hows my tune ???????????????????

Discussion in '2-Stroke Engines' started by wrongway, Aug 16, 2012.

  1. wrongway

    wrongway New Member

    hi alll i was just wodering what people thought of my tune, when it sounds like its four stroking the throttle is backed of a fair bit just kinda coasting,i weigh about 80-85kg it dose 40-44 Kph, is their also to much machical noise, hears the vid :grin5:

    thanks guys:cool:
    Last edited: Aug 16, 2012

  2. thearcticfisherman

    thearcticfisherman New Member

    get a bigger air cleaner!!!!!!!!thats what made my 4 stroking stop, as for the noise pack some grease behind your clutch plate
  3. Fabian

    Fabian Well-Known Member

    Be done with it and get yourself an Exhaust Gas Temperature gauge and fit it to your bike.
    You will then be able to reasonably tune your engine without going to the expense of getting an air/fuel ratio measuring device.

    An EGT takes a lot of the guess work out of the equation.
  4. FelipeCobu

    FelipeCobu Member

    I kind look like being rich at high RPM, try put the needle down one spline and check again.

    Whats the fuel/oil ratio?

    Whats the spark plug, grade an how it looks?

    You don't need an EGT just learn to feel what's going on the engine, and do plug chops.

    I would try a non contact thermometer method, to check how hot is it going and what is the hottest (pipe or head)
    it helps to know if you're running poor.

  5. Fabian

    Fabian Well-Known Member

    You are right: you don't need an EGT, but having an EGT on the bike is a night and day difference in quickly zoning in on the correct jetting.

    I've been playing with 2-strokes for years and participated in amateur racing so i'm not a complete f*&kwit when it comes to setting up a carburettor.
    Having an EGT makes the process so much easier and it lets you know if you are actually going in the right direction and if the changes are making a real difference; not simply going on a wild goose chase.

    You certainly do not need it, but life is all rainbows and strawberry cheese cake with an EGT on the bike.
  6. wrongway

    wrongway New Member

    hi i agree that it needs a bigger air cleaner when i take it off it does pull out to 49kph, im running 25/1 with castrol activ motor bike oil, it a brown slightly grey colour, if i put the needle down its to lean and rev of idle and one clip richer it fourstrokes its head off, i think it needs main jet work, the noise seems to be from the crank case, the intake manifold has being grinded out to port size and the exhaust it the same, i have lots of greese on the gears in the clutch :cool:
  7. motorpsycho

    motorpsycho Active Member

    remember, changing the needle setting does not have any effect at w.o.t.
    the needle setting is only effective from idle until about 3/4 throttle.
    If you're getting 4 stroking at w.o.t., chances are, you'll need to re-jet the carb.
    at w.o.t. the needle is out of the equation and the main jet is doing all of the fuel metering at that point.

    your idle seems way too high.
    are you sure that you're not fighting an air leak?
  8. Fabian

    Fabian Well-Known Member

    This thread is going to go for 6 pages, yet an EGT could identify and fix the problem within 4 posts.

    Why do people insist on doing things the hard way!
  9. wrongway

    wrongway New Member

    Hi guys the idle is set high in that part cause I had the screw out and hadn't botherd to set it yet and it help it run cold :) these no leak on the manifold 100% sure, where do you buy a basic jet kit and where's a good size to start ?
  10. motorpsycho

    motorpsycho Active Member

    If you had the idle screw out (removed) from the carb, that could be part of the problem right there. with no idle screw you will have an air leak there, and it won't idle.

    an egt could solve the issue, but where do you get one? Where do you install it? How much is it? And what will it tell you?
    It will tell you if your fuel-air mixture is too lean or too rich based on exhaust gas temps .
    but if you know how to read a spark it & know how to jet a carb, you won't really need an egt .
    even if you do use an egt you still have to tear the carb apart & re-jet it, re- check it and go through the whole re-jetting procedure until its jetted right (or as close as possinle)so its not like you'd be saving much time.
    Check with sick bike parts for carb jets.
  11. Skyliner70cc

    Skyliner70cc Active Member

    The problem is you are tuning your engine for kph, you need to tune for mph, it makes all of the difference in the world!
  12. Fabian

    Fabian Well-Known Member

    Scroll down to Number 38 for info on setting up an EGT on a motorized bicycle
  13. Fabian

    Fabian Well-Known Member

    Simply playing around with jets can be problematic because it doesn't take long for the I.D. threads to wear. This allows fuel to potentially leak along the threads making the mixture richer than the jet number may suggest.
    I have been through this process and it was the EGT which allowed me to find out why the jetting changes were not doing what they were supposed to be doing.

