So to dispel a few myths about big bore SV's - Page 2 - SV650.org

northwind · 02-11-06, 05:35 PM

Playing devil's advocate here... (here we go again

)

That's still very low miles by comparison with a road machine, call it 1500 miles? While the short-term stresses are much higher for a race bike (in terms of acceleration loads etc) longer duration usage puts totally different stresses on the rods and bottom end- a hard-ridden road bike may well spend longer at 9000rpm in a year than most race bikes.

Running up the M6 at 120 for 2 hours with just a stop for fuel (as, ahem, one mildly tuned standard bore SV I can think of did after the AR) doesn't put the same stress on over any one mile, in fact in terms of acceleration stresses it's trivial- but puts some repetetive stresses on that a short-race bike doesn't see. There's a reason manufacturers stress test their engines over long periods as well as extreme stresses over a short term, they have different impacts.

Remember the Honda VFs with the chocolate cam chain sprockets? That made it into production because Honda tested the engines under high-stress conditions. They passed that with flying colours, then fell apart on the road as they could deal with any amount of abuse you wanted for a short term, but couldn't deal with low stress for a long term.

Nobody's ever maintained on here that these bikes will "self destruct at the slightest sign of use or abuse when bored out or tuned!". Sarah said, "it isnt as bad as people make out!....." but tbh I don't see where anyone on here's ever made it out to be particularily bad. Just did a search and the worst I can find is me, saying much the same as this

What people do say is "It might cause you problems" and "The risk of failure is increased". Which it might, and it almost certainly is- the SV can suffer catastrophic engine failure as standard under road conditions, this is known- putting an extra 4% mass in the pistons alone inevitably increases the stress on those parts, leaving aside the extra stress caused by the higher power.

But that's a long way from saying "It's a ticking timebomb", and I don't think anyone's ever said that. It's like any tuning, run an engine harder and you probably reduce its lifespan- just as it'll last longer if you never rev above 6000rpm. Nobody knows how long an SV engine will last though, it's at least 125000 miles if looked after, so if it cuts the lifespan by 10%, who cares? And if it does increase the risk of a short-term catastrophic failure, as it might, the odds are still very long.

We have a sample here of 2 bikes. It's just not enough to draw any useful conlusions off. If you choose a larger sample- say, the various US race series, where big-bored SVs used to be much more common... engine failures were still not common, but you lose this 100% success. Even then, you can't draw any useful conclusions off that, because these are bikes built by 20 different tuners, all treated differently, and any one of them might have failed if they were standard bore anyway- just becase they were 700cc and had a rod failure or snapped the crank by teh oil hole, doesn't mean it happened because they were 700cc.

So, the smart thing to do if you're considering it, isn't to say "Well, Sarah and Rob's bikes haven't exploded, so it must be fine". Equally, it's not "Well, Rictus's bike exploded, so it must be deadly to engines". It's to say "There's probably some risk there, but you can't really say how much... What am I happy with" It makes no sense to never rev above 6000rpm in order to lengthen your engine's life, the cost outweighs the benefit. Does the same apply to 700cc? Not so clear is it...

Anyway. We've had this thread before, but since it's started again I thought it could do with the "on the fence" view

Maybe someone will come along this time and offer the total opposite, and actually say it is certain death, that'd be fun

northwind · 02-11-06, 05:41 PM

Another thing, which I meant to mention

is on piston slap. James Holland of JHS says this:

"Been there - seen it - done it - got the t-shirt !
We have probably done more big bores on the sv650 than all the other so called sv650 tuners worldwide put together.
If you build a motor and use a Wiseco shelf stock CK114 piston kit, sooner or later they will start to clatter at tickover ! it's in the nature of the piston design.
That's not to say they are not good value for money though !
jh
www.jhsracing.co.uk"

"It's in the overall piston design, just get a stock sv650 piston side by side with a ck114 piston and all will be shown to you, if you know what you are looking at.
A clue would be ring design to start with?
jh
www.jhsracing.co.uk"

Now, I make no secret of not being a JHS fan. But you can't deny he's built a lot more 700cc bikes than just one. Me, I'd sooner trust SV650racer but that's by the by.

