dadof2 Posted February 16, 2014 Report Share Posted February 16, 2014 Lead was added to fuel to increase its octane rating so detonation does not occur at higher compression ratios, if your engine does not detonate on regular or super unleaded there is no need to use leaded or avgas. In a 4 stroke engine the lead also coats the exhaust valve sealing area to prevent wear. There is a theoretical risk that if lead deposits coat the parts rolling bearings in a 2 stroke crank case, running clearance will be reduced and the bearings may fail. The other problem from deposits of lead in fuel is that they cause galvanic corrosion on steel. That galvanic corrosion will occur is an established fact, however the rate and extent of corrosion on steel bearings may well be insignificant in a typical trials engine. I would think in general that modern oils do not contain additives to counteract the corrosive effects of lead as the general expectation is that leaded petrol will no longer be used. Lead damages spark plugs and catalytic converters. Quote Link to comment Share on other sites More sharing options...
slicktop Posted February 17, 2014 Report Share Posted February 17, 2014 Good points. I had not thought about Lead and Steel being dissimular metals inviting galvanic reactions. I have the high compression gasket installed so I may need race fuel and the choice of fuel came about by trying to eliminate ethanol. I run this same blend in my Husqvarna 125-167 so it was a benefit not to change fuels. Quote Link to comment Share on other sites More sharing options...
0007 Posted February 17, 2014 Report Share Posted February 17, 2014 (edited) Dadof2 has a lot of good points on his obviously well educated post "On 2 strokes good, high film strength synthetics such as Belray MC1 prevented the wear that was an essential part of the running in process. When the engines were subjected to full power use post running in, problems, usually piston / bore seizures occurred because the parts were not actually fully run / bedded in. These problems became quite well known in karting and 2 stroke road racing in the late 1970s / 1980s. Mineral oils contained impurities that "chemically" burned off high spots during running in whereas synthetics do not. " A little input from the Japanese side here is that during this time frame, essentially the edge of the envelope and pinnacle of the 2 stroke development, a lot of metallurgical processes changed as did a lot of machining processes, most significantly iron liners and iron rings went away and plated cylinders were in development there are a lot of different plating methods (not just "Nikasyl") which now consist of a method of applying ceramics to the cylinder, essentially this plating does not really "wear" under normal circumstances (it really can't as there is less than 1mm of material applied) and the final machine process is "plateau honing" which removes the high spots essentially breaking in the cylinder, so all that needs to happen is the ring (it's plated too) needs to ever so slightly bed to the cylinder, probably within 20 minutes or less, so a Japanese bike pretty much comes broken in, some would call Bull on this but that's why there are pretty much 0 warranty and oil consumption issues on 4 strokes and crazy low failure rates on modern Japanese 2 strokes, also means things we did with engines 20 or 30 years ago don't apply to today's engines However, I know very little about the plating methods of Italian and Spanish cylinders, Dad can you comment on plating and ring construction on euro bikes? Edited February 17, 2014 by 0007 Quote Link to comment Share on other sites More sharing options...
dadof2 Posted February 18, 2014 Report Share Posted February 18, 2014 Unfortunately specific information about exactly what ring / bore materials euro manufacturers use is not readily available, for example Sherco state the cylinder is nikasil but there is nothing on the ring material. Gasgas look like nikasil bores. I suspect the ossa will have a ceramic composite bore and possibly aluminium nitride type coating on the rings to withstand 100:1 premix ratio. There is such a range of ring bore material combinations its impossible to know, and although rivals will be able to get them analysed, they may not be able to replicate them. In the UK I would probably seek advice from Phoeton Aptec or Langcourt. One area where there have been big improvements in recent years is analysis of dimensional changes in pistons due to thermal effects and changes to metallurgy and machining techniques to minimise the negative effects of these. This alone will have reduced running in times. The advantages of stressing the barrel and raising it its operating temperature during final stages of boring and honing were known to a few select tuners in the 1970s, possibly before, yet as far as I know it is not yet used in manufacture of mass produced engines. I think Beta still advise 10 hours running in and many oil manufacturers still supply running in oils so there is obviously still believed to be a need for it. It would probably be technically possible to make an engine that did not need running in but it would probably be prohibitively expensive to machine to the tolerances required as witnessed by the price of very high precision needed for high pressure or DI injection parts. Cheaper and more convenient to let the user do final machining by running in. A few years ago I came across an internal grinding machine used for the production of 2t motorcycle barrels in Germany (so presumably Maico or MZ). This produced an exceptionally good finish and it was possible to vary the ratio of reciprocation speed to rotational speed to vary the angle of the cross hatching on the bore. This high quality ground finish probably explained why original bores seemed to last much longer than subsequent re bores using a boring bar and hone. I think Fantic also used to internally grind their bores then find a exact matching piston by an air blowby test. Quote Link to comment Share on other sites More sharing options...
beta zero gara Posted February 23, 2014 Report Share Posted February 23, 2014 (edited) Ethanol and methanol have higher octane rating to begin with, but this only matters in very high compression engines with dramatic advance curves on their ignition. Trials engines do have higher than normal compression but they don't rev much and the ignitions don't need to be so aggressive. What happens with eth/methanol even when used as additives to improve octane rating is that the fuel/air ratio is affected. The engine will run leaner and that will cause more heat. Hotter engines may run into trouble with pinging and dieseling while running lean. So you can kill a good engine running premium fuel if you don't adjust your jetting to that specific fuel. The only alcohol that will run right and have higher octane is butanol. It is harder to find and it is a carcinogen. More oil.fuel ratio will result into a leaner air/fuel mixture as the extra oil displaces fuel from the formula and oil doesn't really burn all that well. So you may have an oily plug confused as a rich plug on a motor that is about to seize-up from being too lean. That pump premium gas that you pay dearly for, they may have brand name formulations for it Race/Ultimate etc., I believe is just diluted gas/petrol with alcohols and maybe some synthetic nasty stuff. If straight regular gas doesn't goes preignition and overheating there is no need to pay for anything else. Manufacturers make money and have their owners/service manuals printed free by Fuel/Oil industry to add their crap into it. If you see some fuel/oil brand name on the owners' manuals just ignore all the crap that relates to them Edited February 23, 2014 by beta zero gara Quote Link to comment Share on other sites More sharing options...
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