machine new cylinder?

Discussion in 'Motorized Bicycle Welding, Fabrication and Paintin' started by commuter, Jun 7, 2013.

  1. commuter

    commuter New Member

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    been playing with the idea of machining a new cylinder for a 66cc china 2 stroke.

    had a cylinder at work to weld up and machine a gouge in the wall and was thinking how much longer an iron sleeve would last. I checked around the shop and found some aluminum blocks large enough to make jugs out of.

    idea is this, basically machine an aluminum block to same dims as stock jug except leave a lot more material for a sleeve. it looks to me that if the wall thickness on the factory jugs was a lot thicker you could just bore it out and drop in a sleeve. So if it is just a wall thickness issue then why cant i just make a new jug with a larger outside cylinder dia. to leave enough wall thickness for a sleeve?

    if the stud/cylinder wall thickness will be an issue i could always make a spacer/adapter plate to allow for a wider bolt pattern.

    -shrug- i havent really looked into it too much yet, figured i must be missing something since it seems simple and i havent heard of anyone doing it yet.

    so what am i overlooking?
     
  2. maniac57

    maniac57 Old, Fat, and still faster than you

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    I think you should go for it. I've wished for a steel sleeved cylinder ever since I first saw the ht! Build 2 and sell me one.
     
  3. Huffydavidson

    Huffydavidson STREETRACER/MANUFACTURER

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    sounds like just another place for an air leak .good luck
     
  4. maniac57

    maniac57 Old, Fat, and still faster than you

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    In all my years of messing with engines, I have NEVER seen an air leak from a sleeve.
    Ever.
    Never ever heard of that happening.
    If its good enough for top fuel, its good enough for me.
     
  5. commuter

    commuter New Member

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    sorry for the pic quality, quick shots with phone.

    the pics show why i am wanting to try a sleeved cylinder. this is the 2nd, and this one is being returned to dealer for exchange, cylinder i have came across with porosity in the wall so plating didnt stick, a dead/low spot in the cylinder.

    if a seller will send it to me like this, how many engines out there have spots like this or worse already installed?
     

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  6. curtisfox

    curtisfox Well-Known Member

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    I like your idea and don't see any reason it won't work. Briggs IC used a cast iron sleve for years.As well as a lot of race cars as you say.
    Makes you wonder how many of then engines are out there running and no one knows about the defect.............Curt
     
  7. commuter

    commuter New Member

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    well, actually having to do my job at work has kept me from being able to work on anything not company related :( I am going to try and get the cylinder, adapter/spacer, and sleeve rough cut tonite.

    I will post pics of whatever progress i make.
     
  8. BigBlue

    BigBlue New Member

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    No one has done a iron sleeve because of the cost. Here's a link to a company in Portland, Oregon that will bore your cylinder, install a sleeve and cast a liner. $55 to bore your cylinder, $175 to $275 to install the sleeve and an unknown amount to cast the sleeve. So, your looking at least $230 to $330 just for boring the cylinder and installing the sleeve. I guess you could find some one else that uses precut liners, but I doubt you'll find anyone that has precut for our 2 strokes.

    http://smallenginemachineworks.com/cylinder_services

    If you make your own cylinder and sleeve, your way ahead of most people, especially if it doesn't cost you.

    Here's some technical facts that may help:
    http://www.lasleeve.com/technical#c_sleeves_1

    Look forward to your progress,


    Chris
    AKA: BigBlue
     
    #8 BigBlue, Jun 14, 2013
    Last edited: Jun 14, 2013
  9. Tool Maker

    Tool Maker New Member

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    Buy a new cylinder. Accept the fact that they are never round, and the plating is atrocious.

    Take the new cylinder, de-grease it. Put it in your oven, and cycle it to 300 degrees a few times. Let it cool to room temp each time. Do any porting or clean-up it needs before the next step.

    Then, put it in a box, add $230.00 and a new piston (for fitting) & ship it to:
    http://www.usnicom.com/

    They will bore it back to straight, then Nikasil plate it & hone it to size for the supplied piston.

    Nikasil works. Porsche still uses it in aluminum cylinders.

    I have sleeved 2 stroke engines. It is a huge pain in the backside. Making all of the transfer ports line up right, getting the sleeve pressed in to the right spot, finish machine work... Then you still need a good bore & hone to straighten up the bore after you get it assembled.

    230 bucks is a bargain. If it is within .010 of round after heat cycling, they will only charge $198 if they don't have to bore it.

    Just my two cents, based on experience.

    .
     
  10. commuter

    commuter New Member

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    well i really didnt get much done last night. cut/milled block to dims i wanted. drilled and bored block. stud holes are .343" and bore is 2.1". after comparing old cylinder to my block i might re-drill stud holes to original bottom end pattern. i didnt think there would be any wall but it looks like there will between sleeve and stud hole.

    started working on sleeve but got sidetracked by my job.

