Cbr600f4i rear master

[StormShadow3]

Recently I changed my oem rear master with a cbr600f4i rear master on my 98 vfr. I used the internals of the vfr, onto the cbr shell. And the vfr res. Using a new seal kit from all balls.

 

The bike has hel delink, the rear locked on after 30 minutes. I rebuild the caliper New lines,.New pads,  new rotor. Bled it all.

 

And today I rode and 30 minutes the pedal went rock hard so.i stopped, rotor was very hot. 

 

What am i doing wrong, somebody is saying to.make sure the piston is allowing the compensate valve to put fluid back into the res when it gets hot.

 

 

[Captain 80s]

Where did you read to swap the internals?  Put CBR parts back in the CBR unit.

 

Maybe I'm missing something, but I thought the whole idea is that they are different diameter Masters, and CBR unit gives you some pedal feel back.

 

Perhaps you need to shorten the CBR threaded section for clearance and/or pedal height adjustment.

 

Idk...   just going off what I have read over the years.  Somebody else will come along.

[StormShadow3]

5 hours ago, StormShadow3 said:

Recently I changed my oem rear master with a cbr600f4i rear master on my 98 vfr. I used the internals of the vfr, onto the cbr shell. And the vfr res. Using a new seal kit from all balls.

 

The bike has hel delink, the rear locked on after 30 minutes. I rebuild the caliper New lines,.New pads,  new rotor. Bled it all.

 

And today I rode and 30 minutes the pedal went rock hard so.i stopped, rotor was very hot. 

 

What am i doing wrong, somebody is saying to.make sure the piston is allowing the compensate valve to put fluid back into the res when it gets hot.

 

 

 

[Terry]

I agree with the Captain. There are some critical dimensions between the brake pushrod (which locates the piston) and the master housing and its ports, and assuming the ports are clean then your lock up may be due to fluid being unable to escape after applying the brake.

 

I used an unopened CBR600F4i rear master when I delinked my last VFR and did as Mike suggests and cut some length off the threaded rod to get the VFR pedal in the right location for my big feet.

[StormShadow3]

2 hours ago, Terry said:

I agree with the Captain. There are some critical dimensions between the brake pushrod (which locates the piston) and the master housing and its ports, and assuming the ports are clean then your lock up may be due to fluid being unable to escape after applying the brake.

 

I used an unopened CBR600F4i rear master when I delinked my last VFR and did as Mike suggests and cut some length off the threaded rod to get the VFR pedal in the right location for my big feet.

So your using the f4i push rod cut down?, none of the vfr parts

[mello dude]

I did the same....used a new RC51 rear master and hacksawed the threaded rod down to length.....

[StormShadow3]

10 hours ago, mello dude said:

I did the same....used a new RC51 rear master and hacksawed the threaded rod down to length.....

Being shorter it does it still engage all the way

[Terry]

The threaded rod just moves the resting position of the pedal. I found the pedal sat much too high for comfort with the original length of the CBR600F4 master, even with the clevis adjusted to the minimum where the end of the rod starts bottoming out and can go no further. Once I shortened it, it was fine.  

[mello dude]

On 11/5/2022 at 5:50 AM, StormShadow3 said:

Being shorter it does it still engage all the way

I believe I just shortened it to OEM length, it functions normally....

[wawasonqo]

@Captain 80s @Terry @mello dude

 

Hi Folks,

 

What is (are) the part number(s) for the CBR600F4i rear master cylinder or the RC51 rear master cylinder?

 

Please comment on my following topic too.

 

https://www.vfrdiscussion.com/index.php?/forums/topic/108977-brake-pedal-height/

 

Thanks

[Terry]

https://www.partzilla.com/catalog/honda/motorcycle/1999/cbr600f4-a-cbr600f4i/rear-brake-master-cylinder

[wawasonqo]

51 minutes ago, Terry said:

https://www.partzilla.com/catalog/honda/motorcycle/1999/cbr600f4-a-cbr600f4i/rear-brake-master-cylinder

Hi Terry,

 

Is it just the Master Cylinder Sub-Assy. (No.5, 43510-MBW-E12) that is needed or the whole Master Cylinder such as the following?

 

https://www.baboon.eu/en/part/honda-cbr-600-f-2001-2006-cbr600f-cbr600f4i-pc35-brake-master-cylinder-rear-2001/000000224195#

 

I am trying to see if the RC51 parts are available,

 

Thanks.

[wawasonqo]

@Terry

 

If I decide to get the CBR600F4i master cylinder, would it be safe to reuse the copper washers for the banjo bolts that were installed when I delinked (de-linked)?

 

When such a modification is done, do you use the reservoir of the VFR or the CBR?

[Terry]

New washers are cheap to buy; for brakes I would be using new for sure.

[wawasonqo]

@Terry

 

According to page 1-11 of the Service Manual, the Outer Diameter of the Piston of the Rear Brake Master Cylinder for the 5th Gen. VFR800 is 17.417 - 17.444 mm (0.6857 - 0.6868 inches).

