4wheelfurry
Posts: 712
Joined: 10/31/2003
From: Deep South Louisiana
Status: offline
|
I have had quite a few questions concerning clutching for drag racing lately, it seems as though drag racing is getting popular with this forum so I want to try to provide some insight to the theory in tuning for drags.
First thing you want to do is get the Dalton override clutch cover (or machine your stock) for the primary. This will lighten up the primary and give you 1-2mph on top end. Only drawback is it takes the KEBC out of operation but it is most useful for drag racing. If you are or know someone who is a machinist then you need to do the "primary clutch mod" this is outlined on kissofdeath website (he is on HL forums) This will also give you another 1-2mph on top. There are also professionals who do this mod but it can get a little costly from them. I did mine myself.
The secondary spring: The theory is the stronger the secondary the tighter it holds the belt. This is great for mudding but not for drags, to much belt tension drag ultimately takes away hp and really effects top end. In the Prairie 650/700's the stock spring is a great drag spring, the Brutes were upgraded with a heaver spring and really can stand to go back down, this will lessen belt drag and increase pickup. . In drag racing you don't need to hold the belt extremely tight because it is only under rider/bike weight strain. Also the belt is being pulled in by the primary so hard at WOT it usually will not slip.
Primary spring and weights really go hand in hand, they work as: the spring pushes against the weights. As the clutch spins up the weights fly outward and force the spring to collapse inwards "shifting" the belt upwards the pulley. So a heaver spring will cause a slower shift (more RPM to shiftout) and lighter spring will cause a faster shift (less RPM to shiftout). NOW heaver weight will cause a faster shift (less RPM) and lighter weight causes a slower shift (more RPM).
A primary spring has 2 numbers, ie: 1/170... The first number is stall meaning this is where the engine RPM will be when it begins moving, the second number is shiftout meaning this is where the RPM will be when the clutch maxes out or "shifts out". After shift out it will still increase RPM until the engine hits the rev-limiter or quits revving, this is where people get confused - the clutch shifts out quite quickly compared to the engines overall abilities. The primary can shift out anywhere from 200ft to 500ft depending on primary spring and weights. To high stall and you break traction and waste low end torque, to high shiftout and you over-rev the engine wasting its potential peak power.
The idea is to get the upshift in the ideal RPM range where your engine makes its most HP. The Kawie clutch setup has 4 weights, they can be mismatched ie: 2 lighter opposite of each other and 2 heaver opposite of each other, or they can all match in weight. Most people just fool with the primary spring and then if needed fine tune with weights. I will say there is no one spring for all situations, long drag courses and short drags, asphalt and dirt, wet and dry... I have 2 springs I like to run depending on if I am on dirt or asphalt.
All engines are different in how they make power and each time you add a mod you change the peak output and where it is in the RPM range so you will have to experiment with a few springs and check your findings (race someone else each time or time your runs). For example I once had a spring that was unreal acceleration but I switched tires (droped dia by 1.5") and lost 5 bike lengths because it overrevved badly. Basically the ultimate goal is to hold the "upshift" at peak HP making RPM for the duration of shift until it is shifted out, this is all done with the primary spring/weight combo AND hold the belt with the secondary as light as possible without slipping it. Hope this helps some of you guys...
_____________________________
BF750 - A few mods
Prairie650 - A few more
"TEAM SOUTHERN SWAMP BOYZ"
|
Inbox 
Printable Version
Clutch setup drag racing, what ya need to know - 
New Messages
No New Messages
Hot Topic w/ New Messages
Hot Topic w/o New Messages
Locked w/ New Messages
Locked w/o New Messages
Post New Thread
