Leaky Front Master Cylinder and Need New Final drive fill bolt

[Ccitis]

Hey All, I seem to have a front master cylinder that is weeping from the plastic base... anyone have a good source on a replacement? Also, my fill bolt for the final drive is stripped out... again, any replacement? Thanks!

[DiverRay]

Mikesxs has replacement MC's. Just make sure you buy the one for two front disks. On the final drive, is the bolt head stripped, or the threads in the case? Partzilla can probably get you a replacement, but again, that I'm not sure of as it's been about 15 years since I've last stripped on.

[DEEBS11]

This is another good source. You need a 16mm piston for dual calipers. Not 12 or 14mm. I use these on several bikes. They work great. Some in service for over ten years.

https://www.ebay.com/itm/203479587747

[Ccitis]

Does the brake light switch integrate into that lever? As for final drive, it is the head... the PO must have used an impact driver on that sucker... took all I had including a heat gun to get it out. Looks like you can just get a new one from Yamaha.

[DEEBS11]

Brake light switch.

[DEEBS11]

Plug.

https://www.ebay.com/itm/16638799776...Bk9SR6bs3bPcYw

[Radioguylogs]

Hey All, I seem to have a front master cylinder that is weeping from the plastic base... anyone have a good source on a replacement? Also, my fill bolt for the final drive is stripped out... again, any replacement? Thanks!

All of my XS bikes have had this problem.

You can carefully pry the nylon resevior from the metal base. There is an O-ring that seals the nylon resevior to the base. It becomes compressed by crystalized brake fluid and then it leaks.

Take the old O-ring to the hardware store and find the best fit.

I have fixed all of mine this way.

Sorry, I didn't take any pictures to help you visualize.

[Ccitis]

All of my XS bikes have had this problem.

You can carefully pry the nylon resevior from the metal base. There is an O-ring that seals the nylon resevior to the base. It becomes compressed by crystalized brake fluid and then it leaks.

Take the old O-ring to the hardware store and find the best fit.

I have fixed all of mine this way.

Sorry, I didn't take any pictures to help you visualize.

This is good to know. The leak is not major, just weeping over weeks enough to make it damp. My plan was to replace anyways, does not hurt to give this a shot. Do you have to use some type of glue or sealant to re attach the reservoir to the metal? I will give it a shot.

[DEEBS11]

Marty knows. 39.7mm x 3.5mm.


https://www.xs650.com/threads/brake-...-o-ring.60701/


https://www.allworldmachinery.com/it...?itemCode=P-40

[DEEBS11]

https://www.ebay.com/itm/36478165784...Bk9SR8zHud7cYw

[LAB3]

Somebody correct me if I'm wrong here, it's my understanding that ordinary hardware store o-rings are made to seal water and won't hold up to gasoline or other auto type fluids. Generally speaking I get mine from auto parts stores, they tend to keep them in an assortment behind the counter.

[DEEBS11]

LAB3, Brake fluid is silicon based (should not corrode a Nitrile O-ring) and since the master cylinder is so far away from the hot calipers, there is not much heat to deal with. However, if you can get Viton, that would be the better material. I think Buna/Nitrile would work fine. I use Nitrile in my KZ1000/750 rear master cylinder cups and they have lasted for many years. I have that part reference if anyone needs it.

[Radioguylogs]

This is good to know. The leak is not major, just weeping over weeks enough to make it damp. My plan was to replace anyways, does not hurt to give this a shot. Do you have to use some type of glue or sealant to re attach the reservoir to the metal? I will give it a shot.

No sealant- just the O-ring.

When you are tring to get it apart, it helps to twist the nylon resevoir and roate it on the metal base to break it loose.

[Larrym]

Oopsey....(⊙_◎)

I replaced the MC Reservoir O-ring on my 79 Special this year cuz of the same "weeping".

But in my Inter-Web searches I got conflicting info about whether (or NOT) nitrile rubber was safe with good-ole-DOT3 brake fluid. (⊙﹏⊙)

Imma chickened out 'bout Nitrile and went with EPDM instead. (◠﹏◠)

Purchased from-

https://www.oringsandmore.com/metric...minimum-5-pcs/


Goin' on over six months and no problems.......yet. Feeling like a guinea pig/test subject but we'll see. ¯\_(⊙︿⊙)_/¯

[Ccitis]

Oopsey....(⊙_◎)

I replaced the MC Reservoir O-ring on my 79 Special this year cuz of the same "weeping".

But in my Inter-Web searches I got conflicting info about whether (or NOT) nitrile rubber was safe with good-ole-DOT3 brake fluid. (⊙﹏⊙)

Imma chickened out 'bout Nitrile and went with EPDM instead. (◠﹏◠)

Purchased from-

https://www.oringsandmore.com/metric...minimum-5-pcs/


Goin' on over six months and no problems.......yet. Feeling like a guinea pig/test subject but we'll see. ¯\_(⊙︿⊙)_/¯

Cool. I don't have much to lose... if it fails I will get a whole new unit as planned.