billyt Posted July 10, 2012 Report Share Posted July 10, 2012 Cope. Scottish pork is made out of beef and our other national drink is made out of girders (I know that went right over your head) Quote Link to comment Share on other sites More sharing options...
ham2 Posted July 10, 2012 Report Share Posted July 10, 2012 Cue Scottish / American humour /interface video:- 2 Quote Link to comment Share on other sites More sharing options...
dadof2 Posted July 10, 2012 Report Share Posted July 10, 2012 There will never be a definitive answer to this until manufacturers and oil companies publish wear rates and actual lubricating properties. There are too many miths about also. I recently striped a 17 year old gasser engine that had been run at 30 : 1 on Putoilne MX5 and latterly a semi synthetic. No wear and virtually no coke. Also a 348 Mont run at 25:1 on various mineral oils and semi synthetics. Virtually no wear and little coke. I have stripped much newer engines (2007 on) run at 60 :1 to 80:1 on modern synthetics and found they have significant wear and coke build up I belive the folowing to be true: 1) More oil = more power 2) More oil = Less wear. There seems to be a significant increase in wear rates as ratio moves from 32:1 to 40:1 and leaner. 3) More oil = Better piston sealing and lower piston crown temperature = less coke and less detonation 4) The fuel oil ratio is not the main factor in exhaust clogging. Against higher oil ratios, is the cost of oil. When you consider the cost of a piston & replate, possible mains and conrod + gaskets + labour my feeling is more oil is a wise insurance policy. Quote Link to comment Share on other sites More sharing options...
pindie Posted July 10, 2012 Report Share Posted July 10, 2012 Better use A747 more then! If you do take the time to get your jetting right for where you ride most. i.e at sea level, at higher altitude or somewhere in the middle. A friend who used to race at the IOM TT on a TZ 350 always says they used to have real nightmares getting jetting right for the long fasts bits low down and then making it also still work over the mountain. The IOM is not that big so height is pretty crucial to jetting and sweet running. Quote Link to comment Share on other sites More sharing options...
pindie Posted July 10, 2012 Report Share Posted July 10, 2012 (edited) I found this interesting in one of the replies: About 100:1 Premix Oils - Since the 70’s there have been repeated advertising claims made by various oil brands claiming that their oils can offer suitable lubrication for competition two-stokes on a 100:1 or 80:1 premix. In many cases, these claims are “supported” by testimonials from various users. Despite the oil makers claims, and the sincerity of the testimonials … it’s not so. Running a 100:1 premix would be much like running only 2 quarts of oil in your truck, expecting that the quality of the oil can make up for the quantity …. It cannot….. no matter how good the film strength is “claimed” to be. The truth is, many two-stroke engines can “operate” on a 100:1 pre-mix so long as rpms are kept very low (as might be the case on a novice class open bike). But the first time that 100:1 engine makes an extended higher rpm run … it will lose the mathematics of oil migration, and score a piston. There is just no way around the math. This must explain why it is fine to use next to no oil for a trials bike as we don't rev them really? When we do though are we scuffing up pistons etc? I am sure the bike makers know their onions so if they say 80:1 then they must be about right as a conservative measure ratio. If you want to go leaner feel free. Just don't moan your piston or crank is made of cheese. If you want to use 30:1 then feel free also - just don't take offence when those behind frown at you or you wonder why the bike has lost it's zing. Me personaly? I'm sticking at 60:1 as I do different types of riding slow-medium speeds not just sections. Edited July 10, 2012 by pindie Quote Link to comment Share on other sites More sharing options...