    -shrug-

    if anyone from my work is reading this, look away now! :eek:

    the bridgeports were tied up last night so i went to scratch out a quick program and make up tooling for one of our larger horizontal MORIs, not a problem except one idea led to another, to another, and so on. the program ended up written to run 3 operations at once. 1st op is just block horizontaly in vise to mill length, drill stud holes, and bore cylinder. 2nd op is sleeved cylinder, loaded same as first op but on opposite side of tomb to re-bore sleeve and mill/interpolate intake port. 3rd op is cylinder vertically on top of fixture to cut cooling fins, mill/interpolate exhaust port, and notch cylinder skirt.

    so after setting up tooling and building the fixture i didnt have any time left to actually make the part. the really nice thing about all the extra time i spent going so in-depth on the program and fixturing is that its written like a production part. after i tweak everything and get it just right, its just a matter of loading parts and pushing a button to make new cylinders.

    hmmmm, how to make the machine cross hatch it also? ;)
     

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  11. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

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    I don't get it.
    Liners are made of cast iron not steel.

    How are you going to machine the intake, exhaust and transfer ports
    in your block?

    The original 66 cc chrome cylinders aren't too bad.

    I have one messed up cast iron lined 50 cc cylinder from a Grubee Starfire.
     
  12. Master-shake

    Master-shake New Member

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    What's your engine vendor? I got an engine from gasbikes.net and i took it apart and it looked really good inside. Also, I think pirate cycles sells just the "jug" is that what you call it for 15$ it might be more productive to just buy a new one?
     
  13. 16v4nrbrgr

    16v4nrbrgr New Member

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    I had a PK80 that died die to my own mistakes, and it went through 2-3 owners before me on the OCC, and even though the motor ate some metal (my fault), the cylinder finish and hone looked pretty damn impressive compared to what I'm used to seeing in small motors.

    I didn't put a bore gauge in it to see how wobbed it was, but I couldv'e sworn my engine had a ferrous liner too, maybe it was a Grubee Starfire instead, I dunno.
     
  14. commuter

    commuter New Member

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    for all the replies telling me to just buy a new cylinder. this reply from someone else on another forum sums it up perfect for me.

     
  15. Technocyclist

    Technocyclist Motorized Bicycle Senior Technologist

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    Actually, I've been waiting for someone to come up with this. There are lots of different kinds of billet cylinder heads, and i have been wondering why is it that nobody has ever thought of a steel sleeved cylinder for the HT. I guess my wait won't be long now. I'm really excited to see the results of this project. Most of my engine that failed, was because of this, and secondly the wrist pin bearings. Currently, i'm using needle bearings from a chainsaw and seems to be ok. Actually, in my engine i sanded down or polished the edges of my piston rings so that the wear on the cylinder lining would not be as great as it was. Seems to be working. I also think that the carbon build up also contributes a lot on wear of the lining. So decarbonizing is highly recommended.
     
  16. Master-shake

    Master-shake New Member

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    What is this I hear about chromed piston rings or sanded down ones? I have an extra set that I'd like to experiment with. Also, these wrist pin bearing things, would I be able to take em out, take em down to Home Depot and find an upgraded set or do I have to have bearings specific to the grubee gt5 sky hawk? I polished the inside of my cylinder with scotch bright when I first got it, got it to almost a mirror shine. I guess it helped?
     
  17. mew905

    mew905 New Member

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    anything you ever need to know about replacing these motors hardware: https://docs.google.com/document/d/1RmylZRkp8GEe0wYJ7nOkT1DRwFpLltRC5SZSBa9WmIY/edit?usp=sharing

    As for the OP... thats sweet, I had been toying with the idea myself but not having the tools to do so (and a dremel would be notoriously difficult to do with) I never got around to it. However three suggestions: For the intake and exhaust ports, make em wide. if you use a 40mm intake spacing, make the intake port 28.1mm wide. If it's a 30mm, then 20mm wide (leaves 2mm walls between the port and the screws, if you widen it on the inside, you'll lose intake velocity, just make it 20mm all the way in). Exhaust port make it ~30mm wide with a 40mm bolt spacing. And the transfers, match them to the base like you planned but when it comes up to where the transfers meet the combustion chamber, aim them toward the intake side of the cylinder, this'll reduce short-circuiting allowing a more efficient flow and give more power. Also if you can figure it out, make the transfers enter at a sharp 30 degrees on the Y axis (so the airflow skims the piston). I'm not sure how to design for that, but our stock motors enter at 60 degrees on the Y axis and doesnt allow for complete exhaust evacuation.

    Port heights (timing) depends on your application but generally speaking, match the grubee cylinder. They produce good power at low RPM's and aren't designed for high RPM's anyway, so making high ports may only hurt them.
     
    #17 mew905, Jun 18, 2013
    Last edited: Jun 18, 2013
  18. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

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    Maybe performance isn't an issue for you so you will copy the original
    badly designed porting?

    The only way to really correct the port timing on the original cylinders
    is by stroking the crank but you are starting with a clean slate so you
    could make the port timing correct.
     
  19. Tool Maker

    Tool Maker New Member

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    Wow. That will be a very expensive cylinder for someone. I expect to see at least $200 per hour for time on my Mori-Seiki SH-500. I also expect to see it making chips for paying jobs as much as possible.

    Programming time, fixtures, machine time & raw materials. If you paid your employer shop rates for all of that, you could send several cylinders out for Nikasil for that price.

    Next time someone complains about the prices a machine shop charges, I will link to this thread.

    .
     
  20. Mr. Minecraft

    Mr. Minecraft Visionary

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    I think this is great. When I was into gopeds, people would always do this kind of thing and get great results out of it. Good luck with this, I really hope it works out. I will be following this thread very closely.
     

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