02-11-06, 05:54 PM

Quote:

Originally Posted by northwind

Another thing, which I meant to mention

is on piston slap. James Holland of JHS says this:

"Been there - seen it - done it - got the t-shirt !
We have probably done more big bores on the sv650 than all the other so called sv650 tuners worldwide put together.
If you build a motor and use a Wiseco shelf stock CK114 piston kit, sooner or later they will start to clatter at tickover ! it's in the nature of the piston design.
That's not to say they are not good value for money though !
jh
www.jhsracing.co.uk"

"It's in the overall piston design, just get a stock sv650 piston side by side with a ck114 piston and all will be shown to you, if you know what you are looking at.
A clue would be ring design to start with?
jh
www.jhsracing.co.uk"

Now, I make no secret of not being a JHS fan. But you can't deny he's built a lot more 700cc bikes than just one. Me, I'd sooner trust SV650racer but that's by the by.

Me too hence now owning a SV700 built from scratch by Sarahs other half. Personally though i have no opinions about JHS as all i know them for is the bodywork they do and the odd minitwin here and there. It's other so called SV experts i dont like hey John White!!!!

03-11-06, 03:52 PM

Quote:

Originally Posted by chunkytfg

Why would you want to sleeve down a SV1000 to 800cc?

Eh? Why would ya do that?

03-11-06, 05:50 PM

Quote:

Originally Posted by Jdubya

Quote:

Originally Posted by chunkytfg

Why would you want to sleeve down a SV1000 to 800cc?

Eh? Why would ya do that?

well a Sv650 isnt possible to take out to 800cc so i guess the only way to do it is to sleeve down a 1000

northwind · 03-11-06, 05:53 PM

800cc can be done and has been done... While we're dispelling myths about big bores

03-11-06, 06:23 PM

That quote from JHS Racing sounds deeply worrying. Piston slap is caused by the bore becoming out of round, and this is mostly caused by leakage past the piston rings. Now why would that be? Are they not measuring everything correctly? Are they using the wrong honing grade for the rings? The wrong break-in procedure? If the kit is fundamentally flawed by design then why are they taking hard-earned cash from people to do dodgy work?

03-11-06, 06:42 PM

Quote:

Originally Posted by northwind

800cc can be done and has been done... While we're dispelling myths about big bores

Really?? Jeez that thing must be well fragile. Not to mention a level well beyond rediculously expensive to do

northwind · 03-11-06, 06:58 PM

£800, it was, but that's on the old JHS website. A few have been raced in the states in FUSA Thunderbikes among other, I know Ed Kay had one. SV Race Shop had built one too, shortly before the whole criminally-dangerous-shock-rebuilds thing came to light

I wouldn't... But you have to admit it'd be a hoot. If only for the stickers

03-11-06, 07:23 PM

Quote:

Originally Posted by northwind

£800, it was, but that's on the old JHS website. A few have been raced in the states in FUSA Thunderbikes among other, I know Ed Kay had one. SV Race Shop had built one too, shortly before the whole criminally-dangerous-shock-rebuilds thing came to light

I wouldn't... But you have to admit it'd be a hoot. If only for the stickers

£800!!!!!! i'd lay money on it lasting no more than 2 dyno runs for that price. The billet crank for the 750 kit is well over a grand so the only way i can imagine they managed 800 for that price would be to ofset grind the big end onj the crank and bearing in mind the SV cranks have been known to split they would be well fragile with the extra stresses of a bore that big.

I agreee though it's be a right laugh. What seems more interesting to me is the fact the new tuono 750 is eligable for the thunderbikes. Doubt we'll see one next year but it'll be cool if one doesn go out there

