Quick Primary Spring Question - Clutching a 700
- Thread starter 94fordguy
- Start date
So I've been giving this some thought the last few days and I really want to get up a few more RPM to get this sucker ripping the way it should be with all my other mods....
I'm running about 8150 RPM with 60g EPI weights and was thinking about dropping to 58g to get up to peak performance, but haven't been able to decide on what to get... 10-58s, 58g EPI, or 62g MTX adjustables. I have no experience with the MTX weights, but according to their site, the 4g difference should put me where I want to be I would think.
How do the MTX compare in shift and performance to the Belly Busters? I like the EPI shifting performance, but I don't like shelling out that much money and not being able to peak my RPM because my clutch is still too heavy.
My 900 is running 7550 peak whereas rec'd is 7400 and I like how it runs being just a touch high, that way it can 'fall back' onto the peak 7400 power-band when there's a high demand situation and it doesn't struggle to get up to peak either. I'd really like to get the 700 pulling 8450 consistently on the climbs as it was pulling really nicely at that speed early last season.
I'm running about 8150 RPM with 60g EPI weights and was thinking about dropping to 58g to get up to peak performance, but haven't been able to decide on what to get... 10-58s, 58g EPI, or 62g MTX adjustables. I have no experience with the MTX weights, but according to their site, the 4g difference should put me where I want to be I would think.
How do the MTX compare in shift and performance to the Belly Busters? I like the EPI shifting performance, but I don't like shelling out that much money and not being able to peak my RPM because my clutch is still too heavy.
My 900 is running 7550 peak whereas rec'd is 7400 and I like how it runs being just a touch high, that way it can 'fall back' onto the peak 7400 power-band when there's a high demand situation and it doesn't struggle to get up to peak either. I'd really like to get the 700 pulling 8450 consistently on the climbs as it was pulling really nicely at that speed early last season.
Well I went ahead and ordered some 58g Belly Busters from Carl's and got them installed, but have not had the sled out for a ride yet. I am planning on taking it out next weekend as there is no significant new snow forecast and the 900 gets a little hot on the low snow conditions getting to the good stuff. I'll report back on how the new 58g BB's perform then.
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volcano buster
Well-known member
Try a spring with a 140 - 340 rate. I had a Black/Pink (120-340) and fought top rpms like you are. I installed a Blue/Pink (140-340) and rode it yesterday. Boy howdy, with the 10-62 weights at 5800' it would run to 8300 then settle down to 8250. At 3900' I was hitting 8500', but I don't do much riding at that elevation besides to and from the truck.
Springs are cheaper than weights so see if you can round one up to try.
I've got a theory on why it works, but no one on here would chime in. I think most of the true gear heads have wandered off...
Springs are cheaper than weights so see if you can round one up to try.
I've got a theory on why it works, but no one on here would chime in. I think most of the true gear heads have wandered off...
I've already got the new weights installed, gonna see how this setup does before I change anything else. I changed from a black 140/330 spring to a black/green 120/340 spring to drop my engagement down as I hated it slamming the clutch so often riding slow stop and go through the trees. I really don't want to go back to a 140 initial load spring if I don't have to as the sled doesn't seem bothered in the least by the lower engagement (4K RPM). With the old spring I was engaging at 44-4500 and that's where I spend half my day at when riding my 900 in the trees, lol.
If I can't get what I want with these weights then I will be looking into spring rates a lot closer.
If I can't get what I want with these weights then I will be looking into spring rates a lot closer.
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rbanan
Well-known member
I would spend my money on a PCV or PVIII. you can get em used...
The topend on the 08 mapping is way too rich, don't know if they changed anything to the 09. And i would not aim at 8400 as the horsies drops after 8200 with the SLP single. I run my sled with 10-66 Blue/pink SLP primary and Team black/white 160/260 19-41 at sealevel up to about 3000 ft. Put on some weight and you will have a much smoother engagement + you can use the 140 primary.
The topend on the 08 mapping is way too rich, don't know if they changed anything to the 09. And i would not aim at 8400 as the horsies drops after 8200 with the SLP single. I run my sled with 10-66 Blue/pink SLP primary and Team black/white 160/260 19-41 at sealevel up to about 3000 ft. Put on some weight and you will have a much smoother engagement + you can use the 140 primary.
Target RPM achieved!
Well I finally got a chance to ride the 700 this weekend with the new 58g BB's in it. Conditions were good for climbing, about 14-18" fresh light powder on top of a crust with decently packed snow underneath at the climb. Track speed was a consistent 38-39 MPH and RPM (though I was paying more attention to the trees and trenches I was dodging) seemed to be between 8250-8400, pretty much where I was targeting for. I think that I'm pretty happy with the performance of the sled as it is now, though I will continue to monitor when I get on some less technical climbs. I was actually surprised that I was able to make it out the top of the hill on my 2nd attempt in a decently fresh line, I thought it would take some more effort than it did.
