How durable are these engines?? 66cc

Discussion in 'Motorized Bicycle General Discussion' started by kyle5647, Oct 6, 2013.

  1. kyle5647

    kyle5647 New Member

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    ok so i ride motorcycles and i ran into these little things, and i would like to build one. my question is how reliable are they?? im looking at a silver eagle engine from jakes custom bikes (pk-80) and im going to get all possible upgrades for that engine...i mean everything..lol :D but my only concern is that these are chinese, so how much can they stand?? i will be putting it on my mountain bike and i will go trail riding with it, which means frequent hills at full throttle,.wee. i would be riding this thing as if i was riding my own dirt bike.

    so assuming i will be doing all this how well can it withstand this abuse??

    few months?

    few years??

    or not at all??
     
  2. crassius

    crassius Well-Known Member

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    depends a LOT on your mechanical skills - good luck
     
  3. Dan

    Dan Staff
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  4. Will122391

    Will122391 New Member

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    As a motorcyclist I imagine you would have no trouble taking good care of the little engine. They are a little random in their lifespans because of Chinese mannufactueing, but they should easily make it past 300 miles, possibly 1000 and if you are lucky, some people here have engines with over 5000 miles on the China girl.
     
  5. bluegoatwoods

    bluegoatwoods New Member

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    Don't count on a lot. The guy above me is correct. Still, these are not Rolls-Royce engines.

    And the way you intend to use them is gonna be hard on 'em.

    Still, you sound like the sort who can use tools and learn about your machine. You'll probably be able to make it work. But count on some headaches.

    The good news is that you'll be able to replace engines with little more than pocket change. That's an exaggeration, yes, but they're inexpensive.
     
  6. mapbike

    mapbike Active Member

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    https://www.youtube.com/watch?v=1OVj_cYtI1I&feature=youtube_gdata_player

    https://www.youtube.com/watch?v=Scq0YuUbWto&feature=youtube_gdata_player






     
  7. kyle5647

    kyle5647 New Member

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    Thanks for all your quick posts guys!!

    If you think about it...what would wear out?? a piston?? i can replace that for $20



    if i put a mikuni vm-18 carb on it, aftermarket piston, and a high compression head, it seems like nothing really would brake on it?? except maybe the crank bearings but i can fix that

    i might last longer than 100 miles, cause i can fix and take VERY good care of it
     
  8. Russell

    Russell Active Member

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    I got 3k+ on my 50cc HT china girl, well worth the $120 I paid for it!
     
  9. maniac57

    maniac57 Old, Fat, and still faster than you

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    I sold a bike recently with well over 10k miles on a stock chinagirl with a tuned pipe and a 36 tooth sprocket.
    It still gets ridden every day and is doing fine.
    It's all about how you take care of stuff. If it runs more than a week, it can easily last years.
    Most problems seem to crop up fairly soon. If you tune it a bit rich and keep the rpm's below 8k, they just keep on running.
     
  10. Toadmund

    Toadmund New Member

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    I think the week link is probably the connecting rod bearings.
    The lower needle bearings failed in my first motor, causing bad damage to my piston and cylinder.
     
  11. mrfubs

    mrfubs New Member

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    Get SKF or some quality 6202 bearings you'll need 4 because the clutch uses the same ones. somtimes the cranks need to be trued' and also if you want more rpms youll have to drill some more out of the crank for the higher rpm you desire.

    A big factor in longevity of the engines is crank balance/true-ness the other half is the thick 2mm thick steel piston rings on a flash chrome bore. I found a piston that will work on the crank with the shorter con rod that uses 2 1mm thick piston rings that are chrome plated that will be a lot more friendly on the thin cylinder wall
     
  12. xseler

    xseler Well-Known Member

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    They are kinda like Forrest's box of chocolates --- you never know what's inside until you open it up.................

    There's one guy from Australia that just posted that he has about 40,000kms on his (about 25,000 miles)!!
     
  13. mapbike

    mapbike Active Member

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    Some may or may not agree with what im gonna tell you here but im gonna tell it at ya anyway......lol!

