Moto Rumi technical problems or solutions
10 posts • Page 1 of 1
Both the Formichino and I are about to take to the road after a 51 year break. Having a newly rebuilt engine (by Ken Brittain) I'm a little uncertain about what petrol/oil ratio to use. Originally it was 16:1 but I've heard of ratios of up to 50:1 with modern oils. Recommendations, please, including which brand to use. I have some Halfords two-stroke oil for garden machinery - date I use this?
I have used exol ultima fully synthetic at 33/1 in everything two stroke I own = rumi,s / maicolett,s / velocette viceroy,s / and all my two stroke work tools for the last 5 years without any issues. it can be purchased through ebay, if you buy a big tub it is delivered for a price cheaper than most basic mineral oils. you will be told that synthetic will gum rings etc but this has never happened to me however I do use my rumi,s as the designer intended "with enthusiasm", if you are going to pootle about you may be able to reduce your ratio to 50/1 with this type of oil.
oh yeah!. if you do decide to use your halfords oil it will be fine but I would mix it at 25/1, whatever you do don,t venture out onto todays public roads at 16/1 = you will be chassed down by mobs of sandal wearing unwashed vegans on push bikes . you will then need to flush the tank clear of mineral oil before using synthetic as they are not compatible.
I had a chat today with a respected uk rumi owner/restorer/crankshaft builder, who said I should mention that my rumi,s all run caged roller big and little end conrods, and that owners still running with old fashioned uncaged big/ bushed little end type conrods may be better off with a 25/1 two stroke mix.
I have been looking into this a bit recently. Comments from many owners of D and LD Lambretta,s "caged big end / bushed little end" have been running their machines for many years and thousands of miles on between 4% = 25-1 and 3% = 33-1, using mostly semi and fully synthetic. I am not sure of the ratio of oil used by people using the Rumi engine weak link uncaged big ends, but the French club have in the past advocated the use of 3% mix on the literature of their sortie road runs, however many French owners sensibly use upgraded caged big and little end bearing cranks.