Kawi2strokes.com Forum

Enthusiasts from around the world dedicated to the preservation and ritual flogging of the infamous Kawasaki 2-stroke Triples
It is currently Sun Apr 22, 2018 1:06 pm

All times are UTC - 5 hours




Post new topic Reply to topic  [ 9 posts ] 
Author Message
PostPosted: Sat Apr 14, 2018 9:58 pm 
User avatar

Joined: Thu Jun 23, 2011 2:26 pm
Posts: 1780
Location: Running Springs Ca
So I'm trying to find the cause of a brake problem on my Aprilia RS250. Symptom is the front calipers will apply more and more pressure on there own
and try to lock the front wheel. I've had this problem before on other bikes when the caliper pistons stick and don't release freely. The first time this
happened I took apart the calipers and made sure everything was clean and not binding on release. After bleeding all is well for a short time and
then the free play in the lever goes away and the calipers start grabbing more and more. Could this be a problem with the master cylinder? The pistons
look perfect and show no signs of wear or corrosion, seals are pliable and everything is clean. This is a radial master cylinder type and the bike is
super low mileage (less than 400 miles) so it has sat for most of it's life in a guys living room. Could rubber brake lines cause something like this?
They feel pliable and not dry and brittle.


Top
 Profile  
 
PostPosted: Sat Apr 14, 2018 11:21 pm 
User avatar

Joined: Thu Sep 29, 2016 4:32 am
Posts: 322
Location: Indianapolis, IN
The tiny master cylinder bleed hole is blocked, usually from being dirty, and you have some adjustment keeping the master cylinder piston pressed so the seal is covering the hole, but probably it's stuck so it won't return fully. Likely it needs the cylinder rebuilding, you can get lucky and 'carefully' poking a tiny piece of wire through the hole from the open cylinder cap. Don't operate the brake while doing this or the seal will be damaged.

_________________
1974 Kawasaki H2B 750, 1981 Yamaha XV750 Cafe, 1983 Kawasaki KZ1100 Spectre, 1986 Kawasaki KDX200, 2003 Honda XR100, 2004 SDG140.


Top
 Profile  
 
PostPosted: Sun Apr 15, 2018 12:19 am 
User avatar

Joined: Thu Jun 23, 2011 2:26 pm
Posts: 1780
Location: Running Springs Ca
Thanks for the reply, going to take it apart tomorrow.


Top
 Profile  
 
PostPosted: Sun Apr 15, 2018 12:55 am 
Site Admin
User avatar

Joined: Tue Jun 07, 2011 6:37 am
Posts: 9934
Location: Rio Rancho, New Mexico
And make sure there is a bit of clearance from the lever to piston. Some aftermarket levers are off a bit and don't let the piston return fully. And one other thing that is probably not the cause, but older rubber line can start to come apart inside and the flap clogs the fluid flow.

_________________
I can teach your triple how to "reed"........
http://kawatriple.com/aylor


Top
 Profile  
 
PostPosted: Sun Apr 15, 2018 7:25 am 
Moderator
User avatar

Joined: Wed Jun 08, 2011 5:34 pm
Posts: 2152
Location: Front Royal, VA
Plus one on old hose if the little return hole aint plugged and the calipers aint nasty that is about all that's left.

_________________
I Love the Smell of Blue Marble in the Morning!!!
Tim Steele in Front Royal, VA
Home of the Phoenix Project
Stay in it when it comes on the pipe, no need to be scared...


Top
 Profile  
 
PostPosted: Sun Apr 15, 2018 3:56 pm 
User avatar

Joined: Thu Jun 23, 2011 2:26 pm
Posts: 1780
Location: Running Springs Ca
Fixed the brake issue, yes it was the bleed back hole was plugged :thumbup: Also got the Cougar Power valves installed yesterday.
The one bad issue with these motors (RS250's use Suzuki RGV250 motors) is the stock power valves. The stock PV's use roll pins
to hold the 3 piece valves together and the pins will get loose and fall out. Both of my RGV's had pin failures when I bought them.
The Aprilia only was 350 miles one it but cheap insurance for the future. It's amazing in so few miles how much carbon was starting
to build up on them. The new Cougar PV's have the pin part of the casting so nothing to get loose. Plus the add another 6hp. It's
a fun little bike.


You do not have the required permissions to view the files attached to this post.


Top
 Profile  
 
PostPosted: Mon Apr 16, 2018 8:18 am 
User avatar

Joined: Wed Feb 24, 2016 5:55 am
Posts: 107
Location: Hollister, CA
I am having the same problem with my H1.

Is there a bleed hole in the master cylinder some where that could be clogged?

_________________
75 H1F, 72 H2, 75 H2C


Top
 Profile  
 
PostPosted: Mon Apr 16, 2018 2:42 pm 
User avatar

Joined: Thu Sep 29, 2016 4:32 am
Posts: 322
Location: Indianapolis, IN
Take the cap off the master cylinder, look in the bottom, there will be two small holes, the one closest to the outlet, hose end of the cylinder will be tiny and blocks easily.

_________________
1974 Kawasaki H2B 750, 1981 Yamaha XV750 Cafe, 1983 Kawasaki KZ1100 Spectre, 1986 Kawasaki KDX200, 2003 Honda XR100, 2004 SDG140.


Top
 Profile  
 
PostPosted: Tue Apr 17, 2018 4:19 am 
User avatar

Joined: Wed Feb 24, 2016 5:55 am
Posts: 107
Location: Hollister, CA
Thanks for the info.

I did find the hole yesterday while looking at the inside of the master cylinder.

It is a tiny hole about 12 to 15 thousandths. Used a very small drill bit to check it. 20 thousandths safety wire was too large.

You can blow air up the exit of the master cylinder to see if it's clear or not.

_________________
75 H1F, 72 H2, 75 H2C


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 9 posts ] 

All times are UTC - 5 hours


Who is online

Users browsing this forum: No registered users


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group