Topic: Front brake feel/bleeding

[millla03]

I'm currently wrapping up a CB350G project and have a question about the front brake. It's a twin but the parts are essentially the same so this would apply to SOHC/4's as well.

Bled the brakes like normal and taped the lever back overnight to get any residual air out, but I still feel like the brakes should be firmer. I'm running OEM repro lines from Slingshot with rebuilt master cylinder and caliper, both functioning properly.

I can pull the handle back to about 1" from the grip with what would be a typical firm brake pull, and could probably get the lever to the grip if I really wanted to. Can't comment on actual braking performance since the bike isn't quite back on the road. Wanting some input on how much I should be able to pull the level back if the brakes are properly bled. They're spongier than my 750, as you'd expect for brakes without stainless braided lines, but I have no frame of reference for what's normal with rubber lines.

Any guidelines or personal experience with this would be appreciated. If there is still air trapped in there, are there any tricks I should try to bleed it out?

[DH]

Try bleeding only using short strokes of the lever, and let it gravity bleed on its own for a bit, topping off whenever the
reservoir gets low. Watch for air in the reservoir to escape from the small return hole.
Be careful if you've got the lid off during the process, or you'll get a shower of fluid. Slow and ez.
There are other ways used by other folks, this worked for me.

[grcamna2]

Try bleeding only using short strokes of the lever, and let it gravity bleed on its own for a bit, topping off whenever the
reservoir gets low. Watch for air in the reservoir to escape from the small return hole.
Be careful if you've got the lid off during the process, or you'll get a shower of fluid. Slow and ez.
There are other ways used by other folks, this worked for me.

Yes,
I 'snap' my lever a few times which tends to release more air bubbles also,let the lever Fly back under spring pressure a few good times until all the air is released.The other thing too is when you pump it,go Slow and don't pull the lever all the way to the grip(don't bottom it out on the bars)but pull it close with-in about an inch or less.
I believe that pulling the lever all the way to the bars when it bottoms-out keeps some air trapped inside the master cylinder.

[Duanob]

I bought one of these a long time ago. Its worth it's weight in gold when it comes to bleeding the brakes on these bikes. And all of my other vehicles too. Without it I find it hard to really bleed the brakes good after taking them a part.

[strynboen]

you bloks for the air to leave up in the reservoir.. loking the handel in pulled posision.
.and strap it there.

.then no air can come aut...the pressure build up can brake some airbubbels free..by kompreess them...but they dont escape before the handel are relased...they just build up,,just before the main cylender...

i often just let the bike...the night over..after a rebuild and pump up the new fluid,,, and the air komes aut ...just leave it  some time...

[ADW]

One other thing, there's a bulletin on not over-stroking the lever when bleeding. It's attached here. I got it from this site, but don't know where. There's a section on service bulletins, you can search it out.

[millla03]

Thanks for the input guys. So it sounds like the consensus is "too spongy" aka air still trapped in the system? I'll take a look at it this weekend and see if I can squeeze some more air out of it. Good thoughts on the service bulletin, I always use a block of wood between the handle when bleeding to avoid this issue.

[camelman]

I agree. Spongey with new lines usually means air still in there. I've always had luck with just wiggling the lever just at the point it begins to apply pressure (with the cap off master) about ten times, and then slowly pulling the lever. The wiggling helps air bubbles break free throughout the system and migrate up. You'll see them quickly reach the exit hole in the master and bounce in and out as you wiggle the lever. The slow pull on the lever allows the bubbles to be expelled without brake fluid rushing past them first. It usually takes me less than 5 minutes to bleed a newly filled brake line doing this (after bleeding the caliper of course).

Good luck with the bubbles... they're really only good for champagne!

[millla03]

Just wanted to say thanks for the replies.

I was able to squeeze a bit more air out of the system using camalmans wiggle method, while turning the bars side to side. Good to go now, just didn't take the time to properly bleed them the first time.

[ofreen]

My 750 has always been the most problematic for me getting all the air out after the lines are drained. Including all my bikes with dual discs. An air bubble hangs up somewhere even when using a power bleeder. So what I've done for many years is bleed the brakes as best I can. Usually the lever remains spongy. I'll then take the two bolts out of the caliper and pump the piston out of the caliper (stopping before it comes all the way out, doh). Then I push it back in. This pushes that damn bubble out of wherever it is hanging up every time. Pumping the fluid from the caliper to the master cylinder would no doubt have the same effect, but I've never set up to do it that way.

[grcamna2]

I've used a special size brake bleeding 'syringe' on a few bikes and 'pushed' the air back up toward the top(air naturally wants to rise) & it works ok as long as I seal the bleeder screw threads w/ some teflon tape.