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Thread: Back Burner Engine Project

  1. #1
    Gabriel's Avatar
    Gabriel is offline At The Back Of The Pack Arm chair racerAt the back of the pack
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    Back Burner Engine Project

    Ok, so I just rebuilt the ATC200 engine I will be using on a 200S frame.

    The 200S engine is mostly there, what's missing, I have from other engines. SO, I would like to slowly rebuild this one and have it on standby when the need arrives.

    I would LIKE to put a little more into this one than just an overhaul. Nothing stupid mind you, but I have a junker head I can practice porting on. Those ports look really tight in there. It would HAVE to help to open them up a little. Anything to look out for; do's & don'ts?

    Also, what's the biggest bore that can feasibly be used on a 200 engine? By biggest, I mean retaining ALL reliability this engine is known for. Race engines are not for me but a little more pep in the step wouldn't be unwelcome.

    Stock cam profile is fine but I wonder about the compression ratio. How far can you bump that up without running into ANY issues?

    I will look into an aftermarket pipe for it maybe and a slightly bigger carb to feed it.

    Again, this might be a year or two long project as it is NOT a priority.


    As always, Thank you guys.

  2. #2
    125Mmadness's Avatar
    125Mmadness is offline At The Back Of The Pack Arm chair racerFirst time rider
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    The all around best way to upgrade it would be a 200x or xr200 cam, carb, and piston. The xr200 parts will net you a bit more power than the 200x stuff, but the 200x parts will bump it up quite a bit, and you may think the stock cam profile is ok but imo it really isn't, my 200s had a large but unknown race cam that came in a 200x head and that thing would SCREAM, it was way fast, but had constant piston issues, which brings me to my next point, don't run a wiseco piston, you'll regret it.
    1985 ATC125M: Parts
    1985 ATC200S: 84 200S Bottem end, 200x Head, 200x Carb, S&S Cycle Exhaust, Wiseco 10.25:1 Piston, Reground Cam with About 1mm more lift(unknown specs).
    1988 TRX250X
    1983 ATC200E: Total Pile.


    "Bout Tree Fiddy" Master of Thy 22RE

  3. #3
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    Quote Originally Posted by 125Mmadness View Post
    which brings me to my next point, don't run a wiseco piston, you'll regret it.
    This is like leaving a loaded gun on the table with the safety off!! WHY
    If its on the internet its got to be true they can't put any lie's on the internet

  4. #4
    Gabriel's Avatar
    Gabriel is offline At The Back Of The Pack Arm chair racerAt the back of the pack
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    I always thought Wiseco was a quality piston. Please elaborate if you would.

    Thank You.

  5. #5
    125Mmadness's Avatar
    125Mmadness is offline At The Back Of The Pack Arm chair racerFirst time rider
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    Well, from my own personal experience, they have two main flaws that put me off of them. First one being lack of oiling to the wrist pin. When I took my 200s engine apart after a month because of it smoking (will get to this later) the wrist pin was completely stuck in the piston, so apparently piston got so hot in the wrist pin journal that it deformed, because I tried putting another pin in the piston and it still wouldn't go in. My second reason is because with the same riding style/break in that I did when I had put a 200x piston in my 200s (which I had in it for 6 months before I broke the engines crankshaft and the valves slammed into the piston) the engine never smoked with the 200x piston and after 2 weeks with the wiseco, low comp and smoking. Maybe I just have bad luck with wisecos, but next time I build a 185/200 engine for high performance it will have a xr200 or helm and son piston
    1985 ATC125M: Parts
    1985 ATC200S: 84 200S Bottem end, 200x Head, 200x Carb, S&S Cycle Exhaust, Wiseco 10.25:1 Piston, Reground Cam with About 1mm more lift(unknown specs).
    1988 TRX250X
    1983 ATC200E: Total Pile.


    "Bout Tree Fiddy" Master of Thy 22RE

  6. #6
    Gabriel's Avatar
    Gabriel is offline At The Back Of The Pack Arm chair racerAt the back of the pack
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    SO, back to my initial query.
    IF I were to track down an XR donor engine, will the entire top end fit the 200S bottom end; Jug & head both?

    Just so I know, 200's and 250's do NOT swap, correct?

  7. #7
    125Mmadness's Avatar
    125Mmadness is offline At The Back Of The Pack Arm chair racerFirst time rider
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    Yes, so long as it isn't a 84-85 rfvc motor. And the 250's are a whole nother story.
    1985 ATC125M: Parts
    1985 ATC200S: 84 200S Bottem end, 200x Head, 200x Carb, S&S Cycle Exhaust, Wiseco 10.25:1 Piston, Reground Cam with About 1mm more lift(unknown specs).
    1988 TRX250X
    1983 ATC200E: Total Pile.


    "Bout Tree Fiddy" Master of Thy 22RE

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