This is my first post after introducing myself. I have built many performance pwc (jetski) engines before but Im very new to scooters. Like most people, I want my aerox 50 that I don't own yet to go faster. I have a few questions and appreciate every response as scoot info is near non existant down under. 1: 70cc kits. I see many kits online but Im thinking there are three basic types. Cast iron cheapies, Aluminium single ex. port and aluminium bridge port. Are the bridge porters high rpm peaky buggers or do they still pull ok through the midrange? Is it possible to get port duration specs? What is the mhr replica ex. port configuration? 2: Will the standard crank and wrist pin dia. handle a decent 70 kit? 3: Carbs and pipes?? I know in the pwc scene that there are good and bad available in pipes and carbs and bad combinations of either. So I ask the question. What do i buy? Say scoot is a 02 aerox 50, I would like to get 100km/h out of it but midrange torque is where my fun is. It will have a 70 kit installed so I would love some info and results on working combo's. 4: Does moto tassanari or Rinaldi make reed assy's for the horizontal Minarelli? What reeds should I run? Also I see you can fit a 26mm stop to stop reed in the cases, How wide do I run the stops on stock cages with .4mm biaxial carbon reeds? I made some out of some reed sheet I had lying around. 5: Is there anywhere online that i can get tuning and tech. info on the transmission system? I need to lean this from scratch. 6: What is the stock timing on the aerox minarelli and is it linear through the rev range or does it have an analogue retard curve? Sorry for being an info sponge but Im very new to scooters but build 2stroke race engines for a living. All responses are appreciated and If I can help anyone, I will within my knowledge. ps. I need to buy a new angled handpiece for my CC Specialties hang up motor to get into these little cylinders. Smallest bore I usually work with is 81mm! Case porting will be no drama though. Cheers, eel. ps. I realise much of the info I'm looking for can be found with the search button but it may not be current, and as I'm starting from scratch I would like up to date advice. Thanks in advance.
1. they are more high-end power but on a scooter that's where you mainly use the revs as long as the variator is set up correctly. 2. yes if it's not had the usual abuse that an average 16 year old over here throws at it, if you are looking at serious horsepower gains then replace the crank for somthing with a little more meat on it to increase the bottom-end compression and also look into the 12mm little ends (stock i beleive are 10mm). 3. for mid-range power you want a 19mm carb on a 70 bore (21 gives a little bit better top range). as for exhausts, the possibilities for the aerox are endless (try the 50/70 tuning guides on the homepage) 4. i'm unfamiliar with moto tassanari and rinaldi reed assemblies and am pretty sure iv'e never heard of them being used on a minarelli 50/70. 5. A scooter (CVT) transmission is a fairly simple system that most people make into a big deal, the best way of learning is to take one apart. basically as the revs increase the variator pushes the belt higher on the front pulley and in turn it goes lower on the rear pulley. the clutch system is a standard centrifugal system (same as the old suffolk lawnmowers). all you really need to know is that the rollers in the variator affect the revs in relation to the acceleration, the lighter the more the bike revs, the ideal is to get it to rev to it's peak RPM at full throttle all the way through the variator movement. this takes patience and becomes a bit of an obsession. 6. i'm not sure on the tining figures but i can tell you that the CDI does have a pre-programmed ignition curve (programmable ones are available) What kid of race engines do you normally do?
I think theyre the Vforce reedblocks mate, and these are used ALOT in tuned engines in europe, including minarelli and piaggio engines.
Thanks for the reply, wobbly 51. I found out moto tassanari do make reeds for minarelli's. Vforce 3's. Dunno about scooters but they work KILLER on most jetski's. I build jetski race and freeride (what you call stunt) engines. Seadoo (rotax) 1040 big bore. 92mm bore X 78 stroxe twin cyl, twin pipe. they make about 225hp @ 7700rpm Yamaha 701's for free ride and race, low to mid 100's hp. Kawasaki 800 engines for race, up to 160 or so hp. I was recently involved with a kawi 4stroke turbo that made 400+hp. The "normal" carb size I run is 48mm! I will post some pics one day.
yup, deffo Vforce are available for minarelli. the aerox will be a "little tame" then. EDIT: just checked the website and they do reddblocks for the banshee which is the same motor as my RD. i know whats on my next shopping list.
Hey wobbly, do you have a rd 250 or 350? I rode a 250 when I was about 17, they were a peaky fuker! I liked the RZ better. The vforce larger reeds have adjustable stops that you slide in and out to vary the tension. In my 1040cc rotax engines, the vforce last about 35 mins until you lose a shitload of power. Easy to diagnose though, there is a carbon petal in the carb throat! But thats feeding a 520cc cylinder with 208/133 durations. The rinaldi's are even bigger so you lose a bit of initial snap but once the cadencies harmonise HANG ON! Also, the only way you can root a rinaldi is to hydrolock the cases. The petals last a couple of years when asked to feed sensible sized cylinders though.
if you are after port spec's for any 70 barrels just let me know an myself or terro will try an dig them out. you have to remember tho these are full auto's so nothing under 7k really matters. max power rather than max spread as the transmission compensates for any iregularitys in a power curve (saying that some of the kits out there make massive max power while still producing torque at lower rpm's) as for learning your way through the transmission there is a rough guide to how it works on the main site in the guides section but please ask if theres anything specific you dsont understand. good to have somone onboard with a fair bit of experience with 2t's. and dont panic, you will soon apply your knowledge to these simple little engines.
