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View Full Version : 70cc kits-worth it or not



riejurs2pro
04-20-2006, 04:56 PM
hi i am seriously considering wheather to kit a 70cc kit for my bike but there are several drawbacks that take my concern;
1. is the bike more likely to blow up if i get a 70s kit
2. will it effect the sale of my bike,buyers thinking it has been "ragged"
3. will i need to buy stronger bearings and get a strong crankshaft etc if i add a 70cc kit
any help on this querie would be really helpfull, and a ropugh price would be great too

many thanks

RiejuR51
04-20-2006, 04:59 PM
hi i am seriously considering wheather to kit a 70cc kit for my bike but there are several drawbacks that take my concern;
1. is the bike more likely to blow up if i get a 70s kit
2. will it effect the sale of my bike,buyers thinking it has been "ragged"

any help on this querie would be really helpfull, cheers plus rougly how much would this cost
well firstly, do you plan on keeping it more than a year, im guessing your 16 and gna move to something bigger at 17 or a car?

If you are getting something bigger, why not spend the money on that instead as your gonna keep it longer, if your getting a car then you might cosider it as it gets you some more spped, it wont give you great loads more power but its something. Any modding you do will effect the bike whatever way you look at it, the stock crank could probably take the 70cc kit tho

riejurs2pro
04-20-2006, 05:04 PM
cheers im still not entirely sure what to do,i have around 4 months untill im 17 where i am taking my car test along with the other test for bikes. since i have started riding my bike i have to say that there so much fun i would never not get a bigger bike in the future i am hopeing to get an aprilia rs125 or 250 not sure yet but i have to get a bike for sure.

RiejuR51
04-20-2006, 05:07 PM
cheers im still not entirely sure what to do,i have around 4 months untill im 17 where i am taking my car test along with the other test for bikes. since i have started riding my bike i have to say that there so much fun i would never not get a bigger bike in the future i am hopeing to get an aprilia rs125 or 250 not sure yet but i have to get a bike for sure.
well yur in the same position as me, well i dont want a car yet but, i dont really see the point in modding a 50 to get what another 10-15mph when you can get a 125 at 17

a 70cc kit isnt going to make ur 50/70 a pocket rocket

IM just gonna w8 till 17th bday comes round and i can jump on a 125 using me cbt, simple, then bout 6 months into it, take me restricted access test 2 get rid of the loser plates

RS_Patrick
04-20-2006, 07:56 PM
If you fit a "normal" 70cc kit the bike can hold out really long.
With "normal" i mean a Cast Iron Cilinder with a Maximum diameter of 48mm and a Round exhaust port, so No butterfly or W-exhaustports because these generaly have a powerband thats higher than 10.000rpm.

You can get a Cilinder like that for Under 90 euros / 60 pounds / 100 dollars.
It will give you a lot of extra power especaily with a bigger carb.
Keep in mind that you will need to change the springs in the clutch for stiffer ones but thats really easy to do.

Cilinders like a black 73,5cc, Red 75cc Top Performances, Airsal/Eurokit butterflyport 70cc, Polini W-port 75cc and more relative cheap cilinders like that are high performance cilinders that you can fit on the stock crankshaft but i dont think that it wil last longer 2500km/1500mi with cilinders like that.
For those cilinders and up your better of replacing the crankshaft too, unless you want to wait till the crankshaft does fail, but than its most likly that bit of the crankshaft and stuff end up ruining the cilinder.

:cheers:

williamr
04-21-2006, 03:39 AM
If you want to sell it when you're 17, don't do it.

Cops are starting to look at 50s and even dyno test them, so why risk a fine or getting the bike impounded for 4 months.

As for resale value, it will reduce the value if you intend to px through a dealer, although it might improve it a bit in a private sale if you can find some idiot willing to pay over the odds - you often can.

Rob

fast_tzr
04-21-2006, 10:37 AM
Cilinders like a black 73,5cc, Red 75cc Top Performances, Airsal/Eurokit butterflyport 70cc, Polini W-port 75cc and more relative cheap cilinders like that are high performance cilinders that you can fit on the stock crankshaft but i dont think that it wil last longer 2500km/1500mi with cilinders like that.
:cheers:

Alot of people have run the tp 73.5 with on a stock crank though without problems, another guy on here ran a red top for 12000km on the stock crank without probs. But how much power difference is there between the cheap 70cc cylinders and a black top?

RS_Patrick
04-21-2006, 12:24 PM
Alot of people have run the tp 73.5 with on a stock crank though without problems, another guy on here ran a red top for 12000km on the stock crank without probs. But how much power difference is there between the cheap 70cc cylinders and a black top?

He must have had a stock carburetor than on that Red Top, never seen anyone drive that long with a cilinder like that, you sure that the 12000 wasnt the over all distance on the bike and he only put the cilinder on there at like 8000km?

But anyway i can get 12hp out of a Black Top 73,5cc/49mm, managed to get 9,5 out of a cheap 70cc/48mm taiwan cilinder.
So lets say there is a 2hp difrence at least.
But the horse power is not so much the problem, its the way it responts to wen you open and close the throttle quick at more than 7000rpm, a Black Top will really give a "bang" in power wich causes a lot of stress on the Crankshaft, Clutch, Gearbox, Chain and Sprockeds and Rearwheelbearings, but the Crankshaft will suffer the most because of it having tospin the mass of the huge flywheel on there. After a few 1000km the stock crankshaft just rips off at the flywheel side.