    #1 get you a kit from a vendor that has been spoken about on here taht has been known for a quality kit and most of all good customer service in the event that there is a problem with any of the parts and pieces in the kit.

    #2 once you get your engine and parts, make or purchase a better intake gasket and use a bit of gasket dope for a good seal after you grind off any burs from the inside of the ntake tube or better yet buy a shorty type billet intake that is port mached to the jug from a vendor here on forum.

    #3 get some good quality nuts to use in place of the junky acorn nuts that come on most of the engines, and if you wan to add reliabilty, while you have the head unbolted go ahead and install a better quality writ pin bear which is one of the most common catastrophic failures the engines have, the jug and piston are normall completely destroyed if the upper bearing comes apart......... ask me how I know....lol!

    #4 get the engine securely mounted on the bike with NO RUBBER OR OTHER SQUISHY STUFF BETWEEN ENGINE AND BIKE FRAME.... get it running and put a few miles on it as you get the little bugs worked out, the carb tuned and some break in time on it.

    #5 now one item at a time start to work in the mods you want and be sure to study up on each one here on the forum so you'll know for sure what actually helps and what is just snake oil, you will learn many new things by this time about these little engines......lol!

    Best wishes to ya and by the way if you go dax..... you wont go bax....."

    .wee.
    Map
     
  14. mrfubs

    mrfubs New Member

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    the cylinder wall is only flash chrome plated and is very thin. it has a tendacy to chip, flake, wear, score really quick. so take note when your breaking the engine in. The piston rings are 2mm thick, thats 1mm thicker on each ring than they should be and are bare steel riding on a thin layer of chrome. pick out a good oil.
     
  15. BarelyAWake

    BarelyAWake New Member

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    "most of all good customer service in the event that there is a problem with any of the parts and pieces in the kit..."

    Just for the sake of another viewpoint, this could be a bit controversial with these engines in particular. When I built my first inframe kit & started participating on this forum, I too recommended the above as it's wise advice for most products, vendors that support their products must be good ones right?

    There's a couple of catches though, ones almost unique to this product and those that sell them & that's overall cost and your convenience.

    Most of the factory issues with these engines are defective/damaged components and poor assembly - the assembly issues you'll need take care of yourself regardless of warranty and the vast majority of defective or damaged components are simple and inexpensive to replace, a carburetor can be had for a mere $12 for example.

    So the question arises, is it really cost effective to pay extra for a warrantied engine that may be of no better quality, from a merchant that charges more for the customer service they're known for - to then pay for the return S&H, wait for it to get there, wait for it to be "approved" for replacement and then if it does, pay the return S&H and wait some more... when you could have just bought a new carb or whatever?

    When the parts are so cheap that S&H alone can exceed their cost, you have to wonder if it isn't far more cost effective to simply ignore the warranty and fix it yourself.

    So what about something more serious? What if you get a terminal lemon, one that just detonates on first start up or gimps around making horrid knocking noises, one that's definitely not long for this earth? Well, that's when the warranty returns are most disputed by the vendor - if it's just a little part you'll probably get it, if it's the entire engine it's far more likely to be judged "operator error", "incorrect break in procedure" the "wrong oil/mix" or whatever else seems "likely" to them - many won't accept a return on an engine that's modified in any way, mounted or even just been run... which effectively means the only problem that might be covered at all is obvious and grave S&H damage.

    I don't mean to infer that all these merchants are deliberately misleading you to get your money - some may well intend their customer service to be good, to establish a reputation for support... the problem is they do have to charge somewhere to recover their costs, to pay for that support and the question is, is it really worth it to you?

    My first two inframe kits I purchased warranted from "reputable vendors" - I eventually realized that all the issues I had were minor, too minor for the return & wait process and that even if I did get a lemon I wasn't going to bother to return it, these engines are so cheap I'll just get another & use the dud for parts, those parts even cheaper as I got them as a complete engine.

