B23 600

[wilf]

At the recent Cooma girder fork rally my B23 600 seized with the help of Ian we got a few more kilometers out of it but then ground to a halt. After stripping down the motor the rear  rear cylinder was completely dry, the piston is a throw away job. The front cylinder was perfect, should I consider running an oil line to the rear cylinder like the front positive feed. Wilf

[graeme]

I'd be checking your oil supply Wilf - the rear cylinder should get plenty of oil flinging into it from the crank webs picking up oil in the wells below the crank.

[eddie]

Wilf,
 The LDMCC has been having the same problems with their 4HP Douglas. On stripping the motor, they found the same problem - the back cylinder and crank had been running short of oil - the front cylinder was better due to the drip feed to the front barrel. On careful inspection, we came to the conclusion that this machine had Mr Douglas's 2nd update of the lubrication system. It seems that the engine relies on there being the required amount of oil being put into the crankcase on assembly - it is then topped up by that being fed through the drip feed. Curiously, the cast alloy dipper trays have no means of returning excess oil to the sump - earlier versions had fabricated steel dipper trays with overflows back to the sump - the trays being fed with a constant supply of oil via a branch pipe that entered the crankcase behind the flywheel. At the moment, we are running the bike with a modified dipper tray and positive oil feed (as per the earlier models) - we now just have to play around with restrictors in the oil feed to control the amount of oil going to the dipper trays so that we get good lubrication and not too much smoke!!
   Another detail that didn't make good engineering sense was that the dipper tray had a drain tap situated behind the timing chest that screwed into the side of the tray but only had a locknut  to seal it against the crankcase wall. This was not very effective and had resulted in the tray being pulled to the side (to the point that the bigends had scuffed the side of the tray). With our new dipper tray having overflows back to the sump, we have done away with the drain tap, and plugged the hole in the crankcase.
 Hope some of this helps with your problems,
   Regards,
                Eddie.

[wilf]

Eddie many thanks for you response, I was very interested to hear that you were also having oil starvation issues and do not understand why Mr Douglas would have changed a system that was operating well, to one that has the potential to cause so much mechanical damage. I have had a previous event which was almost fatal for the motor so I am particularly careful to ensure that it is not repeated. As such I felt that a positive feed to the rear cylinder may be the answer but I will also check out the feed to the dripper trays. Curiously, Graeme provided me with a sump which had a pressed steel tray...I have some work to do !!! Kind regards Wilf

[eddie]

Wilf,
       It would seem that there were 2 versions of the steel dipper tray prior to the cast alloy version. I have seen steel dipper trays with just the 2 troughs for the bigend splashers - others also have an extra trough across the back of the tray, which presumably just retains some of the oil that is thrown up.
     Whereas the earlier models had a branch in the main oil line that fed oil direct to the dipper trays, the later models (with the cast alloy dipper tray) relied solely on enough oil passing through the sight glass to lubricate the whole motor. Having got that much oil into the motor, there was no way of returning it to the sump, as the alloy tray sealed the crankcase floor.
     With this lubrication system, the LDMCC machine has had at least 2 cranks in the last 10 years, along with several instances of inadequate lubrication on the back cylinder. The committee took the decision that we should revert to the older system as this seems to be more 'user friendly'. So that we didn't make any irreversible modifications, I made a new dipper tray with drain ports to return excess oil to the sump, a new feed pipe and elbow that screws in behind the flywheel, and a new main oil feed pipe with the necessary branch. As I said previously, we now just have to test and adjust the new setup until we get reliable running without too much smoke!!
     Regards,
                   Eddie.