Have a 1994 CB500, starts OK, revs OK in neutral.. as soon as I put it into gear the power dies. It doesn't kill the power but doesn't seem to deliver it.
could be clutch drag, simple first test is to adjust up the clutch cable at the handlebar lever, try 2 or 3 complete turns of the adjuster, this should take out some slack in the cable, you may also have to adjust the cable at the other end, on the engine case, think this should be a threaded adjuster but with hex locknuts. If this doesn't work you may have warped clutch plates which are still available.
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