Hybrid Questions

[gn83tm]

I'm seriously looking at doing a KX/KDX hybrid and have a few questions I'd like to find detailed answers to. I've searched all the threads I can find on this subject and have gathered lots of info but still have a few unanswered questions. The bike will be used mainly for hare scrambles athough I do some enduros and mx.

I'm looking at using a 1990 motor I have that has been modified by Fredette and runs great for what I am doing. I'm wondering what year KX125 would work best but am thinking of using the '99 and up model. I have found a 1994 that looks promising but wonder how far it would be behind the newer models. According to Eric Gore's book, it was '98 before Kawasaki came out with a bike that was better than the '94. I'm sure the engines have gotten a lot better but has the suspension/chassis improved a lot, especially considering the intended use of the bike? Any thoughts?

The '90 motor has the head mount on the back side vs the mounts on the perimeter frame bikes being on the front. It looks like the rear mount will interfere with the tank although I don't know for sure. How does one go about solving this?

The frame mounts and rear case mounts look straightforward. Is there still a pipe available for these swaps and if so is it more suited for the KX motor or the DX motor? What about the air box/boot?

Any details on this project would be very much appreciated. Thanks!

 

[placelast]

I'm looking at a 1990 motor modified by Fredette and runs great. what year KX125 would work best…thinking of using the '99 and up model. ‘94 looks promising but how far it would be behind the newer models. According to Eric's book, it was '98 before Kawasaki came out with a bike better than the '94. sure the engines have gotten a lot better but has the suspension/chassis improved a lot, especially considering the intended use of the bike?

The '90 motor has the head mount on the back side vs the mounts on the perimeter frame on the front. It looks like the rear mount will interfere with the tank although I don't know for sure. How does one go about solving this?

The frame mounts and rear case mounts look straightforward. Is there still a pipe available for these swaps? What about the air box/boot?

I recently bought a ’98 KX125-framed ’90 KDX-engine bike from a friend; he bought it from the surgeon. E-mail me at [email protected] for more info unless you think others here would benefit from our exchanges.

It’s good to hear your motor runs great. Mine starts & runs OK but is a dog (compared to my RMX – not fair). I haven’t had time nor $$ to go thru it to see how much TLC is needed, but I want to extract more HP for sure, to go along with the chassis.

I cannot vouch for ’99-up frames, nor the chassis performance of one over the other. One would think they’d improve year-to-year but that’s not always the case. Most current should be best, but in your situation you may have to use what is available. This one came with an RMX front end.

‘94 thru ’98 use the same plastics & seat; the rest should be the same. (UFO has flo, regular green, plus white and black available. Mine is all flo, w/FX graphics & a sticky grip seat cover – good looking but too grippy - both will be replaced with less tacky Technosel goods soon.)

The stock KDX head stay appears to have been chopped off & a block of aluminum welded and fitted at the opposite end for securing to the KX frame bracket. My KDX head still contacts the stock tank & needs some add. grinding to clear. I have a separate IMS tank that fits =, although the extra capacity is not needed so it’s off to E-bay soon.

I cannot tell if the KX frame mounts were reused or replaced, nor how the swing arm/bolt/cases interface was modified. I can look at it and let you know if you need to do some custom fitting there.

Dynoport used to make pipes for the conversion. I bought the last NiCr-plated pipe; they have one more in raw steel. They sent me several tips so my guess is custom fitting is required. The bike came with an FMF with a custom stinger by the original fabricator to mate with what appears to be a KX125 TC S/A II.

A non-concentric spacer-ring was machined to mate the KX air boot to the KDX carb.

 

[gn83tm]

Thanks for the reply. It's great to have a resource that actually has a hybrid bike rather than just seeing one or hearing about one. With the RMX forks you really have a unique ride!

I regards to the head mount, I wonder if it would be possible to swap to a newer head from a perimeter frame bike that has the mount in front. Does anyone know if the heads are interchangeable?

I'm still wondering about the choice of model year for the 125 and how much difference there really is. It looks like there is maybe a $1000 difference in the price of a '98 model vs a '94 for instance. That much money could make an old bike like new and also allow quite a bit of upgrading to be done to the suspension.

I'd like to put a call into the doctor himself, but there's some little 6 day thingy going on in Brazil and I'm sure he's a little preoccupied with that.

Thanks for your help placelast. I'll probably be contacting you some as I go thru this process.

