Which is the best 80cc engine kit

Discussion in 'General Questions' started by Randy Garrity, Sep 1, 2016.

  1. Randy Garrity

    Randy Garrity New Member

    I am a seasoned dirt bike rider and racer.And with years of experience working on my bikes and engines.As well many other types engines.Since this is the case.Im after a top quality setup.Meaning I am afraid to buy any of these china produced kits.Or engines.When I already well know from past experience.China produces crap overall.I will say the 150cc 4 stroke engine that came in a small offroad buggy I paid 2 grand for.Was a quality engine.Being a Honda clone. Once I took it apart to do many performance mods.Anyways to my point.Does anyone know the true cc size?When all these engine kits state 66/80cc and there is not a engine of such a rating.There all of one cc rating period.Which tells me these are sadly a 66cc giving the buyer hopes of owning a true 80cc. Which would also explain the poor hp rating of only 2hp. When any quality 2 stroke engine will have a lot more hp than 2hp! No doubt about it. I also noticed the same issues with the high performance crap.Because in order to have a true port job or ported parts.You must have the cylinder and the piston both ported in order to be a top quality and proper working port job.Thats before the right type of port work for the riding you so do.Meaning a full range or low end etc. And that takes years of serious experience found at race tracks and race mechanics. I also know the importance of engine balancing any engine that is not.Will simply kill itself with time.Every engine must be balanced or its junk to start with.Then the kehin styled carb ?What in the hell does that mean?Is it a true replica of a Kehin carb?The bottom line is this.That company makes a good carb.However, for these smaller engines.The two best would be a walbro if made large enough to work on a true 80cc I cant tell you at this point.OR a mikuni carb which simply cant be beat for any motorcycle engine period.I ran these on both 2 strokes and big 74 inch Harleys with excellent results! My plan was to purchase the 80cc and then go to work making it a top performing engine.With a good port job and balancing and most likely milled stock head. OR thinner base and head gaskets.Till I gave serious thought about the real quality of the engine and all my work and added $$.I'm not so sure its at all worth it.Because of the quality of the engines internal parts.Starting with the bearings and rod and piston .Which is all there is less a flywheel and crank. So what can you tell me about any of this? Thankyou Randy
     

  2. FurryOnTheInside

    FurryOnTheInside Active Member

    Welcome and please keep browsing and reading the forum. There's more information already on this forum than anyone can put onto a single thread. :D
    If you're interested in getting into these then you're probably going to read half the posts from this year anyway! :p

    It's a 66. But it is slim and looks like it fits the bike. :cool:
    There's a newish 70 kit with more power if you don't mind a wide-as-a-four-stroke screaming high RPM engine without parts availability. :rolleyes:
    I too am planning a walbro style (and reed). I don't really "get" float carbs on bikes. The walbro style is supposed to be easy to adjust outdoors and won't flood if laid down. :D
    The power depends how you rebuild it and run it. No mods and overly oil rich as per the instructions = 2hp, I guess. Loads of mods but even lower RPM = probably the same hp but quieter, I hope. o_O
    The carb, reed and head cost a few $ but most of the mods are free! :) I'm spending a fortune on bicycle parts, though. :oops:
    Recent posts list loads of fun, free / cheap mods that improve reliability, and efficiency (power without raising the top RPM). :)
    The engine is replaceable. You can even raise the power through RPM if you want to, at worst it's only going to kill the engine quickly, not the really expensive parts. ;)
    Jaguar has a site with loads of info on easy methods of balancing and porting. We discussed how to do balancing without even splitting the case, for those who have limited tools and skills (drill radially!). :D

    It is definitely worth it. :p
     
    Frankfort MB's likes this.
  3. skyash

    skyash Active Member

    By the time you spend all your money on it you should have got a real motor off a dirt bike and put it on a pushbike cost more to start with but will never do you wrong twice the take off and top speed 50cc vesper has 4 gears
     
  4. panmines

    panmines Member

    If you buy from a reputable quality vendor who builds these engines themselves, you shouldn't have too many issues with reliability. Half of the problems come from being massed produced in Chinese factories and the other half comes from bad engineering design. One thing to look for is the wording "machine balanced" crank shaft. I admit I have bought only one kit from one vendor, but it has been running for over a year and I have had no issues with it. I bought the F80 Kit from ThatsDax.com. I hear that some people are able to increase a 66cc to 6 hp with modding, but I can't say if they are reliable. I think the best way to maximize the life and reliability of these engines is to avoid over revving them (above 4800 RPM).
     
  5. skyash

    skyash Active Member

    Still the performance is weak compared to other motors in the same category. All the mods and time wasted when a better motor will do out the box
     
  6. Frankfort MB's

    Frankfort MB's Well-Known Member

    If you don't revv your engine above 4800 RPMs your not using ANY power
    These are two strokes. Powerband is up high up there, probably around 6-7k

    At least that's where my engines power is at:)
     
  7. Jonj57

    Jonj57 Member


    would that be the "bullet train"? I haven't heard that it's 70cc, if so fuuuuuudge ya I want it. Electric start, wet clutch, AND higher power? Sounds like my jam! Wonder if itll work with a sbp jackshaft?
     
