trialsrfun Posted October 5, 2013 Report Share Posted October 5, 2013 Says it all above, what are you using & recommending? Quote Link to comment Share on other sites More sharing options...
dadof2 Posted October 5, 2013 Report Share Posted October 5, 2013 Probably a straight SAE 40 or 50 engine oil, I don't think you should put any oil with EP additive or dispersant / detergent additives. Quote Link to comment Share on other sites More sharing options...
trialsrfun Posted October 6, 2013 Author Report Share Posted October 6, 2013 Any expert advise for Cub engine oil out there please? Quote Link to comment Share on other sites More sharing options...
armac Posted January 14, 2014 Report Share Posted January 14, 2014 Hi, you may have sorted this already, but: use semi-synthetic or fully-synthetic (I use PJ1 and am still running the original big end after at least 15 years). Synthetics have a much higher temperature range and molecular breakdown is much less than mineral oil. It is more expensive, but cheaper than rebuilding the engine. I hope that helps. Duncan, Armac Design 1 1 Quote Link to comment Share on other sites More sharing options...
brucey Posted January 15, 2014 Report Share Posted January 15, 2014 (edited) Duncan, I read with interest that you use fully synthetic oil in your Cub. I have a pretty standard engine with an Oil Tank in the Top Brace (very similar to a Sammy Miller unit but made from bits of train!). I have also fitted a high capacity pump and external (Citroen 2CV) canister oil filter, roller big end and run a side points crank. The engine runs really well but after long periods (usually when trying to catch up by repeating sections without stopping during trials), I find I get a slight smoke mist wafting out the top of the engine. I put this down to the engine starting to run hot. I currently use about 700cc of 10/40 Castrol GTX at oil changes. My theory is it is getting too hot because I don't run a full size oil tank. Someone told me to run it on Castrol 'R'. From my Karting days, I know 'R' smells nice but I'm not sure a 1960's mineral based oil is the solution! If I drain the existing oil with the engine hot and change the canister filter, would it be o.k. to try PJ1 to see if it cures my oil mist problem? I also have the Allan Whitton breather mods but get a small dribble of oil from the RH Cover (I note you run your Cub without this cover fitted). I have been told I should have blanked off a small hole behind the cover. Any advice would be appreciated. Bruce. 16/01/14 Edited as requested........sorry! Edited January 16, 2014 by brucey Quote Link to comment Share on other sites More sharing options...
stickinthemud Posted January 15, 2014 Report Share Posted January 15, 2014 Have to agree with Duncan. I use fully synthetic in my Cub without a filter since Martin Adams formerly of Serco said that if you spend all that money on an engine you should use the best oil. I took his advice and my big end has also lasted at least 5 years and I've only changed the rings once in all that time and it still doesn't smoke - and that's on an original Triumph piston in a Serco alloy barrel. Also have a top tube tank, not blocked the small hole and don't have a dissy hole breather fitted. Suits me sir! 2 Quote Link to comment Share on other sites More sharing options...
brucey Posted January 16, 2014 Report Share Posted January 16, 2014 Thanks stickinthemud, I'll give the PJ1 fully synthetic a go on the grounds that it retains its performance over a larger heat range. The main reason I haven't used it before is I always consider synthetic oil 'a bit runny' (poor excuse I know!). However, after draining my oil from a hot engine, I guess the fully synthetic oil is no less viscous at high temperatures than normal 10/40 oil. Quote Link to comment Share on other sites More sharing options...
trialsrfun Posted January 16, 2014 Author Report Share Posted January 16, 2014 (edited) I run with the timed engine breather but the small hole is blanked off so as to prevent the intake of any water that gets into the side case from entering the engine. This means that a small amount of oil can build up in the side case. I have been told that if using the open tube breather with a closed end camshaft bush the engine then suffers from pumping losses due to the movement of air from the underside of the piston (the reverse of what happens on top of the piston) as well as pushing oil out down the breather tube where the same forces can pull water and mud back up the pipe into the engine. What are your thoughts on this please Duncan. Edited January 16, 2014 by trialsrfun Quote Link to comment Share on other sites More sharing options...
armac Posted January 20, 2014 Report Share Posted January 20, 2014 Brucey, sorry for delay, Cub engines can certainly run hot, one of the tips from Triumph was to ride through puddles in the scottish 6 days to aid cooling. Modern synthetic oils are able to withstand much greater temperature gradients without breaking down and are infinately superior to Castrol R. You had better check with Richard Thorpe ( PJ1 importer) about swapping directly to synthetic, his email is r.thorpe146@btinternet.com (not sure if this is public, might be best to say I gave it to you!). The little hole in the inner case does want welding up as its original job was to suck oil up that had leaked from the camshaft & gearbox. On a trials engine that has been through streams etc , then power washed, you are inevitably sucking up water as well. Best regards, Duncan. Quote Link to comment Share on other sites More sharing options...
armac Posted January 20, 2014 Report Share Posted January 20, 2014 (edited) TrialsrFun, back to you! I run a breather from the crankcase & the rocker box that goes into a one way valve, that exits into the steering head lubing the bearings & preventing any water from being sucked in. It runs a little bit cleaner on the carburation than having no breather at all. All the best, Duncan. Edited January 20, 2014 by armac Quote Link to comment Share on other sites More sharing options...
1961jamie Posted September 26, 2022 Report Share Posted September 26, 2022 Duncan, Would you suggest welding up the hole in the casing even for a road going cub? Quote Link to comment Share on other sites More sharing options...
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