Weak acceleration. Baby fart backfire when I let off the gas

[grouchysmurf]

I just got a used X500.  I have been riding maxi-scoots for a few years, my last mount was a Majesty 400.
The X500 seems very weak off the line, but runs fine once you get it up to speed.  It also makes mild baby fart backfires whenever I let off the gas.  I'm thinking the problems are related, something is causing it to run lean.  Anyone else run into this before?

[spr0k3t]

Do a plug chop and check the carmelization on the top... if it's white, then you are running too lean and may need an upjet if the air/fuel mix is pegged out.  If it's black or wet, then you need to increase the airflow or dail down the air/fuel mix on the carb.  If the color is close to a nice capiccino, your solid and don't need to change much of anything.  Another thing to check is the needles on the carb... it's possible there's debris in there causing the idle jet to letting through too much fuel on down throttle.

Accel wise... I find the X500 a little weak off the line (stock build) in comparison to other 500cc scooters... however, once it has a little bit of a bite to the pavement and the rpms hit about 3.7k, it will keep up with the other 500cc scooters just fine.  Need more grunt off the line, try stepping down to a 28gr roller/slider and see if that doesn't increase the pep.

[jprestonian]

Also wonder when (or if) a valve adjustment has been done on this bad boy. Might wanna check that, or have that checked, if you can.
.

[Hoolander2]

Is yours carbed or injected?  My '07 is carburated and does give teeny tiny backfires on letoff sometimes.  I'm the second owner so don't know if it's been tampered with.  My sparkplug always looks just right when I look at it.  It is a little weak off the line but, as spr0k3t says, has real good pep after that. 

I installed a Dr. Pulley clutch which, when tuned right, helps with the take off. 

[ts1]

Accel wise... I find the X500 a little weak off the line (stock build) in comparison to other 500cc scooters...

Or try the HIT clutch from Dr.Pulley.

[guile]

I changed the variator voor a Malossi Multivar. Everything under 600 cc's cannot keep up with you anymore after that 

[Cortez]

I changed the variator voor a Malossi Multivar. Everything under 600 cc's cannot keep up with you anymore after that 

And you probably got fuel consumption of a CBR Fireblade riding on a track.. 
Seriously though, I'd love to hear MPG figures from youz guys with carbed 500s!

[guile]

Mine does about 5 litres on 100 km (no injection). De variator does not change fuelconsumption; it changes the way you ride your scoot (fast   ).

[ts1]

Seriously though, I'd love to hear MPG figures from youz guys with carbed 500s!

http://www.spritmonitor.de/de/uebersicht/95-Kymco/0-Alle_Modelle.html?vehicletype=2&constyear_s=2005&constyear_e=2006&power_s=28&power_e=28
4.9 and 5.1 litre/100km = 48 and 46 mpg

[Cortez]

Mine does about 5 litres on 100 km (no injection). De variator does not change fuelconsumption; it changes the way you ride your scoot (fast   ).

Lighter roller weights were suggested.. which increase the rpms for any given speed.. and more
revs = more fuel.

I forgot to comment the acceleration part though..
Ever since the Xciting first came out (2006 I believe), every single review I've read mentioned the
rather slow off-the-line acceleration for a 500, and I've seen the 0 to 50mph times to be comparable
to 250-300cc scooters.

Weight plays a big role in this, and the XC500 is on the fat side of 500cc scoots.. and the
variator is (as mentioned before) adjusted more for out of city riding and keeping the revs
low for cruising (which is where the 500 belongs anyways).

The 250 is a lot better in this regard. It'll spin up to red-line from zero and accelerate a lot
better then you'd expect for a 250 of that size and weight.

[ts1]

The Xciting original clutch takes effect at ~2500rpm and you can drive it with <3000rpm (slowly of course).
The Dr.Pulley clutch adds another ~1000rpm but then it's getting difficult to take off on snow & ice.

[Cortez]

The Xciting original clutch takes effect at ~2500rpm and you can drive it with <3000rpm (slowly of course).
The Dr.Pulley clutch adds another ~1000rpm but then it's getting difficult to take off on snow & ice.

I can't imagine riding this heavy pig on snow.. but I'd love to try!
I've been riding every day of snow this year on my Agility 125, but my (twince the weight)
Kawasaki was in the garage.

Can anyone quote some engine speeds vs km/h or mph speeds?
I was wondering how much is the tach showing at 40/50/60/70mph for example.

[ts1]

Can anyone quote some engine speeds vs km/h or mph speeds?

With my 500 carb (the 500i revs lower), the only speed I cruise for a longer distance:
6000rpm = 98-99 kph (GPS) = ~110 kph indicated, belt + rollers 2000km "old", variator already warmed up (cold variator needs more rpm for same speed)

[Cortez]

With my 500 carb (the 500i revs lower), the only speed I cruise for a longer distance:
6000rpm = 98-99 kph (GPS) = ~110 kph indicated, belt + rollers 2000km "old", variator already warmed up (cold variator needs more rpm for same speed)

This is stock variator setup?
I figured it would be lower. The Downtown 300i cruises at 100-105kph @ 6.000rpm!

Didn't know the 500i revs lower, different torque/power curves?

[ts1]

That's stock setup.

The X 500 carb has max. power at 7500 rpm and max. torque at 5000 rpm,
X 500i at 7000 / 5500 rpm,
Downtown 300i at 8000 / 6500 rpm.

I doubt the Downtown has 6000 rpm at _true_ 105 kph.
If 6k rpm @105 kph, then at most 7.4k rpm @130 kph (its official top speed), would be an overdrive.
At ~100 kph the X 500 variator is still in its adjustable range, it redlines far beyond 8k rpm (I don't remember exact number).

And as "Meister Zip" once pointed out, the tach reading may be as wrong (and differently wrong from individual to individual!) as the speedo reading. He always uses his professionel engine tester.