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Discussion Starter #1 (Edited)
Hey guys,

Figured I'd post this as an FYI for anyone who might encounter such problem in the future. Longdistancerider (Jim) pointed me to the solution, so the credit goes to him. This definitely applies to the 400/450 series, but might apply to other bikes as well.

Problem description: Front brakes work, but after several applications/uses, they get tighter and tighter, until they bring your bike to a stop, and you won't be able to push it even an inch forward. If you're going at any significant speed, your brake pads might be smoking when the brakes seize up and force you to pull over. Cracking the bleed screw on the brake caliper resolves the problem only temporarily, and the brakes seize up after few more applications/uses all over again.

Resolution: There are 2 holes on top of your master cylinder, and they both need to be clean and clear. Most likely, the smaller hole is plugged, and you need to clean it out. The smaller hole is the one that allows for pressure to be released after you apply the brakes. Here's what I'm talking about:

1. Condition of my master cylinder prior to cleaning:
0_81d50_cf29f280_XXL.jpg

2. This is how it should be:
0_81d4f_409c40da_-2-XXL.jpg

*Even though these instructions do not cover replacing the piston inside of the master cylinder, it is strongly advisable to do so..

My steps (lengthy):
1. Remove the rear-view mirror
2. Remove the brake lever using a 10 mm socket or wrench on the bottom nut, and a flat screwdriver on the top screw.
3. Remove the brake switch from the underside of the master cylinder using a JIS screw-driver that came with your bike.
4. Crack the bleeder screw on the caliper, and drain the fluid through a tube into some container to dispose of properly
5. Cover up all painted areas (mainly gas tank) with some thick rags/tarp, whatever you have handy, to prevent accidentally spilled brake fluid from damaging your paint.
6. Once your master cylinder is more-or-less empty and the area is prepped, disconnect the banjo bolt (use 14 mm bolt) and the brake hose from the master cylinder. Wrap the hose end in some rags or a zip-lock bag, and secure it to some cables with a zip-tie.
7. Remove the cap from the brake fluid reservoir using JIS screw driver, and clean inside of the reservoir with a rag to remove any loose fluid.
8. Remove the master cylinder from the handlebars using 10 mm socket.
9. Remove the brake fluid reservoir from the master cylinder. It is attached to the master cylinder only by 2 JIS screws that we removed in step 7, and a rubber O-Ring. I used 2 flat screwdrivers to slide between the reservoir and the master cylinder, and pulling on both of them to lift up the reservoir and separate it from the master cylinder. This could also be done without removing the brake cylinder from the handlebar (which would eliminate steps 6 and 8), but it might also cause some spillage and might make it a bit harder to clean it. So I did it off the bike, it could be done either way. You might see something like photo #1 above.
10. Clean that area, reassemble in the reverse order. Fill up the reservoir with new brake fluid. Bleed the brake system really well.

Hope this helps. If you see anything that I missed, or that could be done better, let me know and I'll correct it.
It took me about 1.5 hours, but I was taking my sweet time. I'm sure you can do it a lot faster.
Good luck everyone, and happy riding!
 

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Discussion Starter #3
Jeebus.. that looks terrible. you didn't put a new piston in there after that?
No, but I drove it quite a bit today, and the brakes seem to work excellent.The fluid coming out was clean also.
 

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It's not that.. Z1E_0934.jpg see those two rubber bits.. they have been pushing through and against crunchy rust.. they are also as old as the master.. AND for the last little bit, they've been working doubletime to hold all that pressure when the thing was stuck.
Know what I mean?
 

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Im guessing this is my issue. Was driving to town this morning and it was getting tight, then my rear tire blew out (just put new tire and new tube on!) . Talk about crapping your pants.
 

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any suggestions on what to clean the master cylinder with? I was just gonna use a baking powder solution but don't know if there's anything more recommended
 

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Excellent thread, as my bike has this issue now, took apart master, cannot get small hole cleared, looks like previous owner jammed something in there in the past or used a dull drill bit and covered the orifice, how big is small hole? As I am forced to drill it through, or looking at new master. Thanks!
 

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That hole is quite small, maybe 1mm(.040"). People sometimes break something off in the hole while trying to clear it. I use a needle since it's sharp and not too brittle, drill bits are brittle and shatter
 

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This post helped me get my brakes back in order. I have a helpful hint for others that might try this.

The small hole that gets clogged is only 0.4mm across (very tiny). Mine was solidly clogged and caused brake issues.

I bought this set of inexpensive wire-gauge drill bits from Amazon for less than five bucks when I was working on my carbs.

https://www.amazon.com/gp/product/B000TY190C

The smallest drill in the set (#80) is just under the hole size at 0.38mm. You can carefully twist it with your fingers to work it through the blockage. A pin vice would help hold the tiny drill bit, but you don't need it. Don't bend or force the drill bit or it will snap. Just twist gently with your fingers and let the tool do the work.

