Please Help

Discussion in 'Motorized Bicycle General Discussion' started by vsaxena, May 2, 2014.

  1. vsaxena

    vsaxena New Member

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    Hi!

    So I bought an 80cc motorized bicycle from a guy off Craigslist about 1.5 months ago. I bought it with no idea of what I was about to get. I am about as ignorant of mechanics as anybody can be. I have been learning throughout the process, but there are some serious issues that I need resolved. Any help you could provide would be greatly appreciated.

    #1.

    First of all, the gentleman told me to use 1/4 to 1/2 an ounce every time I fill the 1/2 a gallon tank. Um... I have been doing as he told me, but I finally took the time to read the manual, and it says to use 50 ml per 1 litre, right?

    There are 3.78 litres in a gallon, right?

    So that means 50 * 3.78 (189) mL per gallon, right?

    That comes out to about 6.4 fluid ounces or gallon, or 3.2 fluid ounces per fill.

    ????????

    #2.

    The muffler continually comes off. AHHH. It's a relatively cheap and simple $29.99 muffler. I've tried everything. Different bolts. Clamping it in place. Nothing works. I just set out after the latest try. It sounded beautiful. Few vibrations. I had NICE SPEEDS without feeling fear. Then BOOM all of a sudden it got super loud and started vibrating again.

    The guy recommended I buy an advanced flexible muffler for like $80. But before I make the investment, I need to make sure it'll fix the problem! I mean I see other 80cc bikes on YouTube running just fine . . .

    #3.

    Last but not least, I still cannot get this down right. So I usually ride without a muffler (I don't ride often) obviously. I don't like going too damn fast. I'm a scaredy-cat, okay?

    It starts sputtering when I'm going slower. So I speed up because if I try to hold down the clutch, it almost always revs up. The clutch just makes me very uncomfortable.

    Now earlier today when I was riding with the MUFFLER (when it was nice), I could NOT HEAR any sputtering, but I was going at slow speeds for a bit and then fast, you know. Is it possible that it was sputtering and I just couldn't hear it? Is it maybe THAT that caused the muffler to blow?

    --


    ANY HELP would really, really be appreciated.

    Sincerely,
    V
     
    #1 vsaxena, May 2, 2014
    Last edited by a moderator: May 2, 2014
  2. crassius

    crassius Well-Known Member

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    I use 8oz oil to a gallon (16:1) for the first gallon of fuel for a new engine, then 4oz to a gallon (32:1) from then on.

    Sounds like your muffler hanger wasn't put on - you need this to prevent it's weight from shaking it loose.

    When the muffler is loose, you can expect the bike to run abnormally.
     
  3. CTripps

    CTripps Active Member

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    Hello V, and welcome to the forum.

    First off, the fuel mix thing... If you use the Google site search above (sandwiched between a pair of banner ads near the top of the screen) you'll find a wide variety of opinions on what ratio to mix to. After break in, I run mine at around 40:1, or 25ml oil per liter. But that's me. the ratio can run up to 100:1 depending on the product you use.

    Now, when you say the muffler falls off, do you mean it comes undone from the side of the engine and the whole works comes off, or is it the end cap that keeps going? (I've played find the end-cap a few times, but never had the whole unit drop off..) Does the bike have the holder/support for the muffler, or is it simply hanging off the studs on the side of the motor? Back pressure provided by the exhaust is essential to a 2-stroke's operation, so if the whole muffler is disconnected running that way can lead to damage to the engine.

    As for 'sputtering'.. not quite sure here.. On the bikes I've built the 'sweet spot' in the throttle has been a little different for each, and the motor will sputter and 4-stroke a little just under or over that zone, but once you find it you'll know it. The motor will smooth out and start a nice smooth power climb/ramp-up without having to move your hand/change throttle position until it levels out and is ready for a bit more gas. It's difficult to explain, but you'll know it when it happens.

    Hope that helps a little.
     
  4. 2door

    2door Moderator
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    Welcome to the forum. We're glad you've joined us. Please keep in mind that this is a family forum so we ask that you keep the content of your posts in that context.

    You'll find plenty of help and good advice here to assist you in getting your motorized bicycle up and running.

    As said above, running without a muffler is not a good idea for several reasons. Primarily if the entire exhaust system is what is "falling off" you need to address that because of potential damage to the engine. If it is just the end cap on the muffler that is coming off there are remedies for that such as drilling a small hole and threading in a screw.

    Another reason for keeping the muffler on is the negative attention your bike will draw without it. Our hobby has some legal issues that we try to keep away from and running a bike without a muffler is one of them. Please don't ride the bike unmuffled for your sake as well as the hobby in general.

    When you say the bike "sputters" when going slow, how slow is "slow"? If your speed drops below 10 mph you should disengage the clutch and pedal. The engine will sputter, run rough and jerky below about 10mph with the clutch engaged. Not quite sure what you mean by "The clutch makes me uncomfortable". Can you explain? The clutch is a critical part of the motorized bicycle and should be used as it was designed.

    Hope we've helped a little and we're always here to offer advice.

