How firm should a gen 1 front brake be

I am struggling to get my Gen 1 front brake to firm up. I have re-kitted master cylinder, bleed through - still spongy. Purchased a vacuum bleeder and tried that...still spongy. Took brake system off bike to bleed with master cylinder at the lowest point and bleed nipples at the highest point. Still no better. Have just drained system and replaced all banjo crush washers and vacuum bleed through...same result.

So at present with some pressure I can pull the brake lever to the handle bars. The pads take up at about half the travel. I have had suggested that the brake lines may be swelling but I have checked with verniers and it doesn't appear so. Could it be a fault in the master cylinder?

When I pull the lever in just a little - just far enough to activate the brake light switch - I am often seeing a release of some bubbles in the master cylinder which makes me think it may be leaking air in? But then I would have thought if I keep pumping the lever it could get softer as it let more air into the system - yet this isnt happening.

Suggestions please.....

 

They should be stiff as a wedding dick. You may still have air in the lines--shouldn't be any bubbles in the master. Did you clean the master reservoir and the little pin hole orifice of the return port in the master?

Are those the original brake lines? 27 year old brake rubber lines are likely to have shredded and decomposed internally--the external rubber casing may not be swelling but the soft, squishy internal core rubber is moving around.

 

Air usually gets trapped at the banjo bolt and it's hard to get out if the mc is in it's normal location on the bar. Loosen the mc and rotate it so the banjo points downward. In it normal position it sets higher than the bottom of the mc. By rotating it will be lower and force the air up in to the mc. Also make sure the small hole under the little ss tab is clear that's on the mc floor. For really good solid feel use SS brake lines. It makes a big difference.

Also make sure the calipers are sliding on their pins/slider bolts on the forks.

 

I will suggest you check the calipers and pads, if you get the pads on the wrong side of the little tabs on part #8 in diagram (which is really easy to do) it will hold the pads oot just a bit and will give you a spongy lever.
Ronayers.com Microfiche Honda>Motorcycle>1983>VF750F>FRONT BRAKE CALIPER

 

Great thanks guys. All new things to try - great website!:clap2:

 

I like to back bleed when I'm looking for the best braking. Bleed like normal into the hose attached to the nipple then I attach a small syringe to the tube and push the fluid back into the caliper. You will usually see air bubbles come out of the master cylinder.

 

I think Ive found the issue/s. After looking at Toe Cutters schematic I vacuumed the brake fluid out, took the caliper off and compared it to the schematic. The clips he mentioned dont even exist on mine and also I am missing the clip that holds the 2 pins in place - you know the pins which the pads slide up and down on. It would be a nasty/fatal surprise if the pins fell out whist riding! Also on the master cylinder schematic there is a part between the lid and gasket which I also don't have. Oh where to start:frown:

 

Are the calipers moving on it's sliding bolts also. Those pins won't cause spongy brakes. They just hold the pads in place. You could safety wire those if you can't find the original style clips.