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Discussion in 'The Workshop' started by andrew redfern, Nov 9, 2016.
hi can any one on how to derestrict my new lexmoto-Echo-50- many thanks andy
its a 139QMB engine , fourstroke . some 139QMBs were sent out with 44mm pistons ( whatever was on the shelf at the time got thrown in) these were usually older bikes and not the new ones we see these days . most nowadays are sent out with 39mm pistons, but a 44mm piston motor was naturally faster given the bigger bore size, ( DO NOT expect a 50mph beast you may get 40-45mph thats about it at max you may get 37mph max thats it, fourstrokes are not as tunable as a twostroke engine and require a lot more than just tinkering to get the very best from a thumper engine ( thumper because of the noise a fourstroke makes)
so first off , replace the factory oils for better quality, the stuff they use from factory is just thick gloop, and your going to replace that with a better quailty oil.
Variator, now some bikes do not have a variator restrictor and some do, its usually a wedding rig style restriction, the variator runs on a drive boss ( a long'ish metal barrel and over this barrel is usually a metal ring thats stops the to faces coming together, thats the restriction so its removed) once the restrictive ring has been removed that allows for a slightly higher gearing ratio and hence more top end speed.
CDI , these can be restrictive on RPM , your bike produces around 1.4kw @ 7500rpm, if the cdi is restricted the bike will not go past this 7500rpm , the cdi will regulate the coil charge release to regulate the rpm (kind of pulses the coil on and off). some bikes have a CDI restriction and some do not.
one area thats usually restricted is the throttle diaphram ( under the seat bucket you will find your carb) ontop of the carb is a large round disc held on with some screws, these are removed and that upper plate lifted up ( becareful here theres a spring and your diaphram) usually there is a center post on this upper plate you removed with a brass nut on it, remove the brass nut , reseat the spring and resteat the upper cap plate and screw it down again, being careful not to pinch or catch the diaphram rubber when doing this. that nut was restricting the throttle slide from fully opening.
exhaust you would normally just leave it alone, you can add an aftermarket exhaust but its just going to make the bike sound nicer more Brap brap than Barp barp, some topend exhausts will give a very slight power increase but thats due to better flow and throttle response
Airbox : DO NOT TOUCH IT !!!
SO recap, change gearbox oil and engine oil to a better quality if its not already been done. this is a in the long run better for the motor change. ( change engine oil every 2000-3000 km DO NOT let it run dry or turn Black)
Check variator for the restriction ring ( some are, some are not )
see if CDI is restrictive ( go out for a ride find a hill and ride down it, if the bike speeds up when going down hill cdi is not restricted, if bike does not speed up cdi is restricting rpm limits )
check carb for restrictive diaphram nut and remove. again back to that hill and run down it you should see a marked change in throttle and speed if its all done right.
if this seems a bit out of your league you can pay a bike shop to do these things for you ( except the cdi you may have to buy this via them or from the web)
Everything advice wise is AT YOUR OWN RISK we/I cannot be held at fault for anything if it goes wrong , your scooter is no longer a moped as its power has changed and if your 16yr old ITS ILLEGAL
thanks for all your help andy
for the record, most of these chinese bikes have mainly just an electronic restriction on the CDI.
its either a wire that coils back over into the cdi (peugeot v-clic) or its a seperate wire that goes to a speed sensor on the transmission casing somewhere (peugeot kisbee)
click the search box at the top here, then type in derestriction thread.
we had one going not that long ago, i detailed a lot of bikes as did stevep
Preformace your looking at a scoprion / akrapovic or the likes exhaust and they are not cheap, then you need to remove the baffles/anti spark , and you have a little extra power with a better sounding pipe £400+ on that is not worth the gain you receive. yes if it was a cbr600 or a lush R1 but on a 50cc a waste of money.
reason being you would have to then have the valves reworked and enlarged , possible valve ports reworked or even re-cut to offer better flow into the head, then an uprated cam and rocker arms, but again is a very small gain in power.
The most simple way is a big bore kit taking the 50cc upto something like an 80cc and then its not a power upgrade, fourstrokes are awesome torque providers in a small engine there would be some difference but its felt in pulling power not out right raw power.
there is a few companies doing "power up kits", which consist of a cylinder kit, variator, pipe,CDI and carb or variations of that.
i wouldnt mind getting my hands on a 50cc 4t scooter motor and reworking the head to see how much power i could make....
i have a 50cc cub engine that i have been thinking about tuning...
hi, do you happen to know if a derestricted euro 4 ecu/cdi will work on a euro 5 moped, cheers