Topic: My CB750K1 pushes hard when bars are turned to the left, but not to the right..

[Yamahawk]

I have noticed ever since I have owned this bike, that if I turn the bars to the left, it pushes hard like the front brake is being actuated... the same when backing it up, almost can't move it when turned to the left. I figured it may have been the old steering head bearings, which were 'notchy'. Now, recently, I have disassembled the front end, installed a new front tire, a new steering head bearing kit, and re-assembled, checking the front brake caliper adjustment screw/spring (it's the old style) for proper adjustment, and it isn't binding when centered. I haven't jacked up the front and checked it when turned to the left, but perhaps I should. Anyone have an idea as to why it would bind to the left, and not anywhere else?
The bike rides nice, and I like the new tire and bearings!
Charlie

[PeWe]

My CB750 K6 has been like that too.
I think it was either the caliper bracket hinge without lubrication or brake pads that needed to be grinded around their sides, especially the pad on piston side. Pad need to move freely, not stucked in caliper. Paint too thick on pads when new.
If dual brakes:
The right caliper bracket must sit on the other side of the fender bracket. Fork+ fender bracket + 5mm spacers on top (M6 bolts)/7mm bottom (M8 bolt) + caliper bracket.

The stock left side has fork+ caliper bracket + fender.

[Yamahawk]

My CB750 K6 has been like that too.
I think it was either the caliper bracket hinge without lubrication or brake pads that needed to be grinded around their sides, especially the pad on piston side. Pad need to move freely, not stucked in caliper. Paint too thick on pads when new.
If dual brakes:
The right caliper bracket must sit on the other side of the fender bracket. Fork+ fender bracket + 5mm spacers on top (M6 bolts)/7mm bottom (M8 bolt) + caliper bracket.

The stock left side has fork+ caliper bracket + fender.

Thanks, PeWe
It is a single caliper with the bracket on the left, I haven't lubricated the hinge pin on the bracket itself, I will try that! I haven't replaced the pads, either... May try that, as not sure how old they are! Will check them for free movement in the caliper, too.
Charlie

[PeWe]

I know how it feels man!  I have many memories when I had to roll my bike when parked outside a café and had to push and pull making me to be red and sweat a lot since the front brake gave me hard times. Then getting tired and almost dropping it when it sometimes were sand on the asphalt.

It's a wonderful feeling to roll my bike freely out from the garage with no fu..ing front brake that make it to a hard job, especially when turning the wheel to any side.
I think it was left as yours. Back in the 80's I just smacked it together and ran it. Less time for the fine tuning. I noticed when restoring the bike that the only pilot lamp I had installed was the oil pressure warning.

My front brake work fine, dual stock looking DSS rotors and DSS aftermarket MC.  Rolls free without any problems at all!  
Brake lines and MC the last things....

[Yamahawk]

Yep, the PO slapped this together, and I am thinking there are at least 3 different year components on it lol... The old style caliper on the swinging bracket, the single piston caliper which probably came on the K1, and the forks say 75 on the bottom casting, the front wheel is from a 78 CB750A, (5 bolt rotor) so it is pieced together... I am amazed that it works as well as it does!
Charlie

[Don R]

 Yamahawk, that's a 75/76F or 77/78K caliper, it has the center outlet. That makes it best for dual brakes since you don't need to swap the bleeder front to back.  It might be from an automatic too.

 I have my brothers one owner 74 here, it's also hard to push if the forks are turned. It needs a brake rebuild anyway.

[Yamahawk]

Yamahawk, that's a 75/76F or 77/78K caliper, it has the center outlet. That makes it best for dual brakes since you don't need to swap the bleeder front to back.  It might be from an automatic too.

 I have my brothers one owner 74 here, it's also hard to push if the forks are turned. It needs a brake rebuild anyway.

You are probably right on the caliper, I think the front end may have been entirely off of a '78 CB750A. Been trying to figure out this whole bike over the winter, and not sure if there is anything to alleviate the hard pushing when the bars are turned left.
What do you thing Don, is there a rebuild that will stop that? perhaps just an adjustment hehe I could wish for that! Am also thinking of a dual disc conversion, as the front wheel would support that. Oh well, all in good time.
Charlie

[evinrude7]

Could your brake cable be improperly routed causing a bind up?

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[Yamahawk]

Could your brake cable be improperly routed causing a bind up?

Sent from my LG-H871 using Tapatalk

Well, it's a brake hose, but no, it is correctly routed. Not sure why it does it, I have had cable brakes that would bind, but never a hydraulic braking system. The same with throttle cables... had Them pull from incorrect routing also, makes it a little zippy lol. Has to be something to do with that swinging bracket, I am thinking...
Charlie

[crazypj]

Check clutch cable isn't pulling on brake hose. May be minimal but could be enough to change pressure?
It's more common for clutch cable to 'pull' throttle open

[Yamahawk]

Check clutch cable isn't pulling on brake hose. May be minimal but could be enough to change pressure?
It's more common for clutch cable to 'pull' throttle open

Yep, doesn't seem to be an interference issue, I believe it is an issue with the alignment of the swinging caliper arm, and when you turn the forks to the left, the brake pad skews on the rotor or something. The caliper probably needs R&R along with new pads up there. That's my next step, to remove the pads and check their fit and the caliper piston.
Charlie

