Front Brake Diagnosis Help Requested

[JulianR]

Hello, Here is a problem I have not seen in over 38 motorcycles that I've owned in even more years. Any comments or ideas are appreciated.

PROBLEM: If I "very slowly" pull the front brake lever, it will travel with little resistance all the way to the grip.
If I pull the lever "normally" or fast, I have normal front brakes, I mean brakes with great (normal) stopping power and a hard firm lever with minimal travel.
Now thats wierd, right?? Prior to this starting yesterday, the front brakes have always performed well.

Any Ideas or thoughts on how this can occur are appreciated. Perhaps someone has experienced this??
As a solution, I have a new complete MC ordered. ( how is it that rebuild kits cost more that the entire - aftermarket- assembly

BTW, the bike is a 79 GL1000. , All Brake hardware components seem stock and original, good pads, no fluid leaks.

I'm just at a loss to explain how the speed of the movement of the lever can cause brake failure.

[Rambozo]

That is a common problem in many hydraulic systems from hardened seals. In this case the piston cup seal in the master cylinder. Under low pressure, fluid will leak around the seal. However, with high pressure the cup is forced out to the cylinder walls and seals up. By moving the lever fast you build enough pressure to get a seal before you run out of travel.

BTW you might want to rebuild the original cylinder, anyway. Most cheap aftermarket parts are junk. You get what you pay for.

[JulianR]

Rambozo, Thanks for the prompt reply.
Your explanation makes good sense, and after reading it
I've decided now to get an OEM Honda rebuild kit.
I like keeping things original.
I'll keep and use the aftermarket
master cylinder already on its way for freeing up stuck brake
caliper pistons. Now that's a problem I've experienced often.
Regards,
JulianR.

[WingAdmin]

Also agree. As soon as I started reading that, I thought "master cylinder rebuild." It CAN be caused by a scored cylinder, but 99.9% of the time it's just an old, leaky cup seal on the piston.

[Burkie33]

Hi JulianR just a point of info that may help with your rebuild. I had stuck calliper pistons in my GL1500 front brakes and racked my brain for a solution that wouldn’t wreck the piston. Finally after trawling YouTube I found a video of a bare footed mechanic somewhere in Asia freeing a piston. He had a large Allen key/wrench that he put inside the piston, then slotted a socket into the piston that jammed the Allen key in the piston, he gently moved the key in both directions and freed the piston……and that’s exactly what I did ……… good luck and safe riding…Burkie33

[Nigel Bruce]

The master cylinder makes absolute sense. I had similar problem on my 1983 Aspencade. Bought one on EBay supposedly for my bike and when it arrived, I found that the outlet was on the RH side of the cylinder, and mine is at the end. Apart from listing it as fitting my bike, seller described it as "outlet facing front wheel". Tried to dispute this and was told they sold 100's and they weren't wrong or responsible.
I won't post their name but if anyone wants to follow up with me, feel free. I'm pretty pissed, $50 down the drain.
nigelthebruce@telus.net.

[WingAdmin]

The master cylinder makes absolute sense. I had similar problem on my 1983 Aspencade. Bought one on EBay supposedly for my bike and when it arrived, I found that the outlet was on the RH side of the cylinder, and mine is at the end. Apart from listing it as fitting my bike, seller described it as "outlet facing front wheel". Tried to dispute this and was told they sold 100's and they weren't wrong or responsible.
I won't post their name but if anyone wants to follow up with me, feel free. I'm pretty pissed, $50 down the drain.
nigelthebruce@telus.net.

hmm, that sounds like the selling tactics and customer service of our old friends at Saber Cycle.

[Techdude2000]

The master cylinder makes absolute sense. I had similar problem on my 1983 Aspencade. Bought one on EBay supposedly for my bike and when it arrived, I found that the outlet was on the RH side of the cylinder, and mine is at the end. Apart from listing it as fitting my bike, seller described it as "outlet facing front wheel". Tried to dispute this and was told they sold 100's and they weren't wrong or responsible.
I won't post their name but if anyone wants to follow up with me, feel free. I'm pretty pissed, $50 down the drain.
nigelthebruce@telus.net.

I never buy anything on eBay unless they have pictures and are selling what they are showing. Lots of hacks out there.

[Nigel Bruce]

The photo they supplied was not definitive, and since the description provided looked correct I went ahead and bought it. How many Aspencades have the outlet on the master cylinder on the side and not at the end? Is mine an odd-ball?

[Techdude2000]

The photo they supplied was not definitive, and since the description provided looked correct I went ahead and bought it. How many Aspencades have the outlet on the master cylinder on the side and not at the end? Is mine an odd-ball?

No, if you look up the MC on Honda’s parts diagram, you can clearly see the port at the end. They still sell a new plunger set for $36 on Mrcycles.com A new plunger with all new seals may be all you need.

[Nigel Bruce]

Thanks for confirming that. Will help me in making my complaint to EBay!

[rockford75]

Bleed the Brakes first and see what you end up with? If still no Good. rebuild the front Master Cylinder. I recommend BrakeCrafters for all your Brake needs on your Bike.

[Nigel Bruce]

Yes thanks tried that a few times with same result, was why I posted some time ago that I thought Aspencade brakes were feeble for the size of the bike. I'm leery about a rebuild kit since I'm not so sure of the original master cylinder's bore.
I appreciate all the replies, I'll get 'er fixed come hell or high water!

[WingAdmin]

Yes thanks tried that a few times with same result, was why I posted some time ago that I thought Aspencade brakes were feeble for the size of the bike. I'm leery about a rebuild kit since I'm not so sure of the original master cylinder's bore.
I appreciate all the replies, I'll get 'er fixed come hell or high water!

I was always unsatisfied with my 1100 Aspencade brakes...until I replaced my original rubber brake lines with braided stainless lines. Absolutely the best upgrade I did to that bike, it transformed it: the brakes went from vague and spongy to powerful and razor sharp. I'd highly recommend it.

[Nigel Bruce]

I've heard nothing but good results by swapping to braided steel lines, makes you wonder why they don't use them as o.e.
Thanks, I will consider that.