brake and clutch master cylinder question

Hey, new to the forum and the world of motorcycles so hang with me here lol.. so I picked up 87 vfr 700 and my friend, who is a motorcycle mechanic said that both the clutch and the brake master cylinders need be rebuilt or I need new ones. My question is are they universal items? Can I replace them with any bikes master cylinders? Ive seen a few on ebay from other vfr 700s but im not too sure how reliable those are gonna be since there just as old as mine.. any advice would be appreciated..
THanks in advance

 

also whats the handle bar diameter on the vfr 700s?

 

Welcome to the forum.

The Best thing to do, is to start searching the forums for what answers you are looking for in the form of a question or using key words. that will usually get you the information you are looking for, if not then go ahead & ask your question.

I am currenty having my clutch MC rebuilt. From what I have been reading on various websites, & seen on you-tube, they should be able to be rebuilt relatively easily.
I am handy with my hands & tools, But opted to let someone that has done this more then once, do the work so I know it is done right.

Sincerely,
Paul

 

Most of us have never needed to rebuild either unit, so what makes him think they're both bad ?? Rebuild kits would consist of 2 rubber seals and maybe a spring, should cost less than $20.

 

You can get rebuild kits for both master cylinders here:

CLUTCH MASTER CYLINDER REBUILD KIT for HONDA VF500 CB550 CB650 CB700 VF700 VT750 PC800 VFR800 VT800 CB1000 CBR1000 VF1000 VTR1000 CBR1100 ST1100

 

My 1972 CB750 is still running in Duluth MN. with the original un-rebuilt master cylinder. Clean, Change the fluid and check for leaks.

 

Thanks for the replies every one! I'm gonna try to clean it first without the rebuild although I think I'm still gonna have to get a new sight glass for the clutch mc... I'll update when done

 

By now most of us have cloudy sight glasses, but you're complicating things alot if you want to change them. Clutch master ?? I wouldn't bother. Fill and forget.

 

Actually, replacing the sight glass is a very simple process. If you are going through the effort of rebuilding them, you might as well take the few extra minutes.

Or, you could just epoxy a coin/blank over the hole and be done with it.

 

sorry if I sound like an idiot but just trying to clear things up.. on the brake master cylinder i see the numbers "18" and "5/8" .. Does this mean it is an 18mm piston and 5/8th inch handlebar?

 

you can barley see it since im lazy and didnt take the mc off but the 18 is in the circle and the 5/8 is in the square

 

Rebuilt front calipers maybe 4 years ago, nasty shit was in there. Musta spent an hour cleaning and carefully scraping with a blunt tool. Brake Master was re-built as it developed a leak where the lever pushes.

Clutch side: installed a braided clutch line, used to bleed and clean fluid regularly. Started losing fluid in master, turns out its the slave cylinder, replaced that. At that point, I was like, WTF, so I rebuilt clutch master too. My rear master and caliper have never been touched, I rarely use the rear brake anyway, so the fluid doesnt get nasty.

Point is, if its an old bike, all the parts are kinda worn. You re-build these items and your starting new at least. Just some food for thought. If its broke, Fix iT

My YSR 50 I just over-hauled the front caliper along with a re-build kit for the brake master. Painted em up nice with (shameless plug here) VHT Caliper paint.

 

5/8 -11 is a course thread size. 5/8 - 18 is a fine thread size. I have no idea why this would be on a metric Master Cylinder, unless it came off a Harley. These numbers could just be a part or lot code from the manufacturer.

Bottom Line..... I have no idea!

 

Can anyone else that has an 87 vfr700 verify if these numbers on the brake mc? I ordered a rebuild kit and wanna make sure it's for the right part.. For all I know the previous owner switched the mc on it

 

Not because I like re-hashing old threads, but I am also having some issues. I rebuild all my brake and clutch systems. The bike sat for 19 years and needed some serious cleaning. The brakes are good, but the clutch master cylinder continues to give me issues. I have rebuilt it twice. The symptoms have been sitting at a light with the clutch pulled in, or as I'm cycling it 1/2 way in traffic, it starts to bleed off pressure. It got so bad that the engagement was so far off that the bike was stalling. Now I notice that it's doing it just a bit again and the fluid is turning dark. I am not losing any fluid so I know the slave is OK. I have cleaned the barrel of the master cylinder thoroughly but I'm wondering if there was some corrosion after sitting for all those years and that maybe it's just a bit rough and that's what keeps tearing up the plunger.
Long story short, I know, too late, I think it's time for a new MC. Anybody have any luck with sourcing a new MC?

 

Since this thread has been brought back to life, are there any better master cylinders that could work on a 5th gen? My goal is to improve braking, as it takes too much squeeze to slow the bike. I know, bleed the brakes, which I'll do, but some modern sportbikes have such excellent brakes and I'm wondering if perhaps a radial master cylinder could help?

 

The 5th gen uses a 1/2" master cylinder, which is on the smaller size used by Honda. The force that squeezes the pads onto the disc is in proportion to the ratio of the master cylinder area to caliper piston area, so if you put a smaller diameter master on there, you get more force at the pads for any given amount of squeeze. the trade-off is you also get more m/c piston travel so a softer/mushier brake feel.

In your position I would be doing some good basic maintenance if you haven't already, clean and lube the lever pivot, and clean the caliper pistons and sliding mounts, just so everything is moving as freely as possible. After that, try some EBC HH pads, as these in my experience provide a lot more bite than the standard pads.

If that still does not get you to braking nirvana, then there are aftermarket radial master cylinders that can be had in small diameters. As most OEM radial m/cs also work with twin 4-piston calipers, they will generally be of a bigger diameter than would be preferred to work with the 5th gen (where you are only activating a total of 4 pistons).

Or do as I have and ditch the linked brakes, bolt in VTR1000 fork lowers, add your choice of 4-piston opposed calipers (CBR954 would be my suggestion) and matching master cylinder (2003 CBR600RR), and stop on a dime.

 

I had a situation with a GPZ500 or in this country EX500, where the initial touch of the brake lever had some resistance or stiction in it, after that brief nano second it would be free. I inspected the system where I took off the brake lever and rubber thingie and looked at the rod that went into the master cylinder. It had some white crystalization, so I thought to myself, why not invest in a re-build. I did it, bear in mind that the front brake system is up to snuff, new pads, pistons were cleaned as much as they could while still in situe. Anyway, long story short, after spending money on an OEM re-build kit from Kawi, I still got the same lever action from the initial bite after the bike sat or night or at work, (you get the idea.) No weeping or crystalization though.

I gave up on the idea of having a stock master for this bike, I had a friend who warped a front disk on his bandit 1200 and ending up using one disk, he still used the same master cylinder though with no problem, and he rode this bike slow, (no-not slow, bike was a built bandit that needed an extended swing arm to enter the hightway.) So I looked around ebay and ended up buying a SV650 master brake cylinder, I got it, it came with the banjo bolt which was a good thing, I installed it with the same braided brake line and all was well with the world. Sometimes you can take a chance on some stuff and end up ahead. Keep us posted and pictures are always appreciated. Cheers

Wha