Ducati Sporting Club UK > DesmoDue Race Series > DesmoDue - General Questions and Chat > Lack of acceleration possible Eng swap

[skidlids]

Leak down test needed

[Lee M]

Can you please explain a "leak down test"?

[skidlids]

You pressurise the cylinder on The compressions stroke with both valves closed using compressed air through a leak down tester that contains a pressure regulator and a couple of gauges, the difference in the gauges then tells you your losses.
Any leaks can often be heard either by listening to the end of the exhaust or the airbox inlet or the crankcase breather

[Lee M]

Rings a bell, I will look in to it.
Thanks

[skidlids]

one of these
http://www.ffx.co.uk/tools/product/S...oJwwo dsF4A8w

maybe a local garage has one

[SeeleyG50]

Nice maths Lee, but flawed. Your calculations do not take into account that the compression ratio is theoretical and that it doesn't take into account valve timing. i.e. The inlet valve doesn't close until well after the piston's on the way back up the bore from BDC. A leak down test will reliably indicate any problems, but doing the valves and rings will always help an old clunker 😛

[badgerpilot]

Speak to the Ghostmeister, sounds exactly like the problem I had (fat arse too). He did lots of lapping and magicery with my engine and it improved many fold.

Other than that you can buy my engine at the end of this season.

[Lee M]

Umm, the old dynamic Vs static, I have ordered a leak tester as recommend by Kev, so I will be able to find out more when it arrives.

I have stripped the bike down in preperation (removed - fairing, battery and tray, air box, carbs etc). I also removed the rocker covers and cannot get my smallest feeler gauge 0.05mm under the inlet shim on either cylinder and only just get it under the closing shim though all four shims can be rotated. So perhaps that's part of the problem.

Shame I didn't know about your engine earlier as I brought a winter project engine today, was advertised as a 1999/2000 engine with approx 8000 miles. With my limited knowledge spotted it was a 600SS engine, I now think it's also 1994/1995, but Kev is helping me identify the bad boy.

I will post the leak test results when known.