valve springs ??? - Yamaha Raptor Forum
 
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post #1 of 8 (permalink) Old 07-18-2012, 10:43 AM Thread Starter
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valve springs ???

Hey all.. A while back i was adjusting my valve lash on the 660 and I'm thinking about installing a hcII and thought about when we use to kart race.. Some of our motors ran exhaust valve spring on the intake valve, so the motor had all exhaust springs in it..The benefit was that the stiffer(and slighty taller) exhaust springs would control valve float at high RPM..Has anyone ever tried this instead of aftermarket springs...

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post #2 of 8 (permalink) Old 07-18-2012, 12:38 PM
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The extra 1.75mm or so might be something to try if you're running a stage 1 or stock cam but you should be shifting long before you get to the point where you'd experience valve float as the power drops off too sharply to rev that high.

The pressures on the aftermarket springs are considerably higher than what I believe you would achieve with simply swapping in the exhaust spring judging from the OEM springs compressed force. And you're still left with the issue of how to stiffen up the exhaust springs. I haven't seen anyone suggest putting a spring that is too long in the intake or any other alternative to purchasing aftermarket valve springs for the more aggressive camshafts.

That said, everytime I make a blanket statement like that shunning a cheap shortcut or improbable adaptation someone comes along and directs me to put my foot in my mouth. So with that corollary in mind I'd suggest taking a look at the information and drawing your own conclusions. The basic specs for the valve springs are in the manual in the specifications section. If you go to the hot rods website you can see their (admittedly not identically laid out) specifications for the HD spring kit. Compare and contrast.

Mike

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post #3 of 8 (permalink) Old 07-19-2012, 08:31 AM Thread Starter
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Very good point mad dog i was thinking about the intake valves.. Thats normally what i always see fails or breaks on here not the exhaust.....lol Foot in the mouth huh..I will try to make that happen then for you, hopefully not for me when i get my hcII. I got to do some research and see if can find a suitable spring replacement for less $$$. That will be my contribution to this great forum and my raptor family..
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post #4 of 8 (permalink) Old 07-20-2012, 03:04 AM
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The cost to repair an engine that has dropped a valve isnt worth going the cheap route on the springs for me.

2003 Limited Edition Raptor
Kenz 720cc 11:1 stroker, +1 valves, Mega Cycle X-4 Cam, Sparks 6x Big Core, Keihin 35mm FCR's. 158 mains, 52 pilots, fuel screws 2 turns out.

97 Banshee
F.A.S.T. Dune Ported 4mill, CPI Inframes, Keihin PWK33's, Direct Drive Lockup. 158 mians, CEL needles second clip, #48 pilots, air scews 2.0 turns out.
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post #5 of 8 (permalink) Old 07-20-2012, 05:51 AM
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Quote:
Originally Posted by drag+6blaster View Post
Hey all.. A while back i was adjusting my valve lash on the 660 and I'm thinking about installing a hcII and thought about when we use to kart race.. Some of our motors ran exhaust valve spring on the intake valve, so the motor had all exhaust springs in it..The benefit was that the stiffer(and slighty taller) exhaust springs would control valve float at high RPM..Has anyone ever tried this instead of aftermarket springs...
The reason you ran two exhaust spings on those Briiggs engines is because they were stronger then the intake spring, you rev these motors around 7500 rpm, normally they rev around 3600.................


686 three plugger with HV porting, 39 FCRS, Curtis Sparks exhaust, Dyna FS CDI
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post #6 of 8 (permalink) Old 07-22-2012, 01:01 AM Thread Starter
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Well, if WILLY said it then its probly true,,,, going to save up and buy springs... Which should i get wit a stage II hot cam... hc springs. webb springs or what... i got my wiseco 11:1 piston on the way... I'm doing a summer freshing up cause its TOOO HOTTT to ride around end of july and most of august..Getting ready for the fall..and i ordered a Tusk top end rebuild kit..Mic'ed the new head gasket at .073mm ...how much would this compress after the head is torqued down.. I just trying to fiqure some clearances.. ALSO to anyone wondering my piston was in the hole about .040mm at TDC(stock motor).. I mic'ed it thinking i was going to deck the cylinder but dont want to push this thing to a early crank failure...
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post #7 of 8 (permalink) Old 08-07-2012, 12:37 PM Thread Starter
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I got'em KIBBLE WHITE DUAL SPRING KIT




Last edited by drag+6blaster; 08-07-2012 at 12:39 PM. Reason: cc
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post #8 of 8 (permalink) Old 08-07-2012, 01:37 PM
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Looks good. I had my springs coated with a Dry Film lube. It is supose to attract oil to help pull heat out of them.

2003 Limited Edition Raptor
Kenz 720cc 11:1 stroker, +1 valves, Mega Cycle X-4 Cam, Sparks 6x Big Core, Keihin 35mm FCR's. 158 mains, 52 pilots, fuel screws 2 turns out.

97 Banshee
F.A.S.T. Dune Ported 4mill, CPI Inframes, Keihin PWK33's, Direct Drive Lockup. 158 mians, CEL needles second clip, #48 pilots, air scews 2.0 turns out.
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