liviob Posted December 30, 2011 Report Share Posted December 30, 2011 (edited) I cannot find in my 2009 evo 290 owners manual what the minimum and maximum play is between the the piston skirt and the cylinder wall. Anyone know in inches. For example .002-.004 Thanks Livio Edited December 30, 2011 by Liviob Quote Link to comment Share on other sites More sharing options...
joekarter Posted December 31, 2011 Report Share Posted December 31, 2011 Check your e-mail Quote Link to comment Share on other sites More sharing options...
dan williams Posted December 31, 2011 Report Share Posted December 31, 2011 Oooo must be secret! Quote Link to comment Share on other sites More sharing options...
joekarter Posted December 31, 2011 Report Share Posted December 31, 2011 Oooo must be secret! Naw. just the location of the elusive, often rumored to be in existence, Beta service manual. (it's hidden with the chalice) Quote Link to comment Share on other sites More sharing options...
copemech Posted January 1, 2012 Report Share Posted January 1, 2012 Ok, I will guess here! Optimum sizing at .001-.0015 Doubt the give you a table of limits, yet in practicle terms, one could double that. If it's rattling, next size up and a decent light hone may fix it if the bore is ok, second option is a 2 size up and a professional fiting hone, Honing can be critical and it really takes a professional setup to do it correctly, be your own judge on this! Quote Link to comment Share on other sites More sharing options...
liviob Posted January 6, 2012 Author Report Share Posted January 6, 2012 I spoke with one of the guys over at American Beta. He said the minimum piston to cylinder space is .002 and the max is .004. Mine is .003 after approxmatly 320 hours. Quote Link to comment Share on other sites More sharing options...
peterh Posted January 7, 2012 Report Share Posted January 7, 2012 Workshop Manual from American Beta is here http://www.americanbeta.com/sites/default/files/pdf/2012Support/Service%20Manuals/Mototrial/2009-2012%20Evo%202%20stroke%20Engine.pdf Page 45 has the details. Quote Link to comment Share on other sites More sharing options...
copemech Posted January 8, 2012 Report Share Posted January 8, 2012 Well, if one is able to interpolate all that mexican dribble, what I got was replace piston if over .00236 loose! Good luck, but getting back to my original guesswork, I cannot see running a piston in a water cooled motor at .003 or more if you have it apart, as the whole idea behind service limits is the fact that when you put it back together you kinda want it to last for a while, and not be at or above limits upon reassembly! Kinda defeats the purpose if you know what I mean, unless youm are selling used cars on ebay! Quote Link to comment Share on other sites More sharing options...
liviob Posted January 9, 2012 Author Report Share Posted January 9, 2012 (edited) It did take two and a half years to wear .001 of the factory new piston and the motor is still quiet. No piston rattle. So why change a perfectly good piston? I spoke with the parts guy. He said that the company who replates the used cylinders for them said min clearance .002 and the max is .004. He also measured a refurbished matched set new piston and replated cylinder and said that the biggest feeler gauge he could fit in between the two was .002. He also said that Beta recomends no more than .006 as max clearance in the manual. My Scorpa SY250 had a piston about the same size as the Beta 290 and they have a very easy to use owners manual which recmended min .002 and the max is .004. With ring end gap set at min .012 and max at .014. My new evo 290 rings had .012 end gap and the worn rings had .015 end gap. I rode the bike yesterday and new rings and the .3mm base gasket seemed to bump the bottom power easily 20%. Edited January 9, 2012 by Liviob Quote Link to comment Share on other sites More sharing options...
copemech Posted January 9, 2012 Report Share Posted January 9, 2012 It did take two and a half years to wear .001 of the factory new piston and the motor is still quiet. No piston rattle. So why change a perfectly good piston? I spoke with the parts guy. He said that the company who replates the used cylinders for them said min clearance .002 and the max is .004. He also measured a refurbished matched set new piston and replated cylinder and said that the biggest feeler gauge he could fit in between the two was .002. He also said that Beta recomends no more than .006 as max clearance in the manual. My Scorpa SY250 had a piston about the same size as the Beta 290 and they have a very easy to use owners manual which recmended min .002 and the max is .004. With ring end gap set at min .012 and max at .014. My new evo 290 rings had .012 end gap and the worn rings had .015 end gap. I rode the bike yesterday and new rings and the .3mm base gasket seemed to bump the bottom power easily 20%. Well that is good! Bottom line here, if it don't rattle much? RUN IT! They always say fresh rings make a difference in themselves. Seems you are still in there at .003, wear it out! One good thing about trials bikes is we do not generally have to worry about piston breakage due to fatigue. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.