KymcoForum.com
Scooters - 50cc => Super 8 => Topic started by: AylmerFreerider on May 20, 2019, 01:21:12 PM
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Hey all trying to figure out why I can't get a solid 70-75 km/h out of my 2015 Super8 4T. I seem stuck at 65km/h
I have done the following
72cc BBK
Polini Hi-Speed Variator w/ 6.5 weights
1000RPM Contra Spring (was a 750 stock) - Looking to go to the 2000 RPM spring with the new power from the 72cc BBK
Technigas Silent exhaust installed.
derestricted CDi (removed purple wire)
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What is your carburetor set-up?
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Big bore kits offer more torque for hills and headwinds, but the drive pulley ratio remains the same relative to crankshaft revolutions . . unless rear gears are changed.
Unbalanced rotational dynamics (http://49ccscoot.proboards.com/thread/7767/39mm-47mm-piston-compairson-video) also enhance the odds of crankshaft and connecting rod bearing failure. Pretty much a lose/lose situation!
For others researching . . initially select a scooter model with an engine size suitable for your speed expectations, and keep it stock!
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What is your carburetor set-up?
I upped the main jet to a 92 from an 82 (10% ish for the BBK)
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Big bore kits offer more torque for hills and headwinds, but the drive pulley ratio remains the same relative to crankshaft revolutions . . unless rear gears are changed.
Unbalanced rotational dynamics (http://49ccscoot.proboards.com/thread/7767/39mm-47mm-piston-compairson-video) also enhance the odds of crankshaft and connecting rod bearing failure. Pretty much a lose/lose situation!
For others researching . . initially select a scooter model with an engine size suitable for your speed expectations, and keep it stock!
I have read many different things and most say that the bottom of the motor is pretty much the same from 50cc-125cc.
I wasn't looking for great speed gains 5-10km/h I am not looking at turning my scooter into a hotrod just a safe rod.
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I have done the following
72cc BBK
Polini Hi-Speed Variator w/ 6.5 weights
1000RPM Contra Spring (was a 750 stock) - Looking to go to the 2000 RPM spring with the new power from the 72cc BBK
Technigas Silent exhaust installed.
derestricted CDi (removed purple wire)
What is your air filter set-up?
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Also, what was your top speed on level ground before any modifications?
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Also, what was your top speed on level ground before any modifications?
Air filter is the same (mechanic said he expanded the opening only)
My top speed before was 65km/h on the flat
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allHey trying to figure out why I can't get a solid 70-75 km/h out of my 2015 Super8 4T. I seem stuckat 65k
You don't seem to have improved your top speed at all. Is that correct? Did you do upgrades incrementally or all at one time? Oh...did you ever install the smooth boss bushing?
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You don't seem to have improved your top speed at all. Is that correct? Did you do upgrades incrementally or all at one time? Oh...did you ever install the smooth boss bushing?
I did things incrementally. First the smooth boss then the a larger jet (80-82). These both came with the scooter when I purchased it.
Then I upgraded the exhaust and installed the Polini Hi-Speed variator.
Got to 65km/h then I went the BBK route for more power/ a little extra speed. I didn't have the expectation of doing 90km/h. I just want a steady 70km/h whcih was only 5 extra km/h
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Doing the mods incrementally, did any of them NOT improve performance?
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….initially select a scooter model with an engine size suitable for your speed expectations, and keep it stock!
Amen.
Stig
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Pretty much with the other folks on this one. A 50cc 4 stroke's only gonna take ya so far.
If 50cc is your passion for whatever reason I'd be looking for a 2 stroke before doing more with this one.
If not then look into something with a bit bigger motor.
You can tweak 'em all ya want, in the end There's no replacement for displacement.
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Amen.
Stig
Issue is license. I can use my regular drivers license with this. No need for a special license I would need for anything listed at bigger than 50cc
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Pretty much with the other folks on this one. A 50cc 4 stroke's only gonna take ya so far.
If 50cc is your passion for whatever reason I'd be looking for a 2 stroke before doing more with this one.
If not then look into something with a bit bigger motor.
You can tweak 'em all ya want, in the end There's no replacement for displacement.
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Figured out the issue. Needs a secondary gear upgrade. Seems that with the 4T the limit them 65km/h
With the BBK the power is now there for the for a 10% upgrade.
Now to find the secondary gear
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Sounds nifty.
Please post your results.
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Figured out the issue. Needs a secondary gear upgrade. Seems that with the 4T the limit them 65km/h
With the BBK the power is now there for the for a 10% upgrade.
Now to find the secondary gear
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Installed the 2000 RPM spring and now won't go past 58km/h Tried heavier rollers thinking that it may need this open the spring all the way. Still didn't work.
going to try the 1500 RPM now and see what happens. Also looking at upgrading the exhaust as well. The Technigas Next R is on sale only $150 Canadian shipped to my door.
Also no luck in finding new gears. Seems they are somewhat a myth to suppliers. They can't seem to find them anywhere.
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Can't just use a standard set of 139QMB gears? Bit pain splitting the cases to check the measurements though...!
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So have the Naraku White Contra Spring installed again (1000rpm) with the heavy clutch springs still installed.
Installed a tachometer and I think I need more RPM's
7600 RPM at 65km/h
Thoughts from the group?
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You were right before - you don't need more RPMs, you need different drive gears to get you up to the speeds you want to be at.
Don't go messing with that rev limiter - they don't like high revs very much.
You need to start changing things in the gearbox, unfortunately...
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You were right before - you don't need more RPMs, you need different drive gears to get you up to the speeds you want to be at.
Don't go messing with that rev limiter - they don't like high revs very much.
You need to start changing things in the gearbox, unfortunately...
I hit a downhill and hit 70km/h and was showing 8000 rpm is that to much? When I look up the specs on the exhausts it is showing 9000 rpm as the sweet spot for my exhaust.
Such a pain to get 5 extra km/h
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If I remember rightly they don't wind up much past 9000...
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so I tried an high volume air filter from Malossii.
connection
Ended up being to small to fit the carb. I was expecting a rubber gasket style but it was hard plastic. so in my ;how can I connect this mode I realized that it would fit the front of the current air box. Tried this, and it didn't go so well. The box has a natural reduction in the inlet that was basically choking the engine once I hit 50 km/h
So back to the old air filter, but I had bought these little 1" air filter plugs that I drill the air box cover out for and they pop in just in front of the air filter. This has seemed to help with the power a little. went back to the 6.5 gram rollers and now I am hitting 60 km/h fairly quickly and topping out at 67-68 km/h.
Curious if maybe going to 6.2 grams or doing a 6.2-6.5 mix would get me those last few km/h I am looking for?
Note that I had to switch out the tachometer for w new one as the batter in the first one died and wasn't replaceable. New one is. but it is showing 7600 at 67km/h and showed 7800 when I did hit 70km/h on a slight downhill.
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Hey all looking for some advice on this now. I have upgrade the gears now. It had a 14/54 and I was able to pick up a Vitality 50 2T and swap the gears from it. They are 16/53.
This works out to a 13% increase or remarkably 13kph but my scooter seems to be not able to get past 7000 RPM and still stuck at 68kph. So I am going to try lighter rollers and see how that works. Before I was getting 68kph at 7800RPM
Set up is as follows
72cc BBK
92 main jet
1000 RPM Contra Spring
6.5gr rollers (just installed 6.2 to see how it goes, I also marked the variator with a marker to see how high the belt will go.)