84 KDX 200 rear brake adjustment

travisb · Post by **travisb** » 09:24 pm Jul 19 2016

Hello,

I am looking for some advice regarding the rear brake on my 84 KDX 200.

I installed new rear brake shoes recently. When I tried adjusting the brake, I found that if tightened to the point where the brake is just barely dragging, there is only a short amount of pedal travel before the pedal bottoms out on the foot peg mount. After a short time riding I would expect the rear brake to have little to no stopping power before the pedal bottoms out.

A riding friend suggested grinding the brake pedal where it meets the foot peg mount and grinding some metal off the foot peg mount to allow more pedal travel before it bottoms out.

The other option might be to bend the tab that determines the top of pedal travel, increase pedal height and gain some pedal travel that way.

Do all early kdx 200s have this characteristic? Are there better options?

Thank you,
Ben

BillyWillicker · Post by **BillyWillicker** » 06:12 am Jul 20 2016

There should be far more adjustment than you have used in that assembly. My 87 had the same rear when I got it and the adjustability was quite wide. Try putting the lever on the brake in a different spot on the cam spline.

travisb · Post by **travisb** » 06:36 am Jul 20 2016

I should have mentioned that I tried moving to a different spline position when I fitted the new shoes, since many threads were exposed rearward of the adjusting wing nut. But the rod holding lever only seemed to install at one spline position. It has to be something like that affecting it. I will give this another try.

Thank you

david · Post by **david** » 11:47 am Jul 20 2016

Doesn't really matter if a lot of threads are exposed on the back of the rod, unless you run out of room to tight down the wing nut. If you have no more adjustment of the wing nut left, then you may have a worn out brake drum or you need to move the lever on the rear hub back one or two splines.

Post by **KDXGarage** » 01:58 am Jul 21 2016

Did you center the drum within the hub with the ... pressing the pedal hard while spinning the wheel forward old method?

travisb · Post by **travisb** » 08:27 am Jul 21 2016

Jason wrote:Did you center the drum within the hub with the ... pressing the pedal hard while spinning the wheel forward old method?

I have not centered the hub, but I was able to advance the cam on the splined shaft. The pedal travel is marginally better, the pedal is somewhat higher, although I can still make it bottom out with my hand.

The threaded rod is now just threaded into the wing nut and not quite through it. Some brake wear should help that. Maybe the drum centering procedure will help matters, too.

Thank you,
Ben

david · Post by **david** » 11:28 am Jul 21 2016

Maybe you need to back off on the 'up travel' stop screw that is on the back side of the brake pedal, to allow the pedal to come up higher.

Are you sure you have the brake shoes on in the correct orientation? Maybe the bake cam is worn out. Something doesn't sound right.

travisb · Post by **travisb** » 05:05 pm Jul 21 2016

david wrote:Maybe you need to back off on the 'up travel' stop screw that is on the back side of the brake pedal, to allow the pedal to come up higher.

The 1984 model (or at least my 1984 bike) does not have this adjusting screw. The pedal height stop is not adjustable. There is simply a metal tab on the brake pedal that contacts the frame to determine pedal height. Perhaps the tab could be bent, but the pedal is quite high already, especially after advancing the rod holder on the splined shaft.

Are you sure you have the brake shoes on in the correct orientation? Maybe the bake cam is worn out. Something doesn't sound right.

Yes, I am certain of the shoe orientation. From what I recall, the shoes can only install one way...one end of the shoe has a semi circular female fitting, the other end has a flat fitting. The semi circular fitting mates with and pivots around a rivet on the brake backing plate, while the flat fitting rests on the cam which is rotated when the pedal is depressed to expand the shoes to contact the brake drum. The two shoes looked identical when I compared them (prior to installation) rather than a specific top/bottom location on the backing plate.

I suppose it is possible that the shoes do not actually fit the bike, but they seemed like a close match with the shoes I removed from the bike (maybe those shoes didn't fit either...the same symptoms were present when I bought the bike...in fact, grease on the shoe and drum surfaces rendered the rear brake completely ineffective). I can imagine if the semi circular fitting end is too short, then excessive pedal travel would be required to make the shoes expand to reach the drum surface. Or maybe the backing plate rivet is excessively worn. Or maybe the drum is worn beyond serviceability limits. I am still puzzled.

The braking rod is not perfectly straight. What effect would this have? Wouldn't some of the pedal travel be comsumed to straighten the rod?

Many thanks,
Ben

travisb · Post by **travisb** » 05:14 pm Jul 21 2016

I should point out that the rear brake does actually work now. The issue is that the pedal"free play" has to be zero so that the brake engages sufficently early in the pedal's travel range before the pedal bottoms out on the footpeg mount.

Ben

david · Post by **david** » 08:32 am Jul 22 2016

Worn cam or worn out brake drum. How about having a welder build up some material on the cam to give the shoes more travel when applied? Should only take about an 1/8". Like lay a bead on each end of the cam then grind smooth.

scriberman · Post by **scriberman** » 01:23 pm Jul 22 2016

I used to wrap some sheet metal around cam to get a bit more life out of the shoes. The rod not being straight will not help, it increases the pedal movement needed to work.

travisb · Post by **travisb** » 03:07 pm Jul 22 2016

Thank you...I will try one or both of these cam related suggestions.

Post by **KDXGarage** » 05:29 pm Jul 22 2016

It sounds like a good time to measure the internal ID of the drum.

KDX Geoff · Post by **KDX Geoff** » 03:49 am Jul 24 2016

I've never liked that little rear brake so l fitted a 250 one to my 200 which slots straight in but you need to use the axle spacer from the 250 because the bearings on that side are different between them.

travisb · Post by **travisb** » 01:49 am Jul 29 2016

Jason wrote:It sounds like a good time to measure the internal ID of the drum.

Jason,

Do you know the spec and tolerance on the drum diameter? I have a spare wheel, but would like to measure the old and new during the swap.

Thank you,
Ben

Post by **KDXGarage** » 09:54 am Jul 29 2016

Sorry, but I don't have my manual handy.

travisb · Post by **travisb** » 06:59 am Aug 17 2016

I bought a service manual that includes the drum inside diameter specs. Here they are for reference.

Front (1983-1985) standard: 120.00-120.16 mm; wear limit:120.75
Rear (all models): standard: 110.00-110.16 mm; wear limit: 110.75

Ben

travisb · Post by **travisb** » 08:25 pm Sep 16 2016

Thread update...the brake drum diameter measured within spec. The brake pedal is missing the height adjuster bolt (there is no hole for it in the pedal) and the tab was bent, perhaps intentionally by the previous owner, to lower pedal resting height. With the tab bent to raise the pedal, the range of brake adjustment and brake effectiveness were increased. Pedal height is a bit high, so this is not the right long term fix.

Thank you,
Ben

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