Right side vs Left side drive
Road Captain
Joined: Aug 2011
Posts: 538
Likes: 3
From: Florida
Here's one explantion I've read:
Shaft Flexing. Take a good look at the H-D Twin-Cam engine. Notice how far away the end of the primary cover extends on the left side of the engine. It is hanging way out there in space and so are the abnormally long crankshaft and transmission shafts and here is the danger as those shafts can not be supported by a bearing so the shafts bend, flex and break not on the shafts, but the bearings and cases and also the transmission gears are twisted. Yikes! This is due to a poor engine design. If you look at the H-D Sportster engine it has none of these problems, the shafts are short and the transmission is reversed so the output drive pulley is on the right side of the engine curing the shaft length problem. I told you the Sportster engine is a perfect, perfected engine, and it is way advanced over the archaic, defective plagued Twin-Cam engine/transmission/primary design. The shaft flexing is a serious problem on a stock engine. If you add power you add more breakage, simple as that. There is no real cure except to convert to a belt drive primary with a Baker 6-speed transmission that will put the drive belt on the right side like the Sportster engine. You will need a new rear wheel too. The fix is not cheap, it will cost you less than $10,000. The shaft flexing is a problem, so don't ride hard, don't take off fast from stops, don't speed-shift through the gears. If you want to do these things buy a brand new Sportster for it can handle abuse because the engine is sound, solid and strong due to a superior engine and transmission design
Shaft Flexing. Take a good look at the H-D Twin-Cam engine. Notice how far away the end of the primary cover extends on the left side of the engine. It is hanging way out there in space and so are the abnormally long crankshaft and transmission shafts and here is the danger as those shafts can not be supported by a bearing so the shafts bend, flex and break not on the shafts, but the bearings and cases and also the transmission gears are twisted. Yikes! This is due to a poor engine design. If you look at the H-D Sportster engine it has none of these problems, the shafts are short and the transmission is reversed so the output drive pulley is on the right side of the engine curing the shaft length problem. I told you the Sportster engine is a perfect, perfected engine, and it is way advanced over the archaic, defective plagued Twin-Cam engine/transmission/primary design. The shaft flexing is a serious problem on a stock engine. If you add power you add more breakage, simple as that. There is no real cure except to convert to a belt drive primary with a Baker 6-speed transmission that will put the drive belt on the right side like the Sportster engine. You will need a new rear wheel too. The fix is not cheap, it will cost you less than $10,000. The shaft flexing is a problem, so don't ride hard, don't take off fast from stops, don't speed-shift through the gears. If you want to do these things buy a brand new Sportster for it can handle abuse because the engine is sound, solid and strong due to a superior engine and transmission design
to late haha been doing it for years on all my big twins...I agree from an engineering standpoint that the sportster is less susceptible to the shafts flexing and the twin cam/evo more susceptible, but it is hardly as big as a problem as you describe... lol A stock bike with an average rider will never see the conditions to manifest these types of failures. There's guys running 120+ci motors on these bikes and they never snap/bent the mainshaft. I've got an 800lbs bike with a chain drive that sees holeshots, powershifts, drag races at the track, wheelies, and 5th gear burnouts on a regular basis. Its running a HD 5 speed that I dug out of a buddies junk box. 20,000mi, no bent or broken shafts...
And If you're really that concerned about it you can run a torque arm on the right side to help with drivetrain flex between the trans/motor. Although this is hardly necessary except in racing applications. To take it a step further you could run a 4" belt drive primary from ultima with carrier bearings on the end of the crank and mainshaft, solving the "problem" for a couple grand.
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cousinitt
Primary/Transmission/Driveline/Clutch
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Dec 17, 2018 01:59 PM
drive, engine, harley, left, line, motorcycle, offset, shift, shifter, side, ss, transmission, transmissions, triumph, versus
