Carby Soaked air filter, NO power, (I have to pedal to keep it running) New carb, same prob

Discussion in '2-Stroke Engines' started by StrangeTechnician9, Mar 20, 2013.

  1. StrangeTechnician9

    StrangeTechnician9 New Member

    66 cc bought w/ the racing carb. Ran very well while I was breaking it in... rode it in the rain one time (im not sure if that has anything to do with anything)

    anyway, after a few weeks it ran terrible.

    you could sit there and watch all sorts of fuel spitting out where the air filter goes.

    I could ride maybe 2 minutes at most before the filter was soaked and I had to either take it off or pedal to keep the engine running.

    Adjusted the float over and over and over again for weeks until the carb broke from trying to tighten it enough to keep it on the intake.

    YAY to get rid of this eyesore in the shed I bought a new carb... some SHA clone that they have on for way too much money, I bought the exact same one from and got a $15 deal :) go me.

    Put the new carb on and it started right up... at WOT it seemed to have almost 1/2 the power I expected it to have. after running it with the rear wheel off the ground for a good minute and a half, the performance dropped, and after about 5 min trying to adjust things, it wont even stay running for 5 minutes at WOT, half throttle, Idle... It just doesn't matter what I do.

    I've been trying to get it to run at least "ok" so I can sell it, for about a year now.

    Can anyone help me? I've heard some things about reed valve kits, but I'm not familiar with them nor will I pay an additional $100 or more for one to have this engine run like its "SUPPOSED TO"

    Thanks in advance

  2. crassius

    crassius Well-Known Member

    sounds a bit like a leaking crank seal or a case screw that isn't tight
  3. StrangeTechnician9

    StrangeTechnician9 New Member

    thanks but I tried that :/

    I forgot to mention that I rebuilt the entire engine already and replaced all the seals adding black silicone rtv to them.
  4. StrangeTechnician9

    StrangeTechnician9 New Member

    also runs great when I cut off the gas from the tank just before it runs out of fuel in the Carb. just like the old Carb did
  5. BigBlue

    BigBlue Active Member

    Check the magneto coil for any corrosion. It may have gotten wet and is no longer producing the correct spark. You can check it with an Ohms meter or DDM to verify that it is o.k. it should read near 200K Ohms set a a low scale.

    Hopefully it doesn't look like this:

    Here's a guide for no-start cnditions or run correctly:

    Good Luck,

    AKA: BigBlue
    StrangeTechnician9 likes this.
  6. crassius

    crassius Well-Known Member

    that definitely sounds like you're too rich - if leaning the needle & lowering float level help a bit, then think about buying a new main jet
  7. Fabian

    Fabian Well-Known Member

    You are not even in the ball park. I spent 2 years of pain and heartache getting my bike to run the way i wanted.
    My advise is: just accept that you've got another year of pain ahead of you and don't complain too loudly, because your neighbours want to sleep at night and not be kept awake by sounds of fierce cussing coming out of the garage at all hours of the morning.

    Yes, the reed valve intake makes a big improvement to low and midrange power, but it won't fix a carburettor that's in a shambolic state of operation.
    StrangeTechnician9 likes this.
  8. StrangeTechnician9

    StrangeTechnician9 New Member

    Ive tried one size bigger and one size smaller jet. also checked th ohms on the magneto with my multi meter. replaced cdi, plugs, plug cap, cleaned exhaust.

    i did not change out my piston rings which i may have fried breaking the engine in with too much gas not enough oil... im bad at that.

    Im thining about rebuilding the engine again to replace the rings. any thing else i should replace while its torn apart? ill take pics next weekend when im off work long enough take it all apart.
  9. Fabian

    Fabian Well-Known Member

    One single jet size larger or smaller is an insignificant number if we are talking #75 to #76 or #75 to #74. You need to jump 3 jet sizes to feel a noticeable change.

