How many engines

Discussion in 'Motorized Bicycle General Discussion' started by mkatt4x4, Jan 20, 2014.

  1. mkatt4x4

    mkatt4x4 New Member

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    From reading tons of threads on this forum, it seems a lot of motorized bicycle enthusiasts go through many engines. Which makes me wonder if the kits are $170'ish and the engine is $100'ish, whats the range for the GRUBEE SkyHawk GT5A 66cc Angle Fire Slant Head Bike Motor before it dies, with normal use....of course. And is there anything else recommended to upgrade on this kit, to make it more reliable and last longer?
     
  2. maniac57

    maniac57 Old, Fat, and still faster than you

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    It's all about how you ride them (unless it breaks right away). I've had great results from 99% of my motors and I'm convinced it is due to my riding style. I don't scream around at full throttle all day long. I ride it like a BICYCLE. Of course, good maintenance helps prolong engine life too. The last one I ran on the Pig went 3k or so before I pulled it due to top end noise and it was the shortest life of any motor I've owned. (small end rod wear killed it)
    I admit I seem to have better luck than average, but it's not too hard to realize gouging and wailing on a tiny engine made with barely adequate materials will not promote reliability.
    Don't ask it for more than it is capable of and it will last much, much longer.
     
  3. Toadmund

    Toadmund New Member

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    The best thing you can do is disassemble it, inspect the parts and properly put it back together.
    My first motor would not have run at all if I did not do anything to it, it had a loose head.
    Some of them are just plain lemons with a part, like again, my first motor, the lower con rod bearing self destructed, hence my piston and cylinder too as a consequence.

    The best care and driving and using the best of oils and maintenance won't fix a defective component!

    I think my second motor is a good one, smooth as butter, and it was the cheapest one I could find on ebay.
     
    #3 Toadmund, Jan 20, 2014
    Last edited: Jan 20, 2014
  4. Huffydavidson

    Huffydavidson STREETRACER/MANUFACTURER

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    Don't beat it and it won't break.
    Now Lynn at CustomMotorBike said she 10,000 mile out of one of hers.
    But she a girl and probably rides like one.
    LMAO
    laff
     
  5. 2door

    2door Moderator
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    Ditto:

    Abuse any machine and it will eventually fail. Treat them right and they'll return the favor. I've put a lot of miles on my motorized bicycles and have never had a major engine failure.
    Want to go fast? Buy a motorcycle.
    Want to race? Be prepared for things breaking.
    Want to just enjoy the ride? Treat the bike and engine well. Proper use and maintenance will go a long way.

    Tom
     
  6. dodge dude94

    dodge dude94 New Member

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    I've got 450mi on mine and it still runs rather nicely considering I've beat it like a rented mule MORE than once.


    :D
     
  7. crassius

    crassius Well-Known Member

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    I've had several folks here that had engine (and other) problems for the first (and sometimes second) engines - once I got them to take better care and ride at more reasonable speeds, all are now high milers. They're POS engines, just take better care than the average person takes with their stuff.
     
  8. maniac57

    maniac57 Old, Fat, and still faster than you

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    I sold my original Pig with well over 10k miles on it. The new owner still rides it to work every day it doesn't rain. Longest lasting ht I've ever seen by far.
    It was one of the rare RICO kits with the red plastic insert in the clutch lever. Every one of the three RICO motors I've run was much better quality than the average HT, but it's just luck to get one as nobody sells them exclusively. They seem to just show up randomly once in a great while. (I've only had three in over 20-25 kits ordered from my vendor.)
     
    #8 maniac57, Jan 21, 2014
    Last edited: Jan 21, 2014
  9. rogergendron1

    rogergendron1 New Member

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    i ride my motor bike like its the last day on earth and i beat the living crap out of it....

    now that being said... i am a vary good mechanic and i have built my bike ti take the abuse so to speak.

    i have it ported and polished wide open and have a lightend top end, titainium wrist pin and upgraded needle bearings and even modded and trimmed the piston... those mods lighten up the top end and make the motor more reliable at higher rpms with less vibration, i run this motor at a corrected or static 13:1 comp so the higher grade bearings and lightning it up was nessasary..... i run 13:1 comp with 100 octane its actualy my own mixed race fuel... 3 parts 93 oct and 1 part xylene or toulene to get 100 octane.. this prevents detonation and provides better combustion as detonation kills motors by over stressing the bearings.

