0007 Posted December 26, 2014 Report Share Posted December 26, 2014 I don't think liquids increase in density with pressure, then it would decrease in volume as you compress it Hasn't happened on earth yet, it would be like saying fuel volume decreases with cornering or acceleration forces, so what happens when I jump? Fuel volume increases because there is no gravity? Wouldn't humans explode in 0g then?, go drop your jerry can and see if it expands with 0g and suck flat when it hits the ground Is water at the bottom of the ocean thicker? Liquid density does not change as the g force on the float increases, in this case it momentary anyway More like dropping a boat onto water rather than pushing it down A centrifuge is not going to show what happens in a split second shock load so that is junk science And I disagree with "if it ain't broke don't fix it" quite frankly I'm glad all manufacturers DONT do this or we would be stuck in the cave man era Typewriter manufacturers did this, music industry resisted MP3, how about Video tape or audio cassettes Bring on developement 1 Quote Link to comment Share on other sites More sharing options...
steve_earle Posted December 26, 2014 Report Share Posted December 26, 2014 ND I do not mind anyone disagreeing with me or having a different point of view but at times you make statements that are just not true such as saying I do not own a Gasgas or accuse me of not knowing anything about them when you have no means of knowing whether I do or not. The FACT is I own 2 GGs and have worked on or helped diagnose problems on several more recently. If someone does have a different point of view I ask that they put forward a reasoned argument, not just say I am wrong. I and anyone else is fully entitled to post what they like on this forum no matter how tenuous its link to the topic. It is up to the site owner and moderators to manage the site as they wish, not have unofficial self appointed "moderators" say what should or should not be posted. Am I really on nights? In Dabsters defence here, I don't want to get involved in the row but I can see why he thought you didn't own a gas gas. Below is a couple of copy and pastes from posts in the reliability thread, I too were under the impression you wouldn't touch one with a bargepole. "Both myself and a friend had JTXs for a number of years and they were 100% reliable. But since the pro there reputation for reliability has become seriously tarnished. Seeing what happened to friends who bought Pros meant we never did." "Until they sort the frame cracking problems (not all that frequent), fuel tap problems (not all that frequent) kickstart (fairly frequent) and substantially strengthen the crankcases and gearboxes I will not be buying one nor advising anyone else to. That is also the view of several ex Pro owners." Honestly I'm not stirring here, It may be that Dadoff 2 ownes Ec Enduro or older txt's so I'm not trying to imply anything, Maybee just curious that there must be an explanation for the contradictions. In regard to FI on a 2 stroke, Good luck to manufacturers and I hope they all get it right in the end. I have ridden an Ossa that was mapped by Cams and it was the best fuelling bike I've ever ridden, Every other bike at the test day running carbs (dellorto and keihin) were not very good out of the box fueling. The Sherco was the closest to being right. Quote Link to comment Share on other sites More sharing options...
copemech Posted December 27, 2014 Report Share Posted December 27, 2014 Maybe closed loop is a bit OTT for a trials bike,but you are wrong about it doing nothing for performance.It need have nothing to do with maintaining Stoich either,wideband sensors could be a great help with valve problems mentioned earlier.Being able to accurately hold mixture at 12.5/1, air / fuel for max power without the risk of lean mixtures along with a knock sensor could make the motor last a lot longer. That is of course correct, however we are talking much more complex systems. Still not sure wideband would work on 2T with the oil considerations, seems even soot can foul them in diesel applications. Quote Link to comment Share on other sites More sharing options...
copemech Posted December 27, 2014 Report Share Posted December 27, 2014 I don't think liquids increase in density with pressure, then it would decrease in volume as you compress it Hasn't happened on earth yet, it would be like saying fuel volume decreases with cornering or acceleration forces, so what happens when I jump? Fuel volume increases because there is no gravity? Wouldn't humans explode in 0g then?, go drop your jerry can and see if it expands with 0g and suck flat when it hits the ground Is water at the bottom of the ocean thicker? Liquid density does not change as the g force on the float increases, in this case it momentary anyway More like dropping a boat onto water rather than pushing it down A centrifuge is not going to show what happens in a split second shock load so that is junk science And I disagree with "if it ain't broke don't fix it" quite frankly I'm glad all manufacturers DONT do this or we would be stuck in the cave man era Typewriter manufacturers did this, music industry resisted MP3, how about Video tape or audio cassettes Bring on developement Seems to me there would be a lot of sloshing going on in the float bowl over jumps, and this can not be all good for the stability of the fuel level. MX bikes must deal with as well, however on an off road bike tell me when the fuel is not sloshing? Seems the new Vertigo uses some complex mapping stratigy, and apparently a battery to stabilize the electrics! Quote Link to comment Share on other sites More sharing options...
