Commando wetsumpingUp to Commando
Commando wetsumpingPosted by ian_richtsteig at September 15. 2010
I'm new to Commandos as I only bought a 1970 750cc this year. The bike has only done 3,500 miles now but wet sumping is an issue. It wetsumps much worse than the 650SS I have ridden for the last 30 years and also much worse than my 1952 ES-2. Are Commandos more suceptible to wet sumping? Also while it runs well up to 60mph, it wants to start missing at speeds greater than 60. (Ignition is the original twin coil set up). Any comments greatly appreciated.
Re: Commando wetsumpingPosted by mark_woodward at September 15. 2010
Wet sumping on Commandos is a common issue - even with a rebuilt engine/oil pump. Mine has a rebuilt engine with only 900 miles on the clock - the engine runs beautifully and is smooth and quiet but it still wet-sumps. My fix was to fit an in-line tap in the oil tank feed and as a safety measure I fitted an electric switch onto the tap such that the entire bikes electrics are isolated unless the tap is turned on (i.e. it won't start) - this works a treat. Many people don't like the idea of such taps etc. but I think this based on the fact that it is possible to forget to turn it on before starting - with disasterous consequences !
With regard to running over 60 - is it the road speed that's the issue or (more likely) the engines inability to rev higher than approx 3500 rpm ? It may be worth checking the timing and especially the auto-advance mechanism (I assume you're still running on points ignition). The auto-advance units are prone to problems (especially in 'old-age') - the return springs weaken (these can be replaced but ensure you obtain the correct items) - when you check the timing you must do this at full advance - it should be 28 degrees BTDC at full advance - you can check this with points by locking the auto advance at full advance with a washer under the fixing bolt (Lucas used to supply a special washer just for this purpose) - turn the engine over slowly until the mark on the alternator rotor line up with the 28 degree marking on the timing dial inside the primary chaincase - if the timing is correct then the contact breaker associated with the specific cylinder should just be opening. As there are two sets of points you should check the timing for both cylinders separately.
Long term I'd budget for electronic ignition - my personel recommendation is Tri-Spark Classic Twin although the Pazon and Boyer systems are both popular.
I'd also check the carburettors/mixture as per the workshop manual etc.
Re: Commando wetsumpingPosted by ian_richtsteig at October 05. 2010
Thanks for the response. I will look at the coils to see whether they overcome the issue then work back systematically from there. I suspect that electronic ignition will be the way to go.