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Thread: A Rough Guide To: Engine Starting Problems - PART 2

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    Default A Rough Guide To: Engine Starting Problems - PART 2

    Part 2 - For Part 1 please see here

    Kill switch - stock
    Is the kill switch button stuck in? Inspect as necessary. Dirt can get underneath the red rubber cover causing the switch to stick in the pressed position, thereby not allowing the engine to start. Temporarily disconnect it to eliminate it as a possible cause. If it starts up, the engine can be killed by plugging the exhaust pipe or turning choke on.
    Might as well check the wiring and connections to the ignition coil while you’re in the vicinity.
    Kill switch - electronic
    Check the switch is not active – preventing the engine to start. Ensure the 3rd channel tx setting is set to a momentary style of activation (as opposed to a press-on, press-off type – it may be that its simply on).
    Disconnect the 3rd channel kill switch, and try restarting under stock conditions. If it starts – carefully check switch set up. Though rare, faulty 3rd channel kill switches do occur – confirm correct installation procedure, tx set-up and operation with your switches manufacturer/supplier. Often it is incorrect set up which is at fault rather than the product.
    Make sure your linkage is set correctly.
    NB. The black plastic finger push on the stock linkage is a good method to manually open your throttle a little during the start up procedure, if required. It can also easily be fitted to the Yamadude linkage to aid starting.
    Piston Ring / Compression Check
    Remove fan cover and spin flywheel by hand – if it spins easy, it may be that the piston ring requires replacing.
    Take a teaspoon or two of 2 stroke oil and pour down the spark plug hole. Holding the Baja, swirl it so that the oil coats the inside of the cylinder to form a seal between the cylinder wall & piston, albeit temporarily. This seal will aid compression and may get the engine running - though this may be short lived (if it starts at all) if there is an issue with the pistion ring or flaking of the cylinder wall. After replacing the plug, follow the start up procedure, initially without the 'choke off'. If a distinctive pop is heard, and after the engine eventually starts, it again requires oil to start, a replacement ring is probably required. Make sure the piston ring is installed correctly (it is a directional fit).
    Excessive exhaust smoke and the odd fouled plug may be encountered during this process.
    If no success, more checks, as listed in this table may be required.
    Further Info
    Quote Originally Posted by EarthSurfer View Post
    Checking the condition of your parts should ensure you have the compression the engine is suppose to have.
    1) check the cylinder plating for damage. Clean the oil out of the cylinder, and check out the plating for scratches (can have a few, with no performance loss) or the plating peeling off like wall paper. Both of these plating failures happen only on CY cylinders, not zen cylinders. You can clean up the plating with 600 grit sand paper to remove the old tarnish, get a better look at any plating damage that may exist.
    2) As the ring on the piston wears, the \\\"end gap\\\" gets bigger. Zen states a max spec of the ring end gap at .5mm (.020\\\"), and brand new, they should have a small gap of about .003 or .004\\\". To check the end gap, take the used ring off the piston, and use the piston crown to push the ring into the cylinder nice and straight, just above the exhaust port. (note the dirty side of a used ring faces up on the piston and in the cylinder, and the end gap should be positioned like it would be on the piston--near the intake rib). The gap of the ring in while installed in a good cylionder can now be measured with a set of feeler gauges. If the ring has shiney wear all the way around (indication a good seal all the way around), the end gap is good, and the plating is good, the compression should be OK. For info - the G230 size engine has the lowest compression.
    One more thing to look for. Look for burnt oil on the piston sides under the ring. This burnt oil may be a indication that you are getting \\\"blow by\\\" (hot exhaust gas blowing by the ring, and burning oil to the side of the piston). If you only see some burnt oil at the exhaust port side of the piston, it is probably just the pipe hoilding hot exhaust gas against the piston near TDC, which is not blow by.
    Lean Seize
    Two stroke engines can lean seize in seconds if they are running too lean, ie too much air in the fuel/air mix.
    Did the engine stop suddenly at close to, or at WOT? Remove exhaust pipe header from engine block and check piston for score marks – a tell-tale sign of a typical lean seize. If unsure, pull head and inspect piston, cylinder wall and ring for wear. Check for anything else that may clearly look out of place, e.g. piston pin clip dislodged, dirt/sand entry, cylinder plating.
    Install new piston (top end etc) and / or ring as necessary.
    Make sure the needles are set on the richer side, (ie more open), rather than leaner side – then follow the tuning guide instructions. Often the richer the mix, the easier it is to foul the spark plug.
    In addition to inspecting gaskets, also check for holes in the gas intake line and for any cracks to the intake manifold (which connects the engine to the carb). Any cracks here, as well as loose bolts, may also contribute to a lean seize. An upgrade to a billet manifold will pretty much eliminate this as a potential issue.
    NB – its is always wist to retune your carb after fitting a new pipe – stock settings maybe too lean.
    Exhaust blockage
    If the exhaust pipe is blocked the engine will not start. Ensure exhaust is not obstructed by debris or capped/plugged intentionally to reduce fume odours (e.g. following maintenance indoors)
    Fuel mix / age / contamination
    Ensure fuel mix ratio is 1:25 (ie 1 part 2-stroke oil:25 parts unleaded petrol)
    Use fresh fuel. Avoid using old fuel that has been lying stagnant for several weeks. Always thoroughly shake any unused fuel mix. Check fuel for contamination, eg water, dirt/mud in fuel tank or clogged ‘clunk’ fuel filter
    Last edited by Baja Storm; 16-10-2010 at 13:35.

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