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Discussion Starter · #1 ·
I have a ZR 440 that is currently engaging at 5500rpm and holding 8500 rpm all the way thru. I would like to keep the engagement rpm but raise the operating rpm to between 9000 and 9200 to perform along with a new set of twin pipes. I have three sets of weights which I can work on the current ones are 46g I have 45g and 47g How much weight do I need to get rid of in theory to gain 700 rpm and where is the best spot heel or toe or complete surface?
 

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Discussion Starter · #2 ·
Ok the original helix was 53 but I have a Blackmagic BM11 helix and the angles are secret they tell me. I currently have a Blackmagic clutch kit for a stock zr 440 installed I just added Blackmagic twin pipes which should run a 9200rpm for max hp instead of 85-8600rpm now. They do sell a clutch kit for this setup but I don't want to buy it from them because there not helpful at all. I already have one of their clutch kits and they told me three of my current parts will work. But they won't tell me if it's the helix, weights, driven spring or drive spring that I need to buy. So I need to figure this out myself. Right now it runs just as good as before the pipes but I believe if I can just change the running rpm to 9200 and keep the engagement the same it will be even better. I don't think changing the helix is the right move maybe a stiffer spring but not by much is does run really good now.
 

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700 RPM's is A LOT to grind also..yikes..

I think you'd be time and $$ way ahead to be nice on the phone and figure out with them what you need to complete the kit.
 

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<div class='quotetop'>QUOTE (lincoln9 @ Jan 4 2007, 11:25 AM) <{POST_SNAPBACK}></div>
Ok the original helix was 53 but I have a Blackmagic BM11 helix and the angles are secret they tell me. I currently have a Blackmagic clutch kit for a stock zr 440 installed I just added Blackmagic twin pipes which should run a 9200rpm for max hp instead of 85-8600rpm now. They do sell a clutch kit for this setup but I don't want to buy it from them because there not helpful at all. I already have one of their clutch kits and they told me three of my current parts will work. But they won't tell me if it's the helix, weights, driven spring or drive spring that I need to buy. So I need to figure this out myself. Right now it runs just as good as before the pipes but I believe if I can just change the running rpm to 9200 and keep the engagement the same it will be even better. I don't think changing the helix is the right move maybe a stiffer spring but not by much is does run really good now.[/b]
Contact "auggie" He's a member on this site. He was the Black Magic clutch kit designer for Tim Berg when he owned it. Im sure he can get you REAL close without to much wasted time and money. My guesstimate on the flyweights would be the AC stock profile 40.5g The stock primary spring for your sled has almost a 300# finish rate. (yellow/white) The AC Yellow/green Has a finish rate of around 265#. The start rates of both springs are within 10# of each other, so your engagement might increase slightly. (100rpm or so)
BTW...The BM-11 helix is the same as the stock helix that comes from AC in the ZR-8. FWIW...
 

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Discussion Starter · #8 ·
Ok, I talked to a guy name Rory he told me to add Blackmagic orange spring 70-0018 rates 147 297 and purchase three 44gram weights BM part 70-2044 and change the secondary spring to 70-1331 driven spring Black Red Bm and keep the the BM 11 helix. Does this sound right to anybody?
My current setup is:
Drive spring BM part no70-1279 black green rates are 117 295
46gram weights BM part no 70-1339 these are actually stock arctic cat weights they come with the BM clutch kit
BM 11 helix
Stock yellow driven spring which wasn't in the kit but the instruction said to use it. There was no driven spring included with kit.
 

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Looks like a much stiffer secondary spring. Should definitely raise RPM, but the changes to primary have me wondering. Would seem both the change in weights and spring would each raise engagement RPM, especially if a notched weight is used, which I beleive those BM weights are. On my sled, engagement notch is worth 500 rpm, 20lbs in spring force is worth about 200-250 rpm. I suppose yours could vary there.

If it were me, I'd start with what Rory suggested and see how it works I guess but for me I like more backshift then a 55/53 offers but I've never run that spring/helix combo. I also have a BM HeartThrob kit for my 97 ZR 440 and my kit came with BM Orange and 47 notched weights and same BM 11 helix. I actually liked this kit for a "trail" kit but felt it lacked a little on backshift. It did improve my mpg quite abit over my D&D kit, which had my motor spinning 8800 RPM.

If you get around to testing this setup I'd be interested to hear from you on how it affects your MPG on the trails. On my sled higher peak RPM's seem to kill my mpg. Just wondering what happens with the twin pipes at 9200. I've debated back and forth alot on buying these pipes and actually did order them once but they were out of stock and I never did order again. So, it would be nice to hear from somebody that has actually checked them out.

If you are shooting more for as much power as you can get and don't care so much about MPG, slap on a set of 38mm flatslide carbs. The difference is huge and I bet with those twin pipes it would be a major gain. What year is your sled?
 

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Discussion Starter · #11 ·
The timing is to stay stock with twin pipes. I have the installation instruction on my computer and could email them to you if you want. I got this dialed in today thanks to blackmagic tech they turned out to be extremely helpful and told me exactly what to purchase from a Cat dealer to get this done. Luckly my dealer had every part I needed and my sled is now running faster than ever before. It holds a steady 9200rpm now engages about 5700 and I did a long lake run today it got upto 9500rpm Now I can spend my days riding instead of tuning. Until maybe I purchase those 38 flat slide you are talking about. Do you think my clutches would need many changes if I upgraded to 38's and the 99' airbox you suggested? I remember Blackmagic's website 2 or 3 years ago had something about the ZR440 with the twin pipes and 38mm carbs but I don't really remember what it said. Anyways I'll start a new topic if I do more to this in the future.
 

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You're going to like those pipes. Rockerdude
 
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