honda 300 4x4 brake bleeding instructions

Bruce · #1 05-13-2011, 06:32 AM

Hi,

I own a 1990 TRX 300 Big Red. I recently decided to overhaul the front brakes on the bike and replace the fluid. However I'm unable to achieve a good brake lever after bleeding. The shoes are all adjusted correctly, both cylinders are free and there are no blockages in lines etc. I've spent hours trying to bleed the system but still end up with little or no brake! The master cylinder/lever has also been rebuilt with a new kit, but this has not helped.
I've tried back-bleeding several times from the cylinders up and also pressure bled the system, but still nothing. There is fluid getting to both cylinders and the lever seems to be pumping through. Once I tighten up the bleed screws the lever remains spongy with some brake effort but nowhere near enough to stop the bike safely! I'm now fed up of wasting brake fluid and spilling it all over the freshly painted fuel tank!

Any suggestions would be very much appreciated.

Thanks,

Bruce

Here 2 help · #2 05-13-2011, 01:32 PM

Bruce,
You may have the brakes bled, but the brakes have manual adjusters. You might need to simply adjust the brakes. Also, each wheel has 2 bleeders (one for each wheel cylinder). If you have the brakes adjusted properly, sometimes the system will trap air at the banjo bolt attaching the line to the master cylinder. Squeeze the lever, crack loose the banjo bolt and retighten while fluid is oozing out. That might help too. Finally (a little trick I use), pinch the brake hose near the master cylinder with a line clamp just to the point that you can pump fluid past the clamp, but fluid cannot get past the pinch without pressure and bleed the brakes normally. When done, turn the handlebars so the master cylinder is "uphill". Any air left in the system will rise to the master cylinder and escape with a few gentle pumps of the lever and/or cracking of the banjo connection.

phillopino · #3 07-03-2011, 10:29 PM

Just rebuilt the rear caliper on 400trx. Piston was frozen. Now I can't get the master cylinder to pump any fluid. It worked fine before I took everything apart.

clueless

Here 2 help · #4 07-04-2011, 01:33 AM

It gets kinda messy, this is the fastest way I know to get it working without a pressure bleeder.

If possible, raise the rear of the quad or take the caliper off and position the caliper higher than the master cylinder.

Take the hose off the master cylinder (you have to get it bled first) - press down on the brake pedal - put your finger over the bolt hole where you removed the line and let off the brake pedal - remove your finger, press down on the pedal, cover the hole with your finger & release the brake pedal. Repeat the routine until you have fluid coming out the hole. Now press down on the pedal, install the line while holding down the pedal and release the pedal.

With the line installed, open the bleeder on the caliper, press down on the pedal, close the bleeder then let off the pedal. Repeat as often as necessary.

Keep the reservoir full of fluid and insert a something between the brake pads to keep them spaced apart. Good luck.

phillopino · #5 07-04-2011, 09:47 PM

Thank you, heading out to the garage now to make it happen.

Honda4lyfe · #6 01-07-2012, 05:55 AM

what about bleeding the front cylinder? wanting to ride today need help asap please!

Here 2 help · #7 01-07-2012, 01:47 PM

It is the same proceedure, but easier - the TRX300FW and the TRX300A has drum brakes front and rear but the FW has 2 slave cylinders while the 300A only has 1 slave cylinder. If yours has 2 slave cylinders, you need to manually adjust each one the same amount and bleed both. If you only have 1 slave cylinder there is no manual adjustment.
Since the front brake MC is on the handlebar, the brakes will bleed themselves (air will rise to the MC and escape with repeated pumping of the lever. Just turn the handlebars to the right to let air rise from the left slave cylinder. Wait 15 min to 1/2 hr then turn to the left and repeat the wait. Turn the wheels straight forward and pump the lever slowly and gently until air quits coming into the MC. Final step is to pump and hold the lever and "crack" the banjo fitting at the MC to release trapped air, then pump and hold the lever and open each bleeder on each slave cylinder. Repeat till all the air is out and the lever feels right. Be sure to keep fluid covering the bottom of the MC reservoir. If it gets low and you let off the lever, it can suck air in and you might have to start over.

Also, see my post under 400ex Brake Bleeding