moped starting problems..

I recently bought a junk moped for 27 bucks ('78 peugeot 103sp). Since two weeks ago, it seems to have come a long way. besides getting new brake controls, it seems all i need to do is get it started. I assumed i had the wiring hooked up wrong because i couldnt get spark, but i was able to solve that when i found the two wires that goto the kill switch. now, when i hook up a spark plug to the boot, i can see sparks while pedaling. I have gas (cleaned out the carburetor real good), i have air, i have spark, so now what? i cleaned the points real nice (went from 4.5ohm between the points to zero ohm) put dielectric grease on the spark plug seat and tip, made sure engine block ground was good.. the only things i can think of now would be either the condensor being bad (could i just replace this with a condensor from a car?) or the timing being way off. Is there any way on these things to change the timing without taking the magneto flywheel off (i dont have a flywheel puller..)? I had much less trouble getting my '72 beetle to start after it was sitting in a garage for 19 years without being run.. any suggestions?

RE: moped starting problems..

If you've got spark at the plug, it shouldn't be the condenser... you say you put dielectric grease on the spark plug 'tip'... you mean where the plug lead and cap go on right?.... You say you cleaned the carb real good, does that mean you removed the float bowl and removed the pilot jet and the main jet (both brass) and held them up to the light to see if they are clear?... if not you have to do that... To see if a clogged carburetor jet is the problem, get the moped ready to start and squirt some gas directly into the carb and try to start it and ride... if it starts and goes about 50 feet and dies, then you have a clogged carb jet.... clean them.... let us know what works.

RE: moped starting problems..

yeah i put the dielectric grease where the boot goes onto the plug, not on the electrode. i took out all the jets and shot air through them.. if i take out the plug and shine a light down i can see that the piston is wet with gas. ive tried squirting starting fluid both through the air intake of the carburetor and directly into the chamber through the spark plug hole but get nothing.. what else could be wrong if i have both fuel and spark? unless its only sparking for me outside of the combustion chamber...

RE: moped starting problems..

First of all, have you tried a new spark plug?.....2nd... you know its a 2-stroke and you have to mix the gas with 2-stroke oil..right? .....Next... since you are mechanically inclined, go ahead and pull the head and cyl off and take a look at the piston and bore to see what kind of shape they are in.... because if you've got everything else, it could be low compression from old age or more likely a kid didn't use oil in the gas........lastly, if you have to get the flywheel off... a "pittman arm puller" for a car will sometimes work for getting it off.... can prolly rent it for $5...try that stuff and get back

RE: moped starting problems..

You may want to check the ignition timing. Turn the flywheel until the piston is at TDC (top dead centre), the gap between the points should just be starting to open. On some flywheels there's an "F" mark as well as the "T" mark (T for TDC), if you set the flywheel on the F, the gap between the points should be 0.4 mm.

It doesn't sound like the carburettor or jets are the problem, even if the mixture is totally wrong, you'll still have ignition for a couple of strokes.

Like Fred pointed out, the compression could also be the problem. You could have a very low compression because of worn piston springs. You can check the springs by placing the springs inside the cylinder without the piston, now you can easily see if the rings close up or not, there should be a very small opening between the ends of the springs. Also, some mopeds have a decompressor, some kind of valve on the cylinderhead that can be opened for easy starting and killing the engine, if the valve is leaking it would cause a major loss of compression.

RE: moped starting problems..

alright..today i took the magneto flywheel off (before i looked at these replies). I checked ignition coil primary and secondary windings, spark plug wire resistance, condenser, and points and they all seem to check out ok. i found a washer stuck magnetically and rusted on the magnet of the flywheel.. i think this might have knocked against the stator and changed the timing.. i got the washer off and set the timing to 1.5mm before top dead center (or as near as i could get). with high hopes, i cranked the engine again..no luck still. it sounds and feels like theres compression. i hear a nice putt putt as i turn the flywheel and if i put my thumb over the spark plug hole i can feel it. but, tomarrow i will take off the cylinder head and take a peak inside (btw, what's the proper way of cleaning carbon deposits off the cylinder sides without scratching it? very fine steel wool?). im thinking i might just want to go ahead and buy a gasket set and some piston rings and such and attempt to rebuild the thing.. i'd like to get it running before school starts up (im sick of taking the bus). there is a decompressor valve on the engine. is there any way i could test this once i have the head off? oh yeah.. in reply to fred's oil stuff. when i got the moped i poured a tad bit of 2stroke oil into the spark plug hole (it was bone dry inside there) before i turned the engine and i have a 25:1 gas:oil ratio in the tank (normal operating is 50:1 but i figure it'd be better to run on 25:1 for the first half tank to make sure it gets lubed up properly). wow.. who knew this would be such a project to get this started.. but of course i am having some fun putzing around. Thanks for all your help btw..it's always nice to have someone to throw ideas at.

RE: moped starting problems..

Again... did you try a brand new spark plug yet?... the cylinder walls will not have any carbon build up.... the rings keep them scraped clean... the cylinder head and the exhaust port (of the cylinder) might have carbon build up.... just scrape those off with an old butter knife (don't use anything sharp).... also look inside the exhaust pipe for carbon build up.... and even try putting your mouth to the pipe and blow through it.... air should flow easily thru it.... on the piston skirt and cyl walls you are looking for heavy scuffing and gouging which tells you it has seized in the past.

RE: moped starting problems..

If the decompression valve on the cylinderhead is leaking, it's usually because it's jammed open or blocked by dirt and carbon deposits. Open the valve and drown the thing in WD40, keep opening an closing the valve for a minute or two and give it another squirt of WD40 every now and then. The dirt and carbon will come loose and will be washed off by the WD40. There's also some kind of cleaningspray available called "powerclaen", I haven't used this myself (yet) but I've seen it in action, one squirt and a thick layer of grease and dirt will be washed off immediatle. This usually solves the problem of decopression valves, but if it's leaking because of something else (like the previous owner and his obsession of prying things open with a screwdriver), you may have to replace the decompressionvalve or even the whole cylinderhead, it will depend on the damage.

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