I have a “new to me” kart and I’d like to see if I could get some help diagnosing a brake issue.
When I step on the brake the pistons do extend and the pads make some contact with the disc, but under heavy braking there isn’t enough stopping power.
I checked the brake linkage to the master cylinder and that all seems to be fine, I even adjusted it all the way in so that depressing the pedal engages the master cylinder the most.
I see that there are what appear to be shims between the two calipers, are these what is used for adjustment? i.e. Can I remove some of the shims to get the pads closer to the disc?
I was going to attempt a break fluid flush but I don’t know what kind of fluid is in it (nor do I see a reservoir anywhere to add fluid to like there is on my motorcycle)
Sounds like low brake fluid pressure so when you hit the brake pedal although there is some pressure, its not enough to fully engage the brakes. The black rectangle that attaches brake cables to the brake cable is your master cylinder and reservoir of sorts.
Could be either air or low fluid which is the cause of loss of pressure.
I would open the very top of the master cylinder by means of unscrewing the 4 screws. See if there is any fluid, if there is then it’s full and there is air in the system. If there isn’t fluid fluid is low and there is air in the lines.
I dont know what kind of fluid yours takes, I know my reservoir says what fluid on the side of it in fine print (Dot 4) but for karts it’s either DOT 4,5, or 5.1.
Once filling the reservoir to the top hit the brakes a couple times build some pressure then take a tube and cover the brake caliper bleed screw (I think i only see one). Build pressure, Crack screw, close screw, release pedal. Repeat until no bubbles come from the line and also make sure while doing this you are also topping off the reservoir with fluid so more air doesn’t enter.
So you have an MS brake system on presumably an MS (Czech) kart.
The caliper has spring return pads unlike the self adjusting calipers on most karts these days.
Pad to disc clearance is adjusted by removing shims between the caliper halves.
I would go for 0.5- 1.0 mm per side. You may have to recentralise the disc/rotor.
The master cylinder is a pumper type with built in fluid reservoir as suggested by Christian above.
Fluid is likely to be Dot 4 (glycol) .Dot 4 is soluble in water unlike Dot5 (silicon)
The m/cyl will not work if you adjust the pedal rod to move the lever on the m/cyl as this moves the m/ cyl piston down its bore and blanks off the fluid feed from ,and to the reservoir.
You will need to bleed both halves of the caliper separately in the normal way as they are not hydraulically connected.
Without the top cover on the m/cyl you are likely to get fluid spurting everywhere as you bleed.
If you google ‘MS brake systems’ you will find a comprehensive parts list with illustrations.
This looks like an older design ( I am not able to open your pics, so I am just looking at the thumbs). I have seen designs that use shims between the pad and caliper piston to remove any air gap between the pad and the disk and I assume your shim basically do the same thing but brings the two halves closer together or further apart. Typically you want the pad as close to the disk as possible so the pressure created when you depress the pedal isn’t wasted motion. Just enough gap so the pads are almost on the disk.
I am confused at what I see in your pics though. It looks like there is only one line which would mean the fluid travel between the two halves. If there are two lines (one to each side) you can split the calipers easily without requiring a bleeding as they operate seperatly.
More than likely you would be using DOT 3 or 4 fluid. To bleed kart brakes you use a gravity bleeder that mounts to the master cylinder and gravity pushes fluid out through the bleeders on the caliper. A kart shop typically has one on hand to borrow or rent and some racers might have one too. They are expensive for what they are, but it does the job.
The black rectangle that attaches brake cables to the brake cable is your master > cylinder and reservoir of sorts.
I was doing some more researching this morning and came across a few things that said I need a filling tower or some tool to actually do a proper flush. Is that accurate?
I dont know what kind of fluid yours takes, I know my reservoir says what fluid on the side of it in fine print (Dot 4) but for karts it’s either DOT 4,5, or 5.1.
That’s good to know, I stock lots of DOT 4 and DOT 5 for my bikes. When I get to flushing 'll go with that.
So you have an MS brake system on presumably an MS (Czech) kart.
You’re correct, the rest of the cart says MS kart. A lot of googling of the serial numbers led me to: Homologation CIK-FIA 2003 - 2008
Chassis MS KART RA 23 CIK-FIA 49/CH/08
The caliper has spring return pads unlike the self adjusting calipers on most karts these days.
Pad to disc clearance is adjusted by removing shims between the caliper halves.
I would go for 0.5- 1.0 mm per side. You may have to recentralise the disc/rotor.
Good to know, learning something already!
I don’t have a super accurate way to measure this, but eyeballing with a caliper next to the pads there appears to be 0.03" - 0.04" (0.762mm - 1.016mm) between the pads and the disc as it sits.
The master cylinder is a pumper type with built in fluid reservoir as suggested by Christian above.
