1991 KDX 200 Rebuild

TheGriz · Post by **TheGriz** » 06:48 pm Oct 19 2016

I cannot seem to find a front brake lever to work with this master cylinder. Even the OEM part listed doesn't seem to work. The stop on the back side is too short and lets the brake lever flop all the way open.

I may just swap on a more modern master cylinder. I might have one from a later KDX.

To Do:

Finish wiring
Hook up speedo
Add Gearbox oil
Add coolant
Tank/plastics
Check nuts and bolts

TheGriz · Post by **TheGriz** » 08:34 pm Oct 19 2016

Here's the problem that I've been having with the front master cylinder:

I did find this Nissin master cylinder in one of my parts bins It came from a gasgas:

I also found this Nissin rear master cylinder from a gasgas. It has a larger capacity and doesn't need the remote reservoir.

Dekon · Post by **Dekon** » 09:21 am Oct 20 2016

I like the upgrade on the rear master cylinder. I don't you about yours, but my rear brakes are like a light switch, off or locked up. Almost no modulation to them.

Don't forget to put the adjust bolt back in, a guy I ride with had it vibrate out and caught his foot under the brake pedal and it pulled out the piston. Maybe the Gas Gas one is different, but I wouldn't want to take a chance.

TheGriz · Post by **TheGriz** » 08:18 pm Oct 20 2016

Good call... I'll put it back in.

So, a big disappointment hit tonight. First, I realized that I forgot to order new radiator shrouds.

Then, filled it up with oil and coolant and saw a little trickle. At first, I thought it must be some run off from filling it. I wiped it off the left side power valve cover. A few minutes later, it was back and removed the cover:

I wiped it away, thinking that it must have run down the edge and into the exhaust chamber when I removed the cover. A few minutes later, it was back. I watched, and found this hairline crack:

TheGriz · Post by **TheGriz** » 08:22 pm Oct 20 2016

After talking to Millennium, I started to worry. They said that a lot of the KDX castings are very bad. They try to weld on the casting and it gets worse.

So, I have a couple options:
1. Remove the cylinder, clean it up and attempt welding, knowing that I risk making it worse.

2. Drill a couple holes in the ends of the crack and grind out a little groove, filling it with JB weld. If that doesn't work, remove the head and try TIG welding the crack.

Thoughts?

Dekon · Post by **Dekon** » 09:26 pm Oct 20 2016

Someone else had the same problem on here. I think they welded up the crack.

ubareddition · Post by **ubareddition** » 06:13 am Oct 21 2016

Oh man that's very sad.

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Post by **Tyl3r** » 07:16 am Oct 21 2016

awww nooo!!!! Sorry for the bad luck. It was looking soo good and was soo close!

I'm interested to hear what you end up doing. I think that if it were me, I would grind the crack with a Dremel, try to put two little holes in either end of the crack, and have someone who knows what they are doing tig it up (not trying to say that you don't know what your doing, just saying that I wouldn't lol).

ubareddition · Post by **ubareddition** » 07:51 am Oct 21 2016

Didnt you get that cylinder from somewhere because the original one had a big crack in it?

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TheGriz · Post by **TheGriz** » 08:12 am Oct 22 2016

I did. The original cylinder had a big crack over the intake I got this cylinder. Cause it was a "good" core that was in need of replating.

I got the cylinder on eBay, described as "in need of repair" and "might need replating".
I think a crack like that couldn't have gone unnoticed, unless the seller was simply parting out a. On running bike.

Had I known about it, maybe millennium could have welded it while they had it.

So, my TIG skills are very basic and leave a lot to be desired. I'm debating about trying it myself or getting a buddy to stop by. Just depressed about tearing it back down.

ubareddition · Post by **ubareddition** » 02:10 pm Oct 22 2016

I feel you. Nothing quite like getting your hopes up when you see the light at the end of a tunnel but that light is just a sign that says "detour go back the way you came"

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TheGriz · Post by **TheGriz** » 03:52 pm Oct 23 2016

So, I decided to tackle it myself. My TIG skills aren't good and the aluminum alloy isn't either.

Drilled the ends of the cracks to help stop further spread:

My crack kept opening up as I added filler. My weld got a little big, so I ground it down a bit more to keep the chamber volume loss to a minimum. It isn't pretty, , but it should work.

TheGriz · Post by **TheGriz** » 03:52 pm Oct 23 2016

TheGriz · Post by **TheGriz** » 09:42 am Oct 25 2016

I couldn't resist kicking it over and seeing if everything worked. I am still waiting for the new shrouds to arrive and I want to take the tank back off and do a restoration on it.

I've never had a fully rebuilt engine start on the first kick. Usually it takes a few when everything is fresh. Before I rolled it out of the garage, I cycled the kick starter by hand a few times to be sure everything was free and smooth.

[youtube][/youtube]

Post by **Tyl3r** » 10:44 am Oct 25 2016

TheGriz wrote:

Nice! glad ya got it going!

Just my 2cents, but any thoughts on sealing up that weld with some JB weld or something of the like for high temperatures? Being the worry wart that I am, I probably would (just in case) to make 100% sure that no water could come through there.

ubareddition · Post by **ubareddition** » 10:46 am Oct 25 2016

That was great. Almost as great as the snowboarding crash I watched after.

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david · Post by **david** » 03:05 pm Oct 25 2016

I second adding a layer of JB Weld to it, to make sure it's sealed up. I had to weld up the lower case on one of my Jetski engines last year, it also requires a layer of epoxy to seal up the pin holes that the weld creates.

Dekon · Post by **Dekon** » 06:51 pm Oct 25 2016

Nice job! Glad you got it going. You might want to route the front brake hose on the inside of the fork leg. Much to easy to catch it on something and having it torn off.

TheGriz · Post by **TheGriz** » 07:40 am Oct 26 2016

All good advice. Funny comment about the JB weld. I actually did add a small bit around the edges of my weld, just in case. I forgot to snap a pic of it. I knew it might never be this clean again and JB weld works best when super clean.

I'm not really happy with the GasGas brake master and how it matches with the caliper... either that or I need a new rotor. The stopping power was marginal. I'll need to put a few miles on to let the pads seat themselves. I think I have a CR250 brake setup somewhere from another project. I may try that and route the cable on the inside as Dekon suggested.

TheGriz · Post by **TheGriz** » 04:59 pm Oct 30 2016

I'm quite happy with how it turned out. I'm waiting for a new Keihin PWK 36 carb. I can't get the float needle to seal. Even with the float moved up by hand, It will not seal. I've tried a few tricks and had no luck. Brakes are marginal. I may need new rotors.

I wet sanded the tank with 320-1200 sand paper and polished with 3M polishing compound. Other than a slightly different green color, it looks great.

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