So, been tinkering away with my s6 racing build. Now have an excess of power which is very good. Full throttle cannot be used from a standing start even with my weight all the way forward or it will flip, maybe that means a gear up kit would be a good idea I have been getting a little hiccup on sustained full throttle. At first thought it was leakage from HT lead at high rpm so replaced that,checked ignition, cdi etc. Runs great at any throttle opening up to say 90%. But run it longer than 15-20 seconds at full throttle and it will give a little hiccup and misfire. Unfortunately I have always bottled it and shut the throttle straight away in case it is trying to nip up on me. Experimented with 2 sizes larger on the main jet (108 from 102) this made it noticeably rich where it would splutter over 3 quarter throttle. Dropped main jet from 102 to 98, engine runs cleanly again still has hiccup at full throttle. Temperature still okay. Next to check is the "anti surge washer" where the main jet screws in (dellorto phbg 21). Its a stamped brass plate with 4 small holes in. Apparently to stop surging and ensure a stream of non aerated fuel enters the main jet. Apparently most people run without it unless doing silly jumps and things on dirtbikes. It also can cause issues if fitted the wrong way so is currently completely removed. Spark plug ceramic is healthy brown colour, electrode is also a nice shade of brown. The base ring (end of metal part where threads are when looked at end on) is sooty black. This suggests possible rich running. Probable need to drop another size or 2 on the main and see if that fixes it. Its just overcoming "the fear" and keeping the throttle on to see what happens after the hiccup without backing off and worrying about damaging all that lovely kit
interesting! Drop the main jet by 2 points and see. keep an eye on the temp and the plug colour. Good job !
thanks, funny how quickly you get used to the power though. Already have ideas running around my head for cylinder porting and a higher end exhaust. Thinking what can I do to improve the 50-70 pull. Then stop and go hang on, its a moped. Thats damn impressive as it is
hi hi.if you think the mis-fire is a mini nip up,take the head off and an have a look...only a few nuts and your know if its so.im assuming you've got a properly matched exhaust and cdi curve to match the engine..have a look down the cylinder and then if alls well...throttle it ..plug and colour seem good..easy do a few jet changes without worry of it siezing cos of mixture..if your worried still..put a little drop of oil in your tank to offset any lube probes you might have .youve run the engine in i take it...piston/bore change?.
Thanks, I got it sorted. I had been advised to upjet a little when I fitted the inner rotor ignition to allow for the altered ignition timing curve so have been slowly working my way back down in jet size till I can get it to sustain full throttle without splutter/missing after more than 15-20sec. The largest size jet I can get away with that runs cleanly is a 92, coincidentally exactly the same size as the carb was shipped with from stage6. (Wonder if they know something we dont
Plug does look leaner than I would like but temperatures are holding okay and that seems to be whaat it takes to make it run cleanly
nice to see its all sorted(till ya next time)sometimes its best to trust the experts..least you wasn't running too far off their size
