Almost .. but not quite (starter problem)

adamcfc · Borekit Bruiser Joined: 29 Apr 2011 Karma :

Im having problems with this old banger ive had for 6months or so now, a 2001 Motorhispania RX50. Never got round to riding it properly as i bought a Rieju RS2 Matrix 50 instead Very Happy

Starting, well the starter motor turns the engine over but doesnt actually start the engine. If i bump start it, i have to run fast and for a long time and eventually things begin to happen but its hard to understand. It sounds like it sparks a few times, or very loud misfires, and it will keep doing it irregularly as long as im still running at that speed, loads and loads of smoke comes out the exhaust and theres a black liquid around the exhaust rim.

Ive drained petrol out the bottom of the carb twice so i know petrols getting to the carb, ive taken the exhaust off so i know its not getting restricted stupidly, and ive taken the air box off for now so i know its not getting restricted there.

Any ideas? im just banging my head here and need to get it running soon :/

Any help is much appreciated, thanks, Adam

sandman1976 · Nova Slayer Joined: 08 Apr 2011 Karma :

Lots of smoke and black liquid around the exhaust rim sounds like piston rings to me.
Broken rings will allow oil to come up into the chamber and gets spat out of the exhaust more or less unburnt.

adamcfc · Borekit Bruiser Joined: 29 Apr 2011 Karma :

mm that makes sense :/ hope not Thumbs Down

Ive just pulled the spark plug out and it fits quite loosely into the HT lead? I pushed the HT lead into the spark plug, and pushed the tip against the engine casing and turned the starter motor over, there was no spark across the electrodes? Should this happen, and how do i check for a spark properly?

serlant · Brolly Dolly Joined: 06 Jul 2009 Karma :

hows the choke mechanism?
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adamcfc · Borekit Bruiser Joined: 29 Apr 2011 Karma :

Its like a spring one, so you have to hold it down if you want it on. Its pretty stiff, but the whole bikes in a bad condition so it wouldnt surprise me if its not working, but ive tried starting the engine with the choke held on and with it off.

Is there a way of checking it, do i need to?

N cee thirty · Banned Joined: 31 Jan 2010 Karma :

its not sparking

you tryed a new plug?
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adamcfc · Borekit Bruiser Joined: 29 Apr 2011 Karma :

i havent yet, i cleaned the terminals with sand paper slightly, if i put the plug near the engine casing, a spark jumps from the bent electrode to the casing, but i cant see a spark jumping from the centre electrode to the bent one?

Its also a BR8 spark plug, and all teh 50cc engines i know should run on a BR7, so when i get a new plug should i get a BR7?

The Artist · Super Spammer Joined: 06 Jan 2008 Karma :

Very little difference. Either would do.

MarJay · But it's British! Joined: 15 Sep 2003 Karma :

adamcfc · Borekit Bruiser Joined: 29 Apr 2011 Karma :

ok sounds like the piston or piston rings then. Would broken piston rings greatly affect the compression, thus explaining why i have to run with the bike whilst bumpstarting to just get an odd misfire or bang?

I know how smoky some 2 strokes can be bit this is literally clouds of thick smoke that burst out.