ythan Posted June 18, 2008 Report Share Posted June 18, 2008 I own a sherco 125 a 03 model, it is standard at the moment. it ticks over quite well but seems to lack response a little from tickover . I run it on reserve all the time to prevent any issues the stand pipe may cause, i dont know what jets it has in it at the moment. I have read the exelent discription on jeting by wayne on the scerco manuals, but i would like a little more info if possible on how to set up the cerburation practicaly. What i mean is for improved torque and traction better tractibility etc, i have no idea what to look for and what type of tests to perform with a trials bike of any size let alone a small 125. It seems to me to be running quite well but it is a bit all or nothing when it has to pull hard. I realise i am requesting a very tall order here, but any hints on reading how a bike responds and advice on jetting etc would be good. Quote Link to comment Share on other sites More sharing options...
shercoman2k8 Posted June 18, 2008 Report Share Posted June 18, 2008 Dont run it on reserve. i think theres something about reserve it lets a smaller amount of fuel through to make it last as long as possible. Mine runs fine, then on reserve it has what i call a ride like #@$% feature, just to remind you to top up, try starting it in reserve, then give it a quick ride, turn to normal supply and try again, this should make a fair bit of difference. If thats not the problem! Are you warming the bike up properly? does it tickover fine? your airfilter clean and clear? anything in the carb? exhaust in good condition? Right oil/fuel ratio? regards, Jamie Quote Link to comment Share on other sites More sharing options...
ythan Posted June 18, 2008 Author Report Share Posted June 18, 2008 I striped the bike down top end carb and exhaust, burnt out the exhaust with oxy/acet it is clear, the carb was striped and cleaned and the top end generaly decoked cleaned the ring groves out piston crown head ex port good piston rings fitted, built back up. I have a good tickover i fidled with the two screws so as to get the strongest tickover, i am running it on super+unleaded and synthetic two stroke oil at 70 to 1 ratio, to 5 litres i add 70 ml. I have not touched the ignition yet it starts first or second kick every time and i warm it up well, then try and give it a bit of gear work it seems to splutter in the first two gears but by the trime its in third or fourth it clears the spluter away and revs clean, i can run it for a hour and it will still spluter untill i give it some gear work and clear it out, reving it up unloaded does not seem to clear it properly like when its pulling hard. I have explained how it is running as well as i can. i am quite sure it has no mechanical ills or contamination, but i want naturaly to get it tuned to the best performance i can, I have no idea how to read a two stroke engine for timing and fuel settings for torque and smothness of operation, any tests you cary out to decide where it is wrong would be great, I realise trial and error is the only way but any hints to give me a start would be much appreciated. Hope you all understand my above discription i have told it how it is as close as i can. Quote Link to comment Share on other sites More sharing options...
copemech Posted June 19, 2008 Report Share Posted June 19, 2008 Ythan, Having owned and ridden a 125 of that vintage for several years(wifes bike) I can tell you a few things. Number ONE: a 125 is fairly gutless right off the bottom! If you let the revs fall below a certain point it likely will not pull! Technique is different on a 125! You must apply throttle first, then regulate power with the clutch while keeping revs in range! A change to a 46-48t rear gear may help you keep your revs up and make second gear more user friendly. Just rev the crap out of it and go! The gasser guys do this as they have no torque off the bottom- none! I seem to recall the jetting at 32-33 on the pilot and around 118 on the main seemed to work, twith the needle in third groove down and about 2.5-3.0 turns out on the mix screw. Once warm, you still need to rev them out for a good clean run-up after plonking. Riding a 125 well requires more skill and better tecnique! Practice is the key! Seems the later Shercos have a bit more off the bottom, but that has never held back anyone! Your properly operating clutch is your best friend. And a shortie(standard )lever to start, then a medium or long to get a quicker pop when you need it as you have more room for finger feel! Hope that helps! Quote Link to comment Share on other sites More sharing options...
ythan Posted June 19, 2008 Author Report Share Posted June 19, 2008 That is helpfull i dont expect the earth from it but i want whats there runing right, i remember the main jet had 122 writen on it .... so it has different jet there at least to your wifes set up. I will strip the carb off and finfd the jet sizes and look from there. I may try moving the slide nedle a notch to see if it improves response, but from your post i am mabe near now torque wise. thanks Quote Link to comment Share on other sites More sharing options...
