1987 KDX80 Rebuild

Discussion specific to the various air-cooled KDX models sold in the USA
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TheGriz
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1987 KDX80 Rebuild

Post by TheGriz »

I picked up this 1987 KDX80 for $200, thinking it just needed rings and a few odds and ends. It is never that easy! My neighbor's son has been helping me in the shop and this was a great project for the two of us to tinker on.

The day I brought it home:
Image

Image
1987 KDX 80
1991 KDX 200
2005 GasGas EC250
2011 GasGas EC300
2008 KTM 300
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TheGriz
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1987 KDX80 Rebuild

Post by TheGriz »

I found so many surprises:

This previous "fix" had layers of silicone and bondo on it, but was still leaking.

Image

This is what was under all the silicone and bondo:
Image


Fixed the cases properly. Tig welded a big land area to create a new tab and filed it all down nice and flat.
1987 KDX 80
1991 KDX 200
2005 GasGas EC250
2011 GasGas EC300
2008 KTM 300
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TheGriz
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1987 KDX80 Rebuild

Post by TheGriz »

Image

We found the clutch pressure plate was chipped. It looks like someone tried to pry the clutch out with a screwdriver. My partner is installing the new clutch:

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1987 KDX 80
1991 KDX 200
2005 GasGas EC250
2011 GasGas EC300
2008 KTM 300
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TheGriz
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1987 KDX80 Rebuild

Post by TheGriz »

The previous owner "fixed" the leaking forks by piling rtv around the fork tube and slid the boot down over it. LOL

Forks have new seals.

A pile of other parts and work completed:

Stripped and sanded down the frame
Bew ball bearings for the steer tube.
Cylinder Honed
New Wiseco piston and rings
New Stator - Had a very weak spark
Used wheels found on ebay - New brakes
New KX80 Carb
New Boyesen Reeds
New handlebars
New throttle-tube assembly from a KDX220
The plastics were sanded down and cleaned up a bit.
Used airbox found on eBAY & new UNI filter
New tires
Used side plastics found on eBAY. White vinyl added to the number plates
Fabbed a new chain guide out of aluminum
Made a chain slider work...

Probably some other stuff too... too much to remember
1987 KDX 80
1991 KDX 200
2005 GasGas EC250
2011 GasGas EC300
2008 KTM 300
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TheGriz
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1987 KDX80 Rebuild

Post by TheGriz »

Image
1987 KDX 80
1991 KDX 200
2005 GasGas EC250
2011 GasGas EC300
2008 KTM 300
User avatar
TheGriz
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Posts: 148
Joined: 08:07 pm Nov 14 2014
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1987 KDX80 Rebuild

Post by TheGriz »

Finally! I had started to give up hope that this bike would ever run again.

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1987 KDX 80
1991 KDX 200
2005 GasGas EC250
2011 GasGas EC300
2008 KTM 300
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KDXGarage
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Re: 1987 KDX80 Rebuild

Post by KDXGarage »

WOW! Good job on the rebuild! It looks nice!
Thank you for participating on kdxrider.net. :bravo:
To post pictures from a device: viewtopic.php?f=88&t=24128
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Sullyfam
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Re: 1987 KDX80 Rebuild

Post by Sullyfam »

Sweet and that's one happy neighbor!


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TheRadBaron
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1987 KDX80 Rebuild

Post by TheRadBaron »

Looks great. It gives me some motivation. I happen to be rebuilding an '87 KDX80 at the moment as well. I bought mine for $80, though it needed a lot of work. I'm not doing as thorough of a job as you are, either. I just want to get mine mechanically sound and reliable for family use. My wife wants to start riding trails with me and I know she's intimidated by tall bikes so the KDX80 might be a good starter trail bike for her until she gets more comfortable. She's 5'6" and about 120# so she might be a bit big for it but I think she'll like it that way.
Once she outgrows it I have a lot of young nephews and friends' kids around that could use a good trail bike to learn on. Mine has a sleeved cylinder that looks to be well done so I had it bored 0.5mm over and put in a Wiseco piston. The crank seemed good so it was left alone but I split the cases to change the crank seals and all the other oil seals. I should have it back together within a few weeks.
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TheGriz
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1987 KDX80 Rebuild

Post by TheGriz »

Thanks! I had fun working on this little KDX. After selling my 2003 220, it was nice to still have a KDX in the garage.


This had a sleeved cylinder as well. I was going to have it bored as well, but after a quick ball-hone, most of the worst grooves were gone, and I decided to go with it. I'm glad I did! She makes good compression and fired on the second kick.

It is much shorter than the 99' KX80 that I have. I'll try to take a side by side shot of the two, but at 5'6" this thing would be a bit small. It would be good to learn on at least. More mild power and easier to get a kid's (or small woman's) feet flat on the ground.
1987 KDX 80
1991 KDX 200
2005 GasGas EC250
2011 GasGas EC300
2008 KTM 300
Kawai man
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Re: 1987 KDX80 Rebuild

Post by Kawai man »

what air filter did you buy? and carb?

I'm trying to get a kdx running and just wondering what you used. :grin:
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