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Discussion Starter #1
Hey there guys, just wondering if this idea is feasible. I have a 350, and all I need out of a clutch kit is 500 stall springs. OK well since I have a 350, what if I put 400, 450, or maybe even 650 springs. Won't that be the same thing. I asked the parts guy at the nearest yamaha dealer, he said he didn't know. He just deals with parts numbers all day. What yall think I should order to start, 400 or 450?
 

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Clutch stall springs really have nothing to do with engine size.
There size and calibration is based on engine RPM, not engine size or power. Usually the stronger the spring, the more rpm is required to "pull" (for lack of a better word) to engage the clutch shoes onto the drum.
Additionally the actual clutch setup itself decides which spring will work. If other engines use the same style and length spring, then it should work. But thats a guessing game to check, best done by experience of knowing what each machine takes or how it is setup.
 

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The 500 is just saying it takes an additional 500 rpm to engage the wet clutch. You probably don't want them anyway, they are stronger springs to resist the shoes hitting the drum until higher rpm, which also means they don't contact the drum with as much force, so it slips easier than factory. Since you machined your primary they aren't going to help you anyway, save your money.
 

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Discussion Starter #4
Well dang thanks whiskeyMike, saved me some money right there. I'm trying to get it able to handle 27x7.50 interforces
 

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Discussion Starter #5
Dezz, i know they art based on engine size, But you can't have a 350 clutch in a 660. The 660 will be more robust. The dogs on it will probably wiegh more, and therefor it will have to have beefier springs. But your right if the design is different it won't work at all. It's a gamble for sure, but it's only 16 bucks...and if it works it would be handy as crap. The 350 and 660 share some parts, especially in the transmission, it's not an unreal idea
 

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What was the stock ratio? And what is the new ratio?
 

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Discussion Starter #7
As close as I can count, stock was 2.8 to 1, and now it's 3.4 or so to 1. There is a difference I can feel it. Haven't got it in a bad situation yet to need all four to spin, it's out at the deer lease for a while.
 

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You'll be close on the percentage increase of the ratio to counteract most of the drag from the taller tires.
You can measure the current tire circumference to compare the percentage increase with the new tires.
Is the belt rubbing?
 

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Discussion Starter #9
No sir I couldn't get the belt to rub if I wanted too, belt starts to hit seal boss before belt will ride high enough to rub. I had to take .7mm to get it up off seal.
 

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Thanks for the info on the 350. I haven't got my hands on one to experience the results of machining and shim.
On my 660, at a 3.5 ratio the belt is about 1/2 way out of the secondary. Any more and there may not be enough contact to prevent belt slip.
You may be able to remove the seal hump, or part of it, for a little higher ratio.
 

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Discussion Starter #11
I may have to do that. If I could get that .7 back in it then my belt would be about 1/2 way out as well.
 
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