 

According to the following page, the Outer Diameter of the Piston of the Rear Brake Master Cylinder for the CBR600F4i is 13.957 - 13.984 mm (0.5495 - 0.5506 inches).

 

https://cbrforum.com/forum/f4i-main-forum-11/cbr-600-f4-mastercylinder-bore-diameter-120891/#post1012291

 

Which is better, and why, for pushing the 3 pistons of the VFR calipers?

[JZH]

You don't absolutely need to use all three of the rear caliper pistons--you could remove the middle one and save (a tiny bit of) weight!

 

Rear Master Cylinder/Caliper Ratios
Diameter	(in mm)	12.7	14	15.87	17.46	19.05
( ) = # of pistons	(in in.)	1/2"		5/8"	11/16"	3/4"
	Area (mm2)	126.7	153.9	197.9	239.5	285
22.65 (1)	403.6	3.19	2.62	2.04	1.69	1.42
22.65 (2)	807.2	6.37	5.24	4.08	3.37	2.83
25 (1)	490.9	3.87	3.19	2.48	2.05	1.72
25 (2)	981.8	7.75	6.38	4.96	4.10	3.44
25.4  (1)	506.7	4.00	3.29	2.56	2.12	1.78
25.4 (2)	1013.4	8.00	6.58	5.12	4.23	3.56
27.0 (1)	572.6	4.52	3.72	2.89	2.39	2.01
27.0 (2)	1145.2	9.04	7.44	5.79	4.78	4.02
38.1 (1)	1140.1	9.00	7.41	5.76	4.76	4.00
RC46-I (3)	1379.8	10.89	8.97	6.97	5.76	4.84
RC46-II (3)	1520.1	12.00	9.88	7.68	6.35	5.33

 

The above chart shows some data copied from various Honda Workshop Manuals you might find useful.  (Note that there are different RC46 rear caliper piston sizes for 5th and 6th gens--and I believe the only difference with the ABS-versions is the caliper colour, but it has been a while since I looked into this topic.)

 

Using the CBR600F4 as an example, it uses a single 38mm rear caliper piston and a 14mm master cylinder, giving a ratio of 7.41.  Is that also a good ratio for the VFR800Fi?  Maybe...  Check some other non-LBS/DCBS Honda and see what ratio might work best.   (I just checked the 2015 8th gen, and it uses a 14mm master cylinder and 2x 25.4mm pistons, for a ratio of 6.58.  I'd probably use that as a reference point, or maybe split the difference and aim for 7.00?)

 

Using all three pistons of the RC46 rear caliper, your best choice is probably a 5/8" master (giving a 6.97 or 7.68 ratio, depending on 5th or 6th gen).  Those masters are not very common, but you might be able to find another Honda NISSIN rear master which fits using the same mounting locations--alternatively, you could try Brembo or something from another bike.  

 

Using just the outer two pistons on the RC46 rear caliper would give you completely different ratios.  Using the 6th gen caliper (2x 25.4mm) and a 14mm master cylinder would give you the exact same ratio as the 8th gen VFR800F.  Using a 5th gen rear caliper (2x 22.65mm), you would probably have to go for a 1/2" master--but note that would give you slightly less lever travel and more feel than the 8th gen.

 

Ciao,

 

JZH

[ducnut]

Yep. Use the complete CBR master cylinder and just shorten the threaded rod. Did the same on mine and works perfect. For a reservoir, I just went to the bike breaker and found something smaller. I used Sebspeed’s adapters and Chinesium rearsets, for the rest. 

[wawasonqo]

3 hours ago, ducnut said:

Yep. Use the complete CBR master cylinder and just shorten the threaded rod. Did the same on mine and works perfect. For a reservoir, I just went to the bike breaker and found something smaller. I used Sebspeed’s adapters and Chinesium rearsets, for the rest.

 

@JZH

 

Before I go this route, I would like to debug what's happening with the current Master Cylinder as per the following post.

 

https://www.vfrdiscussion.com/index.php?/forums/topic/108993-rear-brake-bleed-delinkedde-linked-caliper-mounting/&do=findComment&comment=1149516

I can crimp the tube from the reservoir above where it enters the Master Cylinder and check that fluid is leaving the reservoir.

 

If so, what procedure(s) should I follow next? I have the Service Manual.

 

The bike was unused for 15 to 16 years, Could the Master Cylinder be gummed up inside?

 

If so, how easy/difficult is it to dismantle and clean and put back together?

 

You can see how my brakes were de-linked in the 4 photos attached.

 

 

If I end up getting a CBR600F4i Master Cylinder, can you connect the VFR Reservoir to the CBR600F4i Master Cylinder using the tubing of the VFR?

 

Thanks!

 

[Terry]

With the bleed screws open, the rear master cylinder should stroke fully to the stopper for the brake pedal; my guess is that would be 20-30mm or more. And you should be seeing fluid pump out of the bleed screws when you do that, with almost no lever resistance. If not then your master cylinder almost certainly has a major clog (or maybe the bleed screws are clogged too). I'd suggest pulling the brake lines off at the master and verifying that fluid can be pumped directly out of the master. 

