Thread: Power Surge
05-23-2010, 11:29 AM #1
XL1200 Ltd. No engine mods. Carbs rebuilt 30 hours ago (2 years). Had a problem with high speed power last week (felt like it was going from 3 to 2 cylinders at full throttle). Did compression test and all at 115. Put in new plugs and checked plug leads and caps, and full throttle now fine (seeing 59 on dreamometer, which is normal for this ski). Now it has a mid range problem! It starts and idles fine. Sounds a bit flat and 'growly' on the exhaust up to 4000 revs (not a noise I've heard before), but smooth enough, then at 4000 to 5000 revs it misses quite a bit and isn't smooth at all, then it goes like a scalded cat from 5000 to 7000 rpm. The change over from closed powervalves to open valves (5000 revs) isn't at all smooth, and when it drops under 5000 it really loses power again. Any thoughts? Cheers, Dave.
05-23-2010, 11:50 AM #2
Sounds like you have one or more PV's stuck open. Pull the covers off and check that they are all operating properly.
05-23-2010, 12:00 PM #3
05-23-2010, 12:58 PM #4
OK. All the valves are working easily, but found a bit of slack between the P/V couplers (waveater ones) had developed, and the 'closing' cable was a bit slack too. #1 valve was staying open by a small degree. Maybe enough to cause the problem, I don't know for sure. Tightened the 'tongues' on the shafts, and reset the cables to spec. Just have to get it back on the water next week and try it. Cheers again. Dave.
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