    So now all I do is find the least expensive kit retailer on ebay or whatever, one who has a good reputation - not for warranty or service but for just getting their product to you in a timely fashion and the product is as advertised.

    Interestingly enough not only has this saved me hundreds of dollars, the engines themselves were some of the very best I've had.


    By all means get a warranted kit if it makes you comfortable, if you feel a need to support a favorite vendor, if it's your first and you want to cover your bases - but know it won't guarantee any better quality and to be blunt with an engine as simple and cheap as these, you're better off on your own, they're all a crapshoot and you'll need fix it regardless.

    Might as well skip the time consuming & costly middle man games and just get another ;)
     
  16. mapbike

    mapbike Active Member

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    Ditto...... what you just said here is exactly what I do, ebay kits...... but ....... lately I hwve bought two of the Gen IV lowers from Duane and Im running on of them now that was put together with parts I bought from multiple ebay sellers and its the best and fastest engine I've had as of yet.....

    I give the advice for customer service as being a good plus because so many people seem to have lots of little issues and I've seen good reviews on here about how some of the vendors how offered some great help and warranteed entire engines along with other parts, personally since parts and pieces are so cheap I could care less about a warrantee, but some feel better knowing there's at least a chance someone will help them out if they have a problem.

    Map
     
  17. BarelyAWake

    BarelyAWake New Member

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    I truly believe you'll get more comprehensive, balanced assistance (differing opinions & multiple solutions) here on this forum than any one commercial retailer - again this isn't a negative against the retailers, rather that a retailer cannot provide the same depth and experience as provided for here.

    One small example would be modification & preformance alteration, another less minor example are competitor's products.
     
    #17 BarelyAWake, Oct 7, 2013
    Last edited: Oct 7, 2013
  18. FMB42

    FMB42 New Member

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    Follow the above suggestions and make darn sure that you always carry a decent tool kit and a few spare parts such as; various wrenches, plug socket, flat and Phillips screw drivers, a tire patch kit, and at least a spare plug, master link, and maybe even a spare tire tube (you'll want to remove the chain so you can more easily peddle home if you have a breakdown out on the trail). I'm sure that you already know this, but I thought I'd mention it anyway...


    I'd take it easy with any "full-throttle hill-climbing" until you become accustom with your kit and it's power and reliability (downhills, as fun as they are, will of course require good, or better, brakes (I much prefer disc brakes myself). Just remember that these things are not Japanese, or European, dirt bikes and you'll probably do OK. A Motorized MTB, sure. A full blown dirt bike? No way.
     
  19. rogergendron1

    rogergendron1 New Member

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    well i had this same question and......... just let me tell you if you buy it and bolt it on your going to be disapointed !!!!

    there are things that NEED TO BE DONE!!!!

    first take the whole top end off and port and polish the intake and exhaust nothing big time just clean up the garbage they sent you.
    then port match the intake and exhaust header as best you can
    tune the carb as best you can be shure to buy a kit with a carb that is tunable
    now pull the gutts out of the stock muffler and drill out the stinger pipe to 1/2 ID
    sand or deck down the head a lot !lol
    cut the piston skirt where it blocks the intake at TDC ... believ me it will !!! mine covered almost half the intake !!!!!

    next forget about the 16:1 ratio they tell you and toss the oil they gave you in the garbage ! go get some full synthetic and break it in at 32:1 and runn it at 40:1.

    you now have a bike motor that will run way better and be more efficiant that stock aso it will pull MUTCH harder up hill just by doing nothing but modifing the stock parts correctly

    none of the china motors are good out the box but some will run fine some wont. i know if i ran mine stock it would have blown in a week !
     
  20. kyle5647

    kyle5647 New Member

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    thanks again for all the replies!!

    what if i put on a 5.4cc high compression head, you mentioned that the cylinder walls where thin so would that blow a hole in it? lol

    also for the silver eagle engine (pk-80) is it really better than those ebay kits out of the box?? cause the description says its a more true crank, and high performance japanese bearings. anyone tried this engine?? or is it just a market scam?

    thanks!
     

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