02-11-06, 05:35 PM	#11
northwind Moderator Mega Poster Join Date: Jan 2004 Location: In the garage where I belong Posts: 17,083	Playing devil's advocate here... (here we go again ) That's still very low miles by comparison with a road machine, call it 1500 miles? While the short-term stresses are much higher for a race bike (in terms of acceleration loads etc) longer duration usage puts totally different stresses on the rods and bottom end- a hard-ridden road bike may well spend longer at 9000rpm in a year than most race bikes. Running up the M6 at 120 for 2 hours with just a stop for fuel (as, ahem, one mildly tuned standard bore SV I can think of did after the AR) doesn't put the same stress on over any one mile, in fact in terms of acceleration stresses it's trivial- but puts some repetetive stresses on that a short-race bike doesn't see. There's a reason manufacturers stress test their engines over long periods as well as extreme stresses over a short term, they have different impacts. Remember the Honda VFs with the chocolate cam chain sprockets? That made it into production because Honda tested the engines under high-stress conditions. They passed that with flying colours, then fell apart on the road as they could deal with any amount of abuse you wanted for a short term, but couldn't deal with low stress for a long term. Nobody's ever maintained on here that these bikes will "self destruct at the slightest sign of use or abuse when bored out or tuned!". Sarah said, "it isnt as bad as people make out!....." but tbh I don't see where anyone on here's ever made it out to be particularily bad. Just did a search and the worst I can find is me, saying much the same as this What people do say is "It might cause you problems" and "The risk of failure is increased". Which it might, and it almost certainly is- the SV can suffer catastrophic engine failure as standard under road conditions, this is known- putting an extra 4% mass in the pistons alone inevitably increases the stress on those parts, leaving aside the extra stress caused by the higher power. But that's a long way from saying "It's a ticking timebomb", and I don't think anyone's ever said that. It's like any tuning, run an engine harder and you probably reduce its lifespan- just as it'll last longer if you never rev above 6000rpm. Nobody knows how long an SV engine will last though, it's at least 125000 miles if looked after, so if it cuts the lifespan by 10%, who cares? And if it does increase the risk of a short-term catastrophic failure, as it might, the odds are still very long. We have a sample here of 2 bikes. It's just not enough to draw any useful conlusions off. If you choose a larger sample- say, the various US race series, where big-bored SVs used to be much more common... engine failures were still not common, but you lose this 100% success. Even then, you can't draw any useful conclusions off that, because these are bikes built by 20 different tuners, all treated differently, and any one of them might have failed if they were standard bore anyway- just becase they were 700cc and had a rod failure or snapped the crank by teh oil hole, doesn't mean it happened because they were 700cc. So, the smart thing to do if you're considering it, isn't to say "Well, Sarah and Rob's bikes haven't exploded, so it must be fine". Equally, it's not "Well, Rictus's bike exploded, so it must be deadly to engines". It's to say "There's probably some risk there, but you can't really say how much... What am I happy with" It makes no sense to never rev above 6000rpm in order to lengthen your engine's life, the cost outweighs the benefit. Does the same apply to 700cc? Not so clear is it... Anyway. We've had this thread before, but since it's started again I thought it could do with the "on the fence" view Maybe someone will come along this time and offer the total opposite, and actually say it is certain death, that'd be fun __________________ "We are the angry mob, we read the papers every day We like what we like, we hate what we hate But we're oh so easily swayed"

02-11-06, 05:41 PM	#12
northwind Moderator Mega Poster Join Date: Jan 2004 Location: In the garage where I belong Posts: 17,083	Another thing, which I meant to mention is on piston slap. James Holland of JHS says this: "Been there - seen it - done it - got the t-shirt ! We have probably done more big bores on the sv650 than all the other so called sv650 tuners worldwide put together. If you build a motor and use a Wiseco shelf stock CK114 piston kit, sooner or later they will start to clatter at tickover ! it's in the nature of the piston design. That's not to say they are not good value for money though ! jh www.jhsracing.co.uk" "It's in the overall piston design, just get a stock sv650 piston side by side with a ck114 piston and all will be shown to you, if you know what you are looking at. A clue would be ring design to start with? jh www.jhsracing.co.uk" Now, I make no secret of not being a JHS fan. But you can't deny he's built a lot more 700cc bikes than just one. Me, I'd sooner trust SV650racer but that's by the by. __________________ "We are the angry mob, we read the papers every day We like what we like, we hate what we hate But we're oh so easily swayed"

03-11-06, 05:53 PM	#16
northwind Moderator Mega Poster Join Date: Jan 2004 Location: In the garage where I belong Posts: 17,083	800cc can be done and has been done... While we're dispelling myths about big bores __________________ "We are the angry mob, we read the papers every day We like what we like, we hate what we hate But we're oh so easily swayed"

03-11-06, 06:58 PM	#19
northwind Moderator Mega Poster Join Date: Jan 2004 Location: In the garage where I belong Posts: 17,083	£800, it was, but that's on the old JHS website. A few have been raced in the states in FUSA Thunderbikes among other, I know Ed Kay had one. SV Race Shop had built one too, shortly before the whole criminally-dangerous-shock-rebuilds thing came to light I wouldn't... But you have to admit it'd be a hoot. If only for the stickers __________________ "We are the angry mob, we read the papers every day We like what we like, we hate what we hate But we're oh so easily swayed"

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03-11-06, 06:23 PM	#17
sdusk Guest Posts: n/a	That quote from JHS Racing sounds deeply worrying. Piston slap is caused by the bore becoming out of round, and this is mostly caused by leakage past the piston rings. Now why would that be? Are they not measuring everything correctly? Are they using the wrong honing grade for the rings? The wrong break-in procedure? If the kit is fundamentally flawed by design then why are they taking hard-earned cash from people to do dodgy work?