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Wufdog

Sy250 hydraulic conversion to cable?

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Hi all. Picked up a 2004 sy250 with a bad slave cylinder I think. Took it with a rebuild kit to my neighborhood Yamaha fixer and he’s stumped. So I’ve searched around the globe looking for a new slave cylinder but have been told it’s probably not gonna happen. So now I’m trying to figure out how to convert to a cable.  I don’t expect to be in any competition I just want to mess around and learn some of the basics.  

 

My other thought is that the actuator and push push rods may be worn a bit as there is a bit of play in the actuator arm and I have nothing to compare to so maybe I’m just a bit confused. 

 

If if anyone has changed to cable maybe some tips for what I need to make (mod) and what cable to use as I’m used to bicycle cables being cut to size not coming at the correct size. 

 

Thanks in advance. 

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The problem with these old things is the actuator arm bends out of shape and no amount of adjustment helps.

Back in the day we used to reinforce the arm, someone out there might have a photo.

The slave cyl is pretty basic and a standard kit should be an easy fit.

Never heard of anyone converting one to a cable though I can't see it being a big deal.

Maybe google an image to see how the set up should look.

All the best. 

 

 

 

 

 

 

 

 

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The original actuating was cable when that motor was fitted to the YAMAHA TYZ. (part # 4GG-16380-00)

The part was modified at Scorpa to make it work with the Hydraulic slave cylinder.

The Cable attachment was removed from the end and a cylinder with a threaded centre was welded on the end. (it then became Scorpa part 3150)

As Breagh states they were never that strong and the end often got damaged, cracked or broke off. The original Yamaha part is still available, so I would think the best solution is to re-kit your existing Slave cylinder (it uses the same DOT4 9.5mm piston and seals as lots of other AJP Brake Master Cylinders - it just uses a shorter spring, which you can use from the original cylinder), and weld a new adjuster threaded piece to the end like Scorpa originally did. 

If you go cable you would need the Yamaha actuating arm anyway, but you would also require the cable and a new lever and perch, so a result that is not as nice as the original.

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Thanks. The info I’m being given is starting to clear things up.  Going to go pick the bike up in whatever state it’s in now next weekend and see what I can figure out.  

 

How much force does does it take to move the push rod with the actuator?  Could I move the arm with my fingers?  Or maybe a tool?   Mechanic doesn’t think anything is wrong inside.  I’d just like to feel the springs doing they’re job before opening it up. 

I ask this because there seemed to be a bit of play which may be normal but I’m no expert.  And if the arm has bent over time as suggested it may be the reason. 

 

Ill see if I can update the issues some time in the next week or so. And post pics if that’s helpful. 

 

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2 hours ago, Wufdog said:

Thanks. The info I’m being given is starting to clear things up.  Going to go pick the bike up in whatever state it’s in now next weekend and see what I can figure out.  

 

How much force does does it take to move the push rod with the actuator?  Could I move the arm with my fingers?  Or maybe a tool?   Mechanic doesn’t think anything is wrong inside.  I’d just like to feel the springs doing they’re job before opening it up. 

I ask this because there seemed to be a bit of play which may be normal but I’m no expert.  And if the arm has bent over time as suggested it may be the reason. 

 

Ill see if I can update the issues some time in the next week or so. And post pics if that’s helpful. 

 

Yes you can normally operate a clutch actuation arm like the one on your bike with a suitable tool to increase the leverage but you might have to make something due to the space being a bit tight on that motor. I have previously operated a clutch arm on other bikes using an 12" shifting spanner to provide the leverage.

It's a very common thing on those motors to bend and sometimes crack that arm next to the weld

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Before taking the time, effort, and money to redesign it, I must ask, is the clutch system properly bled.

This system is a closed dead end with no bleeder.  To get it bled, you must ensure the adjuster on the lever is not depressing the piston where the fill hole is covered / blocked.  

When I bled mine from having no fluid, I followed Ryan Young's tip and moved the slave / arm adjuster jamb nut to the inside of the actuating arm.  Doing this made it less likely to bottom the slave piston against the snap ring causing damage or no clutch release.  Ultimately, The adjuster is proud of flush about 1/2 turn of a thread.

As for bleeding,  it takes patience and time.  You must push the actuator arm to compress the slave piston into the bore.  Then slowly pump the lever as you slowly release the slave piston.  It take a bit, but the system will fill, and you can see air being expelled into the reservoir.

Once you begin to get clutch action, continue a bit more bleeds.  Once confident in the bleed, make the adjustment on the lever, but ensure the plunger on the lever has a couple mm freeplay before depressing the piston in the master cylinder.

