Topic: '78 CB750F - front end assembly (need pic of proper assembly)

[superchode]

so the bike's together and running... brakes up front have been re-done, but they're not biting.  it's also definately not due to air in the lines.

I'm thinking I might have the calipers and fender mounted improperly somehow... please post a pic of your F front end so I can compare.  A manual pic showing proper assembly would also be helpful.

Thanks.

[scondon]

   I should have a pic or two at home and can post them tonite. Just curious as to what it is you are questioning about your assembly. The caliper brackets are marked "L" and "R"(left and right as you sit on the bike) and are mounted at the rear of each fork. Brake calipers are not marked but can only be mounted on the correct side without having to put some serious twist in your brake lines. Fender has four bolts to mount to the forks, and though there are a few loose pieces(rubber bushings, plastic collars) it can only mount one way.

  Are you getting any braking at all? Does the brake lever pull stiff and still no braking, or is it spongy and pulls all the way to the bar?

   Glad to hear the bike is up and running. That's one more F2 gracing the highways

[superchode]

it's spongy and pulls all the way to the bar... was reading elsewhere on the forum that this could be due to improper mounting of the fender relative to the brake calipers (something along those lines) - and i want to have a look.

system has been bled and re-bled - both by myself and a mechanic i trust... the feel in the lever hasn't changed at all.  we even changed a couple of pins in the caliper to ensure it would align with the disc properly.

i can troubleshoot the master cylinder as well, i just want to make sure i've got everything proper at the wheel first.

[flat_black_forever]

I had this trouble after having to drain all of my brake fluid. In order to really bleed the breaks you should take the top line off the brake light switch and bleed it, then attach only the switch to the top line and bleed it then re attach the lower line and caliper or else there will still be air trapped in the lines.

[78 k550]

plenty of pics here. If you need more detail let me know.
http://www.sohc4.us/forums/index.php?topic=24728.0

Paul

[joeb]

I agree with flat black the banjo bolt will hold some air in it and will make your lever feel spongie another thing after you bleed the banjo bolt is to tye the brake lever to where the hand grip is and let it sit over night it will bleed out the air that way to.  When  you do that have the master cyclinder as level as possible. Hope this helps.  

[mick750F]

it's spongy and pulls all the way to the bar... was reading elsewhere on the forum that this could be due to improper mounting of the fender relative to the brake calipers (something along those lines) - and i want to have a look.

system has been bled and re-bled - both by myself and a mechanic i trust... the feel in the lever hasn't changed at all.  we even changed a couple of pins in the caliper to ensure it would align with the disc properly.

i can troubleshoot the master cylinder as well, i just want to make sure i've got everything proper at the wheel first.

   By most accounts the '77/'78F dual caliper system is a total PITA to bleed after the system has been disassembled. I know, I've been there. What you're describing sounds like what I was experiencing half way through the bleeding process...actually most of the way through the bleeding process. It took a long time to bleed it...40 minutes or more. Once it was bled the brakes...rebuilt calipers and master cylinder, new stainless lines...worked great. There is one thing they warn against in the Honda Factory Manual and that's to not bring the lever all the way back to the bar when bleeding...it will send the piston of the MC in too far. I put a 3/4" block on the grip to keep it from coming back to prevent it. Are you sure your MC is good?

   My bike and my manual are at my shop. If nobody posts a pic for you tonight I'll do it tomorrow.

Mike

   

[MrZxp]

Hope these are helpful.... from my copy of the manual...





Cheers, Phil