copemech Posted December 27, 2014 Report Share Posted December 27, 2014 Regarding the floats, Copemech has confirmed my thoughts. This is the way I pictured it, suppose you ride the bike off a 1 m high boulder, initially it accelerated downwards at 1 g and floats and fuel are effectively weightless, then for last 160mm it decelerates at about 6g, Therefore floats and fuel effectively weigh about 6 times as much as normal. Normally the floats have a (a bit loose on the exact physics / terminology here) density about 1/3 that of fuel. Take fuel as 7 gms / cm3 and float as 2 gms / cm3, multiply this by 6g and the fuel is now 42 gms / cm3 and the floats 12 gms / cm3. The ratio of float density to fuel density remains the same so it could be expected that the fuel level / float displacement remains constant during the drop off and land manoeuvre. Be interesting to see exactly what happens if anyone had a centrifuge, a clear float bowl, floats and a high speed camera. On the subject of 4RT cut out at low RPM. Does anyone know at what revs this happens and for sure if this is due to lack of electrical power to ignition or EFI. I wondered if valve overlap could be a factor. When valve overlap is sufficient to give a wide spread of and decent top end power it often results in rough idle or cutting out at low RPM. I could be wrong but best I recall the 4rt is speced to idle at 1500 rpm. Some may set them down a tad. Seems keeping the caps charged up is the key, and they will chug along briefly, however the caps are quickly depleted then things stop! Quote Link to comment Share on other sites More sharing options...
billyt Posted December 27, 2014 Report Share Posted December 27, 2014 Cope You know fine well who wrote the article on the carbs/floats. You are just picking a fight. I will not get drawn into a discussion around floats moving up/ down once a bike has landed abruptly of a jump/rock. I have all the proof I need given to me by my mikuni factory training and through simple science. Bikes are not always parallel to the ground once they land and the fuel can and will slosh either forward or backwards in the float bowl causing a void and thus the floats will move down accordingly. If floats have no weight then why use a float? The fuel level goes down the floats go down. The fuel goes up the floats go, density yes but also due to their weight. If the bike landed perfectly square then the gas would not really go anywhere but just slightly compress thus no movement of the floats. BUT this is not reality, the bike usually lands front wheel first or back wheel first throwing the gas to one side or the other of the float bowl and the floats re-acting accordingly. This is the very reason there are two sets of adjustments on the brass tangs. One to control the travel up and one to control the travel down trying to isolate them somewhat from the movement of the fuel. I wrote a post a while back asking you to be honest with the members on this forum in the fact that you don't actually ride trials and have not been at an event or out practicing for around ten or so years yet you speak like you know all the latest about the bikes. I doubt you have actually seen a trials bike newer than 2003. I still keep in contact with many riders in the NTTA and they have not seen you riding ANYWHERE....... All one needs to do is to log onto the NTTA (North Texas Trials Association) web site and check the results going back for many years. See if Marks name shows up even once! You are Bench or magazine trials rider............ period. Bring it on. Or bury the hatchet. Quote Link to comment Share on other sites More sharing options...
copemech Posted December 27, 2014 Report Share Posted December 27, 2014 Cope You know fine well who wrote the article on the carbs/floats. You are just picking a fight. I will not get drawn into a discussion around floats moving up/ down once a bike has landed abruptly of a jump/rock. I have all the proof I need given to me by my mikuni factory training and through simple science. Bikes are not always parallel to the ground once they land and the fuel can and will slosh either forward or backwards in the float bowl causing a void and thus the floats will move down accordingly. If floats have no weight then why use a float? The fuel level goes down the floats go down. The fuel goes up the floats go, density yes but also due to their weight. If the bike landed perfectly square then the gas would not really go anywhere but just slightly compress thus no movement of the floats. BUT this is not reality, the bike usually lands front wheel first or back wheel first throwing the gas to one side or the other of the float bowl and the floats re-acting accordingly. This is the very reason there are two sets of adjustments on the brass tangs. One to control the travel up and one to control the travel down trying to isolate them somewhat from the movement of the fuel. I wrote a post a while back asking you to be honest with the members on this forum in the fact that you don't actually ride trials and have not been at an event or out practicing for around ten or so years yet you speak like you know all the latest about the bikes. I doubt you have actually seen a trials bike newer than 2003. I still keep in contact with many riders in the NTTA and they have not seen you riding ANYWHERE....... All one needs to do is to log onto the NTTA (North Texas Trials Association) web site and check the results going back for many years. See if Marks name shows up even once! You are Bench or magazine trials rider............ period. Bring it on. Or bury the hatchet. Happy Chrimbo Billy! I just got ck to see if you are OK! Love you man! Quote Link to comment Share on other sites More sharing options...