  8. FurryOnTheInside

    FurryOnTheInside Active Member

    I think they are calling it that now. Last I heard it was pre-order only, they don't/didn't have them yet. There's absolutely no spares back up. They have not been long term tested. We don't know the bugs and fixes. There's no upgrade parts. It is as wide as a 4 stroke so you need the freaky bent cranks. High power with only 3 more cc means that it must be a screamer. So about as antisocial as a petrol scooter I guess, a cop magnet and not a good thing for MB public relations either. Definitely not stealth. It does not mount to the SBP shift kit.
     
  9. jatgm1

    jatgm1 Member

    if you want long term reliability then yea, a dirt bike motor works. but i would get a 49cc 2 stroke motor to have the highest power while being legal. the benifit of the grubee kits is in simplicity, versatility, and size. they are absolutely tiny engines and are specificly made for bicycles so you dont have to go welding up a bicycle frame or making/buying some crazy mount. i have two manic mechanic mounts but thats just to reduce vibration. if you can even fit a dirt bike motor in a bicycle frame your gonna have some wide cranks. and it just looks super illegal. and even if its a 50cc engine, if it has more than one gear its illegal in lots of states too. these grubee engines arent really cop magnets, and the original grubee engine is actually
    1. epa certified
    2. under 50cc
    3. easy to mount and use
    yea, they have their problems, but if your a decent mechanic your shouldnt mind taking a few minutes to fix these things. theres maybe 20 moving parts all together. i mean there arent even any valves. theres beauty in simplicity.
     
  10. jatgm1

    jatgm1 Member

    or just get a new engine for 60$ n swap it.
     
  11. skyash

    skyash Active Member

    So simple so many problems lol . this site should be called motorised problems ...any thing that makes more than 250watt is illegal here so I can't win .I got a 4 stroke and needed to widen the crank .but it's super reliable .so many years fixing 66cc engines I get sick when I see one lol
     
  12. KCvale

    KCvale Motorized Bicycle Vendor

    Hi Randy, welcome to the forum.

    Did you know that hitting enter while you type does not finalize the post, it puts a line break in the text to make the whole post more readable?
    I couldn't get through your first post for example ;-}

    As you have learned in this topic already there is no such thing as a 80cc, most all are 66cc with the exception of the 70cc electric/pull start auto clutch Zelda with on-board power generation.

    The company asked me to review a kit and sent me one all the way from China.
    I was excited as hell but quickly disappointed.
    It is a really fine engine that performs better than a typical 66cc, but I didn't have a battery in for the electric start so we tested it just using the pull start. Pfftt.. ~50 pulls and it broke and I don't mean the rope, the specialty plastic that actives it broke and their are no replacement parts.

    So then I put a battery on and few more cool electric start rides on it and starter motor died, and again no replacement parts so it has sat useless for a few months now because there is no way to start it.

    A great setup if they hadn't cheeped on those 2 crucial parts and I told them so.
    If you want more details my topic with pictures about the adventure is here http://kcsbikes.com/topic.asp?TOPIC_ID=948 if you are interested in more details.

    If your goal is something that really kicks ass, start with a Grubee Skyhawk GT5 engine, give it an expansion chamber exhaust, and make it a shifter via a SickBikeParts.com (SBP for short) jackshaft shift kit. http://www.sickbikeparts.com/catalog/index.php?cPath=21&osCsid=ddcppgjc4n7oao26rbo976r5g4

    [​IMG]

    That combo of parts required the dual disc brakes if that is any indication of how quick and fast you can get with just a simple 2hp 2-stroke and gears ;-}
     
  13. Steve Best

    Steve Best Active Member

    Good advice from KC but I'd suggest to start simple Randy.
    Buy from a reputable supplier (I liked Grubee) and install it as designed. No mods at first.
    Get it running and break it in at 24-32:1 oil mix. Takes about 3 tanks of fuel to break in.
    I had no problem getting 30mph or more with the completely stock 66cc Grubee Skyhawk.
    Pay careful attention to:
    1) rear sprocket centered and running true. Tighten bolts carefully to get true.
    2) Chain alignment from motor to wheel, very important.
    3) Chain tensioner snog so it won't come loose, and of course in line and slight slack.

    Run the motor as is for 3 tanks, but some jets for the carb, 68 and 65 will do. try them. Stock is 70.

    This should keep you happy for a couple months...

    Steve
     
    BikeBuilder43 likes this.
  14. jatgm1

    jatgm1 Member

    well, ive worked on four strokes and ive worked on two strokes. given my experience with four strokes are lawn mowers mainly. there are many more parts on a four stroke, so if its made well and you dont need to mess with it, yes its reliable, but at the cost of speed, for me legallity, and the ability to easily mod it. but ive been using the same grubee engine for quite some time now, and after making a few adjustments and improvements its actually quite reliable. other than the air filter falling off because i didnt tighten it enough, and the headlight dieing because its cheap and chinese, the engine has been running for months, and i go everywhere with it, sometimes i just ride for the hell of it. ive gone through over 3 gallons a month and its still running like a champ. plus you really cant beat the price of these engines. their dirt cheap.
     
  15. KCvale

    KCvale Motorized Bicycle Vendor

    Yep, I don't recommend a rookies first build start with a Jackshaft shift kit, they are not the least bit friendly to assemble without insight of how they work and the right tools to even be able to do one , which is why you don't see many builders of them.

    Once you get familiar with the 2-stroke engine from a DD build or two it's just a couple extra steps as you go to next time to take the machine to the next level.
     
    Steve Best likes this.
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