1979 Kawasaki KDX 400
You’re looking at a 1979 Kawasaki KDX 400, our first featured KDX here on vintage mx. This bike is more than worthy of a showcase and comes to us from Casey K. of Pillow, PA. The KDX 400 line was only made two years, 1979 and 80. They are fast as far as any off-road bike is concerned. Ample power combined with reliability made these all around great bikes. Fun and fast! I’m sure Casey agrees. Here’s Casey’s story:
A buddy of mine bought this from the original owner about in 1997. I was at his house when he brought it home and I immediately envisioned myself riding it into the sunset, but my buddy is a hardcore vintage Kaw guy, and getting this one from him would take some kinda doing. He was told by the original owner that it never did run right, and that it had been parked most of it’s life. For years, I tried to get it, but my buddy was just not willing to sell.
Fast forward to the spring of 2013, and once again I asked about that “old KDX”. This time he said he’d part with it. He said he only had it running once or twice and that it smoked bad, and smelled worse, indicating a bad crank seal. After settling on a very fair price, I got it home and realized that it only had 526 miles on the speedo. After spinning the front wheel, I confirmed that the speedo definitely worked, and there was no indication that the speedo cable had ever been off.
I pulled the motor, split it down, and sure enough, one of the factory crank seals had an obvious imperfection in it, likely caused at the Kawasaki factory. That bearing also had a little bump, bump, bump to it. I put it back together with new seals, and crank bearings, cleaned the carb, and put it back in the bike. It started on the second kick, and has run flawlessly ever since.
It now has just over 800 miles on the clock. I have the title, but am not having much luck tracking down the original owner, to get the title actually put into my name, to register it. I have had it out on the road, and with my GPS, this bike will run 88 mph. Gearing is 16/48. The only things I have replaced are the tires, and the rear shocks. I swapped the stockers for a set of Progressive shocks. Then I put the green fork boots that were on the front, on the back shocks, to keep them cherry.
I have quite a bit of NOS stuff for it, but I’m always looking for more, particularly the plastics, and those two little KDX400 decals on the side panels. I found it impossible to find a stock throttle tube for it, and the original one has the end busted off, so I switched the entire throttle and cable for one from an ’86 KX500. It was not a direct bolt on deal, but I got it working perfectly.
This bike always brings a smile to my face whether it be just gawking at it, or when I hit a long uphill and I just twist on all that luscious big bore two stroke torque. If anyone knows of any parts machines out there, I’m definitely interested, and by all means contact me at caseysback2013@gmail.com.
8 Comments
Where is the best place to buy piston rings for my kdx 400?
I got a 1979 KDX 400. I need piston and rings and can’t find them anywhere, somebody help a guy out?
I just found part number 13008-5017 at my local vintage kaw dealer. I have heard that the HD Evo has a Hastings ring that is the exact same size. I have already contacted the HD dealer at the end of the street and we are going to compare and make a determination weather the rings are indeed similar enough to be used in your 1980 KDX400 before I install them in my KDX . Because I already know that the original ring is dern near impossible to find I am sympathetic to your situation and I am pulling for all of you. Wishing you all luck!
Sorry to inform my new friend that these rings are definitely not interchangeable.
Hello to all KX/KDX vintage owners, I just purchased a survivor 1982 KDX 450, 610 miles on the o.d. REALLY! Now I am going to try something that I think will work!!! First off, the bore on the 400/420/450 are the same! The engine was stroked to make more displacement. Now for all to read! The bore standard size is 83.00mm, YES it is!
Now here is what I am going to try, Wiseco makes a 83.00mm piston #675M08300 is it for a polaris TWO stroke!!! I know the pin size is just a VERY little bit smaller, if they make a pin bearing that is a little bigger for that pin, it would work, if not, I am going to bore the piston to the correct pin/bearing size, they also sell .50mm over sizes. Keep the big-bore KX/KDX’s alive and well. Good luck, Allen.
Loved seeing this! This was the bike I rode all over southern Utah in the 80s growing up. Wish I still had it. I’m now looking to restore my fathers 1973 Husky 460 that he raced and did widow maker back in the 70s. It has been sitting in his shed untouched for 25 yrs. Pulled it out and after cleaning out a mouse nest in the tailpipe, it started right up!
Hi, I race a ’79 KDX400 over here in the UK. I’ve had it about 3 years and its been great. Spares are a problem, especially in the UK. I managed to find an NOS piston on ebay and a set of NOS rings too, but have not seen any for sale since, and no other bike uses an 80mm piston. A friend of mine also races one. He has fitted the KDX420 barrel, it goes straight on, no need to change the carb jetting or cylinder head. These are also a bit rare in the UK. The best bet is to have the piston made, all the barrels are the same size you need to have them plated. Good look in keeping the old girl running!
Andy
I have a 1980 KDX 400. The top end is wasted and I’m looking for a cylinder head, cylinder sleeve or whatever and a piston. Found some parts on eBay but cannot locate a piston. Do you have any ideas? Thank you.