This will clear the hole without enlarging it.

By the way, if you're looking for a high-quality set of wire-gauge drill bits, look elsewhere. These are great because of the price. However, it is not a complete set, and the measurements of some of the bits are substantially off of what they should be. For $5, I consider them disposable.
 

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What I discovered was;
#1, You don't clean the master cylinder with brake kleen as long as the. Cylinder Piston is in it. You will destroy the rubber pieces!
#2, You can use a piece of stranded wire - a single strand - in a drill and very effectively clean out the hole.
#3, Brake Kleen will damage the paint on the handle / grip...
#4, Rebuilding my Master Cylinder was the easiest, most tedious, most difficult (only in my mind) thing I have ever done!

Excellent Post, just about 3 weeks to late for me!
p.s. my time was just about 1.5 hours exactly (for me to rebuild mine!)
 

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Hey guys,

Figured I'd post this as an FYI for anyone who might encounter such problem in the future. Longdistancerider (Jim) pointed me to the solution, so the credit goes to him. This definitely applies to the 400/450 series, but might apply to other bikes as well.

Problem description: Front brakes work, but after several applications/uses, they get tighter and tighter, until they bring your bike to a stop, and you won't be able to push it even an inch forward. If you're going at any significant speed, your brake pads might be smoking when the brakes seize up and force you to pull over. Cracking the bleed screw on the brake caliper resolves the problem only temporarily, and the brakes seize up after few more applications/uses all over again.

Resolution: There are 2 holes on top of your master cylinder, and they both need to be clean and clear. Most likely, the smaller hole is plugged, and you need to clean it out. The smaller hole is the one that allows for pressure to be released after you apply the brakes. Here's what I'm talking about:

1. Condition of my master cylinder prior to cleaning:
View attachment 43022

2. This is how it should be:
View attachment 43023

*Even though these instructions do not cover replacing the piston inside of the master cylinder, it is strongly advisable to do so..

My steps (lengthy):
1. Remove the rear-view mirror
2. Remove the brake lever using a 10 mm socket or wrench on the bottom nut, and a flat screwdriver on the top screw.
3. Remove the brake switch from the underside of the master cylinder using a JIS screw-driver that came with your bike.
4. Crack the bleeder screw on the caliper, and drain the fluid through a tube into some container to dispose of properly
5. Cover up all painted areas (mainly gas tank) with some thick rags/tarp, whatever you have handy, to prevent accidentally spilled brake fluid from damaging your paint.
6. Once your master cylinder is more-or-less empty and the area is prepped, disconnect the banjo bolt (use 14 mm bolt) and the brake hose from the master cylinder. Wrap the hose end in some rags or a zip-lock bag, and secure it to some cables with a zip-tie.
7. Remove the cap from the brake fluid reservoir using JIS screw driver, and clean inside of the reservoir with a rag to remove any loose fluid.
8. Remove the master cylinder from the handlebars using 10 mm socket.
9. Remove the brake fluid reservoir from the master cylinder. It is attached to the master cylinder only by 2 JIS screws that we removed in step 7, and a rubber O-Ring. I used 2 flat screwdrivers to slide between the reservoir and the master cylinder, and pulling on both of them to lift up the reservoir and separate it from the master cylinder. This could also be done without removing the brake cylinder from the handlebar (which would eliminate steps 6 and 8), but it might also cause some spillage and might make it a bit harder to clean it. So I did it off the bike, it could be done either way. You might see something like photo #1 above.
10. Clean that area, reassemble in the reverse order. Fill up the reservoir with new brake fluid. Bleed the brake system really well.

Hope this helps. If you see anything that I missed, or that could be done better, let me know and I'll correct it.
It took me about 1.5 hours, but I was taking my sweet time. I'm sure you can do it a lot faster.
Good luck everyone, and happy riding!
Tyvm! This was my problem and I already did all these steps. My cylinder isnt clogged, the small hole doesnt even go through! I was afraid to punch through until I saw your 2nd pic. I worry mine is a different design piston that looks like a corkscrew 82 cm450
 

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Thanks for the write up SamRus. My front is tight but has never locked like that and I dont feel any grabbing, never noticed any heat but I will add the hole as a line to my maintenance routine.
 

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Thanks for the write up SamRus. My front is tight but has never locked like that and I dont feel any grabbing, never noticed any heat but I will add the hole as a line to my maintenance routine.
Harley151 ; this applies to the disc brakes, you have a drum brake on the T1. I suspect you need new brake linings and arcing the new ones to fit plus lubing the cable or replacing it.
This does apply to any other motorcycle with hydraulic brakes. My son's Buell had the problem recently.
 
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