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Easy questions

  • Thread starter Thread starter mwa423
  • Start date Start date
M

mwa423

Guest
Hey everybody,

Searched the tech forum here and haven't been able to find answers, so I'll just ask straight out. The bike is an 81 gs650

Here are all my problems (I hope):

1. Front brake is all the way pushed into the master cylinder. The person I bought it from said that it happened when he bled it and didn't know why. Will I be able to just take the master cylinder off the handlebars, pop out the cylinder and reinstall it, new brake fluid etc? Or do I have to rebuild the master cylinder with one of the kits, or just replace the whole thing?

2. What would be the best way to waterproof a soldered connection? The previous owner installed a new cdi box and just covered the connections in electrical tape, I have a feeling that that won't cut it when it rains.

3. Is there a consensus on the right size for tires? I've seen 110/90 or 100/90 for front and anywhere from 120-130 for back. Is size really important as long as it fits on the wheel, because it seems people are going with pretty much any size!
 
1/ You can't buy new Suzuki front master cylinders for these bikes to my knowledge. I would suggest that there is a fault with the master cylinder and it has jamed or seized. May be why the PO got shot of the bike? It probably means a strip and repair kit or a replacement cylinder dependant on your budget.

2/ Heat syrink

3/ If you bike had 3.25 front then its 90/90 or 3.50 its 100/90. As for back most bikes were 4.50 which is 120 size I believe.

Suzuki mad
 
QUESTIONS are always easy. It's the answers that can get hard. 8-[
mwa423 said:
Hey everybody,

Searched the tech forum here and haven't been able to find answers, so I'll just ask straight out. The bike is an 81 gs650

Here are all my problems (I hope):

1. Front brake is all the way pushed into the master cylinder. The person I bought it from said that it happened when he bled it and didn't know why. Will I be able to just take the master cylinder off the handlebars, pop out the cylinder and reinstall it, new brake fluid etc? Or do I have to rebuild the master cylinder with one of the kits, or just replace the whole thing?

2. What would be the best way to waterproof a soldered connection? The previous owner installed a new cdi box and just covered the connections in electrical tape, I have a feeling that that won't cut it when it rains.

3. Is there a consensus on the right size for tires? I've seen 110/90 or 100/90 for front and anywhere from 120-130 for back. Is size really important as long as it fits on the wheel, because it seems people are going with pretty much any size!
Click to expand...

1). You might be able to get away with taking the master cylinder apart and cleaning it. There might be some gunk or surface corrosion there that is preventing proper operation. When you put it back together, ALWAYS use fresh fluid.

2) If the connections are already soldered, a couple of layers of tape should do fine. If it rains hard enough to get that area wet, you are going to have other problems, anyway. If the connections are not yet soldered, put a couple sections of heat-shrink tubing on before you solder the connection, then shrink-wrap it.

3) Based on your tire sizes, I am guessing that you have an L model? You probably will not be able to fit a 110 in the front. I have had problems with some 100s, and have had to get creative with the fender mounting hardware. Stock on the front of an L is 90. Installing a 100 tends to eliminate the speedometer error. Stock tire on the rear of an L is a 130. You might be able to fit a 140, but squeezing it onto the rim will change the profile of the tire and actually give you a smaller contact patch. In this case, it's better to stay with the stock size.


.
 
1. What position are the front brake PADS in? Are they pushed into the caliper, are they missing, or do they look normal?

2. You can seal things up with a tube of RTV (Room-Temperature Vulcanizing) compound; I always keep a tube of the blue stuff in my tool box...

3. Steve's advice hits the nail on the head; oversized tires distort the contact patch when you shoehorn them onto the (narrow) rim, and handling suffers. Your GS is a product of the narrow rim era of motorcycling, so choose your new tires accordingly...
 
Little addition to the waterproofing the wires situation:

Heat shrink tubing is always the best bet, but since the wires are already soldered, you'd have to cut and re-solder the wires to put heat shrink on the joints. Electrical tape will work, but don't buy the cheap junk. I only buy 3M tape, it works pretty good and lasts a while. For really long-term waterproofing, you can buy stuff called liquid electrical tape, it's a brush-on compound that will completely seal the connection and won't come off.

Or, to quote many, many people here, scrap the whole CDI system and throw a Dyna ignition in it. I don't have $140 burning a hole in my pocket so I haven't personally gone this route yet.

As far as the master cylinder goes, toss the factory one and get a newer one off of a Shadow or any metric with 7/8" handlebars, just make sure that the master cylinder came off of a bike with the same number of front discs. It'll work, I've got a Ninja master cylinder on my '81 GS750EX. Rebuild kits are easier to find, they look better, newer style switch, etc.
 
txironhead said:
For really long-term waterproofing, you can buy stuff called liquid electrical tape, it's a brush-on compound that will completely seal the connection and won't come off.
Click to expand...
I completely forgot about that stuff. :oops: That is probably your best bet.
I try to stay away from the silicone (RTV) and electrics combination.


.
 
Forgot about LET...

Forgot about LET...

RTV is fine when you use it on wires carrying tiny electrical signals, but NOT good for wires carrying high current (translation: don't try to use it to repair defective coil wires, you WON'T like the results)...

Now that txironhead has jogged my memory, I can also recommend liquid electrical tape (LET)... guess I had another "senior moment" in the earlier post; they're becoming more frequent with each passing year...
 
For the stuck brake, you might try removing the lever and pushing in on the piston in with a screwdriver. The same thing happened to me when I was bleeding the brakes and this worked to free it up. Worth a shot...

Edit:
Regarding tires. For my 650G model I went 100/90 in front and 120/80 in the rear. It was a PITA trying to find a 17 inch rear but I ended up finding the Avon Roadriders, which were relatively inexpensive.
 
Last edited:
If the master goes all the way and doesn't spring back then your cylinder is leaking. You probably need a new piston/cup set for the master. It's possible that something is wedged which won't require a new piston/cup but from my experience the reason it leaks is because the cup was forced in and tore against one of the vent holes. I would take it apart and inspect the cup from any damage.
 
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