Rear friction engine: faults

Discussion in '2-Stroke Engines' started by bilboby, Aug 31, 2010.

  1. bilboby

    bilboby Member

    1: loud motor noise
    2: Motor giving out fumes
    3: Smell of waste petrol mix
    4: Leakage of black oil
    5: Bolt fittings came loose/lost thus stopped riding
    6: Public against the first two described above

    Overall i passed an enjoyable afternoon early evening riding MB around the outskirts of Paris. Infact the MB got so much attention/reaction from the local's young/old that many photo's of the bike + motor setup were taken on mobile phones:cool:. Infact one Harley Davidson owner was so impressed he's invited the MB + myself on a bike run next Sunday near Disneyland Paris.

    However i think i'll decline his offer as i don't wish for such attention ridiculing the MB setup. Afterall it's easy/nice when such people complement other's on such build's but i'm not someone who like's to be a joke of the pack nor will i think my MB.

    I've sent in a photo concerning the problem of the oil leak i had during my recent/this afternoon's MB ride.

    Any help on why such problem's occurred will be received graciously

    Also any reason as to why the motor pipe/exhaust is polluting the enviroment with blue fumes?

    Cheers & 73's

    Attached Files:

  2. Whizzerd

    Whizzerd Member

    The oily residue is no doubt dripping from your muffler. If you've got thick smoke at the exhaust, your mixture setting at the carb is probably set a bit too rich. One screw is an idle stop. The other screw is mixture. Start the engine, after warmed up, screw the mixture screw clockwise IN VERY SMALL INCREMENTS! You should notice the idle speed increase due to leaning the mixture. Now screw the idle stop counterclockwise to acheive desired idle speed. You may need to do this a couple of times. REMEMBER, if you lean the mixture too much you will starve the engine of lubrication and ruin it. Turn in until the slightest bit of light smoke is showing. When you ride the bike, if the engine bogs out or loses power, you've leaned it too far. Richen the mixture a little until power resumes. I have the same engine and it was test run at the factory and left rich on the mixture. This should also help w/ the oily mess but it's a 2 cycle and you'll always have some. Noise and vibration too. But lots of power!
  3. GearNut

    GearNut Active Member

    What oil/ fuel ratio are you using?
  4. bilboby

    bilboby Member

    Cheers guys and @ Gearnut 16:1 ratio @ 125ml oil for a 1/2gallon / 2ltr tank however as the engine is new perhap's the ratio should be higher or less?

    @ Whizzerd that's a very good tutorial you have given thus i'll set about adjusting the screws this afternoon & yes you're correct in stating the oil is leaking from the mini muffler.

    Also whilst i'm on the subject i've read on this forum that MB riders can expect around 120-150 miles per gallon but yesterday's first real test riding the MB full on meant i probably done around 40 miles ofwhich now the tank is nearly empty. Is that normal?

    Hopefully i'll get Whizzerd's advice done later on thus do/enjoy another good 60km their/back MB ride to the Chateau de Versailles:sweatdrop:

    Once again guy's thank's for your help as i'm sure amateurs like myself can learn much more about MB riding from the advice you both give along with other MB members.

    Cheers & Good MB riding
  5. GearNut

    GearNut Active Member

    I suggest using a 24:1 pre-mix ratio for break in.. After you have 600 Km's on the engine, switch to 32:1.
    The fuel mileage should improve as the engine breaks in.
  6. bilboby

    bilboby Member

    Cheers for that

    Good MB Riding

  7. Esteban

    Esteban Active Member

    That is a rich oil mix. What cannot get burned,, goes out the exhaust, dripping, smoking, & " stankin. " I would clean the plug, making sure it is a good brand name, & run a mix of 24-1 & see if that improves things. Also, it is more expensive, but synthetic oil will cut down on the smoke.
  8. Whizzerd

    Whizzerd Member

    Hi Bilbody, I emailed Rick at BGF about a manual for the Friction Drive kit and he replied that he didn't have one yet. So, I looked up the mixture recommended on the so similar HarborFreight engine. 20:1 for break in. 25:1 after. Amsoil, Lucas or other good quality 2 cycle air cooled type synthetic at even 40:1 would be fine. The key here is setting the mixture screw correctly. 40-50 miles on 2litre tank is about the norm on our mb'ing 2 cycle engines. The kit sellers mileage claims are inflated. BTW, on another thread I slyly asked if you are an Amateur Radio Operator. 73's is a common abbreviation used in that activity. You didn't respond so I'll ask more directly. Are you a HAM?
  9. bilboby

    bilboby Member

    Hello MB comerades,

    Sorry for late replying but cheers for your help on mixture ratio's etc and today i've run dry the tank thus therefore from tomorrow i'll be using 2 stroke synthetic where before i wasn't. Today's MB ride was more about breaking in the engine whilst running the tank dry of any old excess fuel though for the last 5km i had to push the MB due to the roller housing bolt nut's untightening & being lost due to the engine vibration.

