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Thread: How to tell if a engine is good?

  1. #1
    Join Date
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    How to tell if a engine is good?

    Hi all, I got a couple parts trikes kicking around. Just finished working on one my projects. I’d like to have a go at rebuilding a top end of a engine / replacing seals piston and so on for a learning experience. None of the parts trikes run.
    Aside from testing for compression, is there anything else I should look at for a good “rebuildable engine “? I’m into atc 200’s myself.
    Also on same similar topic, can I make a big bore say up to 250 for example?
    Looking to Enhance my mechanical skill

  2. #2
    Join Date
    Apr 2011
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    Mexico
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    Aside from the obvious like a rod sticking out of the cases, or a seized piston you can check the condition of the top end of a 4 stroke engine with a leak-down tester. Watch a few videos on how to use one and decide if you want to invest. Unfortunately it can't tell you the condition of bearings and seals, only valves, rings and head gasket.

    Because our trike engines are so old and we usually know nothing of their past history it makes good sense to fully tear down any engine that isn't running when you get it. That's not to say that a barn find that looks otherwise to be in good condition should be torn down, but it sounds like your stuff is in less than pristine condition, so you'd be doing yourself a favor to tear one down completely and do the job right.

    I don't know your exact bore and stroke, but typically a 200 bored out to the maximum will get you up to about 215cc and you won't be able to notice a gain in performance, but your engine will run a little hotter and if you need another bore in the future you'll have to buy or sleeve a cylinder, so do yourself a favor and bore yours as little as possible.

    And if by chance its white knuckle "Big Bore" performance you're after these are not the engines to get your adrenalin fix from. Look for a 350X, or any 250cc 2 stroke for that.


    PS. If you do proceed with a rebuild and plan to post questions as you go PLEASE start one thread and add questions to it as you go rather than starting a new thread for every @#%#$*ing question. Thank you in advance.

  3. #3
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    Yes , makes sense. Big bore is not huge, the little 200s have a nice bit of power for my need, just was curious. Yes the 3 trikes I bought were bought for parts. One has no compression, the other two suppose to run but I’d like to dismantle one to learn about these engines. Ok I’ll post a engine rebuild thread when I go at it. Most likely won’t be touching the bottom end as id most likely be over my head

  4. #4
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    Quote Originally Posted by SteveRoll View Post
    Yes , makes sense. Big bore is not huge, the little 200s have a nice bit of power for my need, just was curious. Yes the 3 trikes I bought were bought for parts. One has no compression, the other two suppose to run but I’d like to dismantle one to learn about these engines. Ok I’ll post a engine rebuild thread when I go at it. Most likely won’t be touching the bottom end as id most likely be over my head
    There isn’t any question you’re going to be able to post on here that somebody isn’t going to be able to answer. All you need to do is buy the right tools and not swing a through the cases while attempting to bypass the use of the proper tool in the process of disassembling the engine and everything will be fine. Clear photos, coherent English and a little respect for your helpers are the keys to getting help on this site.

    You’ll probably end up being an expert on that particular engine before all is said and done.

    If you’ve never opened an engine up before I would suggest you start with the one that has no compression. Get a box of Ziplock bags, a Sharpie and a couple large plastic bins to store your parts and hardware in before you start taking anything apart. Properly labeling and organizing the pieces will allow you to do the job without being rushed, or losing track of any parts.
    Last edited by El Camexican; 02-07-2020 at 08:57 PM.

  5. #5
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    Quote Originally Posted by El Camexican View Post
    There isn’t any question you’re going to be able to post on here that somebody isn’t going to be able to answer. All you need to do is buy the right tools and not swing a through the cases while attempting to bypass the use of the proper tool in the process of disassembling the engine and everything will be fine. Clear photos, coherent English and a little respect for your helpers are the keys to getting help on this site.

    You’ll probably end up being an expert on that particular engine before all is said and done.

    If you’ve never opened an engine up before I would suggest you start with the one that has no compression. Get a box of Ziplock bags, a Sharpie and a couple large plastic bins to store your parts and hardware in before you start taking anything apart. Properly labeling and organizing the pieces will allow you to do the job without being rushed, or losing track of any parts.
    Take lots and lots of pictures maybe even at different angles as you remove pieces so you can refer back for reassembly is something I would add to EL’s advice
    you know whats right therefore you know what is expected

  6. #6
    Join Date
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    Also grab a service manual if you don't already have it.

    http://www.oscarmayer.net/atc/manuals/

    Once you take apart the no compression engine, it should be somewhat clear why it has no compression, blown head gasket, bent valve, hole in piston, etc.

    One tip that I think would help a newer person to engine work is to get some junk cardboard boxes, draw a rough shape of the engine cover, label the front, left vs right etc (as the viewpoint of riding the machine) and push the bolts through the cardboard in order around your drawn shape. It holds the bolts plus tells you where the short vs long ones go. A huge amount of mechanic work is just using common sense, like if you're installing a bolt and it doesn't want to go in all the way... don't just start torquing it down, that's how you end up breaking stuff. The bottom end stuff can scare you, but really it's not bad at all. The most complex part is the transmission and if the bearings are good, you don't even have to take it apart. Careful about thrust washers, they sometimes stick to side covers and such and can fall out after pulling apart. There's also the parts diagrams on http://partzilla.com that can be useful, but the service manual ones should be more accurate for your exact year/model.

