Aprilia RS50

 Hey im new here looking for a bit of help with my rs50 if anyone has any experience with them.

Ok, it's a 1999 Aprilia RS50 again and it wont fire up even though it turns over well, not even a cough or splutter .

There's a spark when I rest the plug on the head and turn it over (it's a new plug and I've gapped it) so I'm assuming the electrics are ok. It doesn't have a kill switch on the bars and I don't think there's any kill switches tied into the side stand or clutch lever but if anyone knows different I'm open to suggestions.

I've stripped the carb and cleaned it, there was a lot of crap in it but that's all clear now, there's petrol in the float bowl and some residue on the plug when I take it out.

Blocked jets maybe? Choke jets may be blocked. Has the bike been sat a while?

If theres a spark then is it firing right?

Whats on the plug when you take it out? Fuel?

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check to see if its sparking then check it's getting fuel. also do you know history of bike?  it might be losing compression coz it needs a rebore hence air + fuel but not firing.

1. check spark

2. check fuel.

3. check compression.

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Mr Marv wrote (see)

Blocked jets maybe? Choke jets may be blocked. Has the bike been sat a while?

If theres a spark then is it firing right?

Whats on the plug when you take it out? Fuel?

 yeah the bike has been sat for a couple of months without being started, when i took the carb apart i blew through the jets, the carb isnt the same as the carb in the haynes manual, its a Dellorto SHA1412M not sure if this is the problem though because it ran when i bought it and nothings been changed that i know of.

And im not sure if it was fuel on the plug but it was coloured slightly on the thread

Is it the same fuel?

If it is and its been sat for a while, chances are it could have gone off.

Modern fuel is wierd. Some of it can last forever, but some can last a month.

I had a problem similar on my 125 some years ago.

Change all the fuel and flush the carb out with some carb cleaner.

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will try this at the weekend as i wont realy have much time during the week and il let you know what happens

cheers for the advice

Right so today i cleaned the tank out and put some new fuel in and cleaned the carb out.

When i start it ti does now start but only with the choke on and the throttle wide open but if i let the choke off and start to ease the throttle off the bike cuts out any ideas why ?

cheers

Im not familiar with the carb, but is the float set right in it? Sometimes on car engine carbs they need to be set right to allow the right amount of fuel into the float chamber otherwise you will get fuel starvation.

What colour is the smoke from the engine? Is it "normal" or is it very black and sooty?

2 strokes should smoke a bit, my old MT used to smoke but that was black/blue smoke which was just the oil. If its excessive white smoke, and its around for a long time then its common with water getting into the bore, but I havent heard of it happening on an RS. Its also common for white smoke when boiling off condensation from the exaust..

.

You could try... A compression test to make sure its good.

Also, when you stripped the carb did you replace or change anything at all?

I've had a mouse nest in the exhaust stop one of my old cars from starting in the past after it was laid up for a while.

its not loads of white smoke when it starts now after running it for a bit it stops and when i cleaned the carb i didnt replace anything and i didnt change anything as far as i know.

my old man seems to think it cuts out due to fuel starvation though...

Well if you've done no damage then yes you were lucky.

You do still need to find out what caused the over heating though, otherwise you'll end up ruining it - especially with summer on the way.

Did the bike lose any performance? Did the engine smell or sound hotter than usual (lots of pinging and clicking as it cooled)? What temperature does it normally run at? Do you often do an indicated 55 or 68mph on it?

Given that it's a 50cc, how are you getting 68mph out of it? Is it over-bored? Is it tuned? If it's tuned, how have you tuned it? Is it carburettor or injection? If it's carburettor, have you re-jetted it since tuning it?

Could it have suffered petrol starvation? Was it low on petrol? Is the petrol dirty? Has the bike been standing for a length of time? 

Does it run premix, or is the oil pumped in from a separate tank? In either case could the oil/fuel ratio have been wrong?

There are a million other questions we can ask - over heating can be caused by a lot of things, but I thought I'd check these first before delving into the ignition and cooling systems...

yeah my RS50 does this aswell if am ragin the arse off it. check ur 2stroke and dont use cheep stuff but just top it up. drain the cooling system and put more water and anti freeze in it then bleed it.

after that run the bike and get it up to operating temp. take it out for a small cruize and then turn it off check the coolant.

take it back out and stay out of the powerband till 4th gear then find a straight and pin it.

this problem happend to mine and a didnt have a clue what was going on and tried loads of things. this seemed to solve it az it hasn't done it since.