I still miss the torque of the 900 when I'm making a pull with the 7, but I'd say that the 700 is a 'good little sled'
Well I finally got a chance to ride the 700 this weekend with the new 58g BB's in it. Conditions were good for climbing, about 14-18" fresh light powder on top of a crust with decently packed snow underneath at the climb. Track speed was a consistent 38-39 MPH and RPM (though I was paying more attention to the trees and trenches I was dodging) seemed to be between 8250-8400, pretty much where I was targeting for. I think that I'm pretty happy with the performance of the sled as it is now, though I will continue to monitor when I get on some less technical climbs. I was actually surprised that I was able to make it out the top of the hill on my 2nd attempt in a decently fresh line, I thought it would take some more effort than it did.
I still miss the torque of the 900 when I'm making a pull with the 7, but I'd say that the 700 is a 'good little sled'
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volcano buster
Well-known member
How did you decide that the 58 Belly Busters were the correct weight?
It had 10-60s in it with the stock black spring and was pulling good when everything was new. I switched to the lower engagement black/green and tried 60 gram BBs, really liked how it shifted but was lacking peak RPM, so I threw in the 58s and I seem to be back up where I want to be on my peak rpm.
I'm by NO means a clutching guru at all, basically just trial and error with a little bit of help from you guys on here.
I may try the other track in my helix just to see what it does, but other than that I am just going to monitor things for a while and see what happens over a few more rides.
P.S. All the climbing I did yesterday and typically do is around 6500-7,000 ft.
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Well I've got a few miles on this new setup now and I'm thinking the 58's may have been a mistake. This past weekend we were riding spring snow and any time that I got the skis up a bit I promptly hit the rev limiter (must have hit it 15 times throughout the day). I think I'm gonna change back to the 60s and try a fresh Black 140-330 primary spring instead of the black/green 120-340 I have in it now. I'm starting to think the 340 was too stiff for my application.
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volcano buster
Well-known member
I am running 10-62's in my 660, that is why I was asking how you came to find the 58's to be your magic bullet. I would agree that the 58's would likely hit the rev limiter quicker.
One thing I have come to notice is the "rate" of the spring between the two values versus the two numbers by themselves. For example, if you are compressing the spring fully between these two values to make it easiest to understand, you would have a rate of: 340-120=220#/inch (assuming 1" of travel, again to make the math easy). Now, change to a 330-140=190#/inch. You will need less weight to push that spring to max compression. I'm thinking that you have less primary spring pressure to force the weights back over to backshift. I'm not sure, but I think you could add some secondary spring pressure to counteract this phenomenon but I haven't gotten that far yet. I'm still trying to figure out what the force generated by a given weight is at lets say 8000 rpms, then what combined spring pressure to counteract it.
One thing I have come to notice is the "rate" of the spring between the two values versus the two numbers by themselves. For example, if you are compressing the spring fully between these two values to make it easiest to understand, you would have a rate of: 340-120=220#/inch (assuming 1" of travel, again to make the math easy). Now, change to a 330-140=190#/inch. You will need less weight to push that spring to max compression. I'm thinking that you have less primary spring pressure to force the weights back over to backshift. I'm not sure, but I think you could add some secondary spring pressure to counteract this phenomenon but I haven't gotten that far yet. I'm still trying to figure out what the force generated by a given weight is at lets say 8000 rpms, then what combined spring pressure to counteract it.
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rbanan
Well-known member
Hey Volcano. Check out this information regarding the force of weights at a given rpm. http://heelclickerclutching.com/tech-info/pdf/HC-2-Speed-Pol-ACat.pdf
The pressure changes as the outshift changes. You want to be at 0.7-1.0 when your in the loose stuff.
Dont forget to look at your gearing when you switch weights. That is the most important thing for riding deepsnow.
The pressure changes as the outshift changes. You want to be at 0.7-1.0 when your in the loose stuff.
Dont forget to look at your gearing when you switch weights. That is the most important thing for riding deepsnow.
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volcano buster
Well-known member
Thanks, I'll check that out.
I was thinking again yesterday that the change in gearing and a change in helix might be complimentary as well as the "load" expressed by the track is altered by the changing of the gearing, therefore changing the manners of the helix to upshift and backshift.
I'm still thinking on this.
I was thinking again yesterday that the change in gearing and a change in helix might be complimentary as well as the "load" expressed by the track is altered by the changing of the gearing, therefore changing the manners of the helix to upshift and backshift.
I'm still thinking on this.
So last time out I changed to an SLP blue/pink primary spring after doing some more searching on here and that seemed to help the 'feel' of the sled. We have 1 more trip to go next weekend and I just installed a fresh stock 155-222 secondary spring as the stock spring had 1200 miles on it. The new secondary spring I installed today was about 1/4" taller and noticeably stiffer than the one that was in there.... I'm looking forward to seeing how the setup works now. Next fall I may try the helix in the other position... I have been running it in the 60-40.40 position all year and haven't tried the other track.
I'll probably take out these new springs after this last ride and just throw the old ones in it over the summer so that I don't loose any spring tension. It will be handy to have something in it though incase I need to move it.
I'll probably take out these new springs after this last ride and just throw the old ones in it over the summer so that I don't loose any spring tension. It will be handy to have something in it though incase I need to move it.
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