    From what i'm seeing you are poking a stick in the air trying to fix things without any real direction of process. Maybe it's best to hand the job over to someone who knows what they are doing, because i'm sensing an impending f*&^up if you go any further, and my word, you can really f#$% things up when trying to get the case halves apart without a case half splitter (and reassembly) tool.
  10. StrangeTechnician9

    StrangeTechnician9 New Member

    I'm 1/2 way there :) lol
  11. StrangeTechnician9

    StrangeTechnician9 New Member

    What I've done so far and a possible solution?

    Short list of thing's I've done to fix this strange problem.

    Spark plug. (many times to see what it tells me. Usually dark and wet meaning running rich right? When I start it and immediately turn off the gas, looks all dry and a lil brownish.

    Magneto. i get 351 ohms, it jumps around a little but thats pretty much the reading from what I remember. I'll check it again.

    CDI. I hear these fail for no reason so I put the back up on

    Exhaust. I blew through it and felt little resistance, but cleaned it anyway. It was very slightly easier to blow through it.

    Crankcase seal was leaking a bit. So I took apart the engine, split the case and replaced every seal I could find, minus the little doughnut looking seals on the inside. Also used gasket maker and tightened everything before it dried. (My seals are holding up nicely :))

    Yes I put everything back together right. (eventually)

    Adjusted the float over and over again on the carburetor. the less fuel in the bowl the better it ran. Literally to the point where I'd start running out of fuel in the bowl at about 35 seconds of WOT and then I'd get power. Of course it'd cut off unless I let go of the throttle and kept the momentum turning the engine while the carb caught up.

    Changed carb jets

    Bought a new carb (new SHA clone type). Adjusted idle and air/fuel mixture a bunch.

    I didn't change the piston rings yet...

    If they are damaged, when the gas mixture ignites, the pressure could go around the piston, and force more fuel toward and out the back of the carb than normal. This would also reduce power by a lot.

    But would it still start running well when the gas gets turned off? It seems to run almost, if not perfectly when I shut the gas off.

    I'll check to be sure in a few days. I've just been working on it on a stand.
  12. Fabian

    Fabian Well-Known Member

    Did you make sure to use a case half gasket, because if you did not, then it's time to pull the engine apart and install the gasket - an important thing not to overlook.
  13. StrangeTechnician9

    StrangeTechnician9 New Member

    If your talking about the crankcase gasket, then yes of course I used one. That's the reason I took the case apart to begin with.
  14. Fabian

    Fabian Well-Known Member

    good to hear that.
  15. StrangeTechnician9

    StrangeTechnician9 New Member

    A couple years, a couple months, and several hundred dollars later...

    I'm thinking I should buy a 4-stroke honda now and just trash the 2 stroke engine I got from piston bikes with their kit.

    I'm just tired of all the hard work replacing parts and being disappointed for so long. Doing some more reading on here a lot of you guys say 2-strokes are just as reliable, if not more reliable than 4 strokes because of less moving parts.

    I sure don't want to spend $800+ on a good 4 stroke honda kit to have MORE problems than the 2 years of headache without transportation that the extra reliable 2 stroke got me lol.

    My goal here is and always was to have transportation to work off fines rather than fund the corrupt system I moved far away from. I could pay them with a credit card.. but I'd rather have a bike lol

    I'm about to give up on this, which may be a good idea since I obviously dont know what I'm doing. I already bought a car and I'm working on printing out a realistic looking license plate for it.. Yeah yeah, I understand the risks.


    What would any of you do? :)
  16. Fabian

    Fabian Well-Known Member

    It may not be helpful, but it took 2 years of engineering and reengineering my bike to make it 100% reliable.

    Fortunately i have compiled the information of my reliability upgrades so those persons wishing to shortcut the reliability development process can make it happen from the word "go".

