onetenor Posted June 16, 2017 Share Posted June 16, 2017 Were Magnums exact copies of O.S. engines or just near enough? Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted June 16, 2017 Share Posted June 16, 2017 A lot of parts were interchangable . The piston liner from the Magnum 40 GP would fit the OS 40 FP. Carbs were the same apart from fixing ,screws were used on the OS and a collet on the Magnum . Not sure about other parts. Quote Link to comment Share on other sites More sharing options...
onetenor Posted June 16, 2017 Author Share Posted June 16, 2017 Thanks E.D. so I assume the piston,gudgeon pin, conrod group are the same too John Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted June 17, 2017 Share Posted June 17, 2017 Pretty sure they are a straight swap if memory serves but it wont take long to test fit on the bench . Parts were half the cost of OS and lasted well . The needle valve assembly was a straight swap but getting hard to find these days for Magnum or the OS probably only found on breakers or when we have a clear out . Quote Link to comment Share on other sites More sharing options...
onetenor Posted June 17, 2017 Author Share Posted June 17, 2017 OK E.D. I actually am having PROBS ungluing the throttle barrel. Can't get it too hot as I could melt the plastic lever. I haven't tried soaking in Methanol yet as I have to work on a lap tray.Any ideas ? I'm waiting for new hips so pretty immobile and seeking other ways to do things so any ideas welcome Re the needle valve assy I think there are some others that fit straight in or can be modded. No rush for one yet though.. I have both the O.S. and Magnum 40 s and have repairs to do to both. One is recasting half the exhaust mounting lug on the O.S. .Do you know the thread size in the lugs. Thanks for your response. John Quote Link to comment Share on other sites More sharing options...
TIM Shaw Posted June 17, 2017 Share Posted June 17, 2017 Could you not remove the plastic arm, then warm it up a little - always found heat is the best way to remove gummed-up throttle barrels if WD 40 has failed. Is the thread not just M3? Quote Link to comment Share on other sites More sharing options...
onetenor Posted June 17, 2017 Author Share Posted June 17, 2017 Not 3m thread. Maybe 3.5 but haven't a means of testing at mo as I can't get to my shed for the tools. Re off the plastic lever .If I do there is nothing to turn or pull the barrel with .I have had it hot enough to recoil as soon as you touch it then sprayed with oil while hot but still no go. Soaking in meths no good either. Needs methanol but not on my lap thanks LOL Quote Link to comment Share on other sites More sharing options...
onetenor Posted June 17, 2017 Author Share Posted June 17, 2017 Just a thought but should I source a couple of NVA's against future loss or damage to existing ones? I think I saw some on the wheelspin models site when I was looking for a gudgeon pin.I'll have a look. Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted June 17, 2017 Share Posted June 17, 2017 Most 40 sized threads are M3 OT, but to repair them I thread them out to M3.5, so maybe they were repaired before? Try, if you will, operating the barrel with a wooden dowel in the venturi hole to free it off And pull out the barrel with an M3 bolt screwed into the hole vacated by the throttle arm Edited By Denis Watkins on 17/06/2017 15:33:17 Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted June 17, 2017 Share Posted June 17, 2017 Hi if the throttle barrel is just gummed then dump it in a cup of boiling water for free minutes. I have Magnum 40 in my engine box I'll measure it tomorrow and get back Quote Link to comment Share on other sites More sharing options...
Nigel Dell Posted June 17, 2017 Share Posted June 17, 2017 Posted by onetenor on 17/06/2017 12:59:57: Not 3m thread. Maybe 3.5 but haven't a means of testing at mo as I can't get to my shed for the tools. Re off the plastic lever .If I do there is nothing to turn or pull the barrel with .I have had it hot enough to recoil as soon as you touch it then sprayed with oil while hot but still no go. Soaking in meths no good either. Needs methanol but not on my lap thanks LOL All the exhaust bolts on OS 40 FSR's are M3.5 so your assumption is correct. Quote Link to comment Share on other sites More sharing options...
TIM Shaw Posted June 17, 2017 Share Posted June 17, 2017 FSRs yes - but I thought we were talking about a FP here... Quote Link to comment Share on other sites More sharing options...
Nigel Dell Posted June 17, 2017 Share Posted June 17, 2017 Posted by TIM Shaw on 17/06/2017 22:21:53: FSRs yes - but I thought we were talking about a FP here... Well in over 40 years playing with OS engines and onerenor saying it was not 3mm possibly 3.5mm and the fact I have the M3.5 tap to clean damaged threads in not only FSR's it is a very good chance it is guess what M3.5. Just trying to help. Quote Link to comment Share on other sites More sharing options...
Nigel Dell Posted June 17, 2017 Share Posted June 17, 2017 Just to be sure I checked the two FP 35's I got in amongst a lot of other bits from the same guy so not new to me and they are both M3.5, there of course is a chance that earlier engines may have been 3mm such as a very early 40 FSR I have is M3. But given Onetenor's information there is a very good chance it is M3.5 Quote Link to comment Share on other sites More sharing options...
