Are stock rods safe ? - Suzuki SV650 Forum: SV650, SV1000, Gladius Forums

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Old 06-14-2019, 07:55 PM   #1
fastegg
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Are stock rods safe ?

I'm going to be using 3mm Wiseco's and shaving the heads to bring it up to 12.5:1 ... not racing but bike gets pushed hard. How safe are stock rods ?... Does anyone know what you can and can't do with them ?
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Old 06-17-2019, 10:05 AM   #2
RecoilRob
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Re: Are stock rods safe ?

Rod strength is only a concern when being pushed beyond stock rpm levels. In compression you are NEVER going to bend a rod!! It's only on the top of the exhaust stroke where the rod cap and bolts get yanked on as they pull the piston back down again and excessive rpm can stretch them and cause failure.

When a rod bends it's almost always due to the little end tightening up in both piston and rod. Severe detonation can cause this but most of the time it's actual contact with the head that does the damage. As the piston rocks over TDC this creates a bending force on the rod when the little end can't articulate and many revolutions works the rod until it breaks. This is one of the reasons we don't want the piston hitting the head. Close enough to work the squish properly, but far enough away to be safe is a good thing.

Years ago I ran RD400's with the squish so tight the piston over-bore numbers were in the carbon on the head. These were real hand grenade engines and never lived long...but ran a lot better when they were alive than most would believe. These were what I called 'reachers'.....they reached levels where they couldn't live very long. NOT a good thing for a street engine.
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Old 06-18-2019, 06:56 PM   #3
fastegg
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Re: Are stock rods safe ?

Quote:
Originally Posted by RecoilRob View Post
Rod strength is only a concern when being pushed beyond stock rpm levels. In compression you are NEVER going to bend a rod!! It's only on the top of the exhaust stroke where the rod cap and bolts get yanked on as they pull the piston back down again and excessive rpm can stretch them and cause failure.

When a rod bends it's almost always due to the little end tightening up in both piston and rod. Severe detonation can cause this but most of the time it's actual contact with the head that does the damage. As the piston rocks over TDC this creates a bending force on the rod when the little end can't articulate and many revolutions works the rod until it breaks. This is one of the reasons we don't want the piston hitting the head. Close enough to work the squish properly, but far enough away to be safe is a good thing.

Years ago I ran RD400's with the squish so tight the piston over-bore numbers were in the carbon on the head. These were real hand grenade engines and never lived long...but ran a lot better when they were alive than most would believe. These were what I called 'reachers'.....they reached levels where they couldn't live very long. NOT a good thing for a street engine.

That makes me feel alot better about using stock rods.. I never go near hi revs so they should be safe...
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Old 06-18-2019, 08:59 PM   #4
rcb78
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Re: Are stock rods safe ?

I always got a kick out of opening my old engines with tight decks. The chambers were almost always clean ;-)
I don't know about these specific engines, but rod bolts were something we generally paid more attention to that rods until boost came into play. ARP for stock rods and a good stretch gauge. But there are few things a sexy as a new set of H-beam Carrillos.
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Old 06-23-2019, 09:04 AM   #5
fastegg
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Re: Are stock rods safe ?

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I always got a kick out of opening my old engines with tight decks. The chambers were almost always clean ;-)
I don't know about these specific engines, but rod bolts were something we generally paid more attention to that rods until boost came into play. ARP for stock rods and a good stretch gauge. But there are few things a sexy as a new set of H-beam Carrillos.

What's ARP for stock rods ?
If I was gunna go for a beautiful set of Carrillo's i'd also be going a 750 stroker crank.... just for fun... i'm not that rich...
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Old 06-24-2019, 03:13 PM   #6
RecoilRob
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Re: Are stock rods safe ?

Fastegg.....remember the SV650 is already a very punched out motor that originally was designed as a 400. There are engineering limits that can be pushed but not exceeded if long term durability is desired. If you want a really BIG SV......the 1000 comes to mind. And it can be taken close to 1200 if you have the $$$$$.
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Old 06-25-2019, 07:11 AM   #7
steveSLO
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Re: Are stock rods safe ?

If you haven't finished your intake experimentation, you might look into this
https://www.svrider.com/forum/showthread.php?t=394515
especially if you already have a PC III
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Old 07-09-2019, 04:40 AM   #8
fastegg
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Re: Are stock rods safe ?

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Originally Posted by steveSLO View Post
If you haven't finished your intake experimentation, you might look into this
https://www.svrider.com/forum/showthread.php?t=394515
especially if you already have a PC III
Yeah would be nice.... I'll put them on the list...
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Old 07-09-2019, 08:12 AM   #9
rcb78
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Re: Are stock rods safe ?

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Originally Posted by fastegg View Post
What's ARP for stock rods ?
ARP rod bolts, I don't see a kit specifically for the SV, but I'd call with dimensions and see what they have.
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Old 07-09-2019, 09:04 AM   #10
fastegg
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Re: Are stock rods safe ?

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Originally Posted by rcb78 View Post
ARP rod bolts, I don't see a kit specifically for the SV, but I'd call with dimensions and see what they have.

If & when I ever disassemble a motor i might... hopefully that will never happen... 2 day cracking road ride this weekend... The SVR is ready for combat...
** Heads are currently getting the multi angle seat cut & port 'clean up'... barrels are bored... everything's nearly ready... One issue that is in the back of my mind is the extra weight of the 3mm OS pistons... The stock SV drive is so sweet no matter how hard it's treated... I remember years ago when Ducati first brought out the 748 & 916.. I test road them both back to back and honestly I preferred the 748... it was just so sweet and right... Sure the 916 had significantly more of everything, but that didn't make it better... I'm just hoping by turning mine into a 700 I'm not gunna make it unpleasant... overdone.... overstepped.... too bangy...

Last edited by fastegg; 07-09-2019 at 09:20 AM.
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