shambles1980 Posted October 15, 2012 Share Posted October 15, 2012 ok its me again.. just want to know if there are issues with opening out the exhaust port on the old rxs 100.. i see it seems to be narrow. I assume this is good for idle but sux for power. I also assume this is something lots of people here will have done. i plan on opening it out some so its closer to the round shape it should be. i dint want to touch the inside of the cylinder though. so is there a max size to use for best all round preformance, or just open it to the max ? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted October 15, 2012 Moderator Share Posted October 15, 2012 I always though the RXS had quite some respectable power for a tiddler Link to comment Share on other sites More sharing options...
shambles1980 Posted October 15, 2012 Author Share Posted October 15, 2012 its just when you look down the exhaust port "if you take the exhaust off" you can see outlet isnt round it has a flat bit on there. I assume this helps with the compression for starting it and then the idle. but it must restrict the exhaust gasses escaping so restricting it.. "atleast thats my understanding." here i found a picture on google.. im thinking if i could take that lip off of there and round it out it would help? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted October 15, 2012 Moderator Share Posted October 15, 2012 is it in the casting...or is that just carbon build up? Link to comment Share on other sites More sharing options...
boon Posted October 15, 2012 Share Posted October 15, 2012 a good decoke would do a world of good, if the exhaust port looks like that, then the exhaust pipe is needing decoke too. Link to comment Share on other sites More sharing options...
shambles1980 Posted October 15, 2012 Author Share Posted October 15, 2012 yeah i see how that could look like crudd.. any way here is a totaly diferent persons totaly diferent picture again found on google.. you can see what i mean though yes? i intend of taking a rasp to that to make it round then polish it a bit but i dont thinnk polishing would be needed, just make sure i clean it up good with wd40 so there is no burr left in there... and i intend on leaving the actual exhaust port on the bore as it were alone, just this stupid looking lip thing that just seems to be a stupid idea to me.... but i dont want to make it totaly round as a 1st step incase that lip helps with idle and starting. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted October 15, 2012 Moderator Share Posted October 15, 2012 lol cant even see it in that pic Link to comment Share on other sites More sharing options...
dt502001 Posted October 15, 2012 Share Posted October 15, 2012 It's more than likely it for exhaust scavenging removing it wil likely make the bike slower and less mid range power. Link to comment Share on other sites More sharing options...
shambles1980 Posted October 15, 2012 Author Share Posted October 15, 2012 i dont have any tools i could use to brighten the pic.. but i can see it on my monitor.. its at the top of the exhaust, maybe you could adjust your brigntness for a bit just so you see it.. It's more than likely it for exhaust scavenging removing it wil likely make the bike slower and less mid range power. i had thought it may be some sort of ventruli effect to help the exhaust gasses travel faster. but i dont see how that would work as it could not increase the volume of gasses escaping. But i supose if gasses at that point traveld faster it could help draw more out of the cylinder. Link to comment Share on other sites More sharing options...
boon Posted October 15, 2012 Share Posted October 15, 2012 mmm not crud? two strokes are tricky blighters , changing the ins and outs is a delicate balance, exhaust back pressures and stuff. Those clever Japanese spent thousands of man hours and yen developing that engine, if you don't know what you are doing , it might run worse. i'm not a motorcycle engineer but i'd give it a try, always remembering that it is easy to cut something out, but not as easy to put it back, If it runs better, BONUS, if not ....do you know any alloy welders that can put it back lol Link to comment Share on other sites More sharing options...
boon Posted October 15, 2012 Share Posted October 15, 2012 Or there is always..... http://www.stanstephens.com/ Link to comment Share on other sites More sharing options...
shambles1980 Posted October 15, 2012 Author Share Posted October 15, 2012 well thats the thing lol.. I was hoping some one would have tried it already and had the answers.. i know this litle engine has more to give. its less than 12 bhp, and surley it must be capable of atleast 14 or so.. i was wondering if this lip thing there was restricting it as i remeber they used to restrict bikes via the exhaust. But i know this bike has really low compression, so it could actualy be there so i can start the thing without having to bump start it. and thats why i asked if any one knew if it would help and if it will how much should i open it by.. if no one knows il just leave it untill i find my self in possession of a spare cylinder for it Link to comment Share on other sites More sharing options...
dt502001 Posted October 15, 2012 Share Posted October 15, 2012 HAHA well some new info If you have to bump start it then it's time for a top end rebuild,new piston/rings and wirst pin and bearring, bore over. Whats the compression readings bet it's under 40.psi Link to comment Share on other sites More sharing options...
Moderator Airhead Posted October 15, 2012 Moderator Share Posted October 15, 2012 yep..check the compression or at least the bore/ piston clearance and ring end gaps Link to comment Share on other sites More sharing options...
boon Posted October 15, 2012 Share Posted October 15, 2012 i think he meant the web was there to give a bit of back pressure to aid starting with the kickstart. Designed in. Not that he was having to bumpstart it. Although while its apart it doesn't hurt to do the rings and wee end Link to comment Share on other sites More sharing options...
shambles1980 Posted October 15, 2012 Author Share Posted October 15, 2012 yep.. I was assuming that the lip was there to help pressure for the starting and idle of the bike.. but i was speculating that it could simply be there as a form of restriction.. I was hoping some one would know one way or the other, and i did not want to just remove the lip if it makes it difficult to start. and if it can help with performance was there a specific amount to be removed before it caused issues. or could i just remove the whole thing? il just leave it for now unless some one chimes in that has already done it and knows either way. but it seems to me any one who looked down that port must have thought "hmm that lip looks like a stupid idea to me, i wonder if it would run better without it" I guess im the only one lol. p.s the comment about "this engine has really low compression" was about the rxs engine in general. not a speciic issue with mine lol. Link to comment Share on other sites More sharing options...
dt502001 Posted October 15, 2012 Share Posted October 15, 2012 Even if you knew the port height speck's that just say "the factory race team" used.. without a flow bench to test your mods you would never know if it made it worse or better. You can make one out of air tight wood box and a vaccuum and some sort of vac gauge /air flow meter if you like. But then you would have to test it in conjunction with your exhaust and carb set up and then it still could flow less. Link to comment Share on other sites More sharing options...
shambles1980 Posted October 15, 2012 Author Share Posted October 15, 2012 yeah think il just leave i for a while.. Link to comment Share on other sites More sharing options...
boon Posted October 15, 2012 Share Posted October 15, 2012 Opened a whole can of worms there Link to comment Share on other sites More sharing options...
shambles1980 Posted October 15, 2012 Author Share Posted October 15, 2012 yeah lol.. i though it would be a reply like "just take it down all the way it helps a lot really you get better rpm through all the gears" or "i tried that once. it was a bad idea bike really struggled to start. the bike would stall when idle, and i lost power through all the gears" im actually shocked no one has done it in the past and have an answer. Link to comment Share on other sites More sharing options...
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