KDXRIDER.NET

Hi All!

It is over a year on since I last tried to get a firm front brake, I put the bike in the shed and gave up - sad I know! I am blo*dy determined to sort it as I want some off road action this summer!

I had the bike out yesterday and used a sealey vacuum bleeder (similar to the mittyvac) and was for some reason optimistic! That was a mistake! I bleed the system and still have a spongy lever action.

It had been some time since I was last on here so re-registered and followed this thread again. I have just reviewed Wibbs video (a BIG thank you for posting!), it looks like I have the same sort of action! I can pull it almost to the bar to! I also ride road/trials bikes and have never had a front brake that feels like this! Not confidence inspiring!

The front end I put on came from a 2000 KX125 which I bought complete. Before I stripped it down the front brake was quite firm, certainly nothing like it is now. With the current amount of travel/feel I do not think it will pass our roadworthiness (MOT) test required here in the UK. Without this I cannot legally use it on our trails (such as they are).

Not sure what else to try! Anyone with any other ideas?

Does anyone know where you can get new mastercylinders at a reasonable price? A year on, its harder to find parts here in the uk!

I wanna ride!!!

I sorta had the same issue. I broke my oem kdx mc and bought a 96kx 250 mc and lever. Tryed to bleed it for 45 mins nothin was happening. Tryed bleeding the banjo bolts too didnt work. Then i took the caliber off pushed all the fluid out the line with the caliber off and replaced the pads and found out the caliber was stuck from sitting. Put everything back together all freed up put fluid in and ten mins it was bleed and stiff. It def a big pain in the arse.

thanks for commenting, the pistons are free to operate so it is not that, sadly! I retracted them to reduce the amount of fluid behind them in which air could be trapped. Hey ho!

If all else fails the 5 to 1 treatment works every time. (5gals of gas 1 match just in case you didnt know.)

trust me, I have been tempted!

It's possible the seals in the m/c are weak and do not push all of the fluid forward. Or there is some air in there you can't get out. Sometimes factory brake lines get weak and expand. Aftermarket braided lines never hurt.

I rebuilt my stock KDX master cylinder, and it is still not very strong. I noticed the caliper is the exact same as my WR 450, which has WAY better brakes. My front wheel also has the WR450 rotor, so the difference is the cylinder or the lines. I was tempted to get a WR450 master cylinder and try it. The WR takes one finger to stop and the bike weighs 40 pounds more, where the kdx takes the whole hand squeezing hard.

At this time, obviously, trying to bleed it any further is a waste of time. I would try a new brake line, then go to a different master cylinder if necessary.

This has me thinking of trying a new brake line. That would explain a lot.

You can get a new master on Ebay for $50 and they work real well. I have one on my GL500. If you get one with a 14mm bore, it will react faster than a 12mm bore and you will get a firm lever faster. They are still a pain in the ass to bleed.

Is your fluid level rising in the master cylinder when you squeeze the lever?
I had a similar problem to yours on an old junker chinese bike and it was because my seals were shot.
Put an old beat up cylinder from a '93 Yamaha Seca II on there and it would stop on a dime after that.

If there isn't air in the system then you are either losing pressure at the cylinder through a leaky seal, losing pressure at the caliper from a leak, or your lines are expanding/leaking.
Should be a pretty simple diagnosis.

I have been away for a short break so apologies for not responding to your posts.

Just to recap,

the brake line is a brand new Venhill unit made up specially

the kx125 braking system as bought gave a firm feel, initially all I did was replace the line with the new one as it needed to be longer so as not to impinge on the front lamp.

the master cylinder was rebuilt using new kawasaki parts. It made no sense but I could not get a firm lever after I had changed the line.

I must still have air in the system!

The way I found best purges air from the system.

Lean the bike over to the left hand side as far as you can, using a milk crate or something to hold it up,
Pull the slack of the brake hose through the hoops on the forks so that the resevoir is the highest part in the system,
Now with your palm, swiftly flick the lever in and let it ping out in one motion while every now and again agitating the hose to free up any air bubbles.

Check your fluid :). Hope this helps.

kyledsmith87 wrote:The way I found best purges air from the system.

Lean the bike over to the left hand side as far as you can, using a milk crate or something to hold it up,
Pull the slack of the brake hose through the hoops on the forks so that the resevoir is the highest part in the system,
Now with your palm, swiftly flick the lever in and let it ping out in one motion while every now and again agitating the hose to free up any air bubbles.

Check your fluid :). Hope this helps.

Thanks for this it has helped immensely. Not perfect but sooo much better. I have also located a new m/cylinder on its way. I will install it and see if it is any better than my existing set up, if it is not then at least I will know it is not down to the old master cylinder.

Cheers

I had similar problem ages ago. Took mine to the local Kawasaki shop & have never looked back!!

I had the same issues with a 2008 YZ250F. After multiple failed bleeding attempts I rebuilt the master cylinder. Still no luck. Next I rebuilt the caliper. No joy. Finally I borrowed a Harbor Freight power bleeder from a friend. This made it much better but still not what I considered acceptable. Overtime just sitting it slowly got better. I would also leave a zip tie on the lever holding it partially squeezed over night which I think helped a bit.

So I learned that conventional bleeding just doesn't work on these brake systems. I also learned that once the bleeder has done its job the brake feel will continue to improve over time.