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Post by bendover on Oct 13, 2017 16:01:16 GMT -5
Have a stock 50cc Piaggio Zip (AC) and a stock Aprilia SR 125 (also AC). Keeping 1 of them. Will BBK and tune the one I keep. Goal: Best takeoff acceleration / red light racer. I care zero about top speed above 70 kph. Question: Which would win at the red light? "Isn't that obvious!?" Well..:The 125cc (stock) takeoff is worse than my previous 70cc Aerox. The Aerox, I could feel the kick jolting, It was ANGRY. The Aprilia is very dull. At the red light, the Aerox would beat the Aprilia first meters, keep lead a while, then of course being beat. Obviously the angry one is more fun to drive than the dull one  Aerox had everything tuned very nicely. Aprilia stock, I feel have a tad too heavy rollers and could use a tad stiffer clutch springs - but it still have bhp lead, and while weight difference might even out the lead, I can't see it accounts for BETTER acceleration on the Aerox. While the 172 cc will win over the Aerox, so will the 70 cc Zip. Which is quickest? My brain say 172 cc with tuned drivetrain, maybe even a slight gear down kit (blasphemy I know), but story above say that little 71 kg Zip just MIGHT be the quicker one. |
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Post by 190mech on Oct 13, 2017 18:34:24 GMT -5
"No substitute for cubic inches" is an old american term,very true though..A big motor(properly tuned) will launch harder than a small one,it will likely be more reliable than a 'hyper race' small motor too..Your choice,both will be fun!!!  |
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Post by bendover on Oct 13, 2017 19:05:02 GMT -5
"No substitute for cubic inches" Yes the good old "No replacement for displacement", but that is only if everything else is equal. The example is much more complex, we have to consider differences in rpm, weight, compression, end gearing, porting options, exhausts etc. We have to look at all this and make an educated guess, or just good old experience. Just looking at displacement is not reliable, hence the question =) For anyone wanting to chip in, lets make it easier: Bike A:Aprilia SR 125 Weight with rider 180 kg Bhp rear wheel estimate: 18 Malossi BBK 172 cc Malossi/polini variator with correct rollers Stiffer clutch springs Stock reed cage with cf petals Stock exhaust Stock carb End gearing: High Top speed 140 kph Bike B:Piaggio Zip AC Weight with rider 145 kg Bhp rear wheel estimate: 8 Malossi 70cc sport Low rpm exhaust (not full expansion chamber) Malossi/polini variator with correct rollers Stiffer clutch springs Stock reed cage with cf petals Stock carb End gearing: Medium Top speed 85 kph Which of the bikes above should have the best launch? |
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Post by pinkscoot on Oct 14, 2017 9:52:32 GMT -5
I vote for the SR125 because I want to see how the Malossi kit works for you. I'm thinking about it for my Scarabeo. I would like to see the results.
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Post by jeff84 on Oct 14, 2017 12:23:02 GMT -5
I vote bike A: with a down gear and lots of weight reduction.
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Post by boostcrzy on Oct 15, 2017 14:28:08 GMT -5
4 stroke can be made faster/quicker with less modification and tuning. But nothing beats the sound and feel of a hell bound chainsaw 2t hanging the front wheel off of a green light. I say go 2t if you’ve got the salt to dial it in.
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Post by aeroxbud on Oct 16, 2017 9:06:25 GMT -5
A lot will depend on what BBK you installed. I know I tried a Runner with a PM tuning 172 kit. It would easily beat my Aerox with a stage 6 racing cylinder, and C16.
In fact it was hard to keep the front wheel down when trying to launch it.
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Post by knobby on Oct 16, 2017 13:36:27 GMT -5
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Post by bendover on Oct 28, 2017 20:33:57 GMT -5
Lol this is what I want  Anyone know what scooter it was? 4t surprise, must be 300cc+ or so? |
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Post by bendover on Oct 28, 2017 20:36:56 GMT -5
I vote bike A: with a down gear and lots of weight reduction. Been trying to find gear down kits but no success? The 125 engine has a bit lower gear than 180, which is good. Not sure what weight to reduce though  |
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Post by boostcrzy on Oct 30, 2017 13:21:51 GMT -5
I just run nitrous oxide on my 4t. 172cc BBK with a cam. on nitrous it moves quite well.
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Post by bendover on Nov 1, 2017 4:47:21 GMT -5
Made some simulations on a site and the 125 kicks ass easy. The weight difference was not giving as big difference as i thought, 17bhp on 77kg scooter and 80kg driver had similar acceleration as 115kg scooter with 19bhp. So instead of hustling with the zip i ordered some extra tuning parts for the aprilia. Gear down kit would be great, are they the same size for all Piaggio engines? If yes i can use secondary gearing from a 13" Piaggio 50cc for lowest possible gear, or from a zip as just slightly lower than the 125. Maybe aftermarket has inbetweens.
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Post by knobby on Dec 19, 2017 20:06:52 GMT -5
The scooter from the video clip was indeed running a 30 shot of nitrous IIRC.
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Post by jackrides on Dec 20, 2017 14:16:19 GMT -5
I have to think the 125 needs more cvt work, and ssome way to lower the gearing. Result should be much quicker.
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Post by Lucass2T on Dec 21, 2017 7:45:58 GMT -5
From a 70cc you can pull about 25hp with plug n play parts. From a piaggio 125cc engine about 30-40hp or so (malossi 172cc or fabrizi 210cc kit)?
Your goals should be specified with a budget. Cc's don't really matter here since a 70cc can easily beat a 125 and vice versa...all depends on the money you wanna throw in it.
Oh btw. When this 125cc is actually a 4t (i assumed 2t since they're quite common)....torch the 4t....they're slow-as-hell.
I once rode an aprilia leonardo 125 and it was a conplete turd...
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