andy Posted June 16, 2011 Posted June 16, 2011 Hi, A n00b biker here I have recently bought an Aprilia classic 125 which had been stood for quite some time apparently.After a basic service (carb cleaned, new plug, new gear oil, new fuel) it started and ran okay (even passed its mot!!).I took my CBT on it and used it to get to work a couple of times with no issues apart from what sounded like pre-ignition at half throttle when cruising but opening it up a little more stopped this.Next day when I went to work, after about 1/4 of a mile it started spluttering and missing and almost died but then appeared to sort itself out. Until I came to go home for lunch when it just refused to fire up... once or twice it almost fired but then nothing.I checked the plug and it was wet & black with a pathetic spark. Put a new plug in it next day and it was back to normal again! Until a few days later then the same thing happened with the spluttering etc but it didn't right itself. I bought a new ignition coil (fitted it on the 12th) and everything was great until today when it did the same thing again... (wet'n'black plug again)I'm beginning to wonder if the CDI is not giving the coil enough power (but as the bike's stuck at work and I'm at home, I can't really check voltages until tomorrow).Would the method described in this article http://www.wgcarbs.com//index.php?option=com_content&task=view&id=12&Itemid=26work with the CDI output? Or has anyone got a more sensible idea ? Thanks in advance. Quote
Lumor_uk Posted June 17, 2011 Posted June 17, 2011 Have you checked the valve gap? if the spark is getting wet it's running rich or the piston rings have gone. Quote
andy Posted June 17, 2011 Author Posted June 17, 2011 I did consider the rings it appears to have decent power when it does run which makes me think that the compression is okay (although I'll see if I can find someone locally with a compression tester to verify it).It's a 2-stroke so valves aren't an issue.I must admit that I haven't cleaned the sponge air filter (although I did check it and it looked okay...) but I'll try that tonight. Quote
Lumor_uk Posted June 17, 2011 Posted June 17, 2011 I did consider the rings it appears to have decent power when it does run which makes me think that the compression is okay (although I'll see if I can find someone locally with a compression tester to verify it).It's a 2-stroke so valves aren't an issue.I must admit that I haven't cleaned the sponge air filter (although I did check it and it looked okay...) but I'll try that tonight. soz never worked on a 2 stroke, my knowledge extends to 1.4 golf engine and cg engines. Quote
Tango Posted June 17, 2011 Posted June 17, 2011 Sounds like the plug is oiling up.Several things I would suggest.Correct plug? Check online or Aprilia dealer just in case you have the wrong plug.Clogged air filter - causing it to run richHead/Piston coked up - whip the head off and check for carbon in the head and piston crown.Clogged or badly fitting exhaust - altering the back pressure which can affect running.Sticking rings - if it was stored for a time the rings may be sticky and you could be losing compression.Just a couple of things to look at. If I think of anything else I'll stick it on here too.Good Luck,Bob Quote
andy Posted June 17, 2011 Author Posted June 17, 2011 That should keep me quiet over the weekend (weather permitting )When I 'behead' the engine, will I need a new gasket or is it possible to re-use the existing one (as long as it survives the head removal)?I'll try cleaning the air-filter although it is in need of replacing... I seem to be able to get a K&N style filter for less than the stock foam one (due to excessive carriage charges!) are they much better?How would I check for sticky rings? (i.e. is it by removing the piston etc or is there an easier way?)Thanks for the input.Andy Quote
Tango Posted June 17, 2011 Posted June 17, 2011 Deffo replace the head gasket if you take the head off.If you do take the head off you may as well remove the barrel and check the piston and rings and the bore too for scoring.I would replace the air filter if I was you......sounds like the bike could do with a bit of tlc if it was stood for a time.Did you replace the 2 stroke oil too? If that has been in the bike for a bit it could have deteriorated. Bob Quote
andy Posted June 17, 2011 Author Posted June 17, 2011 Ok, I'll arm myself with a head gasket before whipping the head off then - thanks.I didn't replace the 2T oil as there wasn't much left in it (around 500ml in a 2ltr tank)... maybe I should have done (fairly new to all this)I'm trying to borrow a compression tester (I'm working to a budget so can't afford to buy one) which should hopefully show up any sticking rings/scoring issues.I'm still concerned about the weak spark though...but I'll check the other bits first as it'll be a dear job to replace the CDI Quote
Tango Posted June 18, 2011 Posted June 18, 2011 Is it a weak spark with the old plug or with a new one? If it's with the old plug it could be fouled and causing the spark to track or offering resistance to the spark.As I say...did you check it's the right plug? Replacing one with the same type that came out is not always the best idea as someone in the past may have just bunged any old plug in there.I don't know this model (or Aprilia's for that matter) but I've seen on other bikes (and cars) the sensor that triggers the spark can go iffy. If there is an Aprilia forum around have a look on there as there may be some tips for checking it. Replacing the sensor would probably be cheaper than replacing the CDI unit.Good Luck,Bob Quote
andy Posted June 18, 2011 Author Posted June 18, 2011 It's a weakish spark with a new plug and weaker with the fouled one (and presumably even weaker under compression).The new plug was bought from a bike shop (the guy there looked it up to see which one was needed) so I'm assuming it's the correct one - but I'll double check it.I've seen an Aprilia forum but it's nowhere near as busy as this one but I'll try putting my post there too and keep 'em crossed.Thanks again for your help though, it's really appreciated! Quote
andy Posted June 18, 2011 Author Posted June 18, 2011 New and fully charged. Or at least it was fully charged after the previous 'episode' as I flattened it trying to get the bike started Quote
andy Posted July 31, 2011 Author Posted July 31, 2011 Ok, finally solved...It was unfortunately a combination of two things...1) Wrong 2T oil (semi synth instead of fully synth)2) 10EG plug instead of 9EGEach of the offending items were recommended to me by 2 different bike shops :/Anyway... She's going like a good 'un now Quote
Tango Posted July 31, 2011 Posted July 31, 2011 Hey Andy glad you got it sorted.I know from an Aprilia SR50 that my other half's daughter had that Aprilia's are fussy about the plug type/grade and the 2 stroke oil.Happy biking mate.. Bob Quote
andy Posted August 18, 2011 Author Posted August 18, 2011 I suppose if I'd actually read the handbook properly I would have realised...but I assumed that by asking for "a plug / 2t oil suitable for an Aprilia Classic 125" I would have been given the right product On a positive note, I now know the carb etc is nice and clean, the compression is good and the ignition electrics are fine!I can also strip it down to its basics in a rather competitive time Now to carry on learning & practising and get my test taken early next year! Quote
Tango Posted August 18, 2011 Posted August 18, 2011 Well I guess it's still running OK then Andy? Last resort....read the owners handbook... Bob Quote
andy Posted August 18, 2011 Author Posted August 18, 2011 It's got the odd niggle... runs a little rough when cruising but I can live with that for now. Acceleration's fine but when sticking to the speed limit it sounds a bit iffy!New chain & sprockets are going on at the weekend - there's no adjustment left and the chain's way too loose for my liking Quote
Tango Posted August 18, 2011 Posted August 18, 2011 That may quieten things down a bit for you....and reduce vibes.....But it is an Aprilia....... Bob Quote
andy Posted August 18, 2011 Author Posted August 18, 2011 Haha yeah! Not the quietest bike around but when I was looking for a learner bike I wanted something bigger than the norm... The CGs etc are too small for me and this one was quite affordable (£460 on a 52 plate - no T&T but it only cost me a few quid for new fork seals which were all that were needed for the test).I was tempted to look for a quieter can for it though... Quote
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