Hello gang - I'm going to do a complete rebuild on the bottom end of an a65 that presently has a siezed conrod bearing. Any suggestions for a shop to do the work? I'm thinking of a roller bearing conversion, balanced crank, and oil pump upgrade. Going to need the top end mic-ed. I think it's fine but want to be sure - new rings and a hone oughta be good, but I want an expert opinion. Q
I suspect if John ends up helping out, it will be in good hands.....
After a recent exchange of comments on this and other boards about the bearing conversions...I finally quit being lazy and did the load/life calculations of the needle bearings used for the conversions....IMO...it isn't pretty. Needle bearings are not made for the loads/RPM an A65 is capable of.
The weakness of A65's has NOTHING to do with bearings or thrust control. That is nothing more than a fairy tale. And not even a good fairy tale at that.
The unit twins had problems with lubrication up until sometime during the 69 model year. It is not insurmountable. There has been plenty of threads over the last year on this subject. Do a search.
You want a big gear pump (67 on); a piston type relief; o-ring seal on the relief to seat it deeper; and for mid year 69 back cases, seal the lowest threads in the relief cavity to provide a seal between the pump oil and drain oil.
The pump needs to be hand fitted to be right, gasket needs relieved to actually fit the pump and cases.
You need a return line oil filter. Period. There is really nothing to discuss on this subject...plain bearing engines HAVE TO HAVE filtered oil.
All of this followed by careful assembly of the bottom end. They work and work well. It just requires some care and understanding.
Life is too short to drink cheap, bad beer.
Re: BSA a65 bottom end rebuild - need shop in NYC metro area#12675 06/29/061:58 am06/29/061:58 am
oh, and what about this balanced crank bull? i realize that a rebuilt crank needs to be balanced to a degree. but what degree? and what happens if you take a stock bottom end such as a 500, and put 650 top end on it? how balanced is that? or how imbalanced is it. even 40 over pistons, any effect?
Re: BSA a65 bottom end rebuild - need shop in NYC metro area#12677 06/29/062:10 am06/29/062:10 am
Hacksaw, To put it very mildly, starting with a factory balance motor, the degree of modifications you would want to do would depend on what your intended use is for the motorcycle. Going all out nuts on a touring Thunderbolt is in my opinion, false economy. If your building a race machine, the options vary substantially.
,_o _ -\_<, (*)/'(*)
Re: BSA a65 bottom end rebuild - need shop in NYC metro area#12678 06/29/061:36 pm06/29/061:36 pm
They are all unbalanced, but 500's and 650's use different balance factors. Careful static balancing (as described in the shop manual) to the recommended balance factor (70%) will go a long way, but dynamic balancing will reduce the 2nd order harmonics that tend to give A65's their "buzziness".
A smattering: '53 Gold Flash '67 Royal Star '71 Rickman Metisse '40 Silver Star '37 Rudge Special sixtyseventy Lightboltrocket road racer...and many more.
Re: BSA a65 bottom end rebuild - need shop in NYC metro area#12679 06/29/063:24 pm06/29/063:24 pm
Balance. Ted Hubbard (bsa's service tech) told me about many A65 BSA's cracking frames,headlamp mounts,oil tank mounts,and fenders because of out of balance cranks. The factory fix was to flip the bike upside down, remove the drain pan, stuff it with rags, and drill one two 1/2 in holes in the crank 180 from the pin. I woul take the time to at least check the static balance. However,dynamic is the best.