0007 Posted July 10, 2012 Report Share Posted July 10, 2012 (edited) There will never be a definitive answer to this until manufacturers and oil companies publish wear rates and actual lubricating properties. There are too many miths about also. I recently striped a 17 year old gasser engine that had been run at 30 : 1 on Putoilne MX5 and latterly a semi synthetic. No wear and virtually no coke. Also a 348 Mont run at 25:1 on various mineral oils and semi synthetics. Virtually no wear and little coke. I have stripped much newer engines (2007 on) run at 60 :1 to 80:1 on modern synthetics and found they have significant wear and coke build up I belive the folowing to be true: 1) More oil = more power 2) More oil = Less wear. There seems to be a significant increase in wear rates as ratio moves from 32:1 to 40:1 and leaner. 3) More oil = Better piston sealing and lower piston crown temperature = less coke and less detonation 4) The fuel oil ratio is not the main factor in exhaust clogging. Against higher oil ratios, is the cost of oil. When you consider the cost of a piston & replate, possible mains and conrod + gaskets + labour my feeling is more oil is a wise insurance policy. I agree that there will never be a definitive answer and the answer wont come from manufacturers, I spoke of variables and one that I never mentioned is the rider Let's say that a manufacturer releases data on eangine wear characteristics, how heavy is the rider?, a 140lb rider would put drastically less load on an engine than a 240lb rider And how about a 140lb rider who rides sections as opposed to a 240lb rider who does a great deal of hill climbing or vice versa Engine testing can only be done on a dyno under controlled conditions with hand built engines at near perfect tollerance, humans cannot do this stuff unless it's the same human in identical conditions who never gets tired or a gets a cold and takes it easy one day, rides in the same terrain at the same temperature altitude and humidity levels etc etc, now imagine this guy putting a couple hundred hours on each brand of oil at each ratio with a fresh spec engine hand built by an engineer each time..........this is the reason I can't take one persons comments about "I used Yada yada oil at Yada Yada ratio for 5 years and have no engine wear" I'm sure there was guys in the 60's using 10w40 motor oil and having these same discussions With regard to carbon build up on a piston crown, the only real way to check jetting is NOT with plug color, it is by the carbon ring on the piston crown, 2 strokes make their most power when they have the right combustion temperature, the fuel SHOULD burn onto the crown to within 1cm of the edge of the piston If you can see clean aluminum it has nothing to do with oil, it's simply that you are jetted too rich Additional note, the shock wave from detonation or pre ignition will tend to remove the carbon on the piston crown Edited July 10, 2012 by 0007 Quote Link to comment Share on other sites More sharing options...
billyt Posted July 10, 2012 Report Share Posted July 10, 2012 (edited) AND to add to what 0007 said one of the biggest variables is the the gas it self. Even within one type of gas it various from batch to batch and geographic location to location oxygenated etc, elevation, temperatures, humidity etc. How long it sat in your bike or its container, in the sun in the shade, in a plastic gas can a metal gas can, pre-mixed, straight gas etc. This is an international Trial site therefore grades of gas with RON or octane numbers will also vary from country and continent. All gas oil ratios quoted on this site or any other bike site are purely subjective, hearsay, tribal knowledge, relative to one's own experience or those handed down from others. Air filter oil and the maintenance of the air filter all play a factor in this equation also. As far as I am concerned any talk of oil ratios are at best academic and riders opinions are like hairstyles ever body has one and they think theirs is the best (that is why I am bald). However there are a basic range ratios that one must fall within, stay in these ranges and fine tune from there. After thirty odd years of riding trials I have never heard a rider say he lost a trial due mixing his fuel at 80:1 instead of 100:1 Lets get pragmatic here. Edited July 10, 2012 by billyt Quote Link to comment Share on other sites More sharing options...
pindie Posted July 10, 2012 Report Share Posted July 10, 2012 Good point Billyt on the age of fuel. I always use fresh Tesco 99 or Shell Vpower each ride. I suck the old stuff out and put it in the mower in summer and the car in the winter. Would this makes burning A747 easier? I don't know but I don't sem to get issues. I like the smell of A747 through my 2.5 turbo Subaru Forester XT though! Quote Link to comment Share on other sites More sharing options...
pete_scorpa3 Posted July 11, 2012 Report Share Posted July 11, 2012 Better use A747 more then! If you do take the time to get your jetting right for where you ride most. i.e at sea level, at higher altitude or somewhere in the middle. A friend who used to race at the IOM TT on a TZ 350 always says they used to have real nightmares getting jetting right for the long fasts bits low down and then making it also still work over the mountain. The IOM is not that big so height is pretty crucial to jetting and sweet running. Yes. Raced a TZ250 at the TT back in the 90's (main bikes were all four strokes) and we gave up trying to use it in early morning practice. Cold damp early mornings (dew) made it very difficult to jet for the fast run to Ramsey which is sea level. It was easier test it in the afternoons when it was generally warmer and drier. Sea level to 3000ft each lap! Quote Link to comment Share on other sites More sharing options...
ham2 Posted July 11, 2012 Report Share Posted July 11, 2012 ............... 3) More oil = Better piston sealing and lower piston crown temperature = less coke and less detonation 4) The fuel oil ratio is not the main factor in exhaust clogging. .................... I once stripped a 10 year old Montesa 242 and it had zero wear'n'tear on the internals yet I stripped a 280 gasser that was only a year old and it was 5hagged....it had done the Scott ,IOM , SSDT and a couple of French 2/3 days though. Also, can you further expand on these two points: More oil= less coke? and What is the main factor for exhaust clogging? Cheers, Wayne Quote Link to comment Share on other sites More sharing options...
