So, you won’t get a chance to talk to the mechanics till Tuesday (not open Monday – speak to Mike, who did the tests, altho Chris is also in the loop), but here are the results, and the background, for you to mull over.


This test showed front cyl compression = 185 psi; rear cyl compr = 205 psi. probable error plus/minus 5 psi.
[comment: it’s ideal to be perfectly the same, but up to 30 psi difference is acceptable: more than that and you likely should do mechanical work.)

This test showed leak-down of: 38% front, 14% rear. (front exhaust valves and rings; rear: rings)
[comment: you want ideally to see less than 10% as ‘perfect’; 20% is acceptable; more than 30% is indicative of a problem – btw, these are ‘relative’ figures, not anything absolute – look up leak down test on wikipedia for more perspective – basically, you can identify the problem area by listening to where the ‘hissing’ comes from - as for the ‘problem’, as Chris puts it, the leak down test is an early indicator – so long as the compression test remains OK , the leak down just shows that something is not right, not that something is ‘wrong’ yet...]


OK, now for some perspective. I’ve had these tests done twice before, so there is previous information to get an idea of a trend from, which could be used to make some guesses about the future from.

In Feb 2012 I had the test done for the first time, at ~94,000 kms. Compr was 180 rear, 200 front. Leak down was 40% rear, 20% front.

I had the rear cylinder exhaust valves repaired after that, kinda ‘resetting’ the clock!

In Oct 2012, after another season of riding (up to ~123,000kms), I had the test repeated ( for curiosity, and because I’m a scientist and I live on ‘data’).
I did only the leakdown, which was: 34% front (exhaust valves); 16% rear.


So, is there a trend to be seen?

Well, for the rear cylinder, it’s already been re-built, so it’s likely to have good life left in it, as shown by the 14% current leakdown with 205 psi compression 30,000kms after the job was done. It’ll go on fine for 50 or 100 thousand kms more.

The front cylinder is showing its age. However, the compression is still very good (not quite ‘new’, but it’s got 125,000 kms on it, and if we took 170-175 psi as a cutoff to react to, and if we thought 205 psi was ‘new’, we could expect maybe 60,000 kms more before to front cylinder dropped to the level at which valve work would be necessary). The leakdown test yields a similar trend. Front was 20% 30,000 kms ago; front was 34% 4000 kms ago... now it’s 38%, 34,000 kms after the initial test... There is an error of maybe plus / minus 5% in the result, but trend seems to be an increase of maybe 1/2% to 1 % per thousand km. Sooner or later, the front cylinder will need valve work too. But this is an early indicator, as Chris says. And it’s no surprise – this is an engine with 125,000 kms on it, so it’s gonna be ‘loose’.

Bottom line, the engine still makes normal power, it doesn’t blow blue smoke, and it consumes very little oil (maybe 200ml per 1000 kms, kinda variable depending on temps and how hard you ride). If this was still ‘my ride’, I think I’d expect to put on another year (30,000 kms), then do the front cylinder valves... or more likely, repeat the test and ‘see’... might get two seasons out of it....

I’m not sure if this helps in your decision or not, but I believe in full disclosure, and I don’t have any intention of ‘screwing’ anyone when I sell this bike. it’s too close to my heart to ‘sully’ its reputation (or mine!) by doing so at this stage!

I look forward to hearing from you after you’ve had a chance to talk to Mike.