Been out for a quick ride yesterday on my 749s and at 5k r.p.m there was some hesitancy/stuttering/ reluctance to rev, as soon as i got to 6k normal smooth running all the way up to the limiter, also the engine performs faultlessly below 5k. I kept noticing exactly the same thing happening every time I was moving through this rev range. Any ideas what the problem might be? Bike has done 24k miles, valve clearances re-shimmed at about 18k, air-filters recently cleaned and plug gaps checked, running on normal petrol any advice appreciated.
749s are prone to a dip in torque at about 5k, is this something that has developed or always there? i had problems with mine but the hesitancy covered from idle all the way to a bit over 5k, was pulling my hair out trying to figure it out. in the end it turned out to be poor valve sealing on vertical cylinder exhaust valves, having only done a few k since main dealer shim service, went away after coventry applied their magic.
The 'hesitancy' is something that has recently developed. I had some issues with the engine late last year , did compression tests on both cylinders that revealed the vertical cylinder was significantly down, so had the valves re-shimmed and noticed an improvement in performance. That was 6k miles ago now though, and I was told at the time that there might be problems in the future due to the fact that the S models have Titanium valves and something to do with the valve seats. I didn't understand what I was being told at the time, just happy to have the engine running well again. Maybe the warning I was given has now come ! I suppose it would be a good idea to do another compression test?
