CB350 Sly... Now with 2 finger braking!!!

overdraft

New Member
Re: CB350 Project 'Sly'... brake disaster

well the brake rebuild didn't go so well... i put a new seal in the caliper, got a stainless brake line and bought a brand new master cylinder. i've bled the thing every way possible... vaccuum pump, injected from the bottom, even old skool open bleeder, squeeze lever, close bleeder, release... result? the brake pumps up, but never gets hard (sounds like a job for viagra!) so i took it apart... no seeping in the caliper... so either i STILL haven't got it bled properly and there's still air in there somewhere... OR maybe the master just isn't pushing enough fluid through to get the system pressurized? does anyone know if these old one pot calipers need a giant master? the one i have is off a cbr125r and is pushing a 2 pot caliper... any thoughts welcome... grrr.....
 

Ringo

Active Member
DTT BOTM WINNER
Re: CB350 Project 'Sly'... brake disaster

Sounds like air in the system or too small bore in the MC. Considering your extensive bleeding, I'd double check the MC size. 11-12mm should be fine for the 360. Is the size marked on it anywhere?

Sometimes it just takes a lot of lever pumping...
 

frogman

'74 CB360, '71 CB450, '75 CB550SS
Re: CB350 Project 'Sly'... brake disaster

Old school way is make sure the bleed valve is closed tight, then pump the lever say 5 times to build up pressure. Then, WHILE holding the lever tight against the handle bar as you can, slowly open then bleeder valve until the fluid/air stops coming out. HOLD the LEVER IN PLACE the WHOLE time. You will feel the pressure release inside the MC. Once all the pressure is gone, tighten the bleeder, THEN LET GO of the lever and start pumping on the lever again. Rinse and repeat until the air is gone and and fluid comes out clear. You will have to refill it at least once. And if you have a bit of clear hose stick it on the end of the bleeder and stick that in a can to catch the fluid because it will come out in a hurry. This will also help to tell when all the air is out because you can see the bubbles leaving. The MC should also be shooting a small amount of fluid back into it so make sure you have the cover on or you will shoot shit everywhere. If it is not, the return passage in the MC is blocked.
 

overdraft

New Member
Re: CB350 Project 'Sly'... brake disaster

thanks for the tips! also i checked the specs... the master i've got has an 11mm bore and the stocker is 14mm... so i guess the other possibility is i'm just hitting the grip before i've pushed enough fluid?
 

Ringo

Active Member
DTT BOTM WINNER
Re: CB350 Project 'Sly'... brake disaster

That sounds pretty likely, overdraft. Going from 14 to 11mm is a pretty big jump down. Even if the line is properly bled, your lever is going to feel spongy. You might have to get another MC... or try to fit a cbr125r caliper/rotor...which sounds like more trouble than it's worth. :)

I went through the same thing with my 400... It's got dual discs, and I was trying to use a MC with a 12.7mm bore. Swapped it for one with a 16mm bore and the lever felt great. There's a website that I can't remember, but it lets you plug in caliper piston diameter, and gives you a "sweet spot" range of MC size to use. But finding a 14mm MC should be pretty easy... Or you could rebuild your old one...
 

crazypj

Split personality, I fake being smart
Re: CB350 Project 'Sly'... brake disaster

What angle is the MC mounted?
you have to have it so any air trapped in banjo bolt/union can move either back or forwards.
It's quite normal to fit MC to different bars and remove a caliper on sportbikes with a line looped over the mudguard (and on MX bikes where line loops under fork leg)
Take a look at your setup, can air 'float' to the surface ?
 

overdraft

New Member
Re: CB350 Project 'Sly'... brake disaster

Ringo,
ya, i'm looking for a 14 now to see if that fixes the problem. i think this is the table you were thinking of?



but the website blurb makes no sense... ( http://www.vintagebrake.com/mastercylinder.htm ) because it talks about a 'sweet spot' for one pot calipers of 12:1-14:1 range... but the stock setup, 14mm master with 38mm pot shows 7:1!!!

so ya, i'm just gonna get a 14 and cross my fingers! too bad cuz the CBR125R master i had was a sweet li'l unit... oh, btw, i'm not rebuilding the stock master because a) i don't have it! and b) i'm deleting the pressure brake light switch so i need a unit with an on-board brake switch.

thanks for your help everyone! i'll keep you posted in case anyone's interested in the outcome!
 

overdraft

New Member
Re: CB350 Project 'Sly'... brake disaster

crazypj said:
What angle is the MC mounted?
you have to have it so any air trapped in banjo bolt/union can move either back or forwards.
It's quite normal to fit MC to different bars and remove a caliper on sportbikes with a line looped over the mudguard (and on MX bikes where line loops under fork leg)
Take a look at your setup, can air 'float' to the surface ?
good thought... i had the reservoir dead level so maybe there was something in the top banjo... that said, i'd have thought that would have been resolved on try 3 when i injected the brake fluid into the system through the bleed screw and filled the res from the bottom up?
 