    At the very least, (with a 2-stroke) you will need to purchase the following reliability upgrade items:

    1) Jaguar CDI
    2) CR Machine Manufacturing billet cylinder head in your choice of compression ratio
    3) Sick Bike Parts Deluxe shift kit, with the optional right hand side and left hand side chain tensioners.
    4) Final drive chain stabilisation system of your design choice
    5) Correctly jetted standard (NT) carburettor
    7) Sick Bike Parts fuel tap
    8) Fuel filter
    9) 2 speed (front derailleur) activated drive system, should you need to climb steep hills or need to tow a lot of weight in a bicycle trailer/s
    10) 8 speed rear cassette system
    11) SRAM twist grip (rear) gear shift mechanism to operate the rear cassette
    12) SRAM 1:1 rear derailleur
    13) Optional bicycle rear view mirrors (that in my opinion are essential), plus brake light, plus a powerful front bicycle light.

    from here on in there are about another 50 optional upgrades that you would want to look at if chasing performance or noise reduction or improvement in torque output.

    Forget the idea of getting away with spending any less than $700 on essential reliability and usability upgrades.
    StrangeTechnician9 likes this.
  17. StrangeTechnician9

    StrangeTechnician9 New Member

    Thank you for your info here and in the private message. I have to say your bike is awesome. Let me buy it from you lol.

    I'm done playing with carbs and jets and CDI's and fuel ratios and air filters and spark plug gaps. Literally the only things I haven't replaced are the engine head/body/and piston. And you say I need a new head for reliability lol

    I don't mind spending up to about $1000 on motorizing a bicycle. Spending that kind of money though, I want it to just work. No tweaking or experimenting to try and make it run correctly all the time because I have to. I'll tweak and play with it in my free time to improve it when I want to.

    I might actually get rid of the idea and buy an enduro.. maybe try to find a 50cc enduro so it'll be legal lol
  18. Fabian

    Fabian Well-Known Member

    Facts are that with a motorised bicycle you "will" spend a lot of time maintaining the bike to keep it reliable, with respect to long distance touring i.e. using the bike for more than just making a nuisance of yourself ripping up and down the street with an outrageously noisy exhaust or going 400 yards to the corner store and calling your bike reliable when only half of the nuts and bolts have fallen off the bike.

    These are some examples of the reliability you can expect when the bike is set up correctly.
    Even though the bike did 3 solid days of alpine hill climbs (requiring no daily mechanical or electrical maintenance; giving perfect reliability climbing Mt Hotham, Mt Buffalo and Mt McKay at Falls Creek) it experienced punishing conditions; working it's guts out the whole time, and needed 2 full days of maintenance when i got home:

    Even with my bike giving excellent reliability, i still spend about 1 hour on maintenance for every 4 hours of ordinary riding time.
    My bike goes up on an overhead bike lift and every single detail is checked, and i mean everything, as per the below link:
    Last edited: Jul 14, 2014
  19. StrangeTechnician9

    StrangeTechnician9 New Member

    Wow.. Again, awesome bike and thanks for the info Fabian.
    It looks like I'll be much better off getting all my reliable transportation issues (license and such) fixed before venturing any further in this MB project.

    I still want it, but I can't rationalize spending the time and money on it for transportation when I have a perfectly reliable car in the driveway waiting for me to get right lol

    I'll be lurking around the threads till then, waiting and learning things :)
  20. Fabian

    Fabian Well-Known Member

    Now in no way do i intend to put you off riding a motorised bicycle, because it is the,,, (hang on let me capitalise and italicise) THE most enjoyable riding experience you can have, and i've owned a lot of road and dirt bikes - how many road or dirt bikes have 16 gears or more, and how many road bikes or dirt bikes have you needing to use every one of them; needing to make road predictions to be in the right gear at the right revs at the right time, or you'll lose that precious 1/2 mph that you've spend the last 300 yards ever so carefully trying to build before the next change in incline.

    In a word, it's an "addictive" , make that a "passionately addictive" recreational pursuit, even if just using a motorised bicycle for transport.
    I can't properly convey how immensely enjoyable the pastime of long distance travel is on this type of transport; more so when you have engineered and/or assembled the necessary components to give total reliability; taking you to some inaccessible and serenely picturesque places; sometimes inaccessible even by dirt bikes.