reliability is a must!

Discussion in 'Motorized Bicycle General Discussion' started by mybike1, Jan 3, 2013.

  1. mybike1

    mybike1 New Member

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    So, I'm just about ready to fire up my Grubee Skyhawk 66cc for
    the first time and Performance is not my priority, reliability is.
    What would you guys recommend to help make this thing a bullet proof
    fun machine?
    So far I've seen two of my friends give up on their motorized bikes
    because of all the constant attention, adjustments and repairs.
    I'd like to keep this thing running for years to come. Any suggestions?
     
  2. Moto

    Moto Member

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    high tensile bolts on ALL mounts (front rear motor mount, chain tensioner, etc.)us 8 grade, ideally upgraded sprocket mount (billet aluminium), greased chain, no chain tensioner or chain tensioner drilled / tacked to chain stay or spring loaded chain tensioner. run high quality oil at a recommended ratio once broken in. Break in at 24 to 1 (there is a LOT of ideas about this but this is my go-to ratio), install a fuel filter. The SBP high tensile head studs are a great option and greatly improve reliability if you take you head off often or have a high compression head. This may be a lot to start but the most important things in my opinion are the upgraded mounting bolts, safely secured chain tensioner, and fuel filter. Best of luck and ride safe MOTO
     
  3. GearNut

    GearNut Active Member

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    In addition to Moto's suggestions,
    Be very finicky with how well the engine is mounted to the bicycle frame.
    The mounting blocks must lay flat up against the frame tubing from top to bottom. Also no gaps are allowed anywhere it cradles around the curvature of the tubing. File or sand the mounts to achieve this. An easy way to accurately alter the size or curvature of the mount blocks is to wrap sand paper around a short section of wood doweling PVC sprinkler pipe or similar that is approximately the size that you want and sand the mount with a back and forth filing motion. Check your progress often. You don't want to make it too large or accidentally go crooked. You can tightly wrap the doweling or pipe with scrap paper to make it slightly larger in diameter if necessary for a custom fit before wrapping with sand paper.

    I always take my sweet *** time and get the mounts to virtually snap on to the frame tubing. Yes, they can be made to fit that good. If you do this too you will never have an issue with them.

    If the engine can wiggle or twist while under the strain and load of propelling you down the road the mounting bolts will snap.
    Also, if the mounting bolts take a sideways load like they are being spread apart to fit around the frame tubing they will snap. They can only withstand a stretching load, not a bending load.
     
  4. Maxvision

    Maxvision New Member

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    Also, don't port and polish, add after market race parts and then every time you ride it see if you can go faster than you did last time!

    I can't tell you how many cylinders, clutch pads, spun bearings, cracked cases and broken bolts I've gone through by not following my own advice!
     
  5. 2door

    2door Moderator
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    All of the above is good advice.
    Here's something else to keep in mind. It's a motorized bicycle built by you with your talents and skills. It is not a motocycle that was designed and built by engineers in a factory. You must determine where the potential for something to fail is and design/buid to eliminate those things.

    You can gain a lot of input from the members here but my advice would be to build it right following advice you see here but then ride the bike for a while to 'work out the bugs' before relying on it as your daily transportation; if that is your goal. Proper break in of the engine as well as the rest of the build, bearings, brakes, chains and sprockets, is essential.

    As with any machine your bike will require periodic maintenance to keep it running properly. Treat it right and it will return the favor.

    Tom
     
  6. mybike1

    mybike1 New Member

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    Thanks guys, My motor mounts are spot on and solid...and so is my chain tensioner and everything else mentioned. I fabricated most of this stuff myself and am pretty confident in my skills.
    I guess I was expecting things like carb issues or clutch problems or maybe even some internal motor issues to watch out for. If motormounts are in the top 3 problems to watch out for, then I should be golden :)
    I understand that these little motors are not going to be as reliable as my honda elite 80 scooter, and I'm capable of the occasional "tune and test" so, it sounds like I might be over-thinking things...again. Thanks!
     
  7. UVsaturated

    UVsaturated New Member

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    On some kits there are problems with main crankshaft bearings that are substandard (missing bearings). I've had mine fail prematurely, causing a huge crankcase vacuum leak. Moisture getting inside the magneto cover causes magneto (coil) failure. If it's worth it for you to disassemble the entire engine to look at these bearings, you might have a 50/50 chance at best to discover if your bearings may be bad straight from the factory. Trust me, you will know when the bearing fails as the metal shielding disintegrates and sounds like the entire engine is coming apart. If you find metal shavings inside the magneto cover, that is what it is caused from. Other things not mentioned are sealing intake leaks with either an O-ring or RTV sealant between the carb and intake. Use one wrap of teflon tape around the throttle cup retaining nut and even RTV around where the throttle cable end inserts into the adjustment barrel. All the crankcase and cover hardware should be removed and treated with sealer or loc-tite to prevent loosening due to vibration.
     
