Triumph Rat Motorcycle Forums banner
  • Hey everyone! Enter your ride HERE to be a part of this month's Bike of the Month Challenge!

1 - 8 of 8 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter · #1 ·
I am having tough time bleeding the rear caliper on 78 bonny. I put on new mc and rebuilt the caliper. I can't get the thing to work. If I block the hose coming from the mc, the perdal is hard. Once hooked up to caliper can't get pedal to have resistance. During bleeding seem to continue to get air released and some fluid. If I put air to caliper it locks up fine. I would think that if I am sucking air from some place then I should have a leak. No leaks. I see the price of calipers is around 300.00 ouch. All ideas gladdly accepted
 

·
Registered
Joined
·
794 Posts
The bleed valve should be at the top to allow air to escape during the bleeding process. If not, air will get trapped in a "pocket", and the caliper will not bleed properly. Not sure if early 78 models still had under-slung caliper as did the 77 (ie on the lower side of the disc, as opposed to the later models which had it on the upper side above the swing arm). To get a proper bleed, you might have to:
- leaving the hydraulic hose connected, take a caliper mounting bolt out, or otherwise take the axle out enough to free the mounting plate, in order to swing the caliper into such a position as to have the bleed valve nipple at the top.
- if the caliper comes more than half off the disc, slip in a large screwdriver or two to ensure the pads stay apart enough to skip back over the disc when done.
- let sit in this position for 20 mins or so, allowing all air to work its way to a bubble near the bleed valve.
- bleed normally.
- replace caliper over disc.

On my 77 with underslung caliper, I find it easier to half-remove the axle, and let the calliper hang on the torque stay arm whilst bleeding.
 

·
Registered
Joined
·
1,123 Posts


I agree with GrandPaulZ, Here's what i use: Mityvac_MV6820
 

·
Registered
Joined
·
161 Posts
The only way I have been able to bleed the rear caliper without additional tools is by removing the caliper assembly from the bike and hanging it higher than the master cylinder (with the bleeder valve the highest point). It is aggravating, time consuming and I waste a lot of brake fluid. Maybe I'll get one of those brake bleeders...
 

·
Registered
Joined
·
49 Posts
Hi to you all,

I have had the same issue with my rear brake, could not get a pedal after several bleed's, i have just done as Ozbloke advised,even with all the work removing the exhaust and rear spindle it only takes around an hour to complete, i have now got the best rear brake ever.

Thank you Ozbloke, Perfect advise.

Regards Simon
 

·
Registered
Joined
·
26 Posts
You can also let gravity play a part by siting the caliper lower than the master cylnder reservior, undoing the bleed nozzles and let the fluid run through. catch the surplus in a clean jar to re-use and ensure the reservior doesn't run dry. Once it starts to come through the bleed nozzles tighten them up and bleed as normal to finish.
 
1 - 8 of 8 Posts
Top