ok, its 4 AM and only one cup of coffee. i look at gear vs chain in a different light since hd developed the new style hydraulic tensioners. there is little pressure on the new chain and of the new style tensioners i have seen or heard of , there has been zero wear!!
now gears are great, and almost required on pre 07 bikes. i had to throw that in before going farther.
chain, we have seen chain drive last for about 8 years now. we have heard of a few failures and some have experienced catastrophic oil pump damage and total engine grenade. we also have heard even more stories about the 100,000 mile or more twin cams that only had oil changes and tire/brakes. is the old style chain risky enough to switch to gears? some say just replace every 20,000 miles. some say you are riding a time bomb from day one! anyone who has released the tensioner and held it in place with the pins knows how much pressure is on the chains! so yes, there has to be some parasitic power loss there. so------if its spring tensioned chains on pre-07 bike, i would strongly consider gear drive.
looking at the new motors, there is very little tension or parasitic loss on the chain setup. the oil pump is much improved, no failures reported that i am aware of. seems like a good system that should be worry free. i would still inspect, or at least monitor what others are reporting, there could be a failure--its still a wearable shoe that could send abrasive chunks through your motor. i trust it.
now lets consider the runout we are seeing with the late motors, add gears without addressing runout and you are whipping the bearing surfaces, oil pump, flexing pinion gear. now you have created the time bomb you were worrying about! in this case, the chain will actually help your motor live longer!
next, lets correct runout, and go with gear drive. is lash set correctly? if not, what is happening with the gear teeth banging into each other? are microscopic pieces of hardened steel going through your motor?
??/ okay, lash is set correctly and shims are used for proper gear alignment. anyone seen a 100,000 mile gear drive motor yet? is lash still sorrect? cam bearings survive? my vote goes for chain because failure rate comparisons are inconclusive.
moving into the high lift, heavy valve spring, steep ramp arena common today. can the chain survive the constant snatching? if so, are the chains buffering the shock that would be sent to the bearing surfaces? now lets install gears in same environment, no runout, propr lash, hevy springs, steep ramps, etc: will the lack of a buffer actually put more side load on the bearing? will it create harmonics through the pinion that will weaken and eventually destroy the pinion/pump? i think maybe so.
in my opinion, a great setup for the new motors would be helical gears with ball bearings in the plate. the helical gears would keep bearing side load in check, and buffering would be handled by the ball bearings.
ultimate solution? anyone check out bob woods belt system? helical gears internal, belt drive external!!!!
okay-------------need more coffee, feel free to agree, disagree, flame, buy me a beer, -------------------
Author
Topic: Gear drive cam VS chain (Read 16033 times)