72cc BBK

[JC]

...lol..i saw that...

..jc, we all had good and bad experiences with even the same makers of bits...

..malossi, polini, dr pulley, gates, oem...


..ive NOT had good (over-all) experiences with some names tho...NCY, Naraku, Kenda, emco, scootertronics...

 
                               

Yeah, seen some BAD reviews about scootertronics. I'm still up in the air about the 72cc NCY cylindar kit and even with all the good malossi variator reviews on here I'm still contemplating the polini from my past experiences. It's gonna be one of those shoot from the hip ordering experiences. Point, click, try what the mailman brings me.

[trninka]

Hello all,

The day has come when I decide to upgrade my agility. So everything is stock for now. I planed to change the cylinder to BBK 72 (NCY) without to change the head. At the same time I will change the camshaft to NCY t2. At this point is it worth to change the camshaft (keeping in mind that everything else is stock), or I need also to change the CVT to NCY Overdrive2 ?
With changed BBK, Camshaft and CVT do I need to change exhaust as well ? The carb will stay the same, and I don know if i can run this setup with the stock nozzle.. What about consumption ? I run my scoot on 2-2.5l/100km (sorry for the measurement).. will it grow and how much to expect ?

Thanks 

[mono]

Only changing the cylinder, camshaft and main jet is fine.
Main jet should be 2..4 sizes up from 50cc, mine was running fine with 86..88 (before I modded the filter box)...

Consumption will increase according to how much of the extra power you really use. Mine went from 1L/43km to 1L/35km..

[trninka]

I am confused now. I was willing to order 72cc kit, but the guy at revolution70 is changing my mind... he says that with 72cc kit I will not get the good torque, and after a while I will want 85cc kit (85cc is marketing name, the true volume is 81.3cc because the diameter is 50mm). But he said I also need to buy a sport head for 80cc kit with bigger valves. The NCY kit consists of 85cc kit and sport head for it.

Please I need an advice: is it better to go with 85cc+head or 72cc with original head + t2 camshaft. (later i will buy overdrive2 vario)
Do I need to change the carburetor for bigger head (85cc), air filters and exhaust, or it can work good with stock parts?

Which setup will you choose, and why?

[mono]

Trust the guy at R70, he's always right.

My 72cc +T2 setup was nice, but I'm running the NCY 85cc + head together with the T2 now - and that is sooo much better that I wish I bought this immediately...

Instead of the Overdrive 2, I would go for the torquedrive (with straight guide tracks) from the same shop, and some 8,5 gram rollers for your stock variator, this gives a very smooth setup, with almost constant rpm and performance...

[trninka]

Yes but with 85cc and head I also need to buy Rocker Arm Assembly, because after 2007 kymco has change something on it, and in 95% the sport head doesn't fit with stock rocker arm. Did you get this problem too? And with 85cc do I need to change filters, exhaust, carb, etc...  ? Do i need to machine the block or something else, or it has a perfect fit ?

[mono]

With my 2010 Agility, the rocker arm assembly was just fine as it was... Even if you need an alternative one, the cost is almost nothing, especially compared to what you will spend over the next few years, now you've started modding...

Just like with the 72cc, the only "mandatory" changes are a larger main jet and heavier roller weights in the variator.

The best way to go about this, in my experience, is to only read the information on the Revolution70 website, and the manual they ship with the cylinder kits. These guys really know their stuff....

The world wide interweb, on the other hand, is full of stories about completely different parts and engines - and also full of morons who don't know or understand anything :-)

[trninka]

Yep.. thanks a lot for your advices mono. The site is in dutch, so with Google translate is very hard to understand what they want to tell you . They also tell me to buy their cheaper R70 80cc + replica camshaft, saying that the reliability is the same as NCY, with much lower price... but i think it is better to stick to NCY as its proven quality.

Why should I put the heavier roller weights, is it because I will run the engine on lower rpms.. so saving fuel...

What about increasing the top speed? Is it the best way (and cheaper) to change the variator only?

[mono]

Although I tend to trust what the R70 guys say, I wouldn't go cheap on things like this myself... It's about my daily transport, so I prefer to spend some extra cash, for that warm and fuzzy feel (or is it an illusion ?) of buying quality stuff...

You'll need heavier weights because the increased torque will pull the variator into a lower ratio, increasing rpm beyond the powerband or into the revlimiter. So it's not meant to lower rpm compared to a 50cc, instead, it's needed to keep rpm in its useful range...

If you want to increase the top speed, you'll need to do the usual variator derestriction (or install the Overdrive 2), and after that, you can also derestrict the CDI if you prefer speed over reliability - you can search this forum for plenty of advice on this...

[trninka]

Hey mono, do you have a cold start problem with 85cc kit ?

[trninka]

... and what about the crank shaft? is it stock? I am beginning to doubt that 85cc is a way to much for the agility... and I am afraid that if I put 85cc, the crank shaft will be gone for 1 year or less.. I watch the video of 85cc agility rs, and the guy in the comments has written that the crankshaft least for a half of year...

I can not decide yet.. in one side I will want the power of 85cc, but on the other i am afraid of overall durability of the scooter...

[mono]

The NCY 85cc starts easier than the 72cc did, the static compression ratio of cylinder and head appears to be lower for the 85cc..

Of course your crankshaft will wear quicker than with a 50cc, but it won't fail in a few miles, if all else is right...

I've been told by mechanics at different shops that a lot of the crankshaft failures they see in these Kymco engines occur with just the stock cylinder, and most failures can be traced back to oil pump failures or low oil levels in the past anyway...

And, if you really worry about durability, you shouldn't own a motorized vehicle I guess - they all tend to break expensive parts at the time your bank account is empty :-)

[trninka]

Haha - motorized vehicle - good one...

Anyway R70 guys warn me that electric start is a way difficult with 85cc than 72cc especially in cold days, that's why I asked you, if you have that problem.. but obviously it is another way around in your case...

[LoveMyKymco]

Its all about compression ratios, if your 47mm kit has 9:1 ratio and your 50mm kit has 8:1 youll be fine, if its the other way you need a high torque starter and or a better higher CCA battery. Do not use your kick starter as an alternative. It is meant for back up only, unless you like replacing kicker covers.
Connecting rod failure on the A50s isnt very common at all.

[trninka]

Well I don't know what compression 50mm kit has, when I look the piston it is some kind of flat top. But it really depends of the head design as well. The stock 50cc has a compression ratio 11:1, I have read that 47mm has indeed 9:1 compression and yet it is harder to start than the stock. If what you say is true: lower compression - the e-start will be easy vs higher compression - hard start... then I am confused .

Anyway is there a high torque starter in the market for AG?