Author Topic: Can I improve my CB400F w/ CB750 front brakes ? (Read 5816 times)

grcamna2 · « **on:** November 30, 2011, 02:32:39 PM »

I want to know if I can install a CB750 front brake caliper & master cylinder on my CB400F?? & will it improve my braking power at the lever ? I have the CB750 front caliper & master cylinder matched pair & the caliper has a large threaded bleeder screw.

HondaMan · « **Reply #1 on:** November 30, 2011, 02:38:06 PM »

You might wish to try the ones from the CB500/550 instead. The 750 disc is stainless steel, doesn't have as much grip as the others. Also, try adding some score mark lines radially, or just drill holes, to improve the grip. Small holes, less than 10% of the surface, will let surface contaminants slide away from the pucks as soon as they grip, improving brake feel and response.

grcamna2 · « **Reply #2 on:** November 30, 2011, 03:00:18 PM »

Hi HondaMan !

Will my CB400F disc be useful, is it stainless? The CB550 disc is the better steel for friction than my own? Will I also have any added benefit by installing the CB750 caliper/master that I have & maybe getting it to fit my fork leg ? I will have the disc drilled as you recommended either way.

Thanks

OldSchool_IsCool · « **Reply #3 on:** November 30, 2011, 03:08:19 PM »

Stainless brake lines help a ton too! I swapped 750 brakes for my 550s. I'm happy with the improved breaking due to the slightly larger disk

grcamna2 · « **Reply #4 on:** November 30, 2011, 03:51:57 PM »

OldSchool_isCool,

Did you use the CB750 caliper & master cyl. also ?

I noticed in your reply that the CB750 disc is larger? then you must have had to remount the caliper bracket on your CB550 fork leg? or not ??

OldSchool_IsCool · « **Reply #5 on:** November 30, 2011, 07:20:09 PM »

GR,

I had to swap out the fork lowers, caliper, disk and fender/brace. I kept the 550 master.

Here is a photo showing the slight difference in disk diameter:

OldSchool_IsCool · « **Reply #6 on:** November 30, 2011, 07:35:22 PM »

Also be aware that there is a flange difference between early 750 and late 550 forks:

Since I wanted to go with caps instead of gators, I bought caps for a different bike (I can look up which bike if you need it) and trimmed the gap with a large O-ring. Here's how it worked:

grcamna2 · « **Reply #7 on:** November 30, 2011, 08:22:28 PM »

Old School,
Those pics and the extra descriptions in your reply really does help ! I have a CB400F & the front disc hub only has 4 mounting bolts.This reply of yours has made it more clear for me to understand that I will either have to get a CB550 front hub & build an 18" wheel around it for my bike? I would rather somehow, (according to HondaMans reply)I guess I can dismount the disc from my CB400F 4 bolt carrier & get a hold of a CB550 front disc(which HondaMan says is a better braking material than S.S. which I guess is what my O.E. CB400F disc must be(?) and remove it from it's 6 bolt disc carrier and try to mount it up to my O.E. 4 bolt disc carrier ??

HondaMan...can you clarify this for me ?

I haven't done too much swapping of parts before & it's all new to me..but don't get me wrong,because I want to get the best set-up for my front brakes possible.I know that Original Equipment parts are ALWAYS the best ones for the long haul & I want to make this CB400F stop GOOD. I will keep my original front brake caliper & fork lowers,but I want to do what HondaMan recommends in his reply; it sounds like great advice.I will drill the front disc also for best all-around performance. I like the look of my stock parts, if I can keep them.
I'll wait to hear from HondaMan about this swap mod procedure...but if it works out....Old School, would you sell me your old CB550 front disc ?

I want to do the S.S. hydraulic brake lines when I get this all together over the next 6 months...you know,with the way auto drivers operate out there...this mod may save my butt down the road !

OldSchool_IsCool · « **Reply #8 on:** November 30, 2011, 08:31:48 PM »

I can prolly sell it to you. Assuming I can find it, I've moved since I did the swap and my garage is much smaller. Had to pack things tight! I have 550 fork lowers and a fender around here somewhere too. The chrome on the fork tubes is shot though. And they are longer than standard too. Maybe 3 or 4 overs??

