Hi, Richard Gibson here, from Rockford, Illinois, USA. I’m new to the Vincent world, but have been wrenching for a considerable time; hot rods & motorcycles in the ‘50’s & 60’s, aircraft 70’s -> 2000, then British cars (Morgan’s) now a Vincent.
I purchased a 1951 Black Shadow, complete, assembled and unrestored at auction in October 2019. It has been in storage since 1991. I plan to clean it up and keep it in its original unrestored condition as much as reasonable.
While adjusting the valves, I discovered that the #2 (front) exhaust valve was not working properly, which led to opening up the timing chest and discovering a multitude of problems, which I have addressed and repaired. (hopefully) Basically, all moving parts in the timing chest are new, including the ATD.
While setting the ignition timing (using rear cylinder) for the rebuilt original Lucas mag, I discovered that the new ATD doesn’t have enough ”range” to allow me to use the ignition specs I got from the Rider‘s Handbook; retarded setting 4’ BTDC, max advance 38’ BTDC. The most range on my new ATD is 25’, so if I start at 4’ BTDC the new ATD will only advance to @ 29’ BTDC. (I’m actually working backwards from that, starting at 38’ full advance, but can only retard to 14’)
Compairing the new and old ATD’s I find that the new ATD has a rotational range of @ .225” measured at the outer ears, while the old ATD has @ .350”.
Something seems out of wack to me. Any suggestions? Any thoughts gratefully appreciated.
1st photo, bike as I bought it, 2nd, as it is now, 3rd, timing chest on initial opening
I purchased a 1951 Black Shadow, complete, assembled and unrestored at auction in October 2019. It has been in storage since 1991. I plan to clean it up and keep it in its original unrestored condition as much as reasonable.
While adjusting the valves, I discovered that the #2 (front) exhaust valve was not working properly, which led to opening up the timing chest and discovering a multitude of problems, which I have addressed and repaired. (hopefully) Basically, all moving parts in the timing chest are new, including the ATD.
While setting the ignition timing (using rear cylinder) for the rebuilt original Lucas mag, I discovered that the new ATD doesn’t have enough ”range” to allow me to use the ignition specs I got from the Rider‘s Handbook; retarded setting 4’ BTDC, max advance 38’ BTDC. The most range on my new ATD is 25’, so if I start at 4’ BTDC the new ATD will only advance to @ 29’ BTDC. (I’m actually working backwards from that, starting at 38’ full advance, but can only retard to 14’)
Compairing the new and old ATD’s I find that the new ATD has a rotational range of @ .225” measured at the outer ears, while the old ATD has @ .350”.
Something seems out of wack to me. Any suggestions? Any thoughts gratefully appreciated.
1st photo, bike as I bought it, 2nd, as it is now, 3rd, timing chest on initial opening