TIM Shaw Posted June 17, 2017 Share Posted June 17, 2017 OK Guys, maybe my bad. I'm also trying to help. but my FP is indeed from 1986, and I remember the silencer bolts being smaller on that engine than they were on the later Magnum Pros, Thunder Tiger Pros and OS FXs I progressed to, which, as reported, were M3.5. Nigel is quite right in that all the modern ones seem to be M3.5 so I might have it wrong. It has happened before, ...... Quote Link to comment Share on other sites More sharing options...
Nigel Dell Posted June 18, 2017 Share Posted June 18, 2017 Actually Tim no one is really wrong there may well have been some in circulation like that hence why I went out and found the 35's to be sure, all the OS engines of that size that didn't have the strap on silencer that I have come across apart from the one FSR have had the 3.5's the same early FSR has a smaller carb too, which when I have something like 20 consisting of 40,45 & 50's OS did it their way changed it and the others picked the better bits to use!👍🏻 😜😎🤣 Quote Link to comment Share on other sites More sharing options...
onetenor Posted June 18, 2017 Author Share Posted June 18, 2017 Thanks gents Inconclusive but useful. I'll get some 3.5Ms sent out .Re the NVA's Wheelspin do hate them. I thought they might. They are a good source for most things modelling.Re using a wooden dowel to manipulate the barrel how would I do that exactly? Just about to reheat with M3 bolt screwed in .Back later Quote Link to comment Share on other sites More sharing options...
onetenor Posted June 18, 2017 Author Share Posted June 18, 2017 That's funny didn't even need the heat just "Came apart in me 'ands Guv "Well whatever object achieved ans many thanks to everyone. I've said it before and say it again now .The people on these forae are knowledgeable and kind. both in giving this knowledge and in items gifted. I have been grateful for this on more than one occasion.I give what knowledge I can and will give what I can in goods.There is one problem though A kind soul donated 2 ltrs of ether for diesel fuel but it's in Blackburn area and T'm in North Wales and stuck indoors at the mo so can't collect.I put out a request for anyone to do me the favour but it seems nobody from up there passes near here so I'll have to wait till I'm mobile again. Well thanks to all once more . Cheers John O/T Quote Link to comment Share on other sites More sharing options...
onetenor Posted June 18, 2017 Author Share Posted June 18, 2017 Back again .Thread in NVA hole appears damaged goes tight about half way in . 2 BA do you think ? Or M.E. thread Edited By onetenor on 18/06/2017 17:30:20 Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted June 23, 2017 Share Posted June 23, 2017 Sorry for late reply but got busy. Magnum 40 exhaust screws are 3.5mm8 X 0.5 mm pitch. Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted June 23, 2017 Share Posted June 23, 2017 OT, I will try again, the OS range you speak of in my possession are M3 all my spare small motor bolts are M3 Due to crash damage or overtightening, I have seen M3.5 threads tapped for the repair for obvious reasons Justengines supply replacement silencers for 25 to 60s including OS types and their bolts are either M3 or M4 for larger motors Quote Link to comment Share on other sites More sharing options...
onetenor Posted June 24, 2017 Author Share Posted June 24, 2017 Thanks Denis Yes I get that. I am waiting for some 3,5 bolts so I can check but M3 s just slip in so must be bigger. Thanks for your effort. Don't suppose you know thread on NVA as there is some thread damage part way into the carb body Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted June 24, 2017 Share Posted June 24, 2017 Am dreading the flak from this OT But a 4mm metric fine pitch. (4mm X .5 pitch) bolt screws into the NVA that I have here Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted June 24, 2017 Share Posted June 24, 2017 Posted by Denis Watkins on 23/06/2017 21:23:37: OT, I will try again, the OS range you speak of in my possession are M3 all my spare small motor bolts are M3 Due to crash damage or overtightening, I have seen M3.5 threads tapped for the repair for obvious reasons Justengines supply replacement silencers for 25 to 60s including OS types and their bolts are either M3 or M4 for larger motors I've dug out the remnants of a wrecked OS32F heli engine that I got bundled in with a Concept heli 20 odd years ago (yes, I'm a hoarder of anything that might be vaguely useful!) and can add some support to Denis on this one - the silencer bolt through holes are 3.2 mm so the silencer MUST have used 3mm fixings unless OS used imperial/unified screws which I'm sure wasn't the case. Interesting piston, BTW - it looks at first glance to have a Dykes ring but, as confirmed by filing the top of the rather pitted piston, it is an A(BC) type but with a thin groove of very little depth machined around the top. Quote Link to comment Share on other sites More sharing options...
onetenor Posted June 24, 2017 Author Share Posted June 24, 2017 Thanks all . I think the threads must have been tapped out The 3.5 mm tap ordered arrived as 3.0 mm So can't confirm.Vernier of the NVA thread is 3.95 mm.The "groove" is present on the 40 piston too. It actually looks as though the crown is a pressed in part. I just realised it is The magnum I'm referring to so hence the differing sizes though almost all the OS parts are a swap .Now having said that I just checked the O.S>. and it is the same in this regard so it too must be tapped O/size I'll just buy a new carb body ............... and some 3.5 mm bolts . Thanks again to all. John O/T Quote Link to comment Share on other sites More sharing options...
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