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  1. hostname

    yz426f wont start....

    I guess that I might have found a problem.... With new carb adjustments: ~2turns fuel screw out and ~3turns idle screw out, totally new spark plug and in 5-10kicks I finally started the bike... done some fine idle adjustments after bike warmed up and it's idling normal, ride few mins seems everything ok, after turning the bike off, it starting in 1 - 2kicks cold or hot that day.... tried to start bike after few days, it started after 1kick, run ~5sec and died, tried more kicking and nothing, looked at the spark plug and new spark plug was totally black, wet and not getting spark at all (like that in picture middle), tried refurbished spark plug and spark is ok... so, done some reading and seems that due to high carbon deposits on the spark plug I can lose the spark even in the middle of the ride (what I have at the end off season?)..., so my guess is: that due rich mix I'm getting high carbon deposits on the spark plug, after bike sits few days, they sinks in fuel or etc. and weakens or totally kills the spark... so when I'm trying to start bike after few days, with weak or even without the spark I'm flooding the engine, but not starting the bike.... Can it be? So I must screw in fuel screw to lean the fuel/air mix or what? Thanks!
  2. hostname

    yz426f wont start....

    Bought a new spark plug (old spark plug was also nearly new), spark is ok (when the spark plug is out of the head), but... bike is totally dead, no more any sounds or other symptoms..., tried kicking and pushing no reaction at all... also tried fuel screw 1-3turns out, idle 0-2turns out, nothing at all.. valve clearance exhaust 0.25mm 0.25mm intake 0.1mm 0.13mm 0.13mm... BTW just remember that have 2 strange situation in the autumn last rides, first that after 20min of the ride bike suddenly shut off, just HRRR BRBRHRRR HRRR... so cheeked the spark plug and no spark, spark plug was very old (so i guessed that will be the problem). After week or so I replaced the spark plug with NGK, spark was OK, pulled out the bike for a ride, ride about 10-15min and same situation suddenly bike shut off, just HRRR BRBRHRRR HRRR and no spark with that new spark plug....
  3. hostname

    yz426f wont start....

    Situation update: So I moved the exhaust cam one pin anti-clockwise, now it's 14pins between 12:00 clock markings (attaching picture before and after cam was rotated), assembled everything back together and kicked few times slow, first notice that appeared area with 3 near spots hard to kick, first 2 spots when exhaust cam even don't touch valve bucket, third when cam touches the valve bucket (attaching a pic with painting) is it normal? Ok next... Compression seems normal all the time, with or without spark plug connected, done some more kicking, but no more bangs poofss and etc., few times kickstart lever kicked back, but after that, bike each 1 or 2 kicks wants to start, but not starting, just GHRGHR ant that's it, 2 times started, but immediately died... later no life from bike at all... ok removed spark plug, it was all wet, checked spark and no spark..., kicked 10-20 times kickstart lever, put new spark plug, tried to start bike, but can't heard any life from it... removed spark plug, this one also wet and no spark... done same thing few times, but results are same.... So I guess bike constantly is flooded? Screw settings is: Fuel screw (was 1 1/4 before carb clean), left 2 turns after was carb cleaned, now lowered to 1 1/2, another black screw (idle?) is 4 turns out...
  4. hostname

    yz426f wont start....

    Sorry about that word, I didn't mean that (I mean POOFF), I wrote topic late at the night with one mind in the head how to start that damn thing... Just edited the post, sorry! I don't know where that cam came from, it just was in the bike, I didn't notice any markings on it, so it may be yz450 cam, I will inspect it closely tomorrow. Yes the pin counts between cam marks (12:00 clock) is 13pins, I will try your advise to move the exhaust cam one pin back anti-clockwise and see what happens..
  5. Hi to all, First sorry for my English, it's not my first language, also I'm new here;) Last year I bought a YZ426F 2002 bike and from then it was like pain in the ...ss, usually hard to start cold or hot (with choke or hot start), wont idle (needs some throttle), it backfires on deceleration but it was runner when it started... After few rides I noticed the engine coolant leaks out thru the cylinder bottom gasket, so in the winter I started replacing it. Disassembled engine, (noticed that hot cam mod is installed) measured valve clearance (ok), checked timing marks (ok), replaced gasket, assembled back together, checked valve clearance again (ok) and tried to start... after few kicks huge BANG, kick kick kick and huge POOOFF, kick kick HUGE BANG (tried with choke, hot start, fuel on/off) and so on.... after 10-20min kick BANG POOOFF, somehow I started the engine (hot start was on), idle run was not ideal but bike run without touching a throttle, hit stop, kicked again and no problems, engine starts in a 1-2kicks (no bangs), came back tomorrow, cold bike with choke on started in 2-3kicks (without BANGS!), ok I completely assembled the bike left for a week in garage, come back and tried to start... same huge BANG POOOFF BANG BANG POOOFF and not starting, or it wants to start but seems that I kicked to light, or starts and shuts off... ok maybe problem is in the carb, so I cleaned the carb in every single hole and screw, assembled everything back together, filled tank with new fresh fuel AND... few kicks and HUGE BANGGG, FEW KICKS POOOFF, FEW KICKS it starts but shut offs or if I give little throttle when it starts jus GHRGHRGHR... and shut offfs.... Notice: When I first started the bike, after gasket replacement, temp outside was around 0C, second day was ~ -1C. After week was ~-5C can't start, after carb clean was ~ +4C can't start . When the spark plug is disconnected, compression is good, but when I connect the spark plug and kick seems like compression very low (seems like it may tries to run from small kick, or something helping to move the piston), also when i hit the stop button and kick, compression is good... mysterious things.... So: btw, Gear sensor disconnected Carb cleaned Valve clearance ok Fuel screw was 1 1/4, now 2 turns out (but no reaction to that) Timing see attached pic ANY suggestion? Thanks.