 

[placelast]

Thanks for the reply. It's great to have a resource that actually has a hybrid bike rather than just seeing one or hearing about one. With the RMX forks you really have a unique ride!

I regards to the head mount, I wonder if it would be possible to swap to a newer head from a perimeter frame bike that has the mount in front. Does anyone know if the heads are interchangeable?

I'm still wondering about the choice of model year for the 125 and how much difference there really is. It looks like there is maybe a $1000 difference in the price of a '98 model vs a '94 for instance. That much money could make an old bike like new and also allow quite a bit of upgrading to be done to the suspension.

I haven’t a clue on the head interchangeability.

Don’t get slowed down by limiting choices to a particular year, seeing they may be similar if not identical. Do be concerned with finding an available motor-less chassis of any year. I’ve found it’s not so much which year is better but rather what condition it is in: wear and remaining life. Making a worn bike like new can be co$tly.

FWIW, the ’94-’98 models have the last of the thicker seat foam; ’99-up are all moto thin. Parts are getting scarce for the older years. And then there’s your budget; a lot of things to consider, and only you can make the final decision.

 

[Kawierider]

If your trying to find out which parts will work on which motors, buykawasaki.com is the place to look.....it has complete part diagrams, that include part numbers. Just remember, on a project like this they dont need to be exactly the same part.....they just need to match enough to work so do some detective work.

good luck.let me know how it goes
Tim

 

[placelast]

Spent some time with my new hybrid. The aft-most bolt of the water pipe fitting on the head and the fitting/elbow itself does contact the bottom of the stock KX tank. There's not much overlap; maybe some heat and pressure to put a dimple in it is all that is needed.

I suspect the bottom-forward engine mount - not the one just under the exhaust, but the one between it and the footpegs - is lower overall than the 125. It appears as if the fabricator relocated these two as evidences by a missing case bolt, and it is too close to the lower frame hoops/under tubes for a standard flange bolt; I will have to go underzied there.

 

[gn83tm]

It must be a tight fit along the bottom frame cradle. I remember reading something about the one frame rail needing to be flattened to clear the clutch cover. The 200 motor must be overall taller than the 125.

I'm still doing some looking and want to talk to the Doc when he gets back from the 6 day before I do anything drastic. I'm kind of leaning towards keeping my bike complete since it's in nearly perfect shape. I could then look for a newer engine and avoid the head mount issue.

The main question I'm still trying to answer is which year of KX would be the most suitable for what I'm trying to do. If any of the ones from the last 10 years would be equally suitable, then I can look according to condition more than year. But if someone says a certain vintage would be better suited for woods racing then I'd look for that.

Thanks for the help!

 

[kx200]

The 94 kx125 uses a larger air boot so if you can use the 1995 other wise you will need to make a spacer ring for the carb. For what its worth I'm using a pair of 46mm 89 KX500 forks I couldn't get rid of the harsh fork on the 94s.

 

[gn83tm]

KX200 do you mean the '94 KX125 fork is harsh or you talking about the KDX fork?
I appreciate the note on the air boot and will try to remember that.
I see you are an Iwegian. What part of the state? I'm in the Omaha/CB area.

 

[mcvtr]

I have a 1990 KDX motor in a 1991 KX125 Frame

the head mount on the top back of the head has been removed, and the bottom frame tubes have been "reformed" i.e. bashed a bit, to get the motor in, if you pass on your e-mail I can send you piccies of the bike and the fit of the engine. the pipe is a pro-circuit and fits fine! there is one mount that does nothing, but it doesnt seem to affect anything!

I'll admit I didnt do the conversion, I bought it, but it looks a reasonably straightforward job, especially if you already have the motor, as certainly in the UK, an old KX125 is worth nothing! I'm heavy, and the suspension copes superbly with me, even if the rear end is a little soft for my liking!

Alex.

 

[gn83tm]

Any pictures I can get would be very helpful. Email them to [email protected].

 

[kx200]

gn83tm I'm from eastern side of Iowa, and I had Jeff build it for me
the KX125 forks were harsh even after using a race tech delta valve and new bushings

 

[gn83tm]

I didn't realize there was a problem with harshness with the KX forks. Is it limited to certain model years or will it be an issue with all of them? I assume it's harsh in the woods vs on the MX track, right? It seems like most posters on this forum like the KX fork swap but maybe they aren't using the bikes in snotty, rock infested woods. How much different are the 500 forks?