Why won’t Aprilia SR50 start well when hot?

By Marc Abbott -

Parts & accessories

 25 January 2011 15:07

My nipper has a fuel-injected Aprila SR50 Ditech. When it runs it has a really good little engine and will fly along at 35mph all day. The trouble is, it’s an absolute pig to start hot or cold. My injected bikes start with no throttle action, but with this you have to thumb the starter, constantly moving the throttle until the engine begins to fire, gradually building up the revs until it will go without constant coaxing on the throttle.
Triumphrider600, MCN forums 
 
The Ditech’s engine is quite a complicated beast using a compression system to charge the cylinder at start-up and with the air and fuel injectors in one housing. There’s also a suggestion the plug can be a grade too cold for our climate, so that it wets up too easily, so try experimenting with a different grade. Other than that, you could check to see if there’s blow back from the air injector. It’s sealed with a ceramic ring, if there’s evidence of burning on that ring, then you are looking at replacement for about £80 (gulp). After that, it’s a dealer job with diagnostics.