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Thread: ATC200M Camshaft Journal issues

  1. #1
    BarnBoy is offline At The Back Of The Pack Arm chair racerAt the back of the pack
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    ATC200M Camshaft Journal issues

    Hi,

    Decided to make a seperate post for hopefully more views than my other thread. And to make the info easier to find, not all cluttered in one thread.

    I am rebuilding my 1984 ATC200M engine now. I found that the aluminum cam journals in the head measure right at the very bottom of spec. 1.3411" Funny thing is, the camshaft itself is worn more than the aluminum journals! It measures 1.331".....that something like 0.005" below spec! Dont understand it, but I quadruple checked my measurements. As it sits it has 0.010" clearance between the cam and journal. I installed a good used cam that mics in spec, and shrunk that to 0.0045". Still too much clearance though, service manual specifies 0.003" max clearance.

    I have also read the from the factory these journals sometimes came with more that 0.003" clearance....with brand new parts!! Certainly seems plausible, based on the measurements given in the manual.

    As I see it I have a few options...

    Option 1: Find a good used head. I believe I may have a good head off a 185S, need to mic it though. It does have a bunch of pitting in the combustion chamber, like from detonation or something. Head gasket sealing surface it intact though.



    Option 2: Weld the journals and bore to spec on a mill. Have access to a machine shop who will do this for free! He does good work, and is the instructor at the machining program in a local tech college (where I go for welding courses).



    Option 3: Bore and machine replaceable bearing inserts into cam journals. Unsure about this?? Seems possible, and would be nice to have something that replaceable.



    Option 4: Install a ball or needle bearing on the opposite side of the cam chain. Exactly like Megacycle does, with their bearing plate, etc. Except I'm not spending $500 on it....I would make my own, or get it made at that machine shop. https://www.megacyclecams.com/catalog/Page22.pdf

    Have also found a few guys over on Thumpertalk who have done this with XR200's and similar bikes.

    https://thumpertalk.com/forums/topic...hy-not/?page=2

    https://thumpertalk.com/forums/topic...omment-8715919

    Any ideas, thoughts, or suggestions are welcome!! I'm curious to see if anyone has done this also.
    Last edited by BarnBoy; 02-08-2019 at 11:41 PM.
    1984 HONDA ATC200M

    Da velder

  2. #2
    barnett468 is offline FACT ! I have no edit button Arm chair racerThe day begins with 3WW
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    wow, lots of options. below are just a few initial thoughts.

    you might be able to have one of the cam mfgs make a cam with slightly larger journals to run in the head without modifying the head, but the journal in the head is likely a bit egg shaped, so measure it in several positions to get the clearance you want if you do it this way.

    welding the head will get weld on the gasket sealing surface, so he will have to clean that off without removing any additional material which might be difficult.

    the cam journals in a used head might be out of spec also.

    the bearing seems like a good idea if it is not overly expensive, but that may limit your cam selection unless you have one custom ground. others here may have tried the bearing and can give you some suggestions regarding it.

    since the bike was running even with .010" cam bearing clearance, you could simply put another cam in that is within spec to tighten up the gap like you already checked out and run it.

  3. #3
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    Quote Originally Posted by BarnBoy View Post
    Option 4: Install a ball or needle bearing on the opposite side of the cam chain. Exactly like Megacycle does, with their bearing plate, etc.

    Have also found a few guys over on Thumpertalk who have done this with XR200's and similar bikes.
    I did this option in a 200X motor and documented it. If you don't mind spending the coin, it's a great upgrade.

    https://r.tapatalk.com/shareLink?url...5&share_type=t


    Sent from my Z958 using Tapatalk

  4. #4
    barnett468 is offline FACT ! I have no edit button Arm chair racerThe day begins with 3WW
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    .

    Also, whatever you do, I suggest you run some good oil.

    .

  5. #5
    BarnBoy is offline At The Back Of The Pack Arm chair racerAt the back of the pack
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    Quote Originally Posted by ironchop View Post
    I did this option in a 200X motor and documented it. If you don't mind spending the coin, it's a great upgrade.

    https://r.tapatalk.com/shareLink?url...5&share_type=t


    Sent from my Z958 using Tapatalk
    Thanks!! I edited my post....I'm not going to spend $500 for their kit. Would make my own. Don't have that kind of money, though I agree that would be amazing! If you get a chance, check out the links I posted to thumpertalk. A guy on there built his own just like megacycles.

    Do you know if I might be able to get my hands on some of the technical measurements of the megacycle spacer? I'm guessing probably not, but worth a shot.
    Last edited by BarnBoy; 02-08-2019 at 11:49 PM.
    1984 HONDA ATC200M

    Da velder

  6. #6
    BarnBoy is offline At The Back Of The Pack Arm chair racerAt the back of the pack
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    Yeah, too many options lol.

    Thank you for your thoughts!! Very helpful. I hadn't considered the sealing surface much....you are right. Hmm.