Kemp · « **Reply #9 on:** November 30, 2011, 08:37:46 PM »

I've used the CB750 rotor, 1976 750F calipher and hanger and Yamaha FZ600 Master cylinder on my CB550 with really good results. The 1976 CB750F calipher has a slightly bigger piston than the normal CB750 which could be an advantage? You must use the calipher hanger from the same model 750 as the calipher is as they are different thicknesses. All 750 hangers also have the spring adjuster hole higher up as the disc itself is an inch bigger. The calipher itself is physically bigger and its mounting holes to the hanger are slightly farther apart than a CB550's. I drilled holes as Hondaman suggests to help improve wet weather performance and reduce brake squeal. The yamaha master cylinder has a 11.5 mm piston which greatly enhances brake feel, more like a modern bike without the wooden feel found in the 14.5mm Honda master. You can actually bring the brake to the point of lock up just like a modern bike and feel it respond at that edge so that you can modulate pressure. Late model CB550's have a longer fork outer tube which is identical in length to the CB750. This longer outer has the advantage of be able to fit the nice Taradozzi CB750 fork brace which has a hump to clear the stock fender.

grcamna2 · « **Reply #10 on:** November 30, 2011, 08:44:37 PM »

Old School, thanks guy. I want to just change over to that CB550 front disc & keep the rest of it CB400F...make it look Original, but with an improved disc & I may drill it out like HondaMan says will be best.
I like what Kemp says about that Master cyl. w/ a smaller piston...it may give it more PSI while making it easier to modulate like he said...Great replies.

Thanks fellow sohc4 members

HondaMan · « **Reply #11 on:** November 30, 2011, 11:26:54 PM »

Sorry, I forgot to mention the hub mounting differences.

One method of getting around this was/is not hard for folks with machine shop access: swapping the hub supports inside the disc. This entails removing the OEM rivets on both discs and trimming the hub arms or discs, then (in some cases) adding new holes to match for the rivets. If you don't rivet, use Grade 8 bolts, short, with Loctite on the nuts and lock washers: jam nuts are adequate, or if you're clever you can tap the disc to receive the new bolts. Use at least as many bolts/rivets on the disc as on the wheel's hub, for a margin of safety.

Technically, there are many discs out there today that will fit these bikes. They are often thinner than the old ones, which broke new ground and were heavily overbuilt for unknown safety reasons. Today's typical dual-disc front ends have 3mm thick discs that are drilled or cut away almost 50%, with wider calipers, and they neither warp nor squeak while delivering nearly twice as much stopping power. They are often not stainless steel, leading to rust issues, but the cast material (like Brembo discs) does have much more friction to it.

grcamna2 · « **Reply #12 on:** December 01, 2011, 05:33:21 AM »

Hey Old School,
Let me know when you find your old CB550 disc, no hurry...I'll wait.

OldSchool_IsCool · « **Reply #13 on:** December 02, 2011, 05:01:44 AM »

OK GR, I'll try to get out to the garage this weekend.

grcamna2 · « **Reply #14 on:** December 02, 2011, 05:12:28 AM »

Old School,
I like those words about "attitude" to the right of your AVATAR...it could be easier for a young person to accept that advice because they aren't so set in their ways; I always appreciate seeing & carefully reading that from you...Thanks.

OldSchool_IsCool · « **Reply #15 on:** December 02, 2011, 06:25:46 AM »

I wish I cold claim credit for those words, but they belong to Robert Pirsig. You can get the full text and all the heady concepts that surround it from "Zen and the Art of Motorcycle Maintenance"

Psychonaut · « **Reply #16 on:** December 04, 2011, 07:54:20 AM »

Going with a larger rotor isn't going to get you much unless you are racing, the feel will be the same. You need to go with dual calipers or a smaller diameter MC and single caliper if want better feel and more bite. You can get a new 12.7mm MC on Ebay for around $45. I've done a lot of reading and everything I see says the FZR and ninja 250 uses a 12.7-13mm. Most dirt bike use 11MM MC's but don't have a mirror mount, might be a bad thing unless you run bar end mirrors. Mikes XS sells a new 11mm MC for around $70 or 80. I'm probably going to use one from a CRF or RM. One has the banjo on front, the other is on the back.

There is a chart here that covers a lot of different combinations. You are 38mm at the caliper and 14mm at the MC.
http://www.vintagebrake.com/mastercylinder.htm

grcamna2 · « **Reply #17 on:** December 04, 2011, 09:13:43 AM »

Very helpful, Thanks Psychonaut ! I like the smaller MC piston idea.
I've seen a small square little master cylinder swap for my bike on the forum,but can't find it.I want to see if it's possible to get a"little" square one rather than a "huge" square one; & I think the best one would have a mirror mount...that smaller piston idea...yeah,yeah that makes sense & that's what I'll be shooting for.

ANY IDEAS ARE WELCOME.

