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Thread: Valve Spring pressure

  1. #1
    apriliaforum expert jess67's Avatar
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    Valve Spring pressure

    Hey fellas, I am looking at different valve springs for an upcoming rebuild. In the manual it shows the spring height measurement so I am good with that. What I need is the spring psi measurement, closed, and open at .450" lift. I have had a search but didn't come up with anything. Thanks.

  2. #2
    apriliaforum expert Gabro's Avatar
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    i think there's no such spec in any manual... best way to check is you to buy a new spring and measure it for reference?
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  3. #3
    apriliaforum expert jess67's Avatar
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    Thanks Gabro, this is the kit I was looking at for the Can Am ds450.

    http://shop.kpmivalvetrain.com/p/rac...008-2015?pp=24

    After reading on the ds450 forum, I was under the impression that these springs are a direct replacement but after looking in the specifications, they have spacers under the inlet valve springs. They give installed height so I will get my engine builder to take some measurements of the stock heads and see if they are compatible.
    The whole kit is reported as being 40% lighter than stock and the spring pressure is impressive compared to other a/market kits I was looking at.

    Also I found some valves, Kibblewhite do a stainless valve but they still have the 3 ring collets like the OEM, there is a small company called BCSpowersports who make their own, very nice stainless valves and single groove colletts.
    All the ds450 valves come in 38mm inlet including oversize but the exhaust are 31mm and oversize to 32mm but no 33mm for Gen2 compatible. I will contact them and see if they will make 33mm.

    https://www.bcspowersports.com/bcs-p...-intake-valve/

  4. #4
    apriliaforum expert Gabro's Avatar
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    truly that's noting wrong with stock valve train BUT the welded valve tulip. it's only weak point. i've never had problems with 3 groves collets, not valve springs over the years, just snapped valve tulips.

    anyway, our motors finish their healty pulling at about 10k rpm, there's no need to use any more rpm past 11k
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  5. #5
    apriliaforum expert jess67's Avatar
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    I was originally looking for a set of valves and came across the valve springs. Going through lots of threads I can't recall reading of any spring assembly failures and only a couple of valve failures so chances are minimal for failure I agree. With my build and money invested so far, I still was still wanting some better stainless valves probably because I just want to bulletproof the motor for peace of mind. I haven't contacted the valve suppliers to find out any weights compared to OEM valves which are hollow stem - and was assuming the afternarket valves being solid, maybe a little heavier. I was going to use the spring kit to offset the weight difference.
    The 3 groove colletts are probably fine for our application but after reading on the ds450 forum that is the failure point for the OEM valves for them - aftermarket solid valves with 3 groove colletts work well and their best solution is aftermarket with single groove collette.
    I watched a couple of ds450 videos and you can understand why they get failures - just banging off the rev limiter for hours on end.

  6. #6
    apriliaforum expert jess67's Avatar
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    I found a valve spring kit for US$100, so I decided to check it out and even if I don't use the springs(which are chrome silicon wire steel) the spring retainers(titanium) might be a good addition to drop some valve train weight. The springs measured up the same dimensions as OEM and the retainers fit the valve and colletts the same as OEM so all good there. Here are the weights compared to OEM:

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    OEM
    Click image for larger version. 

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    Kibblewhite saving 25grams per valve, 200grams from the whole valve train
    Click image for larger version. 

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    Nice 11gram saving on the retainers alone
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    I priced up the same parts in the kit as OEM US$304. Average kit price was US$170 and you need x2. Also if you are using them with RSV or RSVR cams with higher lift, don't use the spacers they provide as the ds450 has lower lift cams.

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