    See that's what I'm saying. Couple local guys said just buy a new head. But I'm not spending years buying random heads off eBay, finding out they are too worn, and trying to find a good one lol.

    The idea I'm thinking of "should not" limit cam selections. Shouldn't. But I would have to draw something up to be sure.

    Yes, and honestly, if it was just an old beater bike I would likely do that. However, I want to do this right, and do it once. Kind of a nostalgic thing so I don't want to cut any corners. This is my kinda "special" bike, not a beater.
    1984 HONDA ATC200M

    Da velder

  7. #7
    BarnBoy is offline At The Back Of The Pack Arm chair racerAt the back of the pack
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    Quote Originally Posted by barnett468 View Post
    .

    Also, whatever you do, I suggest you run some good oil.

    .
    What are your thoughts on Shell Rotella T4 15w-40? Not to start down a rabbit trail haha. I'm currently running Valvoline 10w-30 ATV oil.
    1984 HONDA ATC200M

    Da velder

  8. #8
    barnett468 is offline FACT ! I have no edit button Arm chair racerThe day begins with 3WW
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    I would say from what little I have found out about the 15w-40 t4 oil so far, is that it looks decent at the very least, and is likely better than the valvoline you are currently using, however, since it is a synthetic "blend", it likely still has viscosity index improvers, which can shear, which reduces the oils viscosity range and max viscosity, however, all non synthetic oils have these as well. It mainly means that it will not last as long as a true group IV or V synthetic if all other aspects of the oils are generally similar, although the Group IV and V oils typically have a higher "burn off" point, which in general, means they will provide lubrication at higher temps than non synthetic oils will.

    Here is the MSDS for the T4 15w040.

    http://content.rpgov.net/dpw/right_t...il%2015W40.pdf

    .

  9. #9
    BarnBoy is offline At The Back Of The Pack Arm chair racerAt the back of the pack
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    Talked with the machinist today. Looks like we are going to try machining a bronze bearing for the large left side of the cam. And then also inserting a ball bearing in place of the seal in the pulse generator housing. Now I need to find some bronze 932 (660) bearing material....anyone know where I can get this relatively cheap? Don't need much.

    Also, I am going to try buying a sealed ball bearing, and then popping one seal out so it can be oiled by the cam. Will I have any issues with crankcase pressure pushing out this other seal?

    Don't have enough room to run both a bearing and separate seal. Heard some people say it's ok to run the pulse genny in oil....but why would Honda engineers run a seal there if it wasn't necessary?
    1984 HONDA ATC200M

    Da velder

  10. #10
    barnett468 is offline FACT ! I have no edit button Arm chair racerThe day begins with 3WW
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    Quote Originally Posted by BarnBoy View Post
    I need to find some bronze 932 (660) bearing material....anyone know where I can get this relatively cheap? Don't need much.
    You can just do a google search. There are a few places that have it. One is listed below. Ebay may also have it.

    http://www.bravobronze.com/shop-allo...html?shape=134

  11. #11
    barnett468 is offline FACT ! I have no edit button Arm chair racerThe day begins with 3WW
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    FYI - I would get new rockers also or have yours resurfaced if web or megacycle does it.

    .

  12. #12
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    Quote Originally Posted by BarnBoy View Post
    Now I need to find some bronze 932 (660) bearing material....anyone know where I can get this relatively cheap? Don't need much.
    https://www.mcmaster.com/bushing-stock

    Quote Originally Posted by BarnBoy View Post
    Also, I am going to try buying a sealed ball bearing, and then popping one seal out so it can be oiled by the cam. Will I have any issues with crankcase pressure pushing out this other seal?
    Probably not
    Who is Q?

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    Please document this and post pictures

  14. #14
    BarnBoy is offline At The Back Of The Pack Arm chair racerAt the back of the pack
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    Quote Originally Posted by barnett468 View Post
    .
    FYI - I would get new rockers also or have yours resurfaced if web or megacycle does it.

    .
    Oh, this reminds me. Is it bad to use the old rockers on a "new" cam? I have a cam that mics like new, so I'm planning on using that...saves me $50 over an aftermarket new one at least. I have the rockers from the head that this "new" cam came out of...might just swap them. Gonna be a pain to get that stripped rocker shaft retaining screw out though.

    I looked an its pretty hard to find NOS rockers, and havent found any aftermarket ones either.

    Quote Originally Posted by morgan View Post
    Please document this and post pictures
    Yessir, absolutely will do. I have settled on installing a brass bushing into the head on the left cam journal, and using a ball bearing on the pulse generator cover. Will keep right side cam journal the same with factory steel bushing as its well within spec.
    Last edited by BarnBoy; 02-13-2019 at 12:01 AM.
    1984 HONDA ATC200M

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  15. #15
    barnett468 is offline FACT ! I have no edit button Arm chair racerThe day begins with 3WW
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    Quote Originally Posted by BarnBoy View Post
    Gonna be a pain to get that stripped rocker shaft retaining screw out though.
    Post a photo of the offending item if you can.

    .

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