[crazypj]

If it was an alignment issue it would always be there, if something is moving, something is causing problem. Pads 'loose' in housing won't produce anything like a noticeable drag

[Yamahawk]

And I am not the only one with this issue, seems PeWe and Don also experienced the same drag when forks are far left, so I have some troubleshooting to do. Could be pads are too tight in caliper, not too loose. I agree if it is an initial alignment problem, it would always be there. But, I did center the caliper on the disc, so it rolls free straight, and when turned to the right... might look for an early Gold Wing front end lol... Pat has LOTS of them at the shop.
And the Comstar should fit those forks, and have the ability to add another disc, caliper, and hose to make dual disc front brakes...  just thinking.
Charlie

[Don R]

 Just in theory I'd think the forks as a unit must be twisting or something.

[crazypj]

Yeah, you have a multitude of parts that could be just a few degrees or thousandths's off all stacking up to cause a problem. One thing I just remembered, check swinging pivot 'axle' is parallel to disc, I had to shim the 'stock' side on my 550 as it was about 1mm 'off' and caused drag with new pads but was OK after 3~500 miles. I think top mount on fork slider had been machined but casting wasn't as high as it should have been? (lower 8mm mount was tapped but unmachined on left and right fork legs)
Forks twisting  are a good point, you did tighten everything in 'correct' sequence?

[seanbarney41]

How is that 6 bolt hole rotor bolted to the 5 bolt Comstar hub?  ...Thinking someone got the spacing wrong

[Yamahawk]

Just in theory I'd think the forks as a unit must be twisting or something.

I did notice that my pinch bolt on the center stem nut wasn't tight... I did tighten that up, will try again. That 'might' cause some twisting, between top tree and bottom,  wouldn't take much. It was the same before I worked on the front end and replaced the steering head bearings, and front tire though... Will have to start Monday, if the weather cooperates lol.

Yeah, you have a multitude of parts that could be just a few degrees or thousandths's off all stacking up to cause a problem. One thing I just remembered, check swinging pivot 'axle' is parallel to disc, I had to shim the 'stock' side on my 550 as it was about 1mm 'off' and caused drag with new pads but was OK after 3~500 miles. I think top mount on fork slider had been machined but casting wasn't as high as it should have been? (lower 8mm mount was tapped but unmachined on left and right fork legs)
Forks twisting  are a good point, you did tighten everything in 'correct' sequence?

I will check that pivot pin for sure. Not sure what Honda does for correct sequence, but I tightened the upper left/lower right and vice versa for triple tree pinch bolts. pumped the forks a few times to make sure they were aligned also, and then tightened the lower caps on axle.

How is that 6 bolt hole rotor bolted to the 5 bolt Comstar hub?  ...Thinking someone got the spacing wrong

Hehe its a 5 bolt rotor... bolted to the 5 bolt hub
Charlie

[seanbarney41]

but that is what is confusing me, as far as I know, that style of rotor is all 6 bolt, the 5 bolt rotors look much different and have tons more offset and work with sliding 2 piston or 4 piston calipers, but those calipers don't bolt to those forks

unless that rotor is something oddball Honda did for the automatic...did 750a's even ever come with Comstar's?

[Yamahawk]

but that is what is confusing me, as far as I know, that style of rotor is all 6 bolt, the 5 bolt rotors look much different and have tons more offset and work with sliding 2 piston or 4 piston calipers, but those calipers don't bolt to those forks

unless that rotor is something oddball Honda did for the automatic...did 750a's even ever come with Comstar's?

Yep, 78 CB750A's came with ComStar front and rear... the rear bolts right up, which leads me to believe the PO just transplanted the 78 forks, wheels, and headlight to the '71 I have.
Charlie

[evinrude7]

Could your brake cable be improperly routed causing a bind up?

Sent from my LG-H871 using Tapatalk

Well, it's a brake hose, but no, it is correctly routed. Not sure why it does it, I have had cable brakes that would bind, but never a hydraulic braking system. The same with throttle cables... had Them pull from incorrect routing also, makes it a little zippy lol. Has to be something to do with that swinging bracket, I am thinking...
Charlie

Yes sorry meant hose

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[Don R]

Yamahawk, that's a 75/76F or 77/78K caliper, it has the center outlet. That makes it best for dual brakes since you don't need to swap the bleeder front to back.  It might be from an automatic too.

 I have my brothers one owner 74 here, it's also hard to push if the forks are turned. It needs a brake rebuild anyway.

You are probably right on the caliper, I think the front end may have been entirely off of a '78 CB750A. Been trying to figure out this whole bike over the winter, and not sure if there is anything to alleviate the hard pushing when the bars are turned left.
What do you thing Don, is there a rebuild that will stop that? perhaps just an adjustment hehe I could wish for that! Am also thinking of a dual disc conversion, as the front wheel would support that. Oh well, all in good time.
Charlie

 I'd lube the pivot, check the spring bolt and be sure the pad is retracting. Then with a jack taking the weight off the forks loosen the axle and fork bolts and re-tighten in the correct order according to the manual available at the top of the page.  I'll do all that to the K4 when it's time to fix that one.