 

There are two ports in all master cylinders; the main fluid intake port, and then a tiny compensating port. The piston has to move past the smaller port to generate line pressure, and then relax back and open that small port up to allow pressure to release and for the pistons to move back off the disc/pads. If that tiny port is clogged, or the piston is not able to move back far enough to expose it, then line pressure can't release and the brake will be stuck on to some extent. 

 

[wawasonqo]

1 hour ago, Terry said:

With the bleed screws open, the rear master cylinder should stroke fully to the stopper for the brake pedal; my guess is that would be 20-30mm or more. And you should be seeing fluid pump out of the bleed screws when you do that, with almost no lever resistance. If not then your master cylinder almost certainly has a major clog (or maybe the bleed screws are clogged too). I'd suggest pulling the brake lines off at the master and verifying that fluid can be pumped directly out of the master. 

Hi Terry,

 

When I opened the bleed nipples (one at a time), a little fluid came out but after that pumping the pedal produced nothing.

 

Should I try both bleed nipples open together?

 

At present the rod only moves about 5mm and when you get to the end of the stroke, it feels totally solid.

 

The pads aren't making any engagement with the disc.

 

How messy will your suggestion of detaching the brake lines from the master cylinder be?

 

Thanks!

[wawasonqo]

19 hours ago, JZH said:

Using the CBR600F4 as an example, it uses a single 38mm rear caliper piston and a 14mm master cylinder, giving a ratio of 7.41.  Is that also a good ratio for the VFR800Fi?  Maybe...  Check some other non-LBS/DCBS Honda and see what ratio might work best.   (I just checked the 2015 8th gen, and it uses a 14mm master cylinder and 2x 25.4mm pistons, for a ratio of 6.58.  I'd probably use that as a reference point, or maybe split the difference and aim for 7.00?)

 

Using all three pistons of the RC46 rear caliper, your best choice is probably a 5/8" master (giving a 6.97 or 7.68 ratio, depending on 5th or 6th gen).  Those masters are not very common, but you might be able to find another Honda NISSIN rear master which fits using the same mounting locations--alternatively, you could try Brembo or something from another bike.  

 

Using just the outer two pistons on the RC46 rear caliper would give you completely different ratios.  Using the 6th gen caliper (2x 25.4mm) and a 14mm master cylinder would give you the exact same ratio as the 8th gen VFR800F.  Using a 5th gen rear caliper (2x 22.65mm), you would probably have to go for a 1/2" master--but note that would give you slightly less lever travel and more feel than the 8th gen.

 

I meant to mention this earlier but I was thinking along the lines of how bicycle pumps function. Pumps for tyres that require a high pressure use a smaller diameter piston than a pump for high volume tyres like mountain bikes.

 

So, would the smaller piston of the CBR600F4 create higher pressure which would be beneficial when you are trying to push all 3 pistons of the VFR?

[wawasonqo]

15 hours ago, ducnut said:

Yep. Use the complete CBR master cylinder and just shorten the threaded rod. Did the same on mine and works perfect. For a reservoir, I just went to the bike breaker and found something smaller. I used Sebspeed’s adapters and Chinesium rearsets, for the rest. 

 

 

I see you have only 1 line connected to the master cylinder. How many pistons does the caliper, you are using, have?

[DannoXYZ]

9 hours ago, wawasonqo said:

 

I meant to mention this earlier but I was thinking along the lines of how bicycle pumps function. Pumps for tyres that require a high pressure use a smaller diameter piston than a pump for high volume tyres like mountain bikes.

 

So, would the smaller piston of the CBR600F4 create higher pressure which would be beneficial when you are trying to push all 3 pistons of the VFR?

You're talking about having more mechanical leverage in hydraulics. There's balance where too much gives you soft gooey lever with lots of travel. Going other way gives more solid feel, but less power. Ultimately, it's personal preference because actual braking-power is limited by tyre's traction on ground.

[wawasonqo]

On 3/19/2023 at 9:00 PM, Terry said:

With the bleed screws open, the rear master cylinder should stroke fully to the stopper for the brake pedal; my guess is that would be 20-30mm or more. And you should be seeing fluid pump out of the bleed screws when you do that, with almost no lever resistance. If not then your master cylinder almost certainly has a major clog (or maybe the bleed screws are clogged too). I'd suggest pulling the brake lines off at the master and verifying that fluid can be pumped directly out of the master.

 

Afternoon Terry,

 

I not long ago unscrewed the Banjo Bolt and lifted it and the Line Connectors and Copper washers up and rested them to one side.

 

Pumped the pedal but the action remains the same and no fluid was being pumped upwards out of the opening.

 

So, next step, extract the Master Cylinder?

 

Is it possible to remove it, without removing the Right Footpeg Holder?

 

If not it looks like I need a 27mm socket, correct?

 

Thanks!

[wawasonqo]

@JZH

 

Would a Master Cylinder with an Internal Diameter of 12.7mm be ok to use? What effects could you expect?

 

It may be possible to get one for a Honda CB190R here. The Piston rod looks like it would have to be shortened.

 

Thanks!