Guest Posted July 18, 2014 Share Posted July 18, 2014 Hey peoples..Im at loose ends here.My little sister has a starway 50cc 4 stroke moped, and has been running fine up until the last couple of days..she originally said the moped was slowing down..the ped normally does 45mph, even with an adult on it, but she said at times the ped has struggled to hit 15mph, with her hand pinned back..I looked at it myself, and on center stand, it seamed like it was lacking fuel or something, then it cut out, and now will not start.i have:* removed, checked, stripped and cleaned carb* checked for something blocking fuel to the carb, but the carb bowl is filling up fine..* checked ignition pickup on flywheel, all is fine.* checked coil, even replaced it with a spare one i had, that i know works fine..* replaced spark plug* inspected all wiring, all is fine* inspected all pipes, all is fine* removed and checked starter motor* flushed tank and re-filled with fresh fuel, to rule out contamination (thinking my little sis may have stupidly put diesel in it), but nope* inspected inlet maniforld for splits etc, all is fine* and probs loads more..i have ran out of ideals now..it doesnt start on either electric or kick start..sometimes if i hold my hand back on the throttle, i can get it to momentarily ignite, giving around 2 seconds of "bobb bobb" and then nothing...i really have absolutely no clue now...help please Quote Link to comment Share on other sites More sharing options...
acting_strange Posted July 18, 2014 Share Posted July 18, 2014 Compression test would seem in order to me......last time I was asked to fix one with similar problems the piston had virtually melted....new barrel and piston required and promptly fitted... Quote Link to comment Share on other sites More sharing options...
Guest Posted July 18, 2014 Share Posted July 18, 2014 compression seams fine to me..using the kick start, the kickstar gets stiffer towards TDC and then eases again after TDC.. once the piston stroke is travelling down.. Quote Link to comment Share on other sites More sharing options...
Tango Posted July 18, 2014 Share Posted July 18, 2014 I'm with acting_strange here.....does sound like compression. Check valve clearances? Quote Link to comment Share on other sites More sharing options...
Guest Posted July 18, 2014 Share Posted July 18, 2014 I'm with acting_strange here.....does sound like compression. Check valve clearances? Yeah Bob..The bike was very strange..She said it would be sluggish, like i said, struggle to get 15mph with hand pinned back.. so i started it up and went on it, went fine for me. 45mph quick as you'd expect a little 50cc to be...But then she had issues again.. and then it would be fine etc...and then eventually failed to start..Just get a quick "bobb bobb", the engine would rotate on its own, from ignition of the fuel. then stop..very wierd bike...The bike has only done 6000km... Quote Link to comment Share on other sites More sharing options...
Guest Posted July 18, 2014 Share Posted July 18, 2014 update: just done a compression test..117psi on the guage..Id say compression is not the issue here..there is a good spark on the plug, and like stated, at some stages, the engine fires up for a brief second, then stops...just thinking randomly here..What about the vacuum pedcock on the bottom of the tank?could this be an issue at all??? are they common faults???i removed the fuel pipe off the carb, and sucked on the vaccum pipe, and fuel came out...I really am stuck for ideas here.cheers Quote Link to comment Share on other sites More sharing options...
Mr Fro Posted July 18, 2014 Share Posted July 18, 2014 Have you tried spraying carb cleaner/WD40 around and in to the carb while it's cranking?Also, was the plug wet and are any of the vacuum hoses split/perished? Quote Link to comment Share on other sites More sharing options...
Adam Posted July 18, 2014 Share Posted July 18, 2014 Faulty killswitch or side stand switch? Quote Link to comment Share on other sites More sharing options...
cockercas Posted July 18, 2014 Share Posted July 18, 2014 Has it got a cdi unit? Mine started to go. Lost topend speed. Then struggled to start then woukdnt start. Faulty cdi unit. New Chinese one on the bay was £6. Quote Link to comment Share on other sites More sharing options...
Guest Posted July 18, 2014 Share Posted July 18, 2014 Has it got a cdi unit? Mine started to go. Lost topend speed. Then struggled to start then woukdnt start. Faulty cdi unit. New Chinese one on the bay was £6. But surely it wouldnt spark if the CDI does??Its getting fine spark all the time fella... Quote Link to comment Share on other sites More sharing options...
cockercas Posted July 18, 2014 Share Posted July 18, 2014 True, chokes not stuck on is it? Quote Link to comment Share on other sites More sharing options...
Ricky Posted July 18, 2014 Share Posted July 18, 2014 I've been having trouble with my TZR recently and although I was getting a 'good spark' and fuel in my float bowl it didn't start.I replaced the needle and the seat I also changed the spark plug for the one in my lawn mower and it starts first kick and idles like a king now Not much help but I thought you'd all appreciate a good story about me fixing my TZR Quote Link to comment Share on other sites More sharing options...
eastanglianbiker Posted July 18, 2014 Share Posted July 18, 2014 I've been having trouble with my TZR recently and although I was getting a 'good spark' and fuel in my float bowl it didn't start.I replaced the needle and the seat I also changed the spark plug for the one in my lawn mower and it starts first kick and idles like a king now Not much help but I thought you'd all appreciate a good story about me fixing my TZR but the lawnmower has gone to the garden in the sky forever more ahmen Quote Link to comment Share on other sites More sharing options...
Tango Posted July 18, 2014 Share Posted July 18, 2014 Me? I'm just a lawnmower and I lie on the bench....and I can always hear them talk..... Quote Link to comment Share on other sites More sharing options...
