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I bought an allballs front master cylinder rebuild kit last year and attempted to install it last weekend. One of the two shaft seals is too big to fit in the bore. I actually don't even see a chamfer in the bore to make it easier to get the seal installed. Maybe I'll try to add a very slight chamfer with a grinder when I try this again. I called the vendor I bought it from (Halls of Medford) and he confirmed the part was correct for my kdx. He also said he has not seen this issue before although they sell a lot of these rebuild kits. The seal in question is the 2nd seal that on the shaft - the first seal on the shaft fits in fine. I can take a few pics of the master cylinder so you guys can confirm with me this is indeed an original master cylinder for this bike. Halls of Medford offered a refund but I really just want to get the right size seal. They don't sell the seal separately so I'll try to find it elsewhere maybe.... or try a different kit entirely.

Any suggestions on where to get the seal alone, or what kit to buy that you all have found fits well?

Thanks, Chad

I was looking at master cylinders from 89 and above on ebay and they didn't look exactly like mine. After looking at an 88 kdx master cylinder it appears to be exactly what I have. It has a plastic snap in ring instead of a metal snap ring to hold in the washer and piston assembly. Maybe I don't really have an 89 bike, or maybe the master cylinder was replaced, or maybe it is original and just happens to be fitted with leftovers from an 88.

here is the pic from an ebay ad...

https://photos.app.goo.gl/Wrp9IBw6mcLlbSIG3

Can you post a picture of the bike and master cylinder?

Maybe you do have a different year part. Is it black or gray?

I did an all balls kit from Rocky Mountain. I remember both seals fit snug and I even did it backwards at one point. But everything fit.


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I just bought a used master cylinder from a 90 kdx off ebay today, so I'll use the all balls rebuild kit I previously purchased. All balls was very nice to send me a new cup seal at no cost when I emailed them stating that I damaged one of the seals on accident. They actually sent me 2 of each cup seal so that was really cool of them.

I never was able to find the rebuild kit for the 88 master cylinder... too bad because all it really needs is the new cup seals. I bet there are some other seals from other bikes that would fit but would be impossible to track them down.

Jason wrote:Can you post a picture of the bike and master cylinder?

Maybe you do have a different year part. Is it black or gray?

I took some pics of the bike with new master cylinder.

https://photos.app.goo.gl/iMVn44V9KBVPqLYz1

Nice addition of the period correct numberplate. Look for some KX front brake hose clamps to go with it.