Psychonaut · « **Reply #18 on:** December 04, 2011, 09:55:59 AM »

Most dirt bikes have a small reservoir if that's what you are referring to. Type in CRF or RM front master in Ebay and a hundred will pop up.

I just found that the Honda XR's, atleast the XR600 had a hole for a mirror as they were a dual purpose bike. I would like the option to run a regular mirror if I get tired of bar ends ones. They are 11mm and have a 10mm banjo on the same end as CB's. I just need to find a decent used one. All the dirt bike MC I have seen that are 11mm have a raised 11 on them.

crazypj · « **Reply #19 on:** December 04, 2011, 10:16:24 AM »

Grind the rivet heads off and swap just the rotor.
Used shouldered Allen bolts to re-mount (standard Allen's are grade 9)
You may find something from a different bike with better friction? (Suzuki RM rotor looks close?)
550/750 also has 40 hole hub so you couldn't swap rim off 400 (36 hole)

grcamna2 · « **Reply #20 on:** December 04, 2011, 10:40:46 AM »

Quote from: Psychonaut on December 04, 2011, 09:55:59 AM

Most dirt bikes have a small reservoir if that's what you are referring to. Type in CRF or RM front master in Ebay and a hundred will pop up.

I just found that the Honda XR's, atleast the XR600 had a hole for a mirror as they were a dual purpose bike. I would like the option to run a regular mirror if I get tired of bar ends ones. They are 11mm and have a 10mm banjo on the same end as CB's. I just need to find a decent used one. All the dirt bike MC I have seen that are 11mm have a raised 11 on them.

Hi Psychonaut,
This one in the picture above, is it an XR600 ? That seems like one I should be searching for also; that is the 11mm piston ?

Psychonaut · « **Reply #21 on:** December 04, 2011, 12:06:30 PM »

Quote from: grcamna2 on December 04, 2011, 10:40:46 AM

Hi Psychonaut,
This one in the picture above, is it an XR600 ? That seems like one I should be searching for also; that is the 11mm piston ?

Yes. If click link below and look at the last pic you can see the raised "11" on it. I read a post on the Thumper board and people talked about the crf and yz MC's. They said the crf felt better than the yz even thought they are both 11mm and both made by Nissin. I have never riden either to know though. If you don't need the mirror mount and brake switch built in but if you want a smaller resevouir and unpainted, I would look at the CRF. I did see some new xr MC's on Ebay but they say they are not 11mm. They are not stamped and not Nissin either.

http://www.ebay.com/itm/1990-90-Honda-XR600R-XR-600-Front-Brake-Master-Cylinder-/140578089684?pt=Motorcycles_Parts_Accessories&vxp=mtr&hash=item20bb1b6ad4

grcamna2 · « **Reply #22 on:** December 04, 2011, 01:06:22 PM »

Do you think that 11mm piston will push enough fluid volume to stop my CB400F w/ the stock caliper? or should I be looking for a 12mm MC ?

veloracermike · « **Reply #23 on:** December 04, 2011, 01:23:52 PM »

Quote from: grcamna2 on December 04, 2011, 01:06:22 PM

Do you think that 11mm piston will push enough fluid volume to stop my CB400F w/ the stock caliper? or should I be looking for a 12mm MC ?

Use one off a Suzuki Katana, 12mm and they show up all the time on eBay. Got a brand new one for 49 bucks with the lever. Also Slingshot Cycles (http://www.slingshot-cycles.com) sells a master with a built in switch as well. He is making me a steel braided hose for this set up as we speak.

Psychonaut · « **Reply #24 on:** December 04, 2011, 01:40:02 PM »

I have not tried it yet to say. I have just read a lot on it. If we have one 38mm piston then it should be plenty. You will use more lever than with the 14mm MC but most modern bikes are set up like this. The levers on the XR and CRF's are adjustable too so you can move it out a little if needed. I know my lever is so close now I can't wear a thick glove. As for feel and travel, I rode my friends Busa and almost went over the bars on a slow stop. Ok not over the bars but I could beleive how much better the bite was for the amount of finger pressure aplied. I know it's a different set up but it comes down to the MC bore .v caliper area.

Looking at the ratio chart an 11mm MC with one 38mm piston is still a little harder than a 14mm MC with twin 38's like 750's use. If you aren't in a hurry I will let you know when I finish mine. I should be done in a few weeks.

veloracermike, I saw those on Ebay. They are 12.7mm. They are a good deal too. Something in between.

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Author Topic: Can I improve my CB400F w/ CB750 front brakes ? (Read 5816 times)