    to keep it all lubed up at high rpms... i mix my own concualktion of lubricants and oils into my custom race gas..... first i mix a good quality 2 stroke synthetic race oil in the 100 octaine to get a mix of 40 to1 (lucas oil royal purple, opti 2, husvarna, ipone,...) then with the 40 to 1 mix i add upper cylinder lube to it to get it to 32 to 1 mix (lucas oil upper cylinder lube, or marvel mystery oil) this leaves me with 100 octane mixed 32 to 1 with upper cylinder lube in it for added protection from high rpm riding for extended periods of time ...7500rpms for 30 min strait......

    know even knowing all this and designing my motor to run like soo.... i still tear off the top end EVERY WEEK and inspect it visualy and inspect the tolerances with mcromiters and vernia calipers... it only takes an hour or so for me to do this.

    and so far so good !!!!! its been about 2,000 miles on this 13:1 comp race motor turning 7,000 to 8,500 rpms on the regular and my cylinder shows little signs of scoring and my piston is hardly scored and my rings are still black !!!! my combustion chamber has ZERO CARBON BUILDUP due to the lucas cylinder lube and is still shiny !!!! all my bearings are in verry good condition and the motor over all looks and runs great !

    its been my experiance that motors that have been modded by someone who knows what they are doing and are kept well maintained useually last a lot longer than an out the box slap on and go job...

    i have found that the stock china girl with no mods or work will give you more trouble than its worth,.... but after you mod it a little and fix a few design flaws like the needle bearings and cheap case seals combustion chamber design and comp ratio.... it becomes a sweet little motor !

    i have got 2,000 hard high rpm miles on this motor and it looks like it has at least another 4,000 miles left on it riding the same way...

    i am shure though that if i drove it like my grandpa and babied it it would last forever with only a ring swap every year or so, but what fun would that be ? LOL
     
    #9 rogergendron1, Jan 21, 2014
    Last edited: Jan 21, 2014
  10. rogergendron1

    rogergendron1 New Member

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    i guess the point is... if you want to ride hard and go fast .... expect to do a lot of corrective work before even putting the motor on a bike, you need better needle bearings, a titainium wrist pin to lighten the top end, cut piston skirt and dome ramps,port an polish, port match, free flowing exhaust, 16mm carb, higher compression 10:1 is a good comp ratio to shoot for as it offer performance with out too much stress on the motor... all this will lighten the top end reduce vibrations and allow for higher rpm's safely.
    a motor like this will last a long time with proper riding and matenance, and will be more powerfull and fun to ride than a stocker...


    now if your not into doing work like this and just want to slap it on and go... be aware that you at least need to clean up your ports as a single casting flash from a porly made cylinder will destroy a brand new motor on the first rev!!!!

    after cleaning the ports make shure the intake and exhaust are matched as good as you can and the clutch is adjusted right, check the head to see if its torqued right, and you should be good to go ! if you maintain proper lubrication and ride it easy to normal, it should last at least 5,000 miles !!! remember to keep it under 7,000 rpms or the vibes will destroy the motor real quick and where it out faster, but all in all with some minor corrections like cleaning up the ports, matching the intake and exhaust and retorqueing all the bolts a stock china girl should last a long time !!!


    all this being said.... i still wish they had a cast iron cylinder !
     
    #10 rogergendron1, Jan 21, 2014
    Last edited: Jan 21, 2014
  11. rogergendron1

    rogergendron1 New Member

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    i had a grubee gt5 before my dax race motor.... i spent over3 weeks trying to blow it up !!!! it never siezed !!!! i ran that like motor you never saw motor run before !!! i even heald the throttle wide open in nuetral no load for a good min every day trying to see if i could sieze it !! i would pourposly rid as hard as possable reving it up wide open all the time and holding it there, pulling the clutch in wile rideing at wide open throttle and letting the motor wind out then dumping the clutch and repeteing this over and over, long burn outs on the concrete, super high rpm down hill riding, reving it as high as possable to see if it would blow, i even ran it on a 50/50 mix of rubbing alcahaul and gasoline mixed 70 to1 and reved the crap out of it wile riding as hard as i could for 2 days on that mix and the only thing that happend was she ran a little hot ! finaly i ran it on strait gas with about 25% acetone added in and rode it 5 mile to work !!!! i cant believe it made it like that !!!!! on the way home though it over heated and slowly siezed going up hill 1 mile from my house so i pedaled home.....lol........... before i removed the motor i was riding the bike around adjusting the rear hub for free play and i dumped the clutch on acsident ..... to my suprize she turned over and wanted to start !!! W.T.F......!!! some how it unfroze itself !!!!

