So on a very chilly 26th of February, with an air temperature of just 5oC i went to the runway at Cottesmore/Kendrew to test the Aprilia, with the view to try and get about 3 hours under its belt.
The first few laps were steady but with the water temperature gauge struggling to get above 40oC and there was a real risk of a cold seize, which wouldnt have been good at this stage. So i taped off 65% of the radiator and that made a huge difference with the temperature sitting at about 65-70oC, which is about ideal for a 2 stroke, 4 strokes are happier at about 85-90oC, so now i was happy to turn the wick up.
i must say that for a 70cc bike it pulls really strongly and spins up to 13,000rpm no problem and i was enjoying the acceleration and the noise, just lovely. I was still taking it easy on the straights which is 1.5 miles long and do last forever. What it did show up was how important a racing crouch was as this made a huge difference to revs and therefore speed, if you didnt really wrap round the bike it struggled on the back straight to hold 6th gear and would need 5th and loads of revs. On the main runway straight it would hold top and by really tucking in i got to 12,300 rpm in 6th and when i used the GPS speedo on my phone this showed as 83 mph, none too shabby as on the dyno the best it showed was 84.5 mph. Perhaps there was a tailwind but i didnt notice one.
So all was going well, and i kept warm by drinking coffee from a thermos and going back out again. Despite my best efforts i just couldnt get the second bend smooth, and even when i went back to do more weeding a week later in the car it just kept tightening up and you are forced to run wide, which made me feel better.
After 3 hours as i was finishing the main runway it made a Dooooh noise and stopped! and n amount of down-changing would kick it back in again. It hadnt seized or done anything nasty, it sounded like the carb had fallen off which it hadnt.
Luckily, it wasnt too far to paddle back to the car, and i didnt have to get off and push. Then it became obvious, the base gasket had blown out from under the cylinder losing all compression.
On full stripdown, it became apparent that all the head nuts had worked loose and 2 of the studs were loose. So i have ordered metal locking nuts will re-threadlock the studs, and use my nice new digital torque wrench to make sure all is tight. Then run the bike for 30 minutes and retighten everything. This is why you do testing.
One interesting addition, was that i filmed a lap or 2 with my Gopro camera and despite not absolutely going for it, the lap average speed was 56 mph, the current record is 34 mph, and with some extra effort, i think we can get close to 60 mph.
So overall, i declare myself very happy.
