Compression test passed what now ?

Discussion in 'The Workshop' started by Tamiyacowboy, Mar 24, 2017.

  1. Tamiyacowboy

    Tamiyacowboy Pippa's Owner

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    so heres the lowdown.

    sym jet eurox-basix-red devil 50cc 2006 model , been looked after. filled with fuel rode about 2000yrds
    some white blue smoke then engine stalls and fails to turn over or even catch.

    Compression test result 100psi nailed, service manual reading 99.6psi , test left for 10 mins with no leak at all, two tests run both no leaks ( see attachment)

    Spark plug giving healthy spark and is clean. even when kicking over and plug removed its wet and showing fuel is reaching combustion chamber.

    so guys where next ? bottom end seals ?
     

    Attached Files:

  2. Tamiyacowboy

    Tamiyacowboy Pippa's Owner

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    I think im going to just have to stump up and get those bottom end seals changed, its funny i have all the requirements for a start up ( fuel-air- oil-compression ) yet pedro just wont catch.

    theory would say without enough pressure in the crank case fuel/air would not be forced into the cylinder head allowing for firing, this leads me to either one or two possibles ,

    1: crank seals have gone allowing an escape of pressure , just enough that the fuel/air mix is not being pushed to the cylinder head.

    2: reed valves have outlived life and failing to seal down on the reed cage allowing crank pressure release backwards into carb , if this is the case the airfilter would start to fill up with fuel, its one area i have not checked yet. just checked and its free from fuel build up.

    i would say im right about those two possibles , i have exhausted all other sources of non ignition of fuel and starting up.

    check list for sunday stripdown :

    yank carb out ( its new ) but i was super low on fuel in tank so possible gunk drawn into main jet ? , although fuel filter installed before fuel pump is in good order.
    drop exhaust manifold bolts , and slacken rear hanger, use inspection mirror to check bottom ring ( im running two rings ) but cannot see that as a problem , also gives me entry to exhausts manifold for gunking/blockage.
    direct injection of fuel into cylinder see if it catches ( if so its a fuel to motor issue / bottom end compression failure ) ?

    monday will be a call to bike shop for a 140 quid fix ( thats all i have if i get seals , so hope they take upfront payment and get it done)
    phone gary see if he will take upfront payment of 140 and get pedro running inc new seals put in.
     
    Last edited: Mar 25, 2017
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  3. Tamiyacowboy

    Tamiyacowboy Pippa's Owner

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    Carbs clear dropped it and shot air through, checked jets and all perfect. re-installed and connected back up.

    dropped plug again, gave it a good wipe over , threw it back in gave scooter a good few kicks, drawed plug back out and its wet so fuels jetting to the top of the jug. cannot see to well due to sunlight but looks like im getting a spark to ( old school we just threw plug and replaced for new, never had coil problems on field bikes) but i cannot tell if its a healthy spark or not all i know is im getting a spark of some type ( also hard to record when your trying to kick bike over and film sparkplug at same time.

    so the bottom crank seals see in good nick im getting fuel to the top of jug, carbs clear and not gunked up so thats fuel going in, airbox is clear and drawing air so thats air being fed in, compression hits next to 100psi as shown in attachment and is factory spec for the capacity of the motor and stroke. Plug gap at 0.6mm as stated in service manual yet we are not getting the motor to catch. its got all requirements compression- fuel - air - oil - spark ( maybe weak ? )

    so thats it i have exhausted all routes to a non fire syndrome on pedro the scoot, only other area is the stator - coil . more so the coil as that feeds the spark ? so a replacement coil could be the fix ? whats your idea guys and girls i have run dry on ideas now ?
     
