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Discussion Starter · #1 ·
As some of you are aware,over the past few months in my spare time i have been engineering a hydraulic clutch conversion for the Aprilia Rs 125.Finally,here is the proof of concept.This thread will be a long read with plenty of photos.

I have made this for my own machine.It would not be practical to make this for anyone else,because of the time put into this.It would cost in materials and labour atleast £500 minimum.Therefore this is a one off.I have never seen another Rs 125 with a hydraulic clutch conversion.So maybe this is a first.Hope you enjoy the read.

Danny


So having a spare motor kicking about (Thanks to LTR250).I decided to set to the task in hand.

First off,was to strip the clutch cover of plugs and the clutch cam mechanism.

I set up the sand blasting gear outside (this was done last year in decent weather).



On a low regulated pressure i cleaned up the clutch cover.(Later date it will be degreased and laquered).



So where the original clutch cable located in the case,i needed to blank this off,by making a plug.So i tapped out to m8.



I cut down an allen cap m8 bolt.



I then screwed this into the hole (loctited)



Bolt fully home,and sealed from the weather.



Next was to cut some 3 inch billet for the slave cylinder boss.Bandsaw



So now the billet was ready for some lathe work.I needed to turn it down and machine a thread to fit where the old clutch adjustment screw on the clutch cover would normally have located.





Using an o'ring the boss then threaded into the centre on the clutch cover.



Inside the clutch cover.



Next,i had to position the slave cylinder into the billet,drill and tap the holes to fasten the slave cylinder.





Now i set up the billet in the rotary table on the milling machine to shape the billet,kind of losing excess material.Using a slitting saw.



After an hour with various files and grades of paper,i finished the billet with a high polished surface.





Now screwed into the clutch cover.



Brembo slave cylinder bolted on.





I stripped the bottom end down completely,then fitted the cases back together with just the input shaft and clutch.Then bolted it to my engine stand.



Fitted the clutch cover back on.



At this point i needed to measure up for the clutch push rod.So after drawing up the clutch push rod,i then started machining in the lathe.I'm using Silver steel for the push rod as i can harden and temper this quite easy.The push rod itself is 70mm in length,8.8mm in width,with a bull nose at one end and a dish at the other (to locate on the clutch pressure plate ball bearing).





push rod finished.



So i then fitted the push rod and put the slave cylinder together.



Fitted the braided line.







I then fitted the Brembo master cylinder to the engine stand (for testing/bleeding purposes)



I then bled the clutch.







All finished.Works very well.Light pull on the clutch lever,which is adjustable.

This conversion will be going on my new 169.6cc engine build.

I shall be starting the build in the next few weeks.So another thread will be made.watch this space.

Hope you enjoyed this thread as much as i enjoyed making this
 

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Nice machining work there


This is not a negative, but what is the the advantage of this over the cable set up ?

Or is this just something you wanted to do
 

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Discussion Starter · #7 ·
Nice machining work there


This is not a negative, but what is the the advantage of this over the cable set up ?

Or is this just something you wanted to do
Thanks paul.The main reason for me doing this,is because i have not seen another rs 125 with this conversion.This setup will be going on my new engine build.

Advantages of the hydraulic clutch over the regular cable clutch.

1/ No replacement of worn clutch cables or the chance of a cable snapping whilst out on the bike.

2/ hydraulic clutches never need adjusting.Low maintenance.Just fluid change every 6-12 months.

3/ The actual feel of the clutch is lighter.ie the lever pulls more smoothly/lighter than a cable clutch.

4/ As i'm building a 170cc rs motor,i want to upgrade the clutch plates and fit hd springs,still enabling me to have a light pull on the clutch lever.

Will be intouch with you soon paul,Will need some bits and pieces for this motor.
 

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Thanks paul.The main reason for me doing this,is because i have not seen another rs 125 with this conversion.This setup will be going on my new engine build.

Advantages of the hydraulic clutch over the regular cable clutch.

1/ No replacement of worn clutch cables or the chance of a cable snapping whilst out on the bike.

2/ hydraulic clutches never need adjusting.Low maintenance.Just fluid change every 6-12 months.

3/ The actual feel of the clutch is lighter.ie the lever pulls more smoothly/lighter than a cable clutch.

