minibreaker Posted June 6, 2015 Share Posted June 6, 2015 hi i have got my yamaha v75 all working, only problem seems to be that it accelerates well but then when revs are high it just doesnt change gear. after a while it seems to change gear... the revs lower and the bike starts to accelerate again. any ideas if this is normal or can i adjust when it changes gear? its got a funny lever for high and low and neutral Link to comment Share on other sites More sharing options...
JimR Posted June 6, 2015 Share Posted June 6, 2015 so this is a V75A ... sounds like you will need to look at the clutch rollers & spring to adjust when the bike changes gear. However the bike out of the box would 'rev it's tits off' before it changed into second (this engine has just a 2 speed gearbox) and second being a lot higher than first you do need to get the bike to rev out in first The High/N/Low lever (the low option could only be set by pushing the metal clip back, your clip may have long since broken off) is for High normal riding N for starting the bike Low is only there for very steep inclines (if the bike stalled out in High). Regarding your question about tuning as this is a V75A and not a V75 (V75 had a 3 speed manually selected gearbox with an automatic clutch like the V80/90) you have a totally automatic gearbox, so altering the overall gear ratios (upping the front sprocket) will not work as you don't have the control over the gearbox that the V80/90 has ... The cycle parts are the same across V50/70/75/80/90 so in order to get this bike to go dump the V75A engine and put a V80 engine in the frame. Use a V80 as out of the lot of the V series it was the best motor Link to comment Share on other sites More sharing options...
minibreaker Posted June 7, 2015 Author Share Posted June 7, 2015 thanks for the reply. i have never seen one of these before and when bought it, i did not have a clue what it was . so thanks for letting me know is a v75a. it would sound like my bike is prob still standard and prob has nothing wrong with it as it does rev high then drops dramatically. i will keep m,y eyes open for a v80 engine but i doubt ill find one but as i say ill keep looking. thanks for the help just as an after thought if the engine has rolllers like a modern scooter can i put lighter rollers in to make it rev higher Link to comment Share on other sites More sharing options...
JimR Posted June 7, 2015 Share Posted June 7, 2015 thanks for the reply. i have never seen one of these before and when bought it, i did not have a clue what it was . so thanks for letting me know is a v75a. it would sound like my bike is prob still standard and prob has nothing wrong with it as it does rev high then drops dramatically. i will keep m,y eyes open for a v80 engine but i doubt ill find one but as i say ill keep looking. thanks for the help just as an after thought if the engine has rolllers like a modern scooter can i put lighter rollers in to make it rev higher Back in the day I used to stretch the spring a bit (this encouraged the gearbox to change up earlier if people complained about the 'lurch' on gear change) ... the rollers in this clutch are ball bearings (great for playing marbles with ) maybe some lighter balls may help ? Link to comment Share on other sites More sharing options...
JimR Posted June 7, 2015 Share Posted June 7, 2015 this may help - http://www.ebay.co.uk/itm/Yamaha-V75A-1975-1979-Fully-Illustrated-Parts-Catalogue-V75-V-75-A-Moped-595-/310871351490 Link to comment Share on other sites More sharing options...
JimR Posted June 7, 2015 Share Posted June 7, 2015 here's a motor for you http://www.ebay.co.uk/itm/Yamaha-PW80-Engine-Spares-Or-Repairs-/201366157698?pt=LH_DefaultDomain_3&hash=item2ee25bb982 Link to comment Share on other sites More sharing options...
minibreaker Posted June 8, 2015 Author Share Posted June 8, 2015 thanks for the advice.. is the pw80 engine a straight swap?? Link to comment Share on other sites More sharing options...
JimR Posted June 8, 2015 Share Posted June 8, 2015 PW80 and V80 are the same engine .. as the engine is short of the generator I am hoping the taper on the V75 crank is the same as the PW80 (this means your mag will fit) ... but it will bolt straight in 1 Link to comment Share on other sites More sharing options...
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