I considered converting to cable also, but stuck with hydraulic.  Actually the action is pretty good and the clutch is controlled and predictable.

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Huge thank you to everyone that’s helped.  

As of an hour ago. I took my maiden ride on a fully functional clutch.  Mechanic I guess tried to help. Told me what problems he had with it. 

I told them to stop working on it after 3 hours Labour. It was just the slave rebuild after all. Got the bike back basically in a box.  So now I know how to put it together. And what not to do. 

 

Banjo bolt out of the slave wasn’t terribly tight so leak out the back.  Quick bit of tinkering and re assemble all the exhaust and stuff and she worked great. I believe the actuator screw part broke at some point and it he pin isn’t aligned perfect but it works for now. 

 

My my wife is pretty happy too. We met thru bikes and had to give it up for a while.  She said. Finally something not useless. Lol. 

 

Thanks again all. And I’m going to start practicing as soon as I can. 

 

 

Edited by Wufdog
Incorrect post. I’m new. Posted my thanks for the help now.

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The actuator arm, there is a spring inside the slave cylinder that assures no freeplay between the slave piston and the adjuster pin / arm.

Installing the jamb nut to the inside allows the adjuster to be into the slave slightly further, but do not overdo this adjustment as you may find the adjuster pin will scrape the snap ring.  Worse still is fully extending the slave piston into the snap ring under hydraulic pressure.

Realize too, the slave cylinder is secured via one bolt.  This allows during assembly to obtain the best alignment of the actuator arm pin into the slave pistons cup.

It all sounds complicated, but is not bad if you take your time getting a good bleed and best alignment when setting it up.

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The mechanic has the bike until the weekend. I’m surprised he can’t figure it out. But I’ll give this a try.  To his credit he’s never seen a trials bike nor this type of hydraulic clutch nonsense  :)  

Does your actuator arm have a bunch of play to it?  I thought it may have been more serious and tried to see if the clutch springs would prove to feel normal but it felt like I may bugger something up using a screwdriver as a lever against the case so I stopped.    I’ll see when I get it back if it’s not gonna work out. I’m wondering if it’s bent or stretched but not to the naked eye?  And could I compensate with a home made remedy like a longer screw as the adjustable push thing on the actuator arm.  

Ill update when it’s home again and I have time to try to sort it out. He said he can’t keep pressure in the line and the pin thing goes crooked when he gets it to push the actuator arm. I’m guessing I can tinker as I now have an idea as to how it’s supposed to work. 

 

Thank you so much for responding.  Everyone is so helpful.  I’m 41 moved from a big city for a better life so now I can try to do a sport I could not afford when I was 20. I have the space now and feel like I bought a nightmare. Only 500$ but it’s still annoying with no clutch.  

With the info I have now I should be able to get it going. As long as the internals are ok.  Mechanic seems to think it’s all fine with exception of the clutch nonsense.  

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So I think my slave cylinder is toast. Had the clutch working for 2 short runs and then fluid started p****** out the front.  And now I have decided to go cable. The scorpa actuator has been repaired and not at the correct angle either. Can’t keep throwing money at rebuild kits so I’m going to try to get a cable going which should be a slow process and lots of messing about with the shape of the exhaust. 

 

Thanks for everyones help. Now I just need to figure out the cable I will need for this thing.  

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Please share photos of how you get tne cable setup to work.

I had considered similar and studied the TYZ setup, knowing it would plug and play.  Downside was tne clearance from the Scorpas exhaust.

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Well I’ve ordered the parts.  I have no idea what I’m doing but I have a neighbor who can weld aluminum so I’m thinking of cutting out a section of the mid muffler and welding it back up so the actuator can move under it and not have an issue. All I can do as the slave cylinder is garbage and not able to get a new one. I’ll post whenever I get it going.  This is my first trials bike and so far a bit of a nightmare but I’m determined to ride it. And hopefully get a bunch of years out of it. And if this works maybe help others in the same situation.  

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Has anyone changed or replaced the actuator arm on a sy250?  Just tore it down and it looks like a full engine open is necessary.  This may be above my skill level. In theory my conversion to cable will work I just don’t know how to get the old actuator arm out and replace it with the cable version I bought. 

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On 8/25/2019 at 3:04 PM, Wufdog said:

Has anyone changed or replaced the actuator arm on a sy250?  Just tore it down and it looks like a full engine open is necessary.  This may be above my skill level. In theory my conversion to cable will work I just don’t know how to get the old actuator arm out and replace it with the cable version I bought. 

Have not had my Scorpa engine apart, but typically you remove the clutch pressure plate, slide the pushrod in, then remove the actuator arm assembly.

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