Robin Posted September 11, 2023 Report Share Posted September 11, 2023 The damper oil from my twin stromberg CD150s is draining out quite regularly but can’t see any obvious leak - is there an O ring in the casing where the needle is held in place by a grub screw? I think there is in the CDSE but not sure about the CD150 Link to comment Share on other sites More sharing options...
Iain T Posted September 11, 2023 Report Share Posted September 11, 2023 I don't think there is a way for oil to drain out of the air valve (piston) as its a sealed unit. You don't need to fill to the cap top only to around the top of the piston. You can see the ring line about 1" down from the top of the cap. If you fill to the top it will drain away. Iain Link to comment Share on other sites More sharing options...
johny Posted September 11, 2023 Report Share Posted September 11, 2023 yes I think thats the normal problem, they get overfilled and excess is lost when the piston is fully raised so making it look like theres a leak but of course the level is still correct. This can be verified with the damper in place by lifting the piston fully by hand through the carb mouth and there should be resistance felt all the way... Link to comment Share on other sites More sharing options...
Robin Posted September 12, 2023 Author Report Share Posted September 12, 2023 Ah, ok. Think I may be overfilling Link to comment Share on other sites More sharing options...
Gully Posted September 12, 2023 Report Share Posted September 12, 2023 I seem to recall the manual recommends checking / topping up weekly anyway. Mine do leak - the front carb more than the rear - so I check and top up generally to coincide with when I need to buy fuel every c. 200 miles. Gully Link to comment Share on other sites More sharing options...
Iain T Posted September 12, 2023 Report Share Posted September 12, 2023 22 minutes ago, Gully said: Mine do leak Isn't it really the oil spilling over the sliding joint between the air piston and cap. I agree best to check regularly to dampen the rise in the piston or the mixture will go lean on acceleration. Iain Link to comment Share on other sites More sharing options...
JohnD Posted September 12, 2023 Report Share Posted September 12, 2023 The oil should be 1/4" from the top, with the damper piston in place. That displaces a lot of oil, so that if you fill it 'correctly' and then put the piston back, you'll lose a lot! John Link to comment Share on other sites More sharing options...
johny Posted September 12, 2023 Report Share Posted September 12, 2023 Yes the manual diagram is pretty good and you can see theres no route for leaks and also no point filling above the top of the damper tube and as John says better a bit below... Link to comment Share on other sites More sharing options...
dougbgt6 Posted September 12, 2023 Report Share Posted September 12, 2023 I have CDSE top adjusters which do have "O" rings. A pain to replace. There's a tiny sprag washer that has to be banged out from the needle end. Best to do it in a plastic bag as the sprag can travel a LONG way, generally never to be seen again. Doug Link to comment Share on other sites More sharing options...
Gully Posted September 12, 2023 Report Share Posted September 12, 2023 1 hour ago, dougbgt6 said: I have CDSE top adjusters which do have "O" rings. A pain to replace. There's a tiny sprag washer that has to be banged out from the needle end. Best to do it in a plastic bag as the sprag can travel a LONG way, generally never to be seen again. Doug Likewise! Gully Link to comment Share on other sites More sharing options...
Gully Posted September 12, 2023 Report Share Posted September 12, 2023 2 hours ago, Iain T said: Isn't it really the oil spilling over the sliding joint between the air piston and cap. I agree best to check regularly to dampen the rise in the piston or the mixture will go lean on acceleration. Iain As Doug noted below, the top adjuster CDSEs have O-rings by the needle adjusters immersed in the damper oil, which deteriorate and leak. Gully Link to comment Share on other sites More sharing options...
Iain T Posted September 12, 2023 Report Share Posted September 12, 2023 3 minutes ago, Gully said: As Doug noted below, the top adjuster CDSEs have O-rings by the needle adjusters immersed in the damper oil, which deteriorate and leak. Sorry I forgot about the CDSE top adjusters! I'm blinkered as I've only tampered with the CDS bottom adjuster carbs. Link to comment Share on other sites More sharing options...
Pete Lewis Posted September 12, 2023 Report Share Posted September 12, 2023 yes overfilling will allow the damper oil to get pulled over the top of its tube on a rapid down stroke the spilt just ends up in the mixture and gets burnt Pete Link to comment Share on other sites More sharing options...
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