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I've been tinkering with the idea of boring out my 650, but I'm wanting to hear opinions from those more in the know. The kit I was looking at actually takes it up to 744 cc. I know it probably isn't the BEST idea in the world, but when I think of an SV750 I get a warm, tingly feeling inside...


http://www.zlockracing.com/new_products.html
 

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seems like a bad idea to me. The SV650 crank can't really handle any more power than 85hp, and if you get a big bore kit like that and start making more power, the you'll easily snap the crank. In my opinion, it needs a bore kit and a new crank.
this is just what i've read around here. It'd be worth writing to zoran about from twinworkfactory.com I'm sure he's has plenty of experience with it. He's broken a lot of cranks in his day.
 

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If power is what your after, look no further than a set of cams and your standard intake/exhaust/re-jet.

You could bore it out, but be prepared for a broken crankshaft. 85 is the magic number. :thumbsup:

Do a search on big bore. There is much info archived, search function is your friend.
 

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It's a bad idea. I can't remember his name but we had a member make his bike a 700. He loved the new power, but a month or two later he was here parting out his engine. The SV650 is best left a 650.
 

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An SV750 via *just* a big-bore kit equals:



The 650 motor was designed for two displacements - 400 and 650. The SV400 is a Japan-only model, whereas the 650 is a rest-of-the-world model. The bottom end won't take the abuse for very long. Once you get past about 85 horse - the motor won't live long. By the time you replace all the parts that need it to get to a street-reliable SV750 - you won't have money to buy a tank of gas. Wanna race and have a sizable budget? Have at it.
 

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what about combining that big bore kit with a cam profile from a DL 650 so you beef up the low and midrange and tone down the total top end, much more power in your power band, less peaky and blowy uppy at the top of the range.
 

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wonderjosh said:
Buy a bigger bike. :BangHead:
Exactly.

HP is a function of torque - all that added toque will simply beat the bottom out of the motor. Whether it takes 6 months or 2 years, it's still going to let go at that displacement.
 

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And honestly, an extra 100cc's or 15-20hp isn't that much. I have a feeling you'd be disappointed how little difference there would be.
 

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Email Zoran at Twin Works Factory - he's forgotten more about SV's than most of us have ever known combined. He'll give you the straight dope on if its possible to make it reliable and what it would take.

[email protected]

My guess is that you'll end up spending more money than the bike is currently worth and still not come away with a bike even half as reliable as it is right now.
 

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I've thought about doing this, but only when my available surplus cash is dangerously high. I've thought about combining the overborebore with a Falicon crank, to get a stronger bottom end and rods. Falicon even offers a stroker to take it out to an SV808. That would be just about right, I think. :eek:ccasion14:

I generally agree with the "grenade" cautions, though with a minor disagreement. I'm sure Suzuki didn't engineer the SV to explode at anything over 85 bhp. Bikes have to have some reserve strength built in for reliability. But there are certainly weak links in the bottom end (one of the end bearings and the connecting rods seem to fail more often than other parts). I've looked at the Zlock Racing kit for a while. If you're interested, I'd ask them more about their customers' experiences. I also agree that Zoran (Twin Works Factory) is about as knowledgeable about pumping power out of SV engines as anybody this side of Hammamatsu.

Watch out though, he's some kind of filthy foreigner. :laughing4:
 

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Morpheous said:
Remember the SV650 is a bored out 400 to start with, so the crank engineering is well into the design overhead already. :nono:
This gets repeated so often that people believe it's true. I'm sure the SV650 os not a "bored out" 400. I'm sure the engine was designed from scratch for both capacities. If I'm wrong about that, I'd love to be re-educated. If not, let's stop repeating this bit of questionable "conventional wisdom." :nono:
 

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Fatass SVS said:
This gets repeated so often that people believe it's true. I'm sure the SV650 os not a "bored out" 400. I'm sure the engine was designed from scratch for both capacities. If I'm wrong about that, I'd love to be re-educated. If not, let's stop repeating this bit of questionable "conventional wisdom." :nono:
i don't think it's "questionable conventional wisdom" when zoran has made numerous references to that "fact".
 

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The bike exists as a 400 and as a 650. Always has. Was it a 400 and then Suzuki 'decided' to punch it all the way to a 650? Doubtful. More likely - Suzuki designed it so that it would work in both capacities, with the design brief probably leaning towards the 650, so it would be reliable.

All you need to do is look at the SV400 - and realize it's part-for-part a first-gen SV650/s, with a different bore and stroke. The 400 has a bore/stroke of 72mm/49mm. The 650 81mm/62.6. A 9mm overbore, stroked 13.6mm? Thats not big - its gigantic. Fuggin' huge, even.

[email protected] few 400cc engines that were designed as 400's that will live for any length of time when punched out an additional 38%. That'd be like taking a GSX-R750 and making it a 1035. You CAN'T do that - there isn't enough material to accept the overbore, nor enough space to stroke it that far.

Odd how it works on an SV. Musta been......designed that way?
 

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There have been enough granaded SV650 engines to consider some of the above statements 'fact'. Big bore or no big bore, 85 is still the miagic number.

I'd like to see the big piston/DL camshaft combo that Dichotomous suggested earlier. The theory sounds good, but I'd like to see it happen. At least some dyno pulls to see how this combo will achive 85hps and the shape of the power curve.
 

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I still haven't decided which way to go with my SV, maybe a used motor :dontknow: maybe an overbore rebuild, doubtful I'd go bigger than the 677 kit, don't really care about peak gains, I wouldn't mind a curve that's a little beafier at the bottom though, I'm getting so I like the grunt of my dL1000 Nexus242
 

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I have the JE 2mm over 677 kit in my SV now. Dyno numbers from last Saturday were 75 hp/ 44 ft-lbs of torque for the first run with very fat jetting. After the second run I dropped one jet size and the second run netted 78 hp and 48 ft-lbs with the jetting still fat. I dropped another jet size and called it good till I can get back for another dyno run. I went to a trackday at Summit Point yesterday and the bike ran great. Now I know (And I didn't baby it either) that's only one day and I expect to run it in a 3hr endurance on Labor Day, so we'll see what happens.
I AM NOT slamming Zoran or his experience, but I consulted with Greg Spears from Spears Enterprises, and he was very knowledgeable and helpful in explaining to me what I needed to check for when installing my piston kit. One of the most important things he told me to check was the deck height of the JE pistons. Well, It was ZERO! It doesn't take a rocket scientist to understand what will happen to a motor with no clearance under load. Greg advised me to install two base gaskets and use a .040" thick head gasket to give the proper clearance. Which I did. I also installed his cylinder stud kit to compensate for the increased compression the motor will see. One of the comments that Greg made was that often people (I mean the average guy, not Zoran) expect to be able to drop in something like a set of pistons without taking the time to carefully check the motor and reassemble it accordingly. Additionally he said that he has made successful reliable overbored motors (On stock rods) without breaking cranks.
My point it that these stories about broken cranks don't take into account other possible root causes for crank failure (e.g.poorly assembled motors). We have all seen enough stuff on this forum to know that there is a wide range of mechanical knowledge (or lack therof) that can explain at least some of these failures. If I did it over again would go with a lighter piston than the JE, but I'm just going to go with what I have and see what happens.
wonderjosh said:
And honestly, an extra 100cc's or 15-20hp isn't that much. I have a feeling you'd be disappointed how little difference there would be.
And I just don't buy this comment. 15-20 hp isn't that much? You'd practically have to be dead not to notice a 25% gain in horsepower.
 

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The cranks ALWAYS break at the same spot.

It is a design weakness in the crank that cannot be fixed.
 
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