2nd motor just blew, durable motor suggestions please:)

Discussion in 'Introduce Yourself' started by c3po, Apr 18, 2010.

  1. c3po

    c3po New Member

    I had 1025 miles on my first boy-go-fast motor (80cc but really a 60cc etc),
    it seized - most likely the rings or the bearings, did not take it apart to see where the bits of metal came from.

    my next motor also blew at 586 miles, another boy-go-fast motor, 60cc.

    my question is, is there a known durable motor out there that can last a few thousan miles, or am I barking up the wrong tree and just get a motorcycle.

    ps.... I love riding the gas bike, it is awesome.


  2. Alaskavan

    Alaskavan Guest

    Robin/Subaru, Tanaka, and Honda all make reliable engines. Oh, and Mitsubishi.
  3. Fabian

    Fabian Well-Known Member

    I've had four 66cc engines fail, and all within 500 miles of use, and every time due to big end connecting rod bearings.

    One day i decided to play with the jetting and my current engine that has a partially damaged big end connecting rod bearing and is now past the 1300 mile mark.

    I worked out that the same carburettor is used on the 48cc engine as the 66cc engine with the jetting set up for the 48cc engine.
    When the carburettor is used on the 66cc engine, it runs lean and detonates badly; pounding out the connecting rod bearing.

    My advise (after much experimenting), is to go out and buy yourself a Dellorto No 83 main jet and solve your problems, once and for all.

  4. Esteban

    Esteban Active Member

    I agree ! You get what you pay for.
  5. 210061741

    210061741 Guest

    Buy an engine....Take it apart.....Clean Everything......Use better Gasket Material...Port The Cylinder....Let the exhaust breethe....And change all the bearings.

    The thing will run for a long time.

    Othere than that it ssems to be the luck of the draw with the 2 stroke engines no matter what brand you buy.
  6. Fabian

    Fabian Well-Known Member

    Hi Rich,

    How is the parts development process going - haven't heard from you?
    I'm still interested in the reed valve intake and cylinder and X-can pipe.

  7. Gh0stRider

    Gh0stRider Banned

    peck, peck, peck...... lol

    Anyway, I'm with Fabian on this one. Proper jetting for your altitude and riding conditions are essential to long engine life. I have two jets that I run in my engine - the stock jet works well for summer hot weather but I have a drilled jet so that it runs right in the spring and fall where the stock jetting was too lean at the top end. And being too lean is the death of any two stroke.

    I've also heard that you can get copies of the Dellorto 14/12 and 14/14 carburetors for less than 50 bucks and they can be easily tuned to work well with these engines. Seems no matter what I do, the mix is a little too fat in the midrange even though top end is perfect.
  8. Fabian

    Fabian Well-Known Member

    Although in theory, the needle attached to the slide should be fully clear of the jet orifice at wide open throttle, it may help to drop the needle as far as possible to clear up the midrange if it's running a bit rich.

    Even though i've done exactly as described it didn't make much difference in cleaning up the low end richness, as is to be expected, but then again the shift kit has me running the engine at constant wide open throttle at approx 3500 rpm, so it's not of much concern.

    My main concern is to have a correct jetting setting for the engine and NT carburettor, which has worked out to be a No 83 Dellorto jet, but i run slightly on the rich side (No 84) to prevent any chance of detonation on an already damaged big end connecting rod bearing.
    It must be doing something as i've got 800 extra miles on the engine that i would otherwise fail to realise and a slight increase in midrange torque.

  9. 210061741

    210061741 Guest

    I run an 18mm Dellorto PHBG.

    Honestly the thing is a bear to tune.
    It takes alot of practice to get a good feel for it.
    But everything is easily available.
    Not cheap but easy to get. To get all the working combinations it cost about $100
    At least you only have to buy it once.

    #1 Pilot Jets
    #2 Main Jets
    #3 needles
    #4 Slides

    Now every throttle range is tunable to the utmost perfection.
    But it usually takes me a week or 2 of change ride change ride to find what i really really like.

    You should be able to hear ping when it starts to occour.
    I can hear it in an instant.
    You think the rattle is your bottom end bearing.
    I bet that rattle is PING.
    Also on a 2 or 3 mile wot if the engine starts to loose power and bog you are probably running too lean.

    So what to do what to do.

    #1 I keep 3 ranges of plugs.

    I set the carb up to the last known good running condition.

    For a stock engine a 6 heat range plug should be fine
    For a modified engine it depends.

    to be continued......................
  10. Fabian

    Fabian Well-Known Member

    I'm using the stock NT Carburettor with a Dellorto No 84 main jet and an projector nose NGK-BP8HS sparkplug, all on a stock standard engine, with the exception of a modified intake tube.

    Seems to work well for me, but at very low revs with wide open throttle, the NGK-BP8HS plug is a bit too cold to fire the mixture consistantly.
    Condidering i'm using a shift kit which always has the engine running wide open throttle (effectively a 100% duty cycle) at 3500 rpm, the low rev issues of a cold plug are not relevant to my mode of operation.

  11. Neon

    Neon Member

    The Apocalypse is here.