Fluid is likely to be Dot 4 (glycol) .Dot 4 is soluble in water unlike Dot5 (silicon)
The m/cyl will not work if you adjust the pedal rod to move the lever on the m/cyl as this moves the m/ cyl piston down its bore and blanks off the fluid feed from ,and to the reservoir.
More learning, thanks much! I’ll adjust the screws back to their original positions.
You will need to bleed both halves of the caliper separately in the normal way as they are not hydraulically connected.
Without the top cover on the m/cyl you are likely to get fluid spurting everywhere as you bleed.
If you google ‘MS brake systems’ you will find a comprehensive parts list with illustrations.
I replied to Christian the same, but I was doing some more researching this morning and came across a few things that said I need a filling tower or some tool to actually do a proper flush. Is that accurate?
This looks like an older design ( I am not able to open your pics, so I am just looking at the thumbs).
Whoops, the images should be fixed now!
I have seen designs that use shims between the pad and caliper piston to remove any air gap between the pad and the disk and I assume your shim basically do the same thing but brings the two halves closer together or further apart. Typically you want the pad as close to the disk as possible so the pressure created when you depress the pedal isn’t wasted motion. Just enough gap so the pads are almost on the disk.
Yeah, that makes sense to me. Which is why I jumped to the conclusion about the shims initially.
I am confused at what I see in your pics though. It looks like there is only one line which would mean the fluid travel between the two halves. If there are two lines (one to each side) you can split the calipers easily without requiring a bleeding as they operate seperatly.
There is a single line that comes out of the master cylinder and moves towards the back of the kart. Right before the brake assembly the line has a tee that splits it, one for each side of the caliper.
More than likely you would be using DOT 3 or 4 fluid. To bleed kart brakes you use a gravity bleeder that mounts to the master cylinder and gravity pushes fluid out through the bleeders on the caliper. A kart shop typically has one on hand to borrow or rent and some racers might have one too. They are expensive for what they are, but it does the job.
In my learning this morning I found a lot of references to this gravity bleeder thing that you speak of.
Is it possible to do a decent job of bleeding the brakes without one of these?
Your system is a bit unusual in that it uses a reservoir type master cylinder with a spring return caliper.
Older karts usually have a master cylinder without a reservoir, just a piston moving down the bore.
On these non reservoir systems the only way to bleed the brakes is to run fluid through the system using a gravity feed tower or similar.
In your case it looks as though you could use a tower screwed into the plug thread at the ‘back’ of the m/cyl and purge the lines and the caliper.
The second method would be top up the reservoir and pump fresh fluid through the whole system in which case you would not need the tower.
I would go for the second method.
Yes. This looks essentially the same as the old CRG system I have. Just fill the reservoir with fluid, hold down the top and start bleeding. After a couple times, add more fluid and repeat until the air is all out.
So I went ahead and bled the brakes, things work much much better now!
One of the calipers had a normal bleed screw, the other one had just a cap screw, I’ll need to replace that with a proper bleed screw to make things easier (and less messy!) in the future.
The seal on the master cylinder looked pretty beat up so I’m going to guess that I’ll need new seals all around (gotta figure out where to find these parts!)
The next issue at hand (I updated the thread title from Brake help to Kart help) is that the clutch seals seem to be shot.
Once I got the motor spun up the clutch was leaking oil like crazy around the axle shaft (both on the front and back of the clutch). This is an LT wet clutch on the Kart.
So the question to the group, should I buy new seals for this clutch or should I go with a different type of clutch like a dry clutch? (dry clutch seems easier maintenance wise)
I guess that depends on how handy and resourceful you want to be. I am into mountain bikes too and noticed that there were some similar thread sizes. So I found a bike bleed kit and retrofitted a syringe to basically do the same thing except I have to apply the pressure. It works okay but was much cheaper than a gravity bleeder.
I used to run KT and ran both a wet L&T clutch and a dry Patriot. The L&T must have fluid to work properly or it will fry in about 2 laps. Personally its a matter of choice. I preferred the simplicity of the Patriot but when the L&T was working properly it was good too. Just one more thing to go wrong and you can’t see what going on without removing the cover so I sold the L&T. There really isn’t a seal on the output shaft so it may have been overfilled too.
Welcome Robert, this is a terrific site with great folk.
On your brake issue and having similar issues on my first shifter kart here’s what I’d do. May sound like an overkill but brakes are critical & confidence is high this will solve you concern-
A- Replace you brake pads. They may be contaminated even though they look good. Clean the brake disc(s) thoroughly with an aerosol brake cleaner.
B- Use a vacuum bleeder (Harbor Freight sells a good one for under $30) to evacuate the system refilling as you go (don’t let it go dry) with the correct fluid your kart manufacturer recommends. Do this 2-3 reservoir fillings.
Test the kart being sure to burnish the new pads. If things still aren’t up to snuff, replace (don’t o’haul unless you can’t find a new one) the master cylinder and re-vacuum bleed the system.
Hope this helps Rob,
Denny
