'75 GT250 DOT5 fluid mistake...ugh

[MarkH]

Hi guys,

I restored my GT250 5 years ago. Given it was my first restore...I made the mistake of using DOT5 silicon brake fluid. (I rebuilt the master cylinder and caliber at the time). Since then, the front brake lever has always been a bit slow to return after squeezing it.

Today I decided to attempt to rectify the mistake (I had read up on how silicon brake fluid can cause swelling of these older rubber seals).

Please note...I did not replace the original DOT3 brake hose at the time of restore.

At any rate, I started to purge the DOT5 using the bleeder screw (much like you'd do when bleeding the brakes). I opened the bleeder, squeezed the brake, tightened the bleeder, released the brake lever, and it didn't return (the lever just sat at the handlebar grip).

So after sucking out the DOT5 from the reservoir, I removed the banjo bolt at the master cylinder and inserted a small screwdriver to manually push the piston back in the MC.

In an attempt to free it, I used brake cleaner, marval mystery oil, WD-40, etc. Each time I'd squeeze the brake lever, then push it back with a screwdriver.

Nothing has helped. So from what I can see, it's either swelled seals in the MC, or the original brake hose had some DOT3 embedded caused a slurry of goop in the MC. I'm planning to dissemble the MC tomorrow. It really feels like the seals are swelled at this time.

I'm wondering if there are any resources where I can purchase new MC seals? I'm also a bit concerned about the caliper seals (but the caliper is currently out of the equation with this post...plus I've haven't felt any dragging - so that might be okay).

Thanks all!
Mark

[jabcb]

Caliper & master cylinder rebuild kits are still available from Suzuki. There probably are aftermarket rebuild kits for less $$$ — your local Suzuki dealer should be able to look that up for you.

The brake lines are NLA. Now would be a good time to upgrade to stainless steel brake lines.
A local shop can make new SS lines if you give them your old lines.

HEL sells a SS kit for your bike: https://usa.helperformance.com/motorcyc ... _model=168
Spiegler sells custom SS brake lines: https://spieglerusa.com/brakes/brake-li ... lines.html

[MarkH]

I got the MC apart. Issue was one of the seals had a chunk of rubber out of it and was interfering with the piston action. I'm thinking that might've happened when I assembled the MC. Otherwise, the rubber looks pretty healthy.

I ordered a new kit.

Of course parts flew from the MC when I pushed it out. Grr.

Can anyone confirm that this is how the kit should be assembled (once I get the parts). I've laid out how I "think" it should go back together...the part that's a bit confusing is the seal next to the spring. Should that be turned 180 degrees?

Photos:

[MarkH]

Here's the seal switched around. This way seems to make better sense.

[Evans Ward]

Your first set of pics have the correct orientation except the circlips goes under the dust boot. You should also have a spring that holds and seats the dust cover too- most likely that was went flying away during disassembly. The seal for the spring is for the spring end to sit it- some kits have a male nub built in to that seal that fits into the female spring seat. I’ve found it easiest to seat that seal at spring end by using my pinkie finger when pushing it into the bore gently. Your bore piston pusher butts up against the flat end of that seal. If you don’t have the correct internal circlips pliers, reassembly of that circlips will be almost impossible.

[Evans Ward]

1st pic 100% correct! And I see the dust cover spring too!

[MarkH]

Thanks Evans Ward! I did confirm that the top portion was assembled correctly as I removed the dust cover...thanks for reinforcing that.

Now that you mention it, my original replacement kit actually had that male nub on the spring seal...the reason I know that is because it was the rubber piece floating around the assembly. It had broken off (it's shaped like a cone). And, your description is rattling my ole brain into recalling this MC - thanks.

So something went wrong during assembly...unless it happened when I was manually pushing the piston around. Because I do have a chunk out of that spring seal too (not visible in the photos above). Oh well.

I really appreciate your tip on using a pinky finger to push that seal into place...because that's the next thing I was thinking of...how to get that in there without it rolling over on itself.

Looks like I'll get the kit Saturday. I'm gonna try DOT4 to flush the caliber out using the rebuilt MC. I can't imagine any more harm will come from trying.

[Evans Ward]

I’ll tell you too I really love reverse bleeding! You can get a animal syringe cheaply and fab something up or buy a nice deluxe kit like I did off Amazon. Great for cars too.

[MarkH]

Thanks,

I think I came across a post of yours about reverse bleeding. I have access to syringes so I think I'll give that a go for the caliper and brake line to flush the DOT5 with DOT4. Then hook it all up and do a normal bleed with DOT 4 with the MC connected. I just don't want to introduce DOT5 to my rebuilt MC.

I could be wrong (50/50 chance), it seemed like the DOT5 floated on top of the DOT4. I could definitely tell the DOT4 and DOT5 didn't mix when I was mucking around with the MC. I think a reverse bleed would be beneficial in that case. I'll need to look that up...else do an experiment.

Again, thanks for your assistance!

[Evans Ward]

I personally use DOT5 in all my bikes but they all have aftermarket braided stainless lines. No issues and no worries about spillage ruining nice paint.

[MarkH]

Interesting.

So, here's my experience. I found after my complete rebuild of my front brakes, the MC was always slow to recover...that is, the brake lever was slow to return to completely off.

However, that could've been from a poorly installed spring seal (given it has a small chunk out of it after removal). And I'm guessing that male nipple that broke off was blocking the return fluid.

5 years ago, I mentioned I had put DOT5 into my restore (to my neighbor, a guy with 35 yrs of master mechanic experience...he's a legit rockstar mechanic). Without prompting him, he said that DOT5 will be slow to recover the brake lever. That's exactly what has happened.

I guess I have a few days to consider what to do.

Evans Ward, thank you for your input, it's appreciated (especially since you own 3 of the most sought over two-stroke road bikes in history). ~smile~

Mark

[Evans Ward]

Thank you MarkH- I do love those three 2 stroke bikes and it’s hard choosing which one to take out and ride so I have to rotate and share the love.

I have never experienced a slow to return lever with DOT5 fluid after using it exclusively in all my bikes for 10 plus years.

[MarkH]

Good to know regarding your brake lever return. Mine was slow to return...but again, I might've screwed up the reassembly (I might've pinched something, etc). All I know is the rubber male nipple was floating around and the spring-side seal was missing a chunk. Grrr.

I'm very tempted to try the DOT5 again...as the caliper is just fine (it doesn't drag at all). I'd rather keep the same DOT5 in the system and give it another go.

You do kinda suck for having the three bikes I'd love to have. LOL!

My 74 H2, although I love it, is kinda the red-headed step-child of the H2 lineage. But, at least it's Kawasaki green. ~smile~

I'll follow up once the MC is rebuilt.

Thanks for your help!