General Category > General Discussion
Newbe with v75 problem
simj26:
Thing is, if a cam lobe is worn it would reduce valve lift wouldn't it? Considering that there is back pressure through the inlet port to the carb on part of the sequence...would indicate that the valve is opening longer or at the wrong time? ???
simj26:
Are any Guzzi cams made up of any thing other than a single unit..ie, a two part cam that's joined in the middle?
oldbike54:
--- Quote from: simj26 on December 11, 2014, 03:28:28 PM ---Thing is, if a cam lobe is worn it would reduce valve lift wouldn't it? Considering that there is back pressure through the inlet port to the carb on part of the sequence...would indicate that the valve is opening longer or at the wrong time? ???
--- End quote ---
That is why we suggested measuring the lift . Kinda sounds like a lobe has gone flat .
Dusty
simj26:
Surely if a lobe has gone flat the valve will open less or hardly at all? Am I missing something here? it is the lobe that pushes the pushrod that opens the valve.....right? The valve fully closed position would still be the opposite of the lobe(whether the original lobe was worn or not) on the cam?
It seems like the valve is actually open either for a longer duration than it should be or opening at the wrong time altogether......I've checked the valves and they are definitely fully closing when they do close but am getting a back blast through the carb....in fact it has actually backfired through the carb a few times If the left cylinder wasn't running ok I'd say definitely the cam timing rather than lift. ???
oldbike54:
OK, let's go back to the beginning . Left cylinder runs fine , right doesn't run at all . You switched carbs side to side , and ignition . Doesn't solve problem . You state the valve timing on right side seems off . Correct so far ?
We ask about pushrods , , they seemed alright , compression seems OK . Still no answer regarding the actual overall lift on the offending side , or an actual PSI compression reading . We suggest a flat cam lobe , you basically say we are wrong w/o doing any test . The overall lift might be fine , maybe the ramp on one of the lobes has gone out of shape . The valves spend very little time at maximum lift . We are talking thousandths of an inch here , hard to discern with the eye . Heck , where is the lash set ?
Dusty
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