  4. Tamiyacowboy

    Tamiyacowboy Pippa's Owner

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    Ok so heres whats been ordered so far.

    one ignition coil - ht lead and ht cap , i will replace the cheap shoddy HT cap with my NGK redcap so i dont have problems with those shoddy resisteors in the chinese HT caps , im also thinking of maybe swapping out the lead itself to NGK so its all in good order.
    One E-choke for dello carbs, the one on pedro right now is years old it was taken off my old 12mm carb and just fitted to the 17.5mm dello carb so thats another source of problem firing.

    i covered every other possible except one , one thing that i overlooked and have had problems with in my field bike riding days. and could give the symptoms i saw when pedro just started pouring smoke and stalling out before dropping dead ........ TIMING thrown out due to an excessive worn - fractured - Shattered WOODRUFF KEY . without a woodruff key the magneto is free to spin alone on the crank shaft and this will throw out all timing on the scoot, symptoms can show as a full running to dead motor in a few seconds, backfires and very poor power- idle - running , or throwing timing out so that when it does fire the timing spark is firing at the wrong time in the piston cycle .

    Thats a very likely source to, pedro is six owners in and only the top end has been replaced to my knowledge in the 10+ yrs running. no documentation on the crank or it being replaced, so that could be the problem a sheared woodruff / worn woodruff and thrown out timing. problem is no way to test timing i require motor to be at 1800rpm and the F mark to line up 17 degrees BTDC. need to find a belt wrench to grip the flywheel so i can get it off and inspect that timing key .
     
  5. Tamiyacowboy

    Tamiyacowboy Pippa's Owner

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    STUPID ME ..........

    its very rare a 50cc will throw a woodruff key, lets be honest very unlikely and if it did thats like a one in a million chance. but its still a thought.
    I have checked everything and replacing the coil and choke, BUT theres one item i have not thought about ......... what tells the timing to fire and when the CDI ....

    Now pedros CDI should be right behind the battery in the seat bucket, i stripped the seat bucket out, pulled the battery and guess what, there aint NO CDI . now this is puzzling, how can i get spark if there aint no CDI so its go to be somewhere in that tail end , i have a bracket for the cdi to fit to but there aint one on it........

    we know they are fiddley electronic devices that dont like to be thrown around banged and shaken much, so out came the torch and i poked around in the right side rear vent section ....... ohhh a black box whats that ..... closer inspection its clear the cdi has not been mounted to rubber bracket holder and has been left to dangle and smash around in the rear tail. any bump that cdi gets bashed into the rear subframe.
    im going to install new coil and e-choke , see if i get a change and pedro fires up, if not i have a feeling the cdi has taken so much hammering over its god know how long its been not secured the thing is faulty and not sending the correct timing pulse to the coil, hence i have a spark but no ignition in the jug , now its a case of tearing off the back end and checking if i need a 2x4 connector cdi or a 5 pin single connector cdi.
     
  6. sean178

    sean178 Active Member

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    Any update mate ?
    I'm having exactly the same problem with my blaster. It started running a bit lumpy on the way to work the other day, i got to work and it stalled and wouldn't restart. The story so far is the same as yours, Good compression, which I would expect as the top end is only 2 month old, the carb has been cleaned and replaced and there is fuel there to burn, I too have a spark but like you can't really tell if it's good enough, it doesn't look too bad.
    I've replaced the ht lead, the coil and the plug but it isn't even attempting to fire. The cdi was my next avenue to try. What do you think TC ??
     
  7. Stevep

    Stevep Well-Known Member

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    5,895
    You have my permission to laugh....................TC put derv into his!:D
    It runs agin but is lumpy at the moment, and very smokey and the bandit
     
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  8. sean178

    sean178 Active Member

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    181
    oops, that'll explain that one then :D:D
    mine isn't trying to run on derv so, do you think the cdi is the next sensible step. ive already ordered one as it was only £7
    not really sure where to go next if not
     
  9. Stevep

    Stevep Well-Known Member

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    5,895
    If you have a spark it should be good and strong and blue.
    What was your compression reading?
    Must be 90psi or above. Anything lower is trouble.
    Is the plug getting wet with all the attempting to start or is it staying dry?
     