    Tom
     
  5. KCvale

    KCvale Active Member

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    Just for your reference there is no such thing as 80cc, you see them listed as 66/80cc but it's Chinese BS and they are all ~66cc in actual displacement.

    Was this an experienced builder with multiple builds, or just a guy that built a bike and couldn't make it run right so he dumped it on Craigs?

    Well there is a huge red flag warning right there.
    It is in your best interest to just get a 1 gallon gas or two for bike use and mix good quality gas with your average auto supply stores 2-stroke oil as mixing 'in the tank' is always ifffy.

    32:1 is a good mix, that is 4 oz (1/2 a cup) of 2-stroke oil to a 1 gallon of gas.
    Your builders advice even at 1/2 an ounce to you 1/2 gallon tank was absurdly low at 128:1 and liable to toast your engine in short order.
    Trying to run at a 128:1 mix will do that and the damage may already be done.
    Idle with the clutch in is idle, you set it on the carb not by the cable.

    Hope that helps.
     
  6. silverbear

    silverbear The Boy Who Never Grew Up

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    Not all oils are the same. See what the oil manufacturer recommends. 100-1 is right on for Opti-2, but that ratio for an oil designed to run at 50-1 would be a bad idea. 50-1 using a regular 30 weight oil would be wrong again. They are not all the same by a long shot.

    Welcome to the forum. Keep in mind that we have women members here and even many of the men (including me) would prefer to keep the subject on motor bicyling. This is a great place with a lot of helpful people.
    SB
     
  7. vsaxena

    vsaxena New Member

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    Just now getting back to the forum! WOW @ all the replies. Thank you guys so much! Am tipsy right now but am going to attempt to read all of your replies!!!
     
    #7 vsaxena, May 2, 2014
    Last edited: May 2, 2014
  8. vsaxena

    vsaxena New Member

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    The whole thing fell off. Several times. So the guy who sold it to me installed a clamp to help. Well, it fell off again. Well, it came undone. the SCREWS came undone, but the clamp held it in place. Just happened earlier today. So annoying. I finally had a new muffler installed, screwed in AND clamped. Engine sounded beautiful. Then WHOOP there she go!

     
  9. vsaxena

    vsaxena New Member

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    Absolutely about the family forum. I'm a conservative fellow, but I do curse a lot (much like Sean Hannity's executive producer, ironically enough, LOL), so I do appreciate the reminder :).

    Um I swear like I break and pull the clutch but sometimes it starts REVING like crazy when I do that. It suddenly gets loud and I freak out and let go of the clutch. I know for a fact I'm not revving. I'm breaking. I've loosened my grip on the throttle, etc.

     
  10. vsaxena

    vsaxena New Member

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    I think you're right. He's Brit, so I kind of just trusted him (hard to imagine someone with an accent that thick being full of it), but I think you are spot-on correct!

     
  11. TakeiT

    TakeiT New Member

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    I had issues with the muffler too.

    First thing I did with my muffler is removed the gasket, took a wire brush to it and then applied some high temp gasket maker to the current gasket, on both sides. Put that back on, then I installed the muffler, using 2 lock washers for each bolt, then BLUE loctite. If you use the red, it'll never come off.

    As for the sputtering and reving up, it's because the muffler isn't there. An engine won't run properly without the proper muffler installed. When my gasket went, the engine would sputter and rev up too, now that i've fixed that it's fine, and actually quieter than ever!

    For the fuel, you should run 32:1, you can check a conversion chart. Most pocket bikes/2 stroke bikes run at that mixture, it's a good balance.
     
  12. 2door

    2door Moderator
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    If the engine speed increases when you disengage the clutch that is a symptom of an air (vacuum) leak somewhere in the intake circuit. Most common is where the carburetor attaches to the intake manifold or where the mainfold mounts to the cylinder.
    Start looking there and we can suggest some other places if those prove to be leak free.

    Tom
     
  13. TakeiT

    TakeiT New Member

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    He said he runs without a muffler = wide open manifold, baaaadddd idea.


    I also added gasket maker to the carb, as well as the loctite. I recommend you do the same, it'll save you from issues later.
     
  14. mapbike

    mapbike Active Member

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    In regards to keeping the muffler in place its actually really simple if it has exhaust studs, all you need to do is go to a hardware store and get a couple extra M6x1.00 nuts and double nut each stud after muffler is installed.

    Get the first nut good and snug with even pressure on each side of muffler flange, then put an additional nut onto each stud tighten until it is touching other nut, then with a 10mm open end wrench on each nut, while making sure the first nut you put on doesnt move tighten the second nut down good and tight against the nut that is against muffler flange.

    This simple technique works good for preventing nuts from backing off.

    If. Your engine has socket head screws instead of the studs, I suggest a dab of either blue or red loctite thread locker, I've used both with great results on exhaust studs that were loosening from vibrations.

    I may be way off base here but for aomereason Im thinking to tell you this, if engine revs up when you give it more throttle while clutch is released, your clutch is slipping.... if engine over revs when you disengage clutch and doesnt want to idle down, suggest as others have said, you have an air leak at a gasket more than likely.

    Map
    .wee.
     

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