Well, I am having a problem with my sons 90. It currently has a Hetricks pipe, hi rev cdi, oil injection removed, jetted, K&N clamp on, clutch kit (blue springs in front and red torsion in back) and the variator weights that Hetricks sent (not sure what weight they are). when it catches the powerband, it screams, but, I have lost quite a bit on take off. The problem is that if there is any type of incline on take off, it literally "wont "go. On flats, it is slow off start, but, get powerband within a couple of seconds and screams, but, even on a slight 15-20 percent grade, it will not take off. When the guy that helped me put in the cdi was checking it, he did put it up on a stand and rev the hell out of it, I have read on this forum of the possibility of the latches on the clutch flippng over if there is no resistence (like if one raises the rear and revs it as was done). Just wondering, any info/help on this would be greatly appreciated since, I am quite frustrated. I have a big bore kit which I have not installed because I wanted to get a bigger carb first, plus, I want to fix this problem. There is no more than 5 hours on this bike/clutch, so, I wouldn't think that is is burnt out. My sons friend who has a little Raptor 80, his pred was always quicker/faster from start to finish when stock, not with the upgrades, the Raptor is quicker off start for about 30-40 feet, then the Pred litterally blows by him as if he was almost stopped, but, I just don't think that it should have so much difficulty from take off as it is now. It is as if it has no torque untill it catches the powerband. Shouldn't it rev up to the spring limit and then just start spinning the tires and take off as soon as that clutch engages even on a slight inlcine?

 

I am pretty new to performace mods, so someone else in the forum may have a different opinion. It seems to me that your spring combination on the clutch is to stiff, causing your stall speed to be to high. This will result in the loss of bottom end performance that you are discribing. There is a great article on clutch tunnig here Clutch Tunning Basics. I wish it was as easy as just throwing a set of springs and roller weights in and off the bike goes, however I myself have spent countless hours (due to the fact that a Dyno was not available) in pursuit of the perfect combination. Try putting a softer torque driver spring in and see what you get, and then work from there. Once you get the clutch dialed in then you can play with the roller weight combination. Also you can give Rick Hetrick a call, he will be glad to offer you advice on this...

Hope this helps

 

Hi,

First, give Hetrick a call to find out what roller weights should be. Most aftermarket rollers have the weight printed on the side of roller. Check to be sure they sent the correct ones.

It could be the variator is stuck open or the weights are too heavy. Heavy weights cause the variator to open too quickly, similar to starting your car in 4th gear. If Hetrick set up the clutch, he would have matched the springs to the weights so this is unlikey. The blue springs should allow the pipe to come on before you leave the line (a good thing) , not down the track. If the pipe comes on down the track, I'm lead to think the variator is stuck open (I saw this happen at a race two weekends ago when a boy blipped the throttle as he shut down the engine).

You may want to try this: lift the rear wheels off the ground and slowly apply throttle. If the wheels begin to spin right away, then the problem is in the centrifigal clutch, ie, little springs too weak, stretched, etc.. With the wheels on the ground, it should take quite a bit of RPM before the bike wants to move.

Hope this helps.

 

Thank you for the excellent tips, I will attempt to troubleshoot it this weekend as soon as I have a little time, and will post the results.

 

You need to use the stiffest clutch springs (red) and drill the heck out of the clutch to lighten it up. We had the same problem, then drilled like crazy and it fixed the problem. It rips now!

 

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Here are the instructions for drilling the clutch from Hetricks website. I haven't tried it yet myself, but I've been told it really helps the mini Pred.
Drilling Instructions

 

Exactly, though on the Pred you may want to drill more.