This picture is from a Red Top after 2500km/1500mi with a 19mm carb and race exhaust. Ive seen Black Top kits do the same thing but they normaly last a bit longer.
Think D1mez had exactly the same thing happen to him.
Thats why i recoment a Doppler cranckshaft because its a lot thicker on that point so normal bearing wont fit but you get the special bearing with the crankshaft.

Woodinator
04-21-2006, 01:31 PM
Theres that picture again ... :rolleyes: lol:kidding:

RS_Patrick
04-21-2006, 05:03 PM
Theres that picture again ... :rolleyes: lol:kidding:

Hey, it's a nice picture! :p:

fast_tzr
04-22-2006, 05:13 AM
He must have had a stock carburetor than on that Red Top, never seen anyone drive that long with a cilinder like that, you sure that the 12000 wasnt the over all distance on the bike and he only put the cilinder on there at like 8000km?


No not sure, hes a dutch guy aswell, think he might be on your dutch aprilia forum, rs_power or something? About the black top, well 2hp is quite a difference when theres only 12 or so to play with, and numerous people such a youngun' d148l0 and sanchezz aswell have had them on stock cranks for 5000km or so without probs.

rs1banger
04-22-2006, 07:37 AM
my top75(red top) made my crank rumble within 1000miles of fitting

the kid i bought the top75 off sold it because his conrod had snapped and gone thru his bottom end
its the combination of the higher revs the bbk's porting will allow, the greater torque, and the higher reciprocating mass(bigger piston)

if you have a slower kit and/or use a low revving exhaust (arrow) you will get it to last longer,

but if you wanna get the moneys worth out of your cylinder kit (or even your bike), not to mention be able to do 90mph, get a crank....

IMO theres no point owning a bike with full fairing that looks like it should do 100mph+ and then only doing 60 or 70mph, you might just as well have bought a trail bike or a scooter

RS_Patrick
04-22-2006, 01:10 PM
No not sure, hes a dutch guy aswell, think he might be on your dutch aprilia forum, rs_power or something? About the black top, well 2hp is quite a difference when theres only 12 or so to play with, and numerous people such a youngun' d148l0 and sanchezz aswell have had them on stock cranks for 5000km or so without probs.

RS_Power is a friend of mine and he doesnt have the Red Top anymore and anyway he did not drive 12000km with it. im not sure if he even had a stock crankshaft in there.

And i agrea with rs1banger :p:

fast_tzr
04-22-2006, 01:40 PM
Well I'm only quoting what he said here http://www.apriliaforum.com/forums/showthread.php?t=15458&page=8

RS_Patrick
04-22-2006, 03:19 PM
Thats not what he told me, and the other guy is right with the 3000km, if you fit a Red Top, 19mm+ carb and fast exhaust.
Believe me i never seen any setup like trhat last longer than 3000km with out the stock shaft breaking.

RiejuR51
04-22-2006, 03:25 PM
Patrick, i still cant work out why you dont spend money on a bigger bike? surely it must be worth it, with the amount of money your spending on the 50's, it must of made enough to put money on a bigger bike. and if its the racing/motogp style you like, why not the rs250?

RS_Patrick
04-22-2006, 04:46 PM
Patrick, i still cant work out why you dont spend money on a bigger bike? surely it must be worth it, with the amount of money your spending on the 50's, it must of made enough to put money on a bigger bike. and if its the racing/motogp style you like, why not the rs250?

No, it did not cost that much, remember i did not pay the retail price of the parts but the wholesale price so it was a lot cheaper, And in anycase the bike costs 3000 euro retail, and the parts together were less than 750 euro retail so that makes 3750 euro for the bike in retail value.
You cant even get a New RS125 for that money.
Its verry fast in acceleration and has a really good handeling, for what i would use a bike for its just perfect, i dont need to drive great distances, mostly i just drive it in and out of town, and wen i take it for a spin i take it for a ride along the old dike and river witch are verry twisty roads on wich a RS50 is in its element.

riejurs2pro
04-22-2006, 05:41 PM
roughly how long do u think a standard metrakit 70cc kit would last on the bike i have 5 months left of driving and hope not to repace major parts on the bike during that time. do u think it will be fine to just go for it-the need for speed is definatly there at the mo my bike sruggles to reach 70mph what roughly will the top end increase be -cheers for the help

RS_Patrick
04-22-2006, 07:52 PM
a cheap Cast Iron metrakit should be fine.
Should give you no problem, but dont forget to fit stiffer reeds too.

fast_tzr
04-23-2006, 04:22 AM
Right then so metrakit over dr73.5 then?

RS_Patrick
04-23-2006, 10:02 AM
Right then so metrakit over dr73.5 then?
If its a cast iron Metrakit with a normal exhaust port and no bigger than 48mm he should be fine.
The DR 73,5 is the same cilinder as the Black Top 73,5cc, DR = Top Performances = Motorparts = Minareli