Custom builds and original restorations for all British motorcycle enthusiasts
Oil Filtration on your Oil In Frame Triumph or BSA.
This is for the 4” main frame bikes only and not the TR5T etc.
In 1971 both manufacturers introduced the oil in frame , much loved and hated equally. Well I love it. A great handling frame , being a fully welded twin loop with that huge backbone.
The first 2 years had an oil pickup 3” from the bottom of the tube with a bent pipe going through a screen attached by the 4 studs holding the flat steel tube base plate. 1973 on Triumphs upgraded the design but BSA had gone out of business by then. This upgrade used an aluminium cast plate at the base of the steel frame tube putting the engine oil feed at the lowest point. It still only used a mesh screen , good for rocks but not small fibres or other debris. With a Triumph and its plunger type , spring loaded seated ball oil pump, the efficiency of the pump can be compromised with quite fine debris, if this debris gets between the ball and the seat. This may cause oil pressure loss. It is best to add a paper replaceable oil filter. This can come as kit which fits into the same place at the bottom of the oil tank tube as the screen. This uses a small paper or lately a washable stainless filter. The main point here is the 1971-72 Triumph or BSA cannot just convert to this replaceable filter without some minor work. All one needs is a hacksaw blade. The new oil feed will come from the base so the original feed can be sawn off inside the tube and then blocked off externally with a short piece of hose ,a small stud, bolt or similar to suit the 5/16 hose and 2 clamps. This then allows the new filter to fit up inside the frame tube oil tank and from then on take care of filtering your supply to the engine. Some might think this pull through method of filtering wont work but it does and I have made and fitted this conversion to any oil in frame bikes I own and for many customers when I had my business. Now the only time a problem may arise is if one doesn’t get the oil feed line clamping right and the pump sucks air instead of oil. This will manifest itself with a pool of fresh oil on the floor. I always use pressure gauges on plain bearing engines so I know exactly what is going on. You may also wish to add a Norton Commando spin on filter to the return line , not necessary with the feed line filter but what the heck. I found that any filter will be better than the factory rock catching screen as supplied and will easily double the service intervals of 1000miles recommended . You will be surprised how clean the oil looks after the 1000miles , good for your engine and your wallet if you do lots of riding.