    Tomorrow look's promising for another MB ride once synthetic fuel correctly measured has been mixed and added to the tank. As for the SP i'm using a Active AX 80 which though not new seem's to perform better than the BGF stock plug supplied with the kit.

    Cheers everyone & 73's

    NB: Whizzerd i'll PM you concerning your question about my eating habits:grin5:
  10. bilboby

    bilboby Member

    Made a discovery as to the possible reasons why spent thick black oil/fuel was leaking between the main engine housing & the muffler box. After inspecting a spare Active 50cc engine i have i noticed that there was a metal type card between the motor & muffler box but on the BGF motor there was nothing as the box was bolted directly onto the engine. Needless to say now i've remedied the problem and hopefully no more leaks on the scale which was happening before will occur.

    Also i've noticed after watching some youtube videos concerning rear friction drive engines that when the user pulls the starter cord the MB user's engine + drive roller turns even when placed on the back wheel. However the back wheel only turns when they start pulling the accelerateur handle but on my setup the back wheel turns when placing the drive housing onto the wheel regardless if i pull or not the gas handle. So something's still not correctly setup but what?

  11. bilboby

    bilboby Member

    Took note of your advice & spent a few more euros extra for purchasing the Castrol Top 2T semi synth├ętique oil.

    Attached is a photo showing three types of oil i have

    The Carrefour brand is 2T normal non synthetic oil

    Castrol 2T semi synthetic

    Total 2T synthetique but is over 5yrs old & was kept outdoors in all weathers thus probably not good for MB use.

    Cheers & 73's

    Attached Files:

    Last edited by a moderator: Dec 18, 2015
  12. GearNut

    GearNut Active Member

    Good find on your missing exhaust gasket!

    As for the drive roller issue, Is something stuck or hung up in the centrifugal clutch?
    If I am understanding you correctly, the drive roller on your set up is always driven by the engine at any engine speed, even at idle, as if you have no clutch.
    There should be a automatic centrifugal clutch that disconnects the drive roller from the engine at low engine speeds, and connects the two at higher engine speeds. Some of these clutches have a slight drag to them and can cause the roller to turn when the engine is at idle and the roller is not in contact with the tire. In extreme conditions, such as when the springs in the clutch are weak or the clutch bell is misaligned, the engine is at idle, the drive roller is in contact with the tire, and the tire is lifted off of the ground, the tire will rotate.
  13. bilboby

    bilboby Member

  14. GearNut

    GearNut Active Member

  15. bilboby

    bilboby Member

    Thank's for the URL link as having read it i understand now more about what your saying so now i'll be removing the engine for taking a good look at the clutch area. I'll post a photo of the BGF clutch on this thread along with that of the Active model showing any differences.

    Once again cheers

    NB: Just wondering if i can pick further your MB knowledge by asking if i'm correct in thinking that the photo i've posted show's 'C' as being the fuel/air adjustment screw? Thanks

    Attached Files:

  16. GearNut

    GearNut Active Member

    A= Idle speed adjusting screw.
    B= High speed fuel mixture adjusting screw.
    C= Low speed/ idle fuel mixture adjusting screw.
  17. bilboby

    bilboby Member

    Cheers a million for that as i can now once the clutch problem is resolved progress onto adjusting the fuel/air mix something i was unsure about doing before due to my lack of machanical experience.

    Enjoy yer Sunday & 73's
  18. bilboby

    bilboby Member


    Well having inspected the BGF clutch assembly it would seem i've found the reason for the drive roller turning without gear engaged? A spring inside the clutch are has snapped leaving only one end attached to a clutch plate thus i'm now assuming a major fault?

    Also enclosed is the Active 50cc Clutch assembly which seems to be made of higher quality materials.

    Cheers on your thought's for what i should do next including replacing the spring though such a spring might be hard to find here in France. Should i ditch the BGF motor as a bad job & install the Active, pity really as the BGF was going to be the main MB motor. Still my fault as now i realise that buying cheap chinese engines in the long run can be short lived and very expensive.


    Attached Files:

  19. GearNut

    GearNut Active Member

    While it may not be an exact match for the BGF spring, I bet you could find a suitable replacement spring at a local lawn mower repair shop.
    Drain all the gas out of the tank and bring the engine with you so as to make it easier to match up a proper length spring.
    If one shop gets all snotty over helping you out, try a different shop.
  20. bilboby

    bilboby Member

    Followed up your advice and visited seven shops who all told me the same reply "We don't stock the part" hence i'm now scouring the Internet in the hope of finding an identical spring. I'll let you know how i get on though i'm also going to try using a spring from another 50cc clutch assembly but chances are it won't fit?

    Cheers & 73's for your help