With a thorough refurbishment completed HERE, including repair of a pinhole leak in one of the silent burners, I’ve been enjoying using the stove at every opportunity. Just one thing I couldn’t live with - the O-ring equipped pump. Mostly it worked, but every so often it was possible to push the pump completely home without trapping the air, and that’s with a new and lubed O-ring. At best the action wasn’t smooth or particularly efficient. So, I cut the O-ring piston off, together with a length of pump rod and cut the piston and equivalent length of rod off a spare leather cup washer-equipped pump assembly - Monitor brand I think it was. Silbrazed graft completed ... The pump action is now effortless, with no ‘missed’ strokes and more efficient pumping - sufficient to maintain tank pressure with the two quicklighters burning simultaneously. One of the last of my stock of Sefa’s pump cup washers. John
@presscall Great job, John, and well worth it. I’ve done the pump-cup-from-O-ring conversion on a couple of Optimus 111s (but much more easily achieved by using a “star washer” on the existing pump shaft). I find the leather pump cup a much more satisfactory option. Cheers Tony
@Staffan Rönn Welcome to CCS Staffan and an appropriate question for this thread given your insight as a former owner of Optimus - why the move from pump cup leather to O-ring equipped pump pistons? Cost saving I can understand, though on an otherwise excellent range of stoves it seems hardly worth the saving to introduce what is in my judgement at least a component that compares unfavourably with the type in use since the first kerosene pressure stoves came into being. Please don’t interpret my question as uncivil, but born out of genuine puzzlement! John
@presscall Hi John, please excuse me for not reacting quicker, I have been busy elsewhere this week. Don't worry - I don't find your question uncivil, it probably goes for a lot of us to have been part of both good and bad decisions through our work Lifes.... The decision to move to O-rings was however done before I joined Optimus, so I have no clear answer to this. I have a vague memory saying that the old CTO at Optimus (retired shortly after I got involved) thought it was a way to reduce maintenance for the users (the rationale being that o-rings would require less attention than leather cups). I don't find this a very good argument though. Also, as you mention, the cost argument is not very convincing either. And like most of you - I prefer leather cups over o-rings. So you made a good move with your modification.
@Staffan Rönn Plenty quick enough with your reply Staffan, thank you. Wow, quite an insight, and a pretty hefty endorsement for the modification! John