70cc quad racing

If it's AC you are going for and you want it to be fun, you could also take a Stage6 Racing AC cylinder.

Doesn't cost the world, gives good power (about 17 hp) and is quite reliable.
 
and of course with bigger carb and all racing crank&filter will do so isn't it?but from what i read above the engine will get overheat(if it's AC) from that much hp and that's not something to play with :/
 
reefster said:
and of course with bigger carb and all racing crank&filter will do so isn't it?but from what i read above the engine will get overheat(if it's AC) from that much hp and that's not something to play with :/
Click to expand...

Untuned it won't overheat that fast if you use the right stuff and know how to set it up.

But this is offtopic, ask such questions in the topic you made.

This topic is about a 70cc quad.
 
Big B NRG said:
If it's AC you are going for and you want it to be fun, you could also take a Stage6 Racing AC cylinder.

Doesn't cost the world, gives good power (about 17 hp) and is quite reliable.
Click to expand...

Big B,
17HP would be a big improvement over what we had. You say the Stage6 it is more reliable? Why, does this cylinder turn less RPM's.
The Polini is around 17HP also isn't it?
Thanks again.
 
70cc quad racer said:
Big B,
17HP would be a big improvement over what we had. You say the Stage6 it is more reliable? Why, does this cylinder turn less RPM's.
The Polini is around 17HP also isn't it?
Thanks again.
Click to expand...

No I didn´t say it´s more reliable. But it has a good price/quality ratio. The Evo is just one step higher. It has bigger transfers and higher timings stock. But the price is 1,5 higher.

And with alittle tweak (future) it can produce a good 19 HP.

You are saying that you want to upgrade, but your daughter/son issn't ready for big power; then I think the Stage6 Racing cylinder is the best choice. It's fast enough, it's relative cheap and has great tuning potential for the future.

So like I said; The Stage6Racing cylinder has the best price/quality/fun ratio.
 
Big B NRG said:
No I didn´t say it´s more reliable. But it has a good price/quality ratio. The Evo is just one step higher. It has bigger transfers and higher timings stock. But the price is 1,5 higher.

And with alittle tweak (future) it can produce a good 19 HP.

You are saying that you want to upgrade, but your daughter/son issn't ready for big power; then I think the Stage6 Racing cylinder is the best choice. It's fast enough, it's relative cheap and has great tuning potential for the future.

So like I said; The Stage6Racing cylinder has the best price/quality/fun ratio.
Click to expand...

My mistake, I didn't mean to write that it's more reliable.
My son is ready for the performance, it is my daughter that is not ready. But when she is ready, I know what she will be getting:#

I am going with the Polini Evo 70. Now what do you suggest for the crank. I am looking for what will work with that cylinder not necessarily the most expensive. What are my options?
 
70cc quad racer said:
My mistake, I didn't mean to write that it's more reliable.
My son is ready for the performance, it is my daughter that is not ready. But when she is ready, I know what she will be getting:#

I am going with the Polini Evo 70. Now what do you suggest for the crank. I am looking for what will work with that cylinder not necessarily the most expensive. What are my options?
Click to expand...

Take the Power One crank. Those are Polini copies but don't have a Polini pricetag.

Also available at the webshops I mentioned above. Price is around 100 euro.
 
70cc quad racer said:
My mistake, I didn't mean to write that it's more reliable.
My son is ready for the performance, it is my daughter that is not ready. But when she is ready, I know what she will be getting:#

I am going with the Polini Evo 70. Now what do you suggest for the crank. I am looking for what will work with that cylinder not necessarily the most expensive. What are my options?
Click to expand...

my friend had the polini evo cylinder on his yamaha and he couldnt blow that thing up no matter how hard he tried. his bike was and still is 100% polini evo and that cylinder got him a top speed of over 80mph, 3 or more years of solid running. also his bike is a streetscooter and its always hot where we live, so i dont think you will have any trouble with that cylinder, they can take most anything you can do to it as long as you have good oil in it.
 
Were getting there. Which carb would work best with my set up. I have the Polini EVO A/C 70, Athena crank, case has been ported to match, V force 3 reeds/cage, Malossi adjustable clutch, Koso clutch bell, malossi kevlar belt, Koso pipe. I have a Keihin PE20 and PE24, I also have a OKO 24 flatside. Which of these will work best or do any of you have a better carb in mind. I know this is a scooter forum, can I post a picture of the quad as it progresses?
 
Yeah sure, post a picture, since it has a scooter engine, it's oke ;)

I advice you to use a carb that has a size between 24 and 28mm (keihin, Dell'Orto, Mikuni).

Do you also have some pix of the mods you made?
 
Big B,

No, I forgot to take pictures of the case. I would have been embarrassed to post it anyways. My job was not too clean for the first time. Here are some pictures. The first three pictures are of the 70cc Polini quad. The last picture is my daughters 90cc quad that you can help me build next :#
IMG_3970.jpg


IMG_3969.jpg


IMG_3971.jpg


IMG_3972.jpg
 
Big B,

You say 24 to 28. I was given advice of getting a PWK28 with power jet. Would that be a good combination.

I did get it running with the Keihin PE20 on it. It was a dog off the line but then pulled hard through the mid range. The top end wasn't there either. I'm hoping that this is because the carb is too small. Will the PWK28 make a big difference, or any other 24-28 carb. What are the effects of having a too small and too big carb?
 
70cc quad racer said:
Big B,

You say 24 to 28. I was given advice of getting a PWK28 with power jet. Would that be a good combination.

I did get it running with the Keihin PE20 on it. It was a dog off the line but then pulled hard through the mid range. The top end wasn't there either. I'm hoping that this is because the carb is too small. Will the PWK28 make a big difference, or any other 24-28 carb. What are the effects of having a too small and too big carb?
Click to expand...

A bigger carb gives more torque and with that some small power gain. Since it gives more torque, your top-end will be better and you will gain some power in the low and midrange RPM.

Having a carb that's too small will give powerloss and might cause failure to your cylinder. Allthough the 20mm carb issn't too small, I would recommand you change to a bigger carb.

I would recommand the PWK 28mm carb WITHOUT powerjet. Powerjet carbs are usefull on shifter bikes since they drop RPM at every gear change. They need to get thru that powercurve as fast as possible, with a little leaner mixture in the low and midrange RPM the gas respons / pick up is better. At high RPM the powerjet opens so the cylinder won't seize on lean mixture.

Since CVT engines only do one given RPM, there is no need for powerjet.

Edit; Nice color on your daughters quad! :winner:
 

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