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Thread: CBR TF125 Bucket Racer

  1. #16
    Join Date
    15th August 2011 - 12:25
    Bike
    CBR125TF
    Location
    New Plymouth
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    19
    I've been looking through Piston catalogues and it has occurred to me to ask myself why I'm trying to reinvent the wheel...

    Can anyone convince me why I shouldn't just get an oversized TS125 piston and bore the barrel to suit?
    (currently the piston to bore clearance is massive, hence my desire for new).

    Are the standard rings a bit heavy and flutter prone?
    If so, can I use a thinner ring? Is it an issue if the ring has a bit of extra clearance in the groove?

  2. #17
    Join Date
    25th March 2004 - 17:22
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    RZ496/Street 765RS/GasGas/ etc etc
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    They are a bit prone to cracking the skirt. Rings bit wide. I used an mx wiseco I think, but I cheated but changing the rod which gave me more options.
    Don't you look at my accountant.
    He's the only one I've got.

  3. #18
    Join Date
    18th May 2007 - 20:23
    Bike
    RG50 and 76 Suzuki GP125 Buckets
    Location
    Auckland
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    10,473
    Quote Originally Posted by anglia4 View Post
    Is it an issue if the ring has a bit of extra clearance in the groove?
    Yes, sure is. Instead of a bit of flutter the ring has enough room to get a good swing in and hammer the top of the ring land. Eventually breaking the ring and/or land and causing all sorts of destruction. When the ring lifts off the lower ring land the gas seal is broken and hot gases squirt down the side of the piston. Overheating the piston and charring the lubricating oil. More grief and destruction.

  4. #19
    Join Date
    12th February 2004 - 10:29
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    bucket FZR/MB100
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    Henderson, Waitakere
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    Quote Originally Posted by F5 Dave View Post
    . . . a "bit" prone to cracking the skirt. . . . .
    I radiused the edges and then polished them and they still cracked every meeting. Only a little at the first meeting but by the end of the 2nd the cracks were a problem.

    Standard TS pistons are garbage and have big thick rings.

  5. #20
    Join Date
    15th August 2011 - 12:25
    Bike
    CBR125TF
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    New Plymouth
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    19
    Thanks guys. Good info.

    I got my chamber about a 3rd of the way welded last night. Need to get some more argon as purging got through what was left in my bottle pretty quickly.


    I split the cases on one of my spare engines last night to figure out how it comes apart/goes together before I embark on modifying the crank in my "A" engine.
    Is there a way to get the clutch basket off as a whole assembly? Or do you need to pull all the pins/springs?
    Annoyingly the crank gear doesn't slide off past the clutch basket so I can't get the crank out without removing it.

    Its a little tempting to broach a keyway into the spacer behind the crank gear so that I can slide the crank out without removing the clutch when I put my good engine together. Especially if the balance factor takes a bit of trial and error.

  6. #21
    Join Date
    18th May 2007 - 20:23
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    RG50 and 76 Suzuki GP125 Buckets
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    Auckland
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    Quote Originally Posted by anglia4 View Post
    Is there a way to get the clutch basket off as a whole assembly? Or do you need to pull all the pins/springs?
    Annoyingly the crank gear doesn't slide off past the clutch basket so I can't get the crank out without removing it.
    You need to make some tools so life is a bit easier.

    Click image for larger version. 

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    Quote Originally Posted by F5 Dave View Post
    Enter new spring tool. Let's see if i can reattach this. Larf you might.

    https://www.kiwibiker.co.nz/forums/a...9&d=1580702734

  7. #22
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    15th August 2011 - 12:25
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    I did see that post on your thread... Its what I was hoping to avoid

  8. #23
    Join Date
    25th March 2004 - 17:22
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    RZ496/Street 765RS/GasGas/ etc etc
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    While it is apart you might preemptively beef up the clutch it takes little extra to overwhelm it. Check my Pete's TF post for ideas though I'm not sure if I explain that I hybrid a GP basket etc onto TF gear. Skimming the steel plates to fit a 2nd extra fibre is next step if stiffer spring doesn't work.
    Don't you look at my accountant.
    He's the only one I've got.

  9. #24
    Join Date
    15th August 2011 - 12:25
    Bike
    CBR125TF
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    New Plymouth
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    19
    I got lucky enough to be able to spend a whole night in the shed on Friday. So I kept welding until the pipe was finished...

    It was a massive effort. Severely underestimated.

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    It was race day on Sunday, so I took both pipes along to back-to-back test them. I knew vibration was still going to be a big issue so was gonna run each pipe in one session and then ride an FXR for the rest of the day.

    The new pipe was good, the power band is a little wider and smoother, from ~9000rpm to about 11,700rpm, and I can tell its got a wee bit more power because now I get it to top gear before the end of the straight.

    Unfortunately it only got about 3 laps into the test before I could hear it getting louder, and as I pulled into the pits it got VERY loud.

    Click image for larger version. 

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    The vibrations had made the bolts come loose in the past, so I had tie wired them (loctite and spring washers wasn't doing it). Being tie wired, rather than rattling out, they have vibrated and pulled and stripped all the threads out of the barrel

    Time to balance that crank!

    I'm happy that the pipe has made a gain though. Now I'm going to do the prescribed research about nozzles to increase the stinger size and deal with its length.

  10. #25
    Join Date
    25th March 2004 - 17:22
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    Ahh those threads have all been butchered by now. Careful aim and helicoil. The RG50 start as M6 so think yourself lucky.
    Don't you look at my accountant.
    He's the only one I've got.

  11. #26
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    15th August 2011 - 12:25
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    CBR125TF
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    New Plymouth
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    Pretty sure these are M6 also.

    I was going to drill and tap them out to M8.

  12. #27
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    25th March 2004 - 17:22
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    Hey good effort on the pipe. Well beyond my welding (lack of) skills.
    Don't you look at my accountant.
    He's the only one I've got.

  13. #28
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    15th August 2011 - 12:25
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    CBR125TF
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    New Plymouth
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    Thanks!

    I'm a desk engineer, so it was actually my first foray into SS welding. The last welds were much better looking than the first!

  14. #29
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    15th August 2011 - 12:25
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    CBR125TF
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    New Plymouth
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    19
    Alrighty...
    I’ve made a balancing jig ala 2-stroke stuffing.

    Click image for larger version. 

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    The TF crank however, is non symmetrical...
    Does anyone know how to measure the balance factor of a non-symmetrical crank?
    I’ve done a site google search of the ESE thread but haven’t managed to find what I’m after.

    Click image for larger version. 

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