Minor confusion, thanks alot! for the encouragement. I read the variator article on this site and it put my mind to ease. I been reading a load of shit, googling "variator tuning" and couldn't understand how fucked up a system it was that the weights actually govern the peak front sproket peak gearing in detriment to rate of "up gearing" , ie. big weight = speed, little weight = bottom end free rev and you have to choose between both. I thought "thats pretty fuked, why dosen't the variator weights control the rate of gearing increase and reach a mechanical stop? I'm a genius. I will spend an afternoon on the lathe and these scooter guys will think I'm the schite!" After reading that article I figured out a few things. I'm not the next variator god. Many other people know shitloads more than me. Googling anything about variators puts you in touch with people who shouldn't even own a goat, let alone something with moving parts. Never underestimate little engines, they do stuff that big engines only dream of.
deffo... seing as im getting closer and closer to the 20bhp mark with a 70 engine rollers ARNT that complicated and as you say they simply move out on the ramps due to centrafugal force. this rate controls how fast the bike shifts through diff ratios. you must remember tho you are looking for the peak power rpm with the barrel/pipe your using then tuning the variator to hit these revs constantly. clutch is the same and im sure youve setup ajustable clutches befor now. once again just ask and ill do my best to help out. might even ask you a few things once your up to speed as i KNOW your porting experience will come in handy. remember you can just downscale port timings ether by working out the ratio drop for the difference in stroke or use a timing disk and use the timings you like.
I have all the "black magic" gear to grind a cylinder. (except a small enough angle head handpiece to do transfers on these tiny cylinders, but thats coming, I have the cable drive gear) I even have an assortment of degree wheels, burette's, egt guages, thermo's, mikes, deto gear, gps and access to stalker radar acceleration measurement. And programs that do the degree's for me if I know a few parameters. My two most important pieces of gofast equipment can be obtained anywhere. Pen and paper. Test, record. Try something, test, record. Compare. Keep repeating until you see a pattern and then even when you go slower, you will learn to go faster. Keep records of every shitty little change you do and the result. Buy a top of the line tacho. I have an oppama that can run anything from a briggs & stratton to a merlin with msd. Tiny tachs that seem popular have a sample rate of about a week. They are way better than standard though. 20hp out of a 70 is fuken cool!!!
with the right shape attachemt's (vine bur's are best) you CAN get into the transfers with a straight dremmel pro (triangular and cone shape cutters rule) but remember the plating flakes at the first chance so try and push the plating to a chanferd level around 0.5mm away from where you are cutting the port to, this way you can go rough and fast and not even worry about the lining flaking. selotape works wondersa tho (just peel TOWARDS the port please) 24bhp can be attained with a stock 80 kit and long stroke crank if youre up to modding the case to take the lot. over 15bhp with unmodded barrels on a nice case is more than possible tho so get yourself a nice polini evo barrel and play with it stock first. verry minimal port work is required to max these little jug's tho wrist pin needs enlarging after around 12bhp, the big bang kits have a differewnt small end bearing to accomidate a larger pin in the stock crank but id say just spend youyr dosh on a good evo crank and adapt the rest around this. evo crank/barrel works really well tho and i use nothing else in my high poweer engines
Send me some pics. pwcdenny@bigpond.net.au I would love to see some of the different cylinders, before and after. Im still getting my head around the shitloads of cylinders available! How does the evo pollini jug compare with the mhr replica that I'm reading so much about? It's got me fucked how you can do decent transfer port roof angles with a straight grinder but obviously you are. Whats a vine burr? As I said, I have probably been spoilt by working on larger bores and need to learn new techniques on these little buggers. cheers
I don't know a lot when it comes to this side of scooters but i have the Polini evo cylinder and I've tried to read as much information about them as i can and from what i have read they have very good build quality, they give good hp over a wide power band, at an achievable RPM, and unlike the comparable cylinders it wont go through piston rings as quick [i.e. Malossi 7T]. Also the evo cylinder is better than the Metrakit pro2 [which is another comparable kit ] as it bigger transfer ports as standard so they can be tuned to produce more power. As for the cranks, the Polini evo crank [12mm pin] is one of the best cranks on the market for cylinders around the 20-21bhp potential, some even say it is very close to the expensive MHR team crank. I also have a stock Polini evo cylinders port timings saved on my PC so i will try and find them for you. Hope this helps... *James*
the mhr replica is similar to the port of an evo2 cylinder but uses a w2 ring piston so the secondary transfer ports are nowehre neer as wide. polini all the way my friend. i dont have many pics and the ones i do have are low quality phone pics (im a cheapskate) and it was a typo.. i ment fine burr (lots of tiny little cutters) takes longer but wont ever flake the lining unles you lead onto the port edge. if you have msn send your addy to me via pm and ill chat there later
