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Just installed a set of thundershift arms on an '02 MXZ 800 X. I really like the way they pull. Smooooth. The problem I'm having is that when I pin it, the RPM's shoot right to 8000 (perfect, right?), but then as the track starts to hook the RPM's drop to about 7400-7500 RPM's, then in the next 100 ft or so they climb right back to 8000 and stay there for the duration. I didn't have time to move weights around much and didn't figure out the magic to it. I have 10gm pins, 8.4gms in the first hole, and 6.4 gms in the bottom hole. Running a 52/46 helix (stock is 47/44). Not remembering right now what the spring is. I'll locate it later.

Anyone have the secret for getting these dialed in? I'm thinking too much helix for the start. Or I just am not moving the weight around right.
 

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idooski,

To much helix, 52-46 works good on the old style clutch but not on the new RER driven.  Go back to your stock helix and your problems will be solved.

GLH
 

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Thanks GLH! I understand that this is the helix that is sold with one of the available kits from Canada.  Are you sure that the stock helix is the way to go or is there a better one? The spring I'm using is a 195/295, which I'm told is the spring he recommends also. Would I have to go back to the stock spring also?

The 46 angle on top seems to be about perfect. I was thinking that a 50/46 would work very well. Are there different springs available for the RER secondary? Do you know what the rate is on the stock spring? I was thinking that a little stiffer spring on the secondary would help the primary sense the load a little better. Does this make any sense?

One thing that I really like about this set-up is that the primary is running very cool. The secondary is quite warm, but not hot.

Thanks again for your help!!
 

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I have the same problem with my 2001 800 using heelclicker setup. Running a 48-42 helix. Hits 8000 rpm's but when it starts to hook up it drops to 7200-7400 rpm's but quickly gains it back. Running 25-43 gearing-#21 lbs on driven clutch. I don't thing the 48-42 is to much.
 

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52/46 is definetely not too much helix for the RER, the problem I see here is that you are spining out of the hole which overshifts the clutches so that when the track stops spinning and finally hooks up it pulls the rpm out of the motor because the clutches are in to high of a ratio. The problem the way you have described it is a traction problem not a clutching problem.
 

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Discussion Starter #6
I didn't come to you with this problem Bill because I bought the helix and spring second hand and figured that you were probably busy enough with your paying customers, but if you can help, I would really appreciate it.

I agree with the fact that there was a traction problem where I was running to tune, but when the track starts to hook, the primary should be getting a signal from the secondary to back off a little and get the RPM's up. This is not a drag sled. The traction is never going to be the same. If I try to dig my self out of a 4' drift, it won't even get to 8000. It stops at about 7600 and stays there.

I believe the secondary spring needs to be a little stronger, but no one seems to know or want to tell what is in it now. Do you have different springs for the secondary, Bill?

Thanks!!
 

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Your issue is traction as described.  However you can avoid that by not loading so hard.  There are different springs available from different places.  As far as the HC go I have a setup that does not shift to fast for most conditions.  When a traction issue is encountered you must work with it not against it.  The same reason 280 ramps don't work in the 800, there is lack of traction.  

idooski,

I run the stock spring in the primary but I am not the expert on thundershift  arms.  My sled runs very good but there are some other items on it.  I would use the stock helix because that is what I used with great luck

GLH
 
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