Guest Posted August 4, 2014 Share Posted August 4, 2014 Update:Me and my friend (that restored classic bikes like bonneville's etc)have been scratching our head with this moped just lately..we have checked compression, and fitted new barrel and rings.... Checked and re-ground valves, aswell as re-set valve clearances.... replaced spark plug, CDI, ignition coil, and checked the complete wiring loom for damages.... Replaced the carburettor twice (two difference carbs), aswell as new jets (incase of blockage)... replaced the magnetic timing pickup from flywheel.... replaced all fuel pipes, flushed tank, and replaced the vacuum petcock on the tank....checked and replaced vacuum pipes, engine breather pipes..... replaced air filter.... inspected exhaust (fuel is vacuum fed via exhaust back pressure)..... checked valve timing chain.... inspected con-rod (for potential damage that could cause running problems).... checked, replaced and sealed inlet manifold boot (incase of leak stopping suction of fuel)...and we still cannot get the F**ing thing running...Fantastic spark.. Completely dry plug...when you put your hand over the inlet boot, there is suction, plenty enough to be able to draw fuel in...But no fuel is getting in...We are literally to the point of throwing the spanners at it... We have checked, replaced and re-adjusted everything little bit of the entire engine....HELP... or im going to drop a match in the tank and claim off insurance..My poor little sis has only had her CBT for a couple months and already off the road... Quote Link to comment Share on other sites More sharing options...
Fozzie Posted August 4, 2014 Share Posted August 4, 2014 Turn the fuel tap ON Has it got petrol and a new battery?Take off any fuel tap and direct run fuel to the carb. Quote Link to comment Share on other sites More sharing options...
Adam Posted August 4, 2014 Share Posted August 4, 2014 Faulty killswitch or side stand switch? Quote Link to comment Share on other sites More sharing options...
Guest Posted August 4, 2014 Share Posted August 4, 2014 Tried it fozzy.. and Adam.. a killswitch, wether its button or sidestand.. when activated, cuts off spark to the coil.. thats how it stops the engine..If the killswitch was knackered and engaged.. it wouldnt spark... And since it is sparking.. It isnt that... Quote Link to comment Share on other sites More sharing options...
Adam Posted August 4, 2014 Share Posted August 4, 2014 But if it's faulty it might not function properly. What about the neutral light thingy? Quote Link to comment Share on other sites More sharing options...
acting_strange Posted August 4, 2014 Share Posted August 4, 2014 You say its not getting fuel......Have you actually tried putting a small amount directly into the cylinder and see if it at least fires?If it doesn't fire then you will need to look at the timing...if it does fire then you need to sort out the fuel issue...Obviously that could be blocked jets, or even poor valve timing....did you actually check the valve timing as you would still get good compression... Quote Link to comment Share on other sites More sharing options...
eastanglianbiker Posted August 4, 2014 Share Posted August 4, 2014 spray some easy start or wd40 into air filter area see if it kicks into life then Quote Link to comment Share on other sites More sharing options...
acting_strange Posted August 5, 2014 Share Posted August 5, 2014 spray some easy start or wd40 into air filter area see if it kicks into life then eewww you're dead rough you....lol Quote Link to comment Share on other sites More sharing options...
Guest Posted August 5, 2014 Share Posted August 5, 2014 You say its not getting fuel......Have you actually tried putting a small amount directly into the cylinder and see if it at least fires?If it doesn't fire then you will need to look at the timing...if it does fire then you need to sort out the fuel issue...Obviously that could be blocked jets, or even poor valve timing....did you actually check the valve timing as you would still get good compression... Yeahh i poured a little fuel directly into the inlet manifold and it fired right up..It cant be blocked jets, because its have two new replacement carbs...I originally soaked the standard carb in cleaning fluids over night, aswell as the jets.. and nothing..So, since the carbs are pretty cheap, i bought a brand new one off the internet, with matching jets..that didnt work, So to rule out a faulty replacement, i got another.. and still the same...Fuel gets from the tank to the carb.. but will not get into the engine from the carb bowl. No matter what carb i put on..There is no splits or damage to the inlet manifold boot, as i replaced that.. Crossing that off the list too...Its just a simple problem of not getting fuel from the fuel bowl, to the engine.. But everything in between that could potentially stop it.. has all been replaced with brand new parts.. And still nothing..All valves have been re-ground and re-set by myself, to rule out the valves.. and valve timing is spot on...I have also replaced the piston rings and barrel.. With compression being last on the list..and still absolutely nothing!!!!! Quote Link to comment Share on other sites More sharing options...
Fozzie Posted August 5, 2014 Share Posted August 5, 2014 Is the plug dry?To be fair as it's a 50cc it's hard to get wet (giggity)But maybe the timing is the wrong way round, and this is VERY easily done on little bikes.Fuel could be going in on the wrong stroke, but the beauty of it being the wrong way round means that you won't spot it being that way easily, as no valves will be bent if the valves are opening on downward strokes.I've done it before early into my 4-stroke tinkering days, takes ages to suss it! Quote Link to comment Share on other sites More sharing options...
Guest Posted August 5, 2014 Share Posted August 5, 2014 i can see what you mean.,But the thing is.. this moped have been running flawless for the past couple of months, and then suddenly died to this...The valve timing cannot put itself backwards... The timing chain is on properly, and all in good condition. Quote Link to comment Share on other sites More sharing options...
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