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Project 72 Honda SL125

Discussion in 'Other Projects - Other Bikes (non 250's)' started by Andych, Jun 28, 2020.

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  1. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    My Bike:
    1987 Yamaha SRX250, Honda 1974 SL125 K1, 2022 Triumph Tiger Sport 660
    So head is now off... I will leave it as is until I get the barrel back from boring.
    The info from the seller of the 61mm piston is as follows.
    "Yes we have done these since 2005 and Sammy miller before us
    The 122 cylinder measures between 62.30 and 62.50 outer dia of liner they vary.
    You bore the cylinder to 61mm the 60,97 mm piston giving you 0.03 clearance
    Bobs ya uncle
    Very thin liner/spigot on bottom but always been that way no hassle"
    I will have a chat with the machine shop tomorrow and see how we go. I am expecting them to say all care, no responsibility...lol

    I also finally connected up the rear brake etc (finally) and also sorted my new (incorrect) side stand.
    The spring mount was on the outside of the side stand... so had to cut it off and weld it back on the other side. I really need to buy a better welding helmet... I could barely see a thing doing it today.
    IMG_7284.jpeg

    IMG_7283.jpeg

    IMG_7286.jpeg
     
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    Andych, Jul 10, 2023
    #101
  2. Allan

    Allan Well-Known Member

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    Can you get hold of a sleeve from a CB77?
    That was how I avoided the problem that has you slightly concerned.
    If memory serves me correctly, the CB77 was 60mm bore and the 750 piston (close to the size of the one you are using) was 61mm, so the sleeve itself only needed 0.5mm bored out.
     
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    Allan, Jul 10, 2023
    #102
  3. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    They seem to be available from the US of A. I cant get down the the machinist until tomorrow now so I will see what they say.
    I guess the cases would then need to be opened up to accept the slightly larger diameter sleeve as well... if I go that route.
     
    Andych, Jul 10, 2023
    #103
  4. Allan

    Allan Well-Known Member

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    I don't remember having to relieve the crankcase to allow the sleeve to fit but it was a long time ago. About the same year your SL125 was built.
     
    Allan, Jul 10, 2023
    #104
  5. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    My Bike:
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    Barrel dropped down to the Reco shop. The machinist had a look and discussed it with me and he is fine boring it as long as I am :) Doh.....
    I just need to drop the piston down there tomorrow and he will bore it and then hone it to .03mm over the piston size.
    The standard piston to bore clearance would be .01mm to .05mm so somewhere in the middle should be about right.
     
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    Andych, Jul 11, 2023
    #105
  6. Gen

    Gen Well-Known Member

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    I had a norton 650 barrel resleeved & bored at the local Repco shop, in 1970,,they buggered it by boring one pot off center (heaps) I hope you have better luck Andy
     
    Gen, Jul 11, 2023
    #106
  7. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    These guys have a pretty good reputation so here's hoping... at least Honda SL125 barrels are not as expensive to replace as a Norton 650 barrel. Mind you they are difficult to find.. none in Aus but there are a few in the US. I looked for one as my old one has a small piece of a top fin missing... no big deal though, not worth spend a few hundred $$ on.
     
    Andych, Jul 11, 2023
    #107
  8. Gen

    Gen Well-Known Member

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    My Bike:
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    I might have an XL 125 barrel "in stock" along with a box of used pistons ?
    Most of my **** is XL/CB 100 (smaller little end eye, although, it is possible to open the eye up with a couple of diamond burrs to allow 185/200 top ends to be used (same barrel stud pattern)
     
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    Gen, Jul 12, 2023
    #108
  9. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    I should be OK, the one I have is pretty good in general so as long as they dont kill it when machining it all should be good.
     
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    Andych, Jul 12, 2023
    #109
  10. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    Well maybe my optimism with this engine reco mob was slightly misplaced.
    Had a call today saying it is bored but the wall is super thin and it has taken a chip out near the bottom of the sleeve.
    My bet is he didnt heed my instructions to ONLY bore and finish hone to 61mm.
    I am heading down there tomorrow to have a look but it may well be a case of going to a CB77 sleeve.... grrrrrr
     
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    Andych, Jul 18, 2023
    #110
  11. Gen

    Gen Well-Known Member

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    Maybe some things remain the same ?
     
    Gen, Jul 18, 2023
    #111
  12. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    Maybe so


    Sent from my iPhone using Tapatalk Pro
     
    Andych, Jul 18, 2023
    #112
  13. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    Do you know if the XL125 barrel is listed as 124cc or if that is later SL /CB125's
    Apparently the 124cc is the best option...
     
    Andych, Jul 19, 2023
    #113
  14. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    So.... my machinist did in fact listen to me... he bored and honed it to exactly the 61mm and low and behold... as luck would have it... my sleeve is on the lowest of the lower limit and hence a piece chipped out right at the bottom.
    Worse than that the sleeve is so damned thin it is flexible on the protrusion into the case... just not happening.
    It appears that the XL 125 barrel is 124cc and slightly larger diameter sleeve.
    the other options I have been told are an H4750 sleeve or the CB77 sleeve. Now comes the interesting part... do I risk it all by getting an XL125 barrel (not plentiful I must say) or go the sleeve route which means extra machining etc but is most likely the best option as they can machine down the lower protrusion to match the 63.6mm opening I have available.
    Maybe @Gen can have a dig through his spares pile and find an XL125 barrel and measure the lower section for me..
     
    Andych, Jul 19, 2023
    #114
  15. Gen

    Gen Well-Known Member

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    It's on the list of "to do's" Andy.
    I only have 1 x 125 barrel, I'll make sure its a 124,,,,
    Go BIG,,go 200,,bore the cases:thumb_ups:
     
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    Gen, Jul 19, 2023
    #115
  16. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    I dont want to have to pull the motor completely apart again... lol
     
    Andych, Jul 19, 2023
    #116
  17. Gen

    Gen Well-Known Member

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    Just ring it's neck, those Honda pistonies melt quickly, then big bore it, & ceramic coat the crowns while you're there :help:
     
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    Gen, Jul 19, 2023
    #117
  18. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    Nah... I only want to get a little more grunt than stock so 150cc will do fine. Just got to find a 124cc barrel or decide to go the new sleeve route.
     
    Andych, Jul 20, 2023
    #118
  19. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

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    I would go the sleeve route as you would have more control over the machining and may end up with thicker base area.
     
    Murdo, Jul 20, 2023
    #119
  20. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    Thanks @Murdo, that was the way I was leaning until I found this at Toormina
    https://www.ebay.com.au/itm/182412221186?hash=item2a789d9b02:g:6vgAAOSwehZaCN2Q&amdata=enc:AQAIAAAAwN2nlEjd1dtSzyEyJ6M2f4QKPGoYcEZ/+0yktYq+GEtmTgyK7MwvrhnR1dcUNvwoitByDIaQlzIa8Z6bfbt874JNK1QFgz0NdgiiCLaL0QhgZyQJisglmcGS64NkXGojTnOGZJdN9uOhjz4D53utzCw3MbPZKcRq4vh+PWr/5mWqweKFlQYQhicgLEZAW8X0+JWtxg1iXMGokFSkaVX1GqznD+VUyJxDjp4xMSoKLdUNDJwnnLabtG8AES+LZig/UQ==|tkp:Bk9SR57C94KuYg&LH_ItemCondition=3000
    It is already bored to 60.8mm so it is only another .2mm to the finished size I need... and from the pics there is still a bit of meat on the sleeve.

    Screenshot 2023-07-20 at 10.52.58 am.png
     
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    Andych, Jul 20, 2023
    #120
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