will make it harder to fit radiators.

The KX may require really significant mod (as in both top tube and cradle modification, at that point, all bets are off on fitting any of your bodywork, and you've basically put together your own frame.

Yer i'm not too sure how much work/customisation there will need to be donel. I've seen the halfway KX100/KX125 but also seen other build like TM85/TM125 and on youtube there even a KX80/KX500 . I guess worse case i'm halfway thorough this project and it will not fit at all or there is way to much modifying I will waste money on the spare KX100 frame and rest of parts I will be able to on sell.

[dfeckel]

The H series pipe will fit an E series motor with some BFH massage around the powervalve mechanism.



*BFH = Big Farking Hammer

[deviot]

The H series pipe will fit an E series motor with some BFH massage around the powervalve mechanism.

*BFH = Big Farking Hammer

Oooo! So if the H series pipe fits (with some BFH) then only other major differences are the Kip Valve maintenance and other minor things? Nothing else really to pick a E over H. Thats great because E Series bikes are a lot cheaper here!

[Julien D]

E motor arguably has better power delivery than the H. The pesky powervalves can be a real bummer at times though.

[hadfield4wd]

E motor arguably has better power delivery than the H. The pesky powervalves can be a real bummer at times though.

This is interesting. What about the "E" motors makes the power different? Are they the same hp?

[KarlP]

I would think the availability of the H motor would make it the choice. Either motor would be night and day difference over the KX100 motor.
I sent my KX100 carb and head to Ron Black. It is improved over the stock KX100 motor but it will never be a 200/220 CC KDX motor.

Your project will make a very nifty bike. I really like our KX100. The motor is a real handful, though, and it is too small for me. The thing that really hurts it are the size of the wheels; holes and roots and ledges are just proportionately that much bigger. Then again, there is this young fella running the local Hairscramble circuit on a KX100 that is just smoking the field, even the A guys, and he is still in the Junior class because of his age.

I kind of looked at doing the same thing a few years ago when I had a spare KDX motor. I figured the frame would have to be cut, a second radiator mounted, and lots of custom fab work done, but it can certainly be done.

[KarlP]

Besides, if you have a spare KX100 frame what have you got to lose?

[deviot]

After more researching and like other before I decided against this idea The turning point was exhaust, The KX100 (unlike other minis) runs the exhaust on the LHS. This means whens trying to run a exhaust on the RHS the shock reservoir is in the way as it is fairly large compared to other models. This along with the other modification I would have to do means it not really cost effective for me and would rather look at lowering a full size bike.

Thanks for all your help and comments but sadly at this point it's a no go.

[diymirage]

too bad man
you know, it would only take 2 cuts and 2 welds to turn the neck on the exhaust and run it on the LHS

[UI Vandal]

too bad man
you know, it would only take 2 cuts and 2 welds to turn the neck on the exhaust and run it on the LHS

That is what I was thinking. Knowing you have to pretty heavily modify the frame, having to cut, rotate, and weld the exhaust is very minor.