    The right tool for the job is another thing, being your first time you'll likely need some special tools. The server manual goes over them, you can see where they are used to see if it's a requirement for what you're doing. Also there's several ways you can go about building an engine, the right way is to check all the specs and wearable items. Some people just check the bearings over and make sure there isn't excessive slop and call it good, people with experience can do this pretty well. Generally worn items are pretty easy to spot, but size specs like wear on shafts etc tells you if you need to replace or just a new bearing is enough. Out of 3 engines, any major parts you should have enough to atleast get one engine going, ideally 2 shouldn't be out of the question. Depending why the one has no compression, you could even luck out and get all 3 going.

    Good luck with your adventure, there's nothing quite like hands on experience.

  7. #7
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    Thanks all. I got another question, I was looking online at rebuild kits with like a piston and cylinder and most of the kits i come across say " unsure if kits older atc 200 before 1986" How would i know which kit to buy? I got a copy of a manual now. I will read through it, excited to start learning to process! I tried watching a few videos however theres not many on 200 atc engines.

  8. #8
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    Don’t buy anything besides tools yet. Do you know what year your engine are?

  9. #9
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    Quote Originally Posted by El Camexican View Post
    Don’t buy anything besides tools yet. Do you know what year your engine are?
    For sure I agree, I was just trying estimate prices of things like that. No idea what years yet. The parts trikes are rough shape. I’ll get some pics of them. I don’t even know what the gear pattern is on them yet because I read some are all down and some all are up gears

  10. #10
    Join Date
    Apr 2012
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    Use this page and type in your frame vin and engine serial to find out what year the machine is, and to validate the engine year (could have been swapped). Frame number is on the front of the frame at the steering neck, engine serial is on a flat section on the crank case down low on the left side (from the viewpoint of riding it), should be under the sprocket area.

    https://atvmanual.com/honda/interact...er-atv-and-atc

  11. #11
    BarnBoy is offline At The Back Of The Pack Arm chair racerAt the back of the pack
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    Late to the party but I'll throw in my 2 cents.

    Rule #1: DO NOT FORCE ANYTHING EVER! EVER! if it won't go figure out why. This applies to many many situations, I've found out the hard way.

    Definitely bag and carefully label every part like PS2fixer said. I also high suggest you keep track of which bolt goes in which case hole, as often times they are different lengths. This is easily done by drawing a diagram and labelling each bolt.

    Manual is a must, goes without saying. If you don't have one don't even touch it....they're so easy to get.

    Pay careful attention to thrust washers! Also a dab of grease on the dowel pins, and a very thin film of grease on the gaskets facilitate easy removal down the road.

    Inspect the cam bearing in the head for excessive wear. And also the rocker arms.

    Good luck with your build!
    Last edited by BarnBoy; 02-11-2020 at 12:56 AM.
    1984 HONDA ATC200M
    1985 ATC125M

    Da velder

  12. #12
    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 SteveRoll View Post
    Thanks all. I got another question, I was looking online at rebuild kits with like a piston and cylinder and most of the kits i come across say " unsure if kits older atc 200 before 1986" How would i know which kit to buy? I got a copy of a manual now. I will read through it, excited to start learning to process! I tried watching a few videos however theres not many on 200 atc engines.
    GH Discount ATV should have piston kits, etc.

    Check out my thread...maybe it will help you some:
    http://www.3wheelerworld.com/showthr...TC200M-Rebuild

    Also this one is excellent:
    https://thumpertalk.com/forums/topic...oll-218-build/
    1984 HONDA ATC200M
    1985 ATC125M

    Da velder

  13. #13
    Join Date
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    Oh to add to the above, you don't need anything special on the gaskets for them to seal, but I know it's common to apply engine oil to the gasket faces in the automotive industry (my dad was an auto mechanic). I think the concept is to swell the gaskets up to seal any major imperfections in the matting surface, but if all is in good shape. Ease of removing I think comes more down to how long the gasket has been installed for, like 30+ years, yep it's not coming out in great shape don't matter how it was initially installed lol.


    There's a lot of people that enjoy working on engines and such, I bet if you made a craigslist post or a fb market place post asking for help and you provide drinks/beer, dinner or whatever, you'd get atleast someone to help share what they know. You'll have to weed out people that don't know what they are doing, but act like they know everything though.

  14. #14
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    Well so far I got two of the 200m engines running. They have carb issues, I got them running by priming the cylinder / pouring small bit of fuel in the chamber. The wire harnesses are both toast so I mocked up a test harness for testing that plugs into the cdi. Got two more engines to test!

  15. #15
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    A test harness isn't a bad idea. I've thought about making a tool to plug into the CDI connector (harness side) and test what it can from there (ignition coil primary, exciter coil, lighting coil, and pulse generator. Might have to look into that some day, can't be too hard to build.

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