sirhc Posted June 19, 2008 Report Share Posted June 19, 2008 While my son's bike is an '08 I think this still applies. When I got his bike it was a little fat on the top end but other wise seemed to run good. I was then told by one of the other dads to put a 38 pilot in it. That seemed crazy to me since that's bigger than what a 2.9 uses. Well that bigger pilot really woke the bottom end up. It's no 250 or 200 but it made it much stronger off the bottom. The 125 just doesn't draw as much fuel so it needs a bigger pilot. We're using a 114 main, will probably go bigger when he gets older and more aggressive. A 48 rear sprocket also works well. Quote Link to comment Share on other sites More sharing options...
ythan Posted June 19, 2008 Author Report Share Posted June 19, 2008 The practical advice you guys are leaving here is helpfull, i am ignorant on jet sizes on the pilot jets and mains is the larger number a larger hole flow ? like my 125 has a 122 is that more or less fuel than the 118 main mentioned above? It sounds logical it is but i honestly have no idea. What jet sizes are available ? Quote Link to comment Share on other sites More sharing options...
copemech Posted June 20, 2008 Report Share Posted June 20, 2008 The practical advice you guys are leaving here is helpfull, i am ignorant on jet sizes on the pilot jets and mains is the larger number a larger hole flow ? like my 125 has a 122 is that more or less fuel than the 118 main mentioned above? It sounds logical it is but i honestly have no idea. What jet sizes are available ? Yes, the larger the number, the larger the flow! But there are lots more to it. As mine was tuned softly for the wife, you may indeed find a bit better power with say a 36 or 38 pilot jet, i have not tried ! Mind you, the current comments were for a different year bike and the porting is different so you may not achieve the same results. Some of this also varies from bike to bike, and carb to carb! All this is called TUNING! Done in small changes to check your results! And you will need to adjust your fuel screw setting with a change in the pilot jet! The main jet really takes effect at 3/4 throttle on up! Too big will be difficult to "clean out" but too small will limit power! If you never ride at wide open throttle, a tad rich is ok and can actually help prevent damage in the case of a spill and stuck throttle, as example, i seldom hit WOT on a 2.9. Yet on the 125, I can pin it to the max and apply second gear on a near(not) verticle 6-8 ft rollup wall, and the bike would go with standard gearing, barely! If I had a better gearing, it would scream up all the way! These are all tweaks for personal pref as well, and you are the judge! On a 125 there is only soo much, and you have to use it wisely! Quote Link to comment Share on other sites More sharing options...
ythan Posted June 21, 2008 Author Report Share Posted June 21, 2008 An update! I worked on the 125 Untill 11PM last night and all day today, i tried a great many things, including lifting the nedle a notch to richen it at the bottom range it ended up in the midle grove one up from where it was, it needed to be 3 1/4 turns out on the mixture screw to be near enough, but lifting it a notch got it 2 1/2 turns out with the 38 pilot i settled on, and with both the 33 pilot and the 38 pilot it ran the best throughout in the grove . The top end i never felt was in question but once i put the biger pilot in it improbed noticably at the bottom. I turned my attention to the timing next.. it was set at 2.7mm from TDC . i played and tested and ended up on 3.2MM, It was snapier at 3.8MM but it ran much smother at 3.2mm. I stuck to 70 to 1 synthetic in super+ unleaded, it ran around a recently bailed hay field for 20 mins in top gear flat out most of the time and it never flufed or showed any sighns of pre ignition or il running whatsoever. Its response when pulling was stronger and smother than before and it had more feel to. It responds far better at the bottom end than it did before, i am not sure if i want to play with it any more right now For 1. i am bored just now, and 2. i want to see how it goes in use give me time to adjust to it in its current set up. Thanks for the advice above everyone, The 38 pilot is a improvemet that worked well for me on this old bike. could be worth a try for others. Quote Link to comment Share on other sites More sharing options...
copemech Posted June 22, 2008 Report Share Posted June 22, 2008 Sounds like you had a bit of fun playing with it! How much movement was that on the plate with the timing change? The only downside to a timing advance is that it may be more prone to stalling at low revs. You just need to put it in a section to see. A couple of those can ruin your day! Have fun! Quote Link to comment Share on other sites More sharing options...
ythan Posted June 22, 2008 Author Report Share Posted June 22, 2008 (edited) It is all together a happy little thing right now, it is right there on start up seems to start better. The bolts were about a 3rd back from the front of the slot. I cant see it stalling the way it is set up it is stronger than it was and not at all fussy, you can stall it but it puts up a good show now. Just been on it this morning the sun is shining here today (beauty of a morning) i am pleased with the bike, a good job done cheap. Thinking about changing the reeds now but then again if it aint broke dont fix it aye . Edited June 22, 2008 by ythan 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.