billyt Posted July 11, 2012 Report Share Posted July 11, 2012 Less oil = More Pepsi The main factor for exhaust clogging is a person starting their bike. Sorry, but is early in the morning! Quote Link to comment Share on other sites More sharing options...
dadof2 Posted July 11, 2012 Report Share Posted July 11, 2012 Ham 2 - in answer to your questions More oil = less coke. This is just based on experience of what I see on piston crowns and combustion chamber. More oil conducts more heat put of the piston meaning the temperature is less than that needed to char the oil, the oil therefore remains "fluid" to some extent and its detergents remain active. These lower piston temperatures seem to result in lower head temperatures also. You find that in a bike run at say 32:1 you can usually wash away the deposits with thinners. In an engine run at 60:1 the depostits tend to be burnt on and have to be scraped of. More oil gives better piston ring seaking and greatly reduces blow by to the crank case. You will find much less carbon in the crank case of a bike run at 25:1 than you will in one run at 60:1. Most of the deposits do not come from the oil (which is only a small % of fuel) they come from incomplete combustion of the petrol. It may just be that putting lenty of good quality oil in means there is plenty of detergents to flush away potential deposit forming combustion by products. I do not know what the main factor is in exhaust clogging - I suspect it is oil type, oil quality, running temperature and exhaust design. I know of people who run rich oil mixes like myself and have no clogging, I know of people who run rich mixes and lean mixes who have exhaust clogging. Petrol could be a factor. The following relate to 4 stroke car engines. One had been run on Texaco for years and had significant inlet tract deposits, within a week of switching to Shell (not V power but the standard clean burn stuff) a lot of the deposits in line with the injector spray had been stripped off and the car had an inlet gasket manifold leak (previously sealed by Texaco deposits) A Ford Fiesta lost power a few weeks after switching from Texaco to Shell. Serious loss of compression due to carbon chunks preventing the exhaust valves closing properly. Wnen the head was removed the reason was clear, years of deposits built up using Texaco were being stripped off by the shell, it was like pieces of black fungus coming off. All cleaned out and the car ran perfectly. Cheers Quote Link to comment Share on other sites More sharing options...
ham2 Posted July 11, 2012 Report Share Posted July 11, 2012 Ta ! Quote Link to comment Share on other sites More sharing options...
copemech Posted July 12, 2012 Author Report Share Posted July 12, 2012 I once stripped a 10 year old Montesa 242 and it had zero wear'n'tear on the internals yet I stripped a 280 gasser that was only a year old and it was 5hagged....it had done the Scott ,IOM , SSDT and a couple of French 2/3 days though. Also, can you further expand on these two points: More oil= less coke? and What is the main factor for exhaust clogging? Cheers, Wayne It has to go somewhere, and that is where it winds up, no matter the ratio. There are indeed a lot of theories and wifestales out there, however I did like one thing I found that would apply here: The engine is probably over oiled at low rpm Probably sufficiently oiled at mid rpm And likely under oiled at high rpm These ranges referring to more constant running periods, not just brief blips of the throttle. And as follow suit, one cannot defeat the math of oil migration times so must adjust mix accordingly depending upon what one is doing. The paradox here is trying to find the way to get it moving out of the exhaust, and that still requires heat and velocity to blow ot out of light it off, and without doing such hard runs to deprive the motor in the process of ridding the exhaust! There was a post today about someone taking the bike down the road and back in high gears at moderate speeds and lighting off the muff smoking badly. Well, it was a bit overdue it seems, but at least he managed to get things burning and flowing, and this does not occur in the combustion chamber. Just how much he has been using will effect the accumulation rate, but will not prevent it. Punters, Punters, lend me your ear! 80:1 is fine for trials,, some go to 100:1 but you still need to get some heat into things upon occasion, just do not shag it to death! Quote Link to comment Share on other sites More sharing options...
0007 Posted July 12, 2012 Report Share Posted July 12, 2012 I mentioned it before but may have been missed If you don't have carbon forming on your piston crown you are too rich, it's simple If you want to make power and run clean, you need correct or at least reasonable combustion temperature This will put carbon on the crown It's not an oil thing But this might not be easy to do on a trial bike, it's probably an engine that needs to be jetted by feel rather than this way Snowmobiles are the ideal example of 2 stroke jetting simply because of their CVT transmission Quote Link to comment Share on other sites More sharing options...
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