Paul Marsh Posted April 20, 2015 Share Posted April 20, 2015 The timing is 180 degrees out. The mark should be on the top, and the cam be a 2:30 when piston is TDC. I've done loads of engines, so saying from experience. I'm surprised it runs at all on this setting... Quote Link to comment Share on other sites More sharing options...
Jon H Posted April 20, 2015 Share Posted April 20, 2015 Posted by Paul Marsh on 20/04/2015 21:40:12: The timing is 180 degrees out. The mark should be on the top, and the cam be a 2:30 when piston is TDC. I've done loads of engines, so saying from experience. I'm surprised it runs at all on this setting... Err..no, it should be at the bottom Quote Link to comment Share on other sites More sharing options...
Paul Marsh Posted April 20, 2015 Share Posted April 20, 2015 Yes it is!!! The dot should be at the top when TDC. (inline with the pushrods.) Edited By Paul Marsh on 20/04/2015 21:49:23 Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted April 20, 2015 Share Posted April 20, 2015 as a cam runs at half crank speed it shouldn't make any difference whether you set it on top or bottom. edit - that's the cam mark, not the crankshaft! Edited By Bob Cotsford on 20/04/2015 21:50:50 Quote Link to comment Share on other sites More sharing options...
Paul Marsh Posted April 20, 2015 Share Posted April 20, 2015 Well, if you deviate from what it should be set, there could be a slight timing difference if you set it the other way. Best to do it properly and set it how it should. Trust me, I have over a thousand engines and have taken twins apart to change bearings, etc. I had a old OS engine which was set out like the above, put a new piston ring and set up properly, and had much more power and reliable as anything. Edited By Paul Marsh on 20/04/2015 22:09:05 Quote Link to comment Share on other sites More sharing options...
Paul C. Posted April 20, 2015 Share Posted April 20, 2015 Just found a manual on line shows how to set the camshaft timing Paul is correct the timing mark should be at the top by the push rod tubes. Four strokes Suck, Squeeze, Bang , Blow. The Bang stroke will have the vales closed, at the top of the next stroke there will be a valve overlap the help the exhaust out and the mixture in. Tried to post the link but failed miserably. Paul. Quote Link to comment Share on other sites More sharing options...
Paul Marsh Posted April 20, 2015 Share Posted April 20, 2015 Thanks, Paul. Hope the Op has his engine sorted. Quote Link to comment Share on other sites More sharing options...
jrman Posted April 20, 2015 Share Posted April 20, 2015 Does this help? From the "Experts" **LINK** Quote Link to comment Share on other sites More sharing options...
cymaz Posted April 21, 2015 Share Posted April 21, 2015 Make sure the dot is spot on with the push rod tube, it's very easy to get one tooth out either way. As the gear teeth mesh the cam will want to turn. The trick is to put it in so as it turns the cam assembly comes to the top, clockwise if memory serves. Put it in with the dot about 10 o'clock that should be about right. Edited By cymaz on 21/04/2015 06:38:30 Quote Link to comment Share on other sites More sharing options...
will -0 Posted April 21, 2015 Share Posted April 21, 2015 Jrman, cymaz, do keep up at the back! Quote Link to comment Share on other sites More sharing options...
cymaz Posted April 21, 2015 Share Posted April 21, 2015 Out of breath now...running to catch up! http://www.youtube.com/watch?v=2_OjWeKPHsE&feature=youtube_gdata_player Edited By cymaz on 21/04/2015 06:48:23 Quote Link to comment Share on other sites More sharing options...
Jon H Posted April 21, 2015 Share Posted April 21, 2015 I have rebuilt numerous OS, asp and SC engines, not to mention saito enya and built about 1200 Lasers. I have always timed OS and their clones with the mark at the bottom, its what was shown in the instructions at one stage and is also how each one was fitted up when I took it apart in the first place. That said, as was suggested earlier by Bob it shouldn't actually matter as long as the engine is at TDC, it will just be TDC of the non compression stroke. Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted April 21, 2015 Share Posted April 21, 2015 Posted by Sam Wragg on 20/04/2015 21:32:42: When I run YS an old trick of mine was to rub the joint face of the rocker cover against a flat oil stone to ensure it was flat, as any leak around this area can upset the performance of the engine. Still can't remember what prop I used tho Sam Now why would any leak in the rocker cover have an effect on running or power? there is no connection between the rocker space and the fuel mixture passages or any other part of the engine that might affect the power.. Infact the only connection is through to the crankcase and that is open to atmosphere via the breather nipple Indeed we can see in this thread an engine being run with no rocker cover.Cars have a great big oil filler in their rocker covers...I could go on. Quote Link to comment Share on other sites More sharing options...
