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barrels, variators and tuning
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Posted by: ukguy

being in from the uk there is a limited amount of information about kids quads and tuning so im trying to get a little information if possible.

we currently run pro sharks which i think you call apex and are in 3rd in our kids version of national but one series uses mostly modified bikes and he wanted a go so we fitted a poted barrel, carb ex, etc etc and the bike goes ok but we want a bit more as the bike doesnt stay with the leading riders and you can see the power differances.

with regards to the barrels are the aftermarket barrels already ported or tuned you buy a kit and fit the following and you will get x amount of power or does someone have to port the barrels etc, if so when the barrels are ported is it just the exhaust port that is widened (very similar to mine) or is work done on the inlet and transfer ports, is any work carried out to the casing at all or are they just left as is, would the head also be tuned i heard about squish etc but dont understand what they are refering to

with regards to variators and angles can any one explain what the differing angle will do in relation to rev range, pick up top spead and gearing, can you also alter the angle of the rear pulleys to give better results, and what about the torqu spring i changed mine but if any one can can tell me what this controls and its effectiveness on the bike and its running that would be great.

if some of the things i have said seem to confuse you please be patiant there is a lot to make sense of to get the best from the bike and i`m just trying to get information to make the best informed choice of what route to go down to get a competative bike, why not take it to a shop some one might say but the only problem is the shop isnt going to be at the trackside if or when it breaks down so the knowledge can be put to good use.

thanks

Posted by: jetmedic

Depends on who does the porting on your cylinder. A full race port job should have everything you mentioned re-worked. What size motor are you using? There are cylinders you can bolt on and go fast. If your running a 70cc I can recommend a cyl. made in Spain that is super fast.
Variators- Depends how many rpm's your motor is turning. A race motor can use lighter rollers weights than a stock motor.
Rear torque spring- Depends when you want your pully to shift.
All of this depends on your motor. Dont confuse a slow bike as the motor being the issue. Its all in the clutch set-up. You will be pulling out your hair getting this thing tuned. Be patient a read the abundance of replies you get to this thread and use the knowledge that will be passed on to you.

Posted by: wrhracing

Are the ProSharks coming with a race chamber or are you limited to the old style stock quiet exhaust system?

Posted by: ukguy

no the exhausts are race spec over here we have an import called RMX which comes with bigger car exhaust extended axle and a arms but the barrels are not worked or reeds variators etc

Posted by: wrhracing

Current H2O 90cc cylinders, need transfer and exhaust port change for optimum performance. A simple widening of the exhaust is an attempt at a performance increase, which would work a little but not near enough.
Squish is a measurement of distance between the piston dome and head at it's closest point.
case mods can become extensive. some small mods pay off, especially if it will increase transfer flow.

Posted by: ukguy

are there any barrel options available that are tuned beyond the standard ones and have had the transfers and exhausts done, i`m not happy just using the one i have with the exhaust port done which like you say does increase the bike noticabily butnot enough to compete at the sharp end.

do you have any suggestions or ideas with regards as to where to get the barrel piston and head that has been exstensively modified

thanks

Posted by: ukguy

it also has the ater cooling system removed and has air cooled barrel and head

Posted by: wrhracing

Extensive modifications are best when applied to a 52mm or 53mm cylinder bore. Liners are thicker which allow for more stability.
One ring pistons or just using one ring is sugested for the "Sharpest End" race ported cylinders.
However, if two rings is your ticket those can be made to fly also.
I use the two ring approach on my sons apex..

Knowing the stroke would be important to anyone "in the know" before designing the port configuration . As would Rider capacity and density.

Size carb
A picture of the exhaust pipe, or discription to define the manufacture origin.

The water cooled barrels I use generally have better transfer arrangements then most aircooled that are readily available.

For air-cooled I use aluminum cylinders for any 52mm or 53mm bore which work quite well after having the transfers and exhaust "Put" where they belong.

Posted by: wrhracing

quote:
Originally posted by ukguy

do you have any suggestions or ideas with regards as to where to get the barrel piston and head that has been exstensively modified

thanks

Sorry.. Rule # 5