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Discussion Starter · #1 ·
Ok after i have just rebuilt my bike i have this very bad problem. I bought a new chain rated for 165hp so its strong enough no problems. The real problem is that now i have to much power (toruque) i keep shearing off the studs that hold on the rear sproket. I use new studs and nuts since u can only use them once. Ive put them on it shears them off, so i had a yamaha mechanic do it, and it still wont hold. Do i need to drill out the sproket and hub to something larger and but bigger class 8 nuts and bolts or what do i do now?
 

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Cant you just buy grade 8 bolts that will fit in, grade 8 is made in all sizes.
 

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Metric bolts are available in hardnesses equal to grade 8, they just rate them differently.

I'd look at the hub and sprocket for holes that are egged out and allowing the sprocket to shift around. Also look at the center bore of the sprocket and it's locator on the hub, if it doesn't fit well it will let the sprocket move too.

What did you build that has so much power?
 

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firstraptor said:
What did you build that has so much power?
:stupid: What he said
 

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sheet, how much horse power you got?? sparkysandman has a 700 with 80+ hp and he is not having this problem
 

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Check your chain tension if its too tight when you sit on the quad it gets even tighter. there should be around an 1" of movement, but not more than that.
 

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Discussion Starter · #8 ·
11:1comp, stage one cam, ir plug, white bros exhaust, clear tube method, plastic boot booring, open direct air filter Heres my fuel mix: 5 gals of 110, 4 gals of pump, 1 gal of drip gass (from oilwells). Runs like a striped ape. 14/40 gear ratio. Tweaked clutch. It spanks highly modded YFZ450's, the baddes 450 in area got ate by me. and a honda 250r two stroke so far. That night i learned that june bugs [email protected]$$% hurt. The hub desnt move it had, has around 1 inch of chain travel. the sproket holes are true/round/not broken. I hate easyouting the old studs, it really sucks. i just want to know the cause
 

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you shouldnt have any trouble with the stock bolts, you dont make enough power to justify breaking them. im sure your bike runs great but there are alot of 70+ hp bikes not having anytrouble. so you might want to make sure everything else is good. also when you check your chain sit on the bike, it makes a world of diffrence.
mike
 

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Discussion Starter · #10 ·
It take two people to check the chain i know that. Should i just tap the hub the next size bigger?
 

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Why dont you just buy grade 8 bolts?
 

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Discussion Starter · #12 ·
Werent stock studs grade 8? Ill retap the hub to i believe 8mm one over the stock 7mm. Larger = more strength hopefully, and new threads
 

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Discussion Starter · #13 ·
Is it a good idea to tap the hub one mm over or not? Where would i get the torque specs for my new bolts, so they have their true potential?
 

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I would worry about weakening the hub because of the larger holes.
 

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Discussion Starter · #15 ·
I can understand you weakening theroy, but it is only one mm. Its not that much, so go or no go?
 

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It take two people to check the chain i know that. Should i just tap the hub the next size bigger?
Support the frame and the chain slack should be 1-3/16" to 1-3/4" (30-45mm) with the wheels off the ground.

The sprocket bolts are 8mm, you might try a 10mm but look at the hub to see if it has the material. The stock torque is 17 ftlbs if that helps.
 

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i wouldnt do it. i would find out what is causing your problem. because at your power level there is no way you should have to worry about shearing off the bolts.
mike
 

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02raptor660 said:
i wouldnt do it. i would find out what is causing your problem. because at your power level there is no way you should have to worry about shearing off the bolts.
mike
I'd have to agree, I don't think you would be shearing bolts with your mods. If you are still having problems and can't figure it out, replace the hub and make certain your chain slack and everything is within specs.
 

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I don't think he should be shearing the bolts either. But as an option before buying more parts I'd try the larger bolts. Worst case is he breaks the bolts again. I'd also think that if the bolts have been broken off once that the surfaces of the sprocket hub are fairly beat up at this point and not helping matters.
 

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firstraptor said:
I don't think he should be shearing the bolts either. But as an option before buying more parts I'd try the larger bolts. Worst case is he breaks the bolts again. I'd also think that if the bolts have been broken off once that the surfaces of the sprocket hub are fairly beat up at this point and not helping matters.
Good point, going up a bolt size may kill two birds with one stone (or six stones in this case).
 
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