I suspect that many people did not install gear drive cams due to the .003” runout as mentioned by cam makers. So failures that would be seen from excessive run out were stopped before they ever had chance to fail. Further skewing your result IMO.

 

I installed gear driven cams in a 95" 35K miles ago; runout was .0025" Decided to rebuld a higher compression, longer cam 98" motor and when runout was checked it had grown to .0045". Don't know how many miles I can attribute to the larger runout but, obviously, geared cams can run at .0045" without issues. However, the fact that it had increased with mileage was a concern, so I had Darkhorse true, balance and plug the crank. That cost had not been included in the budget for my original build plan.

 

IMO , installing a good high flow oil pump, hydraulic tensioners like late model TCs and just keep running the chains. Unless you need the last bit of precision for racing or what ever, this set up lasts just fine from what I have experienced, seen and heard. My bike is used for fun, cruising, light touring, and a little hot rodding. Keep it well maintained and spend the extra money on gas and travel. Again IMO.

 

Early TC's simply had better quality, which meant way less crank run out. I believe the entire issue came about around '07. Cam chain tensioners were "upgraded to hydraulic which was a better solution, but not the fix to the problem of excessive crank run out on later model TC's. Gear drives then became "the way to go" to eliminate cam chain & tensioner issues. YES they are superior, yes they out last chain drives, for example.... old chain system might last 10,000 miles, updated might last 25,000 and gear drives 40,000 miles assuming nothing else was checked, or changed. This is obviously a win, for all concerned, but it's only a better fix, but not the solution. Awesome you've had good luck with your conversion, but absolutely nothing last forever, if crank run out is excessive.

 

Old thread, but I wondered this in later years. During the 88 years, it was very common to bore to 95" and to go to gear drive cams. I have to believe many people doing it at home were not checking.

Plus runnot I suspect got worse post timken and as they cheapened up cranks. So I have wondered about this.

I know a guy with a timken, and shop said he had to much runnot for gears.

I checked gear lash, but I don't believe I checked runnout, almost 20 years ago. Over 50k miles, so probably ok. I was one of those guys doing it in his garage, after reading about everyone else doing it on the forums.

 

20+ years ago the directions from S&S made no mention of checking
Therefore, I did not.
YMMV

 

It did evolve a bit. At first there were no undersized gears. By the time I did it in 2006, I believe it was talked about. I bought a GMR kit, was just andrews parts, and he said too.