  8. GearNut

    GearNut Active Member

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    Unless you are mechanically inclined and familiar with small engines, do not take the engine apart.
    Sealing the magneto case is recommended. Use RTV silicone where the wires enter the protective sheath as well as around the plastic retaining nut where the wires enter the engine case.
    RTV is not fuel resistant. Do not use it on or in the intake manifold. Use SealAll or Hylomar instead.
    There is no reason to seal the top cap of the carburetor slide or where the throttle cable enters the adjuster in the top cap.
    Teflon tape can be used to create an interference fit between the threads of the top cap and the threads of carburetor body which will help prevent it from vibrating loose, although I never have had this problem when I tighten the top cap properly.

    Do not under any circumstances what-so-ever use any sort of sealer or Loctite product on the factory side cover screws. They are made of a very poor quality metal and the heads usually strip out when you try to remove them for the first time. Also if you were to seal or loctite them they can easily snap off inside the case when you remove them creating a real nightmare problem.
    The factory hardware should be replaced with quality hardware that will never give you any of the aforementioned problems. SBP sells a very good quality kit at a very good price. Hardware kit HERE
    A small drop of Loctite 242 Blue on each bolt can be used with the SBP hardware if you wish.
    Some folks hate Loctite and never use it. They just check the hardware regularly and snug up anything that comes loose.

    Also read up on the threads for beginners to learn more about these engines and the care and feeding that they require.
     
    #8 GearNut, Jan 10, 2013
    Last edited: Jan 10, 2013
  9. 2door

    2door Moderator
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    Ditto!!!!!!!!!

    Tom
     
  10. UVsaturated

    UVsaturated New Member

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    If his main bearings fail, he may need to do that. You can't encourage people to begin to work with these engines without being a hand's on type of person. They fail often and unless you become intimately keen on these things and know these engines inside and out you are doomed to be standing there looking at a non-working bike.

    Many users of the forum have successfully used black RTV to seal the joint between the intake and carb. It is fuel resistant, which does not mean it is impermeable but it will last a long time in that it is not in direct contact with fuel. I would not use it on a gas tank.

    Yes, unfortunately there is. If you keep your bike outside, water can infiltrate the carb.

    You can also overtighten and crack the top cap trying to tighten it properly so it won't back off, which is why to use teflon tape. Of course a small dab of black RTV on the threads will also work.

    That's the entire purpose of using a sealer on the threads. I have had vibration loosen several case screws because they were not installed with enough torque from the factory. Is someone to say "I can't remove those screws because I am afraid I will strip the heads?". No of course not. The solution is to use the correct size phillips screwdriver in the first place applying enough force to not strip the head. This is also why I choose to use black RTV instead of loctite. It will prevent loosening but it will not seize the screw so tight that you break the bolt when removing. I have inspected all my fasteners after rides and using this type of sealer is foolproof. None of my hardware comes loose at all. Trouble free and dependable. The last thing you want to hear is going on a ride and you hear nuts and bolts hitting the pavement and wondering what it was.
     
  11. paul

    paul Active Member

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    best tip i can give is don't run at full throttle. most all the problems i had with my gas bikes was from vibration. vibration loosens things and cause things to get out of alignment and break. its easy for me to say this but in reality i know 2 positions on my throttle. wide open or off lol
     
  12. Nashville Kat

    Nashville Kat Active Member

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    Yes- a 36 or 34 sprock, and some not-too-fat tires- 1.95 or less- to get a good rolling cruise without the motor wide open-

    I still tout the 415 Trike Industrial chain- for about $15 a 415 size with smaller plates plates vertically- lighter in weight and ROLLS so much better- you can really feel it peddaling and so will the motor

    I've always had good luck with an NT speed carb on a short billet- when the motor is fairly level at least-
    no fuss or muss.

    and -yes- NO tensioner. No experience with CNS and I see there's a newer NT that looks simila to CNS- a choke lever might be nice.

    I like to use sound dampeners, and with the cover off, you can put a little grease around the internal gear, which makes it roll better and more quiet- you can feel and hear the difference, but keep it from around the back and the clutch pads, or that will slip til it dries or removed.
     
  13. LeTweek

    LeTweek New Member

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    Great thread BTW. My 2 cents - Scrap the stock spark plug (with the 3 prongs) and get the old style single prong that used to come stock. Don't use synth oil until your engine is fully broken-in.
     
  14. Predator303

    Predator303 New Member

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    "Reliability is a must!" and a China Kit dont go together - seriously... By the time you got all parts replaced to get it half way reliable, you could have bought more than one good 4-stroke set up.
     

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