Martyn K Posted April 21, 2015 Author Share Posted April 21, 2015 He he Nothing like an engine problem to kick up a debate. However, as Bob said the cam turns at 1/2 crank revs so whether the dot is at the top or bottom it shouldn't really matter, its just easier to see at the bottom.. As all the piston is doing is going up or down - and momentarily stationary at TDC and BDC - then providing the valves open correctly on their respective down (inlet) and up (exhaust) strokes the position of the cam timing dot shouldn't matter - its just there to help alignment Anyway, I reassembled and reran the engine last night. Now getting over 10,000 rpm with a 13x7 prop. I couldn't get 9000 with a 12x8 before so something has got better. Still quite smoky though but I think that may be due to running too rich on the idle jet. As I was running the engine in the shed (by the door with the door open), I couldn't run it for too long but I did wait until the start of Corrie as I know all the sad old peeps would be indoors glued to their goggle boxes. I'll have another play with this later, possibly weekend while someone is mowing a lawn. Thanks all Martyn Edit: forgot to mention - I checked the inlet manifold - no problems looks absolutely fine. I am really puzzled about this engine - it looks like it has had very little wear - just been badly serviced. Edited By Martyn K on 21/04/2015 09:07:26 Quote Link to comment Share on other sites More sharing options...
Sam Wragg Posted April 21, 2015 Share Posted April 21, 2015 Posted by Peter Miller on 21/04/2015 08:44:44: Posted by Sam Wragg on 20/04/2015 21:32:42: When I run YS an old trick of mine was to rub the joint face of the rocker cover against a flat oil stone to ensure it was flat, as any leak around this area can upset the performance of the engine. Still can't remember what prop I used tho Sam Now why would any leak in the rocker cover have an effect on running or power? there is no connection between the rocker space and the fuel mixture passages or any other part of the engine that might affect the power.. Infact the only connection is through to the crankcase and that is open to atmosphere via the breather nipple Indeed we can see in this thread an engine being run with no rocker cover.Cars have a great big oil filler in their rocker covers...I could go on Pete Because in the YS system the Rocker cover holds in the pressure from the super charger system prior to being injected to the cylinder through the inlet valve. Any leak in this area upsets the performance of the engine Any excess flows back down the valve guides through a hole in the Crank back into the super charger Although the OS doesn't employ a super charger system the Rocker Cover still holds the fuel air mixture and speaking from experience any leak in this area does affect the engines performance. The crankcase nipple is so that the engine can breath as the piston goes up and down during its cycle as the bottom end is sealed I Agree with Jon about the Timing marks (From Memory) The timing mark on the Crank should align with the mark on the crankcase The timing mark on the cam should align with the center of the lower tapped hole of the camshaft cover. Sam Quote Link to comment Share on other sites More sharing options...
Paul C. Posted April 21, 2015 Share Posted April 21, 2015 **LINK** My first link hope it works OK if I have picked the correct engine model the manual shows the camshaft timed at the top by the push rod tubes. It looks like a copy of a genuine is manual but worth checking out. In my experience with diesel engines (earthmoving and automotive) vale timing is either right or wrong and when it's wrong it doesn't run as it should if at all. If this is not the correct manual for this engine I am sure that there is one out on the internet somewhere. Hope you get it sorted soon Quote Link to comment Share on other sites More sharing options...
Sam Wragg Posted April 21, 2015 Share Posted April 21, 2015 In reference to my previous post the timing mark on the cam should be at the bottom. I don't know where center line of tapped hole came from. (Probably work related) Apologies for confusion I was rushing to post Sam Quote Link to comment Share on other sites More sharing options...