Ringo

Active Member
DTT BOTM WINNER
Re: CB350 Project 'Sly'... brake disaster

overdraft said:
i'll keep you posted in case anyone's interested in the outcome!

Please do! I'll be in the market for a new MC myself soon...
 

overdraft

New Member
Re: CB350 'Sly'... check out my bottom!

thanks for the tips everyone... i've ordered a master with a 14mm bore that i hope will resolve my brake issue, so in the mean time i'll share what's happening with the bottom end of the motor...

i wanted to make the bike as clean and simple as possible so i decided that i'd delete the electric start. the usual solution with the cb/cl 350's is to remove the starter motor and chain that live behind the lobe in the left case cover...



leaving a hole to be blocked off...



but the SL version of the 350 came for a couple of years in a kick only version that had cases that didn't have the starter lobe so i hunted around and found one...



cleaned it out...



found an SL crank (which isn't as wide as it doesn't need room for the starter chain sprocket)...



and now i'm going to swap the cylinders/head/valve train and transmission from the cb cases to the sl cases...



i have NO idea what sort of hell i've signed myself up for... it's probably going to be a rediculously disproportionate amount of work just to get a slightly cleaner look at the front of the motor... plus i don't have a dial guage or v-blocks so i have no way of determining if my crank is within spec... i'm probably going to rely on the conventional wisdom that the bottom ends of these motors are indestructable (unlike the valve train!) wish me luck! i'll need it!
 

surffly

Active Member
Re: CB350 'Sly'... check out my bottom!

i think that the mounts are different on the early SL VS CB motors.
doesnt that front mount look different?
i would check to make sure it fits in the frame before taking the CB apart.

also find someone local with the tools to check the motor while its apart. its a waste of time to go through the work with crapy parts.
its only alittle more money and time to have it checked out and have the piece of mind that the motor is good.
 

overdraft

New Member
Re: CB350 'Sly'... check out my bottom!

surffly said:
i think that the mounts are different on the early SL VS CB motors.
doesnt that front mount look different?
good eye! hmmm... i may be screwed there...

edit... looked at some pics of an sl case in a cb/l frame and it looks like the wider set right mounting point will attach to the frame, but on the outside of the frame tab instead of the inside... i'll confirm that tonight and then either carry on with the build or seppuku depending on the result...

later edit: all good... it'll work! phew!
 

Ringo

Active Member
DTT BOTM WINNER
Re: CB350 'Sly'... check out my bottom!

Well. That's certainly not the 'bottom' I was expecting.

...

Lookin good man!
 

captainjmash

Working on first build - '73 CB350
Re: CB350 'Sly'... check out my bottom!

overdraft said:
..... or seppuku depending on the result...
That will have to wait until you finish.

Great thread btw, I'm learning tons.
 

overdraft

New Member
Re: CB350 'Sly'... check out my box!

ok, while i wait for my 4th brake master to arrive... 4th time lucky? some more progress on boring stuff... made some cardboard templates...



and cut/bent up some aluminum to fit in the aft compartment...






i'm using the battery from a yamaha ttr110 because it's really small and sealed so it can lie in between the frame rails... luckily i know nothing about electricity so this'll work just fine... i'm deleting the starter so all it has to do is smooth out the lighting when i'm at idle and enable me to go with an electronic ignition if i decide to...
 

overdraft

New Member
Re: CB350 'Sly'... check out my box!

ok! brakes! sort of... i rebuilt the caliper, new paint, new seal, cool chrome bolts, new pads....



and i thought this was cool too... rear brake caliper piston for a cbr600rr specs out the correct diameter to replace the stock unavailable one... it's a few milimeters short, but unless you run your pads to the metal it should be fine... and the bonus is a) fancy coated surface b) hollow interior for lightness and c) like $25 at your honda shop!



got one of those ebay master cylinders... almost as cheap as a rebuild kit if you live in the usa (more in canada cuz $30 to ship a $35 item!) the quality is nice, comes complete with lever, a nice curved classic looking one... it's a sloped reservoir which is a nice match for the angle on my clip ons...




so matched up with my stainless brake line the whole setup turned out pretty nice...




that said... i took a chance on a master with a 12.7mm bore when the stock one is 14mm and i'm not convinced it's gonna move enough fluid to work... but in the meantime i'm gonna press on...
 

overdraft

New Member
Re: CB350 'Sly'... font brake and rolling chassis

and here's the overall look of the thing in case anyone's interested!



i got a slick little integrated tail light too... brake/turn/plate light all in one unit and the curves just magically matched the tail!


 

Jared

...Try the morphine, it's excellent today!
Re: CB350 'Sly'... font brake and rolling chassis

Whoa! nice man! Where did you get the light? I have been looking for one.
 

stonetree

New Member
Re: CB350 'Sly'... font brake and rolling chassis

Really nice man the bikes looking great. And seconded on the light, where did you find that?
 

DTT Bike Of The Month Gallery

DTT Light or Dark

www.cognitomoto.com
https://www.townmoto.com
www.speedmotoco.com
www.jadusmotorcycleparts.com
www.lostapostle.ca/
www.sparckmoto.com
Top Bottom