    Once you have an EGT on your bike, it eliminates going on a wild goose chase.
    The fast response sensor is brilliant, even allowing you to pick up ignition misfires. Typically a spark plug will begin to misfire before you can feel it and the EGT momentarily drops 3 degrees celcius every time the ignition misfires.
    Last edited: Aug 18, 2012
  14. Fabian

    Fabian Well-Known Member

    This also has benefits for diagnosing the rest of the ignition system.
    If the spark plug is replaced and the engine is still intermittently dropping 3 degrees Celsius, whilst the engine appears to be running smoothly, you know to look elsewhere along the electrical path back to the magneto (with a multi-meter), before small issues become major issues.
  15. thearcticfisherman

    thearcticfisherman New Member

    I'll have to keep posting this, RUN CLIP AT TOP NOTCH!!! RUN A UNI FILTER!!!! USE A BR9HS NGK PLUG!!!!!!!!
  16. Fabian

    Fabian Well-Known Member

    The ignition system on a Chinese bicycle engine is barely adequate for the job, so placing a resistor spark plug in the way makes things even more challenging for the already weak ignition system.

    Please explain the logic of using a resistor spark plug?
  17. thearcticfisherman

    thearcticfisherman New Member

    because you haven't tried to use it yet
  18. Fabian

    Fabian Well-Known Member

    Again, i only ask for you to explain your logic in using a resistor spark plug on an already marginal ignition system.

    Try this for a read:

    Recently an interesting thread on this newsgroup discussed the relative merits of resistive plugs as used on many Rotax engines.

    In order to get to the bottom of this Spark plug vs. resistance story I decided to do some experiments. I am a electronics engineer (when I am not flying :), so I have the tools for the job.

    First a coil was rigged for the job to create the high voltage required for the plugs. I used a standard car coil combined with an electronic interrupter/generator. Spark plugs with and without resistors as well as caps with and without resistors where obtained. The plugs where all equally gapped to 0.4mm. I used a scope to monitor the voltage at the plug tip as well as at the coil (via high impedance probe - scopes are expensive !). The result was quite interesting.

    As expected, the voltage at the cable (before any resistor) rises at the same rate regardless of resistance until the point of firing. Thereafter however the picture changes.

    The coil generates a certain amount of energy. This energy wants to go somewhere. At a voltage of about 7KV the plug fires (irrespective of resistance). Until that happens NO CURRENT FLOWS. Whether you have resistance or not does not matter. A paltry 5KOhms does not do anything when compared to the nearly infinite resistance of the gap itself (until the plug fires that is).

    Once the plug fires the resistance comes into being. The coil cannot get rid of its energy in the shortest possible time due to the resistance.

    This reduces current flow in the spark and it takes quite a bit longer until the energy in the coil has expelled itself via resistor and spark gap. This results in a longer spark. However the spark is weaker due to energy loss in the resistor.

    The scope shows this very nicely and it also gives reason why the resistor helps to suppress RF. With the resistor changes in the rate of current flow are much less resulting in "flatter" edges on the voltage vs. time curve that the scope shows you. This implies less high frequency components of the signal in the cable feeding the spark plugs.

    Conclusion: It is quite safe to insert a resistor. It will not stop the plug from firing at all. High values will however lead to a weaker spark -but it is going to spark, no matter what.

    However, contaminate the plug with fuel (even just a little) and a high value resistor will cause the plug not to fire. 10K plugs as are used on some motorcycles now are about maximum I would guess.

    So would it be far to say that a non resistor plug like an NGK B6HS or the projector nose version BP6HS would be a better choice for a spark plug when it comes to a marginal ignition system?

    I have ordered every single spark plug from the SickBikeParts catalogue and found through trial and error that the most consistent running plug (over time) was the NGK BP6HS and BP7HS.
    Surprisingly the thin wire (resistor) platinum spark plugs became inconsistent after a relatively short time with irritating misfires, despite being a better performing spark plug when new.
    My oil/fuel ratio is 20:1 and the thin wire platinum plug should be superior in such circumstances, yet it was not the case in practice.
  19. Fabian

    Fabian Well-Known Member

    The big advantage of a CDI ignition system when used on a 2-stroke is it's ability to create a short duration but a very hot spark in an oil contaminated environment, as is the case with 2-stroke fuel.

    Adding a resistor spark plug into the system just weakens the short and intense energy delivery; negating the benefits of a CDI ignition system.
  20. wrongway

    wrongway New Member

    My bike has the bp6hs 10 and a different cdi and coil which a seperate I will go a video tomorrow over the whole bike