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  10. Tamiyacowboy

    Tamiyacowboy Pippa's Owner

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    CDI would be the next step Sean , thing is even if you have a spark is it triggering at the right time, you could find the flywheel timing all lines up but if that cdi brain just decides to advance or retard that spark on its own due to an electronic fault your in for some rough times.

    normally if im gonna see a spark the first port of call would be replace ignition coil ( a faulty coil may not give enough juice for a full arc spark ) if the coil fails to fix the problem , the CDI is the next best hedge bet , if after both have been replaced i would then be looking at ohm's testing the stator exciter coil just to check its feeding enough juice. ( charging side does not matter its just dumping the battery, but the exciter coils they charge the coil for the spark )
     
  11. sean178

    sean178 Active Member

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    compression tested at 110psi, its a fairly new top end.
    plug is wet when pulled out and the cylinder is filling with fuel. ive stripped the carb and given it a good clean, jets blown through ect
    to be honest, the spark looks ok, the old plug was only a couple of months old but I stuck a new one in anyway and also replaced the coil / ht lead and plug cap at the same time.
    ive got to be honest, I'm stuck. ill be trying the cdi and if that doesn't sort it I may have to bite the bullet and pay someone to take a look !!
     
  12. sean178

    sean178 Active Member

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    just on a side note gents, does the forum not operate through tapatalk anymore ??
     
  13. Stevep

    Stevep Well-Known Member

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    5,895
    Sounds like it's over fuelling.
    I'd strip the carb bowl off again and make sure you haven't missed something/forgot to put something back or got the float stuck against something so it's not closing properly.
    Also, move the clip on the slide needle to the top ring so it puts the needle at it's lowest position.
    No idea about tapatalk, don't know what it is even:confused:
     
  14. sean178

    sean178 Active Member

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    181
    ive ordered the cdi already, as I said its only £7 but I will strip the carb down again, I'm fairly confident ive not missed anything though. its been running sweet since I rebuilt the top end at Christmas and the bugger let me think I might be in for a bit of trouble free riding !!! :D:D
     
  15. sean178

    sean178 Active Member

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    Tapatalk is a mobile app you can use to access forums, it's what I used to use to access this site but it doesn't seem to have worked for ages ??
     
  16. Tamiyacowboy

    Tamiyacowboy Pippa's Owner

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    Back to square one .........

    went for a ride got fuel tank down to 1/4 left , then it happened , scooter tried to stall out, i kept feathering throttle and it cleared. was close to home so decided im not going to risk it. rode back home ....... pulled up to trun onto pathway and engine just dies, no put put just a burrrrrrrrr .... dead .....

    so im thinking fouled plug , i chop out to a brand new plug and gap it to service specs 0.6 - 0.7 mm . install it and have a kick but no go ..... i walk down to the local garage with jerry can and fill it brimmed to the top then head back ...... top up tank in scooter so its 100% full and watered down the rest of the derv left in the tank ... you can still see the fuel is a little cloudy due to being tainted so i thought ill top up and water it down even more.

    i try to start again but this time the electric start has decided to work a few good blats and the scooter starts to try and catch but just does not have the motivation, so i give it a couple kicks,............. its after this i notice a very very strong smell of fuel .. tank cap is on ... jerry can cap is on .... fuel line to carb inplace and not fallen off. then i notice it a river of petrol flowing from the drainer hold in the airbox itself.
    i pull of the airbox to find its full with fuel the foam filter is dripping wet with fuel to.
    I leave the filter out and let the fuel evap away. then i give it a kick without the filter and box cover fitted ... fuel pours out of the carb into the airbox space just one kick and its like flowing out ......


    Flooded motor ?

    blocked carb jets ? ( cant be blocked otherwise it would flow from the overflow pipe ) ?

    other idea ?

    so guys whats causing that then the carb to just eject the fuel into airbox ?, i have cleaned filter washed it and now having it drying out. its a bit dirty gunked but not really bad , i cleaned it not long ago .
     

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