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Discussion Starter · #1 ·
Hello from Knoxville,

I am repairing a magnum to use at work. I am a forester and need the machine to get me back into some pretty remote spots in rural TN. It is in really good shape despite its sordid past.

This quad caught on fire because the rear caliper was seized and some guys rode it anyway, catching the fluid on fire and burning some of the chain guard (very minor fire). It then sat for like 10 years in a barn. I grabbed it because my boss didn't want to buy me a new one, so I decided to fix this one. I am an ASE certified mechanic, just not a quad mechanic. I have worked on vehicles for over 20 years, and while I'm no whiz kid, I'm not a complete idiot either.

Here's what I have done so far:

  • Replaced the whole fuel system
  • rebuilt the carb; engine runs like a top
  • new oil and filter, coolant, etc.
  • replaced tires
  • rebuilt all three calipers
  • replaced all lines
  • rebuilt the master
This is where my problem lies:

I bench bled the MC, then I power suctioned the brakes at the bleeders and got good fluid flow through everything. I then manually bled the brakes, starting at the back.

I get good flow, not squirting, but good solid flow from the calipers. However, the brake lever itself is soft and does not hold the front brakes. I can see the calipers moving, and holding pressure, but just not enough.

The foot pedal will of course stop the bike because the mechanical portion of the caliper has been adjusted properly. This means that I was able to test ride the quad, and make sure everything else works, which it does.

However, I just can't seem to get the front brakes to work, despite no air coming out of the bleeders. Does anyone have any ideas? Should I just replace the master cylinder?

Thanks in advance for your help.
 

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If you have no brake fluid leaks and foot brake is hydraulic it could be a o-ring in the rear caliper. or MC
 

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Discussion Starter · #3 ·
If you have no brake fluid leaks and foot brake is hydraulic it could be a o-ring in the rear caliper. or MC
Well, I rebuilt the rear caliper, and it is mostly identical to the front as far as setup with the orings, etc. It does not have a seperate master. I mean, I suppose I could've screwed something up there, it's just if the calipers were messed up, wouldn't they just leak? They're not like the master where the fluid can pass around the cup seal.
 

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Hello from Knoxville,

I am repairing a magnum to use at work. I am a forester and need the machine to get me back into some pretty remote spots in rural TN. It is in really good shape despite its sordid past.

This quad caught on fire because the rear caliper was seized and some guys rode it anyway, catching the fluid on fire and burning some of the chain guard (very minor fire). It then sat for like 10 years in a barn. I grabbed it because my boss didn't want to buy me a new one, so I decided to fix this one. I am an ASE certified mechanic, just not a quad mechanic. I have worked on vehicles for over 20 years, and while I'm no whiz kid, I'm not a complete idiot either.

Here's what I have done so far:

  • Replaced the whole fuel system
  • rebuilt the carb; engine runs like a top
  • new oil and filter, coolant, etc.
  • replaced tires
  • rebuilt all three calipers
  • replaced all lines
  • rebuilt the master
This is where my problem lies:

I bench bled the MC, then I power suctioned the brakes at the bleeders and got good fluid flow through everything. I then manually bled the brakes, starting at the back.

I get good flow, not squirting, but good solid flow from the calipers. However, the brake lever itself is soft and does not hold the front brakes. I can see the calipers moving, and holding pressure, but just not enough.

The foot pedal will of course stop the bike because the mechanical portion of the caliper has been adjusted properly. This means that I was able to test ride the quad, and make sure everything else works, which it does.

However, I just can't seem to get the front brakes to work, despite no air coming out of the bleeders. Does anyone have any ideas? Should I just replace the master cylinder?

Thanks in advance for your help.
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Right, the foot brake is a mechanical auxiliary brake and a parking brake
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The hydraulic portion is part of the front brake system (all the brakes are applied by the hand brake) - I suspicion you simply have air trapped in the system somewhere. I gave up on conventional and suction bleeding and now only do pressure bleeding (pumping fluid from the caliper to the master cylinder) - if you don't have a pressure bleeder an alternate method is to remove one caliper at a time, remove the brake pads and pump the piston 3/4 of the way out of the caliper - let set about 5 minutes and then press the piston back into the caliper while holding the caliper with the brake line fitting at the apex of the caliper and with the caliper as far below the master cylinder as you can get it. When done pressure bleeding, see if there is an improvement.
 
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