Martyn K Posted April 21, 2015 Author Share Posted April 21, 2015 Thanks Paul My engine is the earlier version of this - its the FS II variant - unpumped (sadly) That does show the timing dot at the top, but I still believe that it makes no difference whether is top or bottom. At the top it is very easy to see that it is correctly aligned - I cant argue with that. However when aligning with the dot at the top, the engine is still on its exhaust stroke and the cam for the exhaust valve is still under pressure (just). This actually deflects the cam shaft downwards very slightly if you check with the head in place - I know this - I tried it.. With the dot at the bottom, I agree that it is not quite so obvious if the camshaft is on the correct tooth, but because the engine is at TDC on the ignition stroke both valves are firmly closed and there is no load on the cam shaft - which is partially unsupported when the end cap and bearing is removed. Martyn Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted April 21, 2015 Share Posted April 21, 2015 Pete Because in the YS system the Rocker cover holds in the pressure from the super charger system prior to being injected to the cylinder through the inlet valve. Any leak in this area upsets the performance of the engine Any excess flows back down the valve guides through a hole in the Crank back into the super charger Although the OS doesn't employ a super charger system the Rocker Cover still holds the fuel air mixture and speaking from experience any leak in this area does affect the engines performance. The crankcase nipple is so that the engine can breath as the piston goes up and down during its cycle as the bottom end is sealed Now I don't know about YS but the OS engines are NOT super charged.. Please explain on an OS engine how the fuel air mixture gets into the rocker cover bearing in mind that there is NO connection between the the intake manifold, the combustion chamber or the exhaust passages and the rocker cover apart from the valve guides and if they are worn enought to allow sufficient mixture through to affect the running the engine is totally useless as it would have no compression. Quote Link to comment Share on other sites More sharing options...
Jon H Posted April 21, 2015 Share Posted April 21, 2015 Im with you Peter. Only the newer alpha series need the rocker cover attached as they blow the crankcase air up the pushrod tube and into the inlet valve pocket. I have run countless OS and asp's without a rocker cover. In fact I have run them in this way so I can see if anything untoward is happening with the valves and can tweak the clearances if they move. The comments about the YS are spot on though. any leak in the rocker cover makes a mess of everything Quote Link to comment Share on other sites More sharing options...
Paul C. Posted April 21, 2015 Share Posted April 21, 2015 Found loads of manuals for download on the osengines.com web site but guess what! It doesn't show how to set the camshaft timing just the valve lash, you have just got to smile . If you current timing option does not make any improvement you could always try the other position just remove the plug and turn the engine over slowly by hand to make sure the piston and valves are not making contact. If that's OK they try firing her up to see if any improvement. I knew there was a reason I decied to go all electric . Paul. Quote Link to comment Share on other sites More sharing options...
Martyn K Posted April 21, 2015 Author Share Posted April 21, 2015 One of the things I love about this hobby is the problem solving challenges that we have to overcome. If all I had to do was simply fly, then I probably wouldn't bother. I am just putting the cylinder head back on a 16valve 400cc Suzuki after replacing 16 x valve stem oil seals. I have exactly the same challenge - getting the valve timing correct - however, if I get it wrong on the bike it is likely to be far more costly and time consuming Martyn Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted April 21, 2015 Share Posted April 21, 2015 I aint an expert on dots n rest of it but they do run a bit ropey for a while if you've over done the after run oil John Quote Link to comment Share on other sites More sharing options...
Adrian Smith 1 Posted April 21, 2015 Share Posted April 21, 2015 Quite right John, as I have noticed this too. As a rule I don't use after run oil if the engine is in regular use. I just make sure that the engine is run as dry as possible and the tank is empty. Quote Link to comment Share on other sites More sharing options...
Martyn K Posted April 21, 2015 Author Share Posted April 21, 2015 I am always a bit puzzled on how the bottom end gets lubricated on a model FS with no sump. I tend to use a liberal does of a light synthetic oil but not sure if that is needed. I always considered that the excess would get breathed out after a few seconds if it was overdone - admittedly, for the OS70 this is directly into the inlet manifold Martyn Quote Link to comment Share on other sites More sharing options...
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