    apon tear down of the engine, i saw the cylinder was severly scored and scratched and the piston dome was blue from over heating and scraped up bad on the skirt, the rings were worn so bad they were rounded out LOL and shiney !! the chrome was flaked off the jug to the tune of 30% of it missing and the play in the needle bearing was real flopy and loose....

    but even with all that castostrofic damage to the top end and running on cheap gas mixed with acetone and no oil ..... it still wanted to start back up !!!!!!!

    this changed my mind on the china girl and this incident is what made me go for another 2 stroke rather than use the 4 stroke i had planned, it would appear that as long as you have a well tunned carb your motor will take a serious beating !!
     
  12. Greg58

    Greg58 Well-Known Member

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    I have a grubee 48cc that has around 1300 miles on it, the only thing that has been replaced is the crankshaft seal behind the magneto. I ride at 25 to 26 mph so the little 48 CC is humming pretty good, some have not had good luck with grubees but all six that I built or helped build are still ruining.
     
  13. Scootmeister

    Scootmeister Member

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    Two more ideas. Excess heat kills these engines so get it tuned properly. Second, the stock airfilters are crap. Grit and debris will destroy any engine so get a good filter with either an oiled foam or filter element to keep the combustion chamber clean. Your rings, your cylinder wall, and your bearings will last longer.
     
  14. Theon

    Theon New Member

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    I am on my motor number 5, but only cause I love em' (3 running and 2 being built).
    My motors don't do that many miles, but I use them hard.
    Only thing that has stopped any of them is the Mag coil (get a spare). and a seal went on an old motor that I didn't build, but there was nothing else wrong with the old girl.
    However, I do recommend going over the motor properly before running it if your going the EBay way.
     
  15. maniac57

    maniac57 Old, Fat, and still faster than you

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    I have long maintained an Air-cooled piston port two stroke is one of the most reliable engines in the world. Only three moving parts if you don't count the reduction gears.
    Crank, rod, piston.
    The rest is details...treat these engines like they were designed and they last forever. Most quality related failures will occur within the first few days so once it's sorted out, they just do miles. I recently sold a running ht with well over 10k miles of 250lb adult use.
    Still running the new owner back and forth from work every day.
     
  16. Allen_Wrench

    Allen_Wrench Resident Mad Scientist

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    Two motorbikes - but only one Dax-purchased China Girl. Don't know how many thousand miles (I keep it as well-tuned as I can). Four years old, going on five I think. What Maniac says is largely true. Maintenance with these two-smokers is minimal, but extremely important: proper oil mix, proper jetting, clutch in good shape, well adjusted magneto, good spark plug that is gapped just right, etc. I even took the time to do port matching, got a performance air cleaner, high-end plug and wire, and other bits. She hums really nicely. Hardly any vibrations at all.
    Now, I've worked on plenty of other small engines for other things. But I've only ever needed the one bike motor. I'll replace it when I have to.
     
  17. maurtis

    maurtis New Member

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    Between 400 and 500 miles on my BGF 66cc before the wrist pin bearing blew. I knew it had to be replaced but I could not get the wrist pin out, so let it ride. I had upgraded pretty much everything except that, which should have been the first thing since they are known to go.

    But I rode it at full throttle whenever possible. Break in was taking it easy for about a mile... LOL.

    I then moved on to electrics which have been nothing but pure joy. And while I do have a real motorcycle, I am sure that one day I will build another gas bicycle since it is a feeling that cannot be reproduced otherwise. If I went with another China Girl, it would be a balanced Dax. But more likely a 4 stroke, either the 79/99cc Preddy or one of the multispeed Lifans on a stretch.
     

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