4/ As i'm building a 170cc rs motor,i want to upgrade the clutch plates and fit hd springs,still enabling me to have a light pull on the clutch lever.

Will be intouch with you soon paul,Will need some bits and pieces for this motor.
Mint


Look forward to seeing how you are going to "swing" a bigger stroke in the crank cases
not much room you know
 

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Discussion Starter · #10 ·
Mint


Look forward to seeing how you are going to "swing" a bigger stroke in the crank cases
not much room you know
Well with the motor in above pics (empty cases) ive done alot of measuring and working out.I can make an offset crank pin and heat treat it.Giving me a stroke of 60mm.This is an extra 2.75mm at tdc and 2.75mm at bdc (which clears the cases) and allowing for expansion.Also machining my cylinder and plating for a 60mm piston.Giving me a square motor.I also need to adjust the ports aswell and machine a billet cylinder base gasket/packer.Also will be machining my own billet cylinder head.

Theres quite a few other bits involved too,but i'm very confident i can get it all to work.Its going to take me a few months to sort it.

Someone else on here has stroked a rs125 crank,but not sure how much.
 

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Well with the motor in above pics (empty cases) ive done alot of measuring and working out.I can make an offset crank pin and heat treat it.Giving me a stroke of 60mm.This is an extra 2.75mm at tdc and 2.75mm at bdc (which clears the cases) and allowing for expansion.Also machining my cylinder and plating for a 60mm piston.Giving me a square motor.I also need to adjust the ports aswell and machine a billet cylinder base gasket/packer.Also will be machining my own billet cylinder head.

Theres quite a few other bits involved too,but i'm very confident i can get it all to work.Its going to take me a few months to sort it.

Someone else on here has stroked a rs125 crank,but not sure how much.
excellent thread and excellent work +1 mate

i have a question with regards to the 60 mm bore job you mentioned

how do you plan to over come the problem of the stud spaceing with the thin bore wall

i know from past experiance that 58 and 60 mm bore jobs fry the oring in the cylinder head

pollini over come this by adjusting the spaceing on there 60 mm kits

 

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Discussion Starter · #14 ·
excellent thread and ecellent work +1 mate

i have a question with regards to the 60 mm bore job you mentioned

how do you plan to over come the problem of the stud spaceing with the thin bore wall

i know from past experiance that 58 and 60 mm bore jobs fry the oring in the cylinder head

pollini over come this by adjusting the spaceing on there 60 mm kits

I shall machine out the steel liner,and plate the aluminium,then regrind to fit the 60mm piston.Ali weld the o'ring groove on top of the barrel,then skim the surface in the miller.cut out a new copper gasket.(may do a few gaskets) just for the future.I'll also machine a new head out of billet.

Obviously as i'm doing this project,things change.I may find some things wont work.But there is always a solution to a problem.Whatever happens,i'm confident of making a reliable motor with bigger cc's.
 

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I shall machine out the steel liner,and plate the aluminium,then regrind to fit the 60mm piston.Ali weld the o'ring groove on top of the barrel,then skim the surface in the miller.cut out a new copper gasket.(may do a few gaskets) just for the future.I'll also machine a new head out of billet.

Obviously as i'm doing this project,things change.I may find some things wont work.But there is always a solution to a problem.Whatever happens,i'm confident of making a reliable motor with bigger cc's.
nice attitude


look forward to seeing it come together mate
 

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Also Pego,do you know of any 60mm pistons that havn't been ported like polini's??To fit the rotax 122 motor.

Could do with a diagram of a standard piston with all the measurements.
unsure on 60 mm

i know wiseco do a 58 mm

best of asking paul see if he can source one for you


should get some awesome torque from this motor
 

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unsure on 60 mm

i know wiseco do a 58 mm

best of asking paul see if he can source one for you


should get some awesome torque from this motor
I may be able to fit a different piston from another machine,aslong as the gudgeon pin dia,pin to crown height are the same.If the skirt is longer,i can just shorten it.

Think paul's the guy to speak to.He isnt far away from me either.So i could just pop into his workshop.

If i used a 58mm wiseco and 58mm stroke.id get 153cc..Need bigger
 
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