jse Posted April 28, 2010 Report Share Posted April 28, 2010 Hi JonI was surprised to read about racing side valves as I had been lead to believe that they were more of an industrial engine. Whar are the limiting factors of S/V engines ? Ross Hi Ross, I've written technical articles for a Trials publication here in the U.S. for about 12 years now (as a volunteer, not paid, I just love technical stuff and like to share my experience) and a little while ago I wrote about the sidevalve engine: a link to it is here http://www.gasgas.com/docs/gg_4str_stood.pdf and that may answer some questions. If it does not pass the filtering process, PM me and I'll send you the link. Jon Quote Link to comment Share on other sites More sharing options...
b40rt Posted April 29, 2010 Report Share Posted April 29, 2010 Hi Ross,I've written technical articles for a Trials publication here in the U.S. for about 12 years now (as a volunteer, not paid, I just love technical stuff and like to share my experience) and a little while ago I wrote about the sidevalve engine: a link to it is here http://www.gasgas.com/docs/gg_4str_stood.pdf and that may answer some questions. If it does not pass the filtering process, PM me and I'll send you the link. Jon Thanks Jon Opens fine, have saved to "Favorites" as I am about to head off to Kinlochleven. Weather's looking fine at the moment, fingers crossed. Ross Quote Link to comment Share on other sites More sharing options...
jse Posted April 29, 2010 Report Share Posted April 29, 2010 Thanks JonOpens fine, have saved to "Favorites" as I am about to head off to Kinlochleven. Weather's looking fine at the moment, fingers crossed. Ross Ross, Well, I'm getting ready to pull out to head for the first U.S. National so my fingers are crossed, as to the weather, for both of us. Say hi to Big John for me. Cheers. Jon Quote Link to comment Share on other sites More sharing options...
b40rt Posted April 29, 2010 Report Share Posted April 29, 2010 Ross,Well, I'm getting ready to pull out to head for the first U.S. National so my fingers are crossed, as to the weather, for both of us. Say hi to Big John for me. Cheers. Jon Consider it done, and enjoy your weekend Ross Quote Link to comment Share on other sites More sharing options...
neo Posted April 30, 2010 Author Report Share Posted April 30, 2010 Any more input on this Gents? Best of balance. Neo Quote Link to comment Share on other sites More sharing options...
copemech Posted May 1, 2010 Report Share Posted May 1, 2010 Any more input on this Gents?Best of balance. Neo I will toss you a couple of things, 1- No replacement for displacement! 2- Side valve motors do not flow well at high rpm's! 3- A high performance 4T motor does it in the wrong rpm range for trials. Quote Link to comment Share on other sites More sharing options...
mikew Posted May 2, 2010 Report Share Posted May 2, 2010 I suspect though you're thinking about production 4 stroke machines versus competition 2 strokes?And presumably not in classes where the two are trying to compete on fairly equal grounds. I've seen cases of GP 250s doing pretty well in powerbike races at some tracks - if you had a capacity limited 4 stroke racing against the 250s, I suspect the 4 stroke would cost a lot more. You couldn't build a 250 four stroke that could keep up with a 250 GP bike. A 250 GP bike puts out close to 100 HP, or 400 HP per liter. I don't think you could build a naturally aspirated four stroke that would put out 400 HP per liter. If you did, it wouldn't last long. Quote Link to comment Share on other sites More sharing options...
tony27 Posted May 3, 2010 Report Share Posted May 3, 2010 You couldn't build a 250 four stroke that could keep up with a 250 GP bike. A 250 GP bike puts out close to 100 HP, or 400 HP per liter. I don't think you could build a naturally aspirated four stroke that would put out 400 HP per liter. If you did, it wouldn't last long. 125GP bikes have been putting out 50+HP for years, read a test on the first KTMs & it produced 55 HP/440 per litre. I'd hazard a guess that the last 250s were producing 110+HP, makes the 800s with their 230 or so seem pretty gutless & the 600 jokes even worse I read yesterday that the penalty for using up the engine allocation in motogp has been halved, wonder who's been crying because they can see themselves starting 20seconds behind everyone else from pitlane, Rossi or Pedrosa? Quote Link to comment Share on other sites More sharing options...
toofasttim Posted May 3, 2010 Report Share Posted May 3, 2010 I'm wiv' Tony on this one.. Remember reading a test of the Aprillia RS250 ten years ago or so where that bike (std) pushed out 70 at the back wheel. The factory 250s must have been comfortably in excess of 110. Quote Link to comment Share on other sites More sharing options...
_g_ Posted May 10, 2010 Report Share Posted May 10, 2010 If you did, it wouldn't last long. Indeed, thus the costs a lot more . I believe your typical club 250 was more around 85hp or so - with the ones making silly power right at the top level with the big teams with big budgets and mechanics that weren't also the rider and trying to keep a 9-5 job going the rest of the time . Oh and my RS250 came out at just over 53hp at the rear wheel on the dyno - with clean pipes and a simple airbox mod I could have easily had 58hp or so. Still the most fun road bike I've had so far (though I have high hopes for my 200EXC with supermoto wheels .) Quote Link to comment Share on other sites More sharing options...
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