copemech Posted December 27, 2014 Report Share Posted December 27, 2014 I have mine at 1800 but I don't see any problem with it No, and I am referring to what may be considered unusual testing, chugging along in high gear, and I do not recco you try it because it can hurt you! Quote Link to comment Share on other sites More sharing options...
0007 Posted December 27, 2014 Report Share Posted December 27, 2014 I have only a couple of issues with Post #69 The compression of liquids, same as the problem with Dad's post, does not happen, that's simple science The only time this changes is in vacuum where the liquids can vapourize The limiter tang has little to do with this, the needle is open or closed, simple as that, like a thermostat, on or off The part about knowledge having something to do do with wether a guy rides or not, the designers and engineers of the space shuttle have never been to space, the designers of F1 cars and MotoGP bike don't race them, many of my mentors were not particularly great riders and many exceptional riders are absolutely useless with mechanical things I do agree somewhat about floats being somewhat erratic due to fuel slosh, most floats are round so that they react similarly to different angles and the float bowl is designed to have the same quantity of fuel in it up to a reasonable angle, but aeration due to impact is impossible to account for 1 Quote Link to comment Share on other sites More sharing options...
baldilocks Posted December 27, 2014 Report Share Posted December 27, 2014 This thread isnt providing much in terms of objective analysis of advantages / disadvantages. My gas gas like many newer bikes has a keihin PWK 28 carb. It does have very smooth power but it leaks a lot of petrol when dropped despite floats being set correctly. In addition the carb is more susceptible to weather / altitude than say a dellorto. When i went to Valtellina 3 day in the alps we were riding between 1500 and 3000m above sea level. I was re setting the mixture screw all the time. So does the fi system on either the mont or the ossa adjust for weather and altitude? Given nobody in this thread has reported an fi system failure it would be a significant advantage to me if fi was self adjusting next time i go to Valtellina Quote Link to comment Share on other sites More sharing options...
the addict Posted December 27, 2014 Report Share Posted December 27, 2014 One of the many things I love about the 4rt is it runs exactly the same every day I start it up no matter where or what time of the year. 1 Quote Link to comment Share on other sites More sharing options...
steve_earle Posted December 27, 2014 Report Share Posted December 27, 2014 A guy in our club had a fuel pump give up on his ossa, I can't remember exactly how much he said it cost but it was stupid expensive and was not covered under warranty even though the bike was around a year old. However It would not put me off buying an ossa as I think when mapped right it's a great bike now with most problems now refined. Quote Link to comment Share on other sites More sharing options...
copemech Posted December 27, 2014 Report Share Posted December 27, 2014 This thread isnt providing much in terms of objective analysis of advantages / disadvantages. My gas gas like many newer bikes has a keihin PWK 28 carb. It does have very smooth power but it leaks a lot of petrol when dropped despite floats being set correctly. In addition the carb is more susceptible to weather / altitude than say a dellorto. When i went to Valtellina 3 day in the alps we were riding between 1500 and 3000m above sea level. I was re setting the mixture screw all the time. So does the fi system on either the mont or the ossa adjust for weather and altitude? Given nobody in this thread has reported an fi system failure it would be a significant advantage to me if fi was self adjusting next time i go to Valtellina Yea, that is a strong point as they will compensate automatically! Quote Link to comment Share on other sites More sharing options...
baldilocks Posted December 27, 2014 Report Share Posted December 27, 2014 Whats the exclamation mark intended to communicate copemech ? Quote Link to comment Share on other sites More sharing options...
copemech Posted December 27, 2014 Report Share Posted December 27, 2014 (edited) Whats the exclamation mark intended to communicate copemech ? That I spelt it correctly! Actually it is somewhat exciting that they are self adjusting for variances in altitude, barometric pressure and I think temps, although not positive or to what extent. These basic inputs allow for modification of the base map profile and good running in even the most basic system. Now all that may not gain you a lot of more power at altitude, but is should at least insure consistent running! Below 1000 meters is should not be a great issue, but above that it can become one, along with the loss of power. Edited December 28, 2014 by copemech Quote Link to comment Share on other sites More sharing options...
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