Reliable 85bhp from a Curvy?

[millemille]

If you've got a bog standard curvy engine making 73bhp on the dyno with a one-off exhaust system and you're looking for a reliable 85bhp, or more, with the same exhaust system would you expect the following to deliver?

• 700cc big bore
• Flowed heads
• Injected cams
• Head gasket with one layer taken out
• Carillo Hayabusa con rods (with cylinders shortened to suit)
• Lightened and balanced crank
• Lightened flywheel (with 3 magnets as bike runs no lights)
• K&N air filter and opened up air box lid
• +4 degree ignition advancer
• Standard carbs jetted to suit

http://www.spearsenterprises.com/99-02-sv650.html
These guys have been building SV650 race engines since the beginning. I think maybe the standard carbs would be your limiting factor...

[DJ123]

Give these guys a call http://www.jhsracing.co.uk/suzuki_SV.htm

[millemille]

I know what the engine builders/tuners say, I'm looking for real feedback from people who've got engines with those kind of mods.

[Red Herring]

I remember one being told by a very well respected engine tuner that you always have to choose between power, flexibility and reliability. You can have pretty much any two, but not all three.

There are a few recognised experts out there who have developed SV engines through the pressure of motorsports, and if there was an easy gain to be made they would have found it by now. Having said that 85bhp isn't a huge ask and I seem to remember when I looked into it a few years back most of the mods you list were mentioned, although I have a fuel injected Pointy.

Have you priced up what you are suggesting yet? I can assure you it's not just a case of picking up a few second hand pieces and throwing them together, so unless you really need that extra few BHP because you are racing in an appropriate class then most people just sell their SV and get a SS600.

[johnnyrod]

Comments added:

Originally Posted by millemille

• 700cc big bore - good for midrange but top end bhp doesn't seem to be restricted by the cc
• Flowed heads - deffo
• Injected cams - absolutely
• Head gasket with one layer taken out - see below
• Carillo Hayabusa con rods (with cylinders shortened to suit) - for reliability above 80bhp, yes, but why not just get the right ones for your bike?
• Lightened and balanced crank - same
• Lightened flywheel (with 3 magnets as bike runs no lights) - maybe, some bikes have snapped off the flywheel due to too many lumpy gearchanges/changes in speed
• K&N air filter and opened up air box lid - not sure
• +4 degree ignition advancer - good for extra bottom end only
• Standard carbs jetted to suit - dyno work here

Really your next port of call for power is the cam swap, and this will give you a healthy top end boost for very little cash and trouble. If you want to look at bhp figures though, you have to ask what for. For starters a Dynojet dyno gives big numbers from any bike at all, so it depends why you're looking for 85bhp.

Re. the carbs, any improvements in gas flow will make it leaner, and dyno set up sorts this out. The stock carbs aren't small so I would think they are good enough.

After cams you are really into head work, and this is where the bhp returned for your cash is tailing off quite badly. With a 700cc kit, midrange is impressive but top end is curtailed (to a similar figure to a 650, from what I've seen, though with that much extra midrange who cares), so you need to up the gas flow, by polishing and porting, and doing some work with the squish. This is all quite intense stuff and really, even for me, isn't worth it. I got hold of a set of polished and ported heads from a Supertwin but I haven' had the dyno work done to sort out the fuelling, but I wouldn't have forked out full whack for it.

For reliability, if you go the 700cc route or really try to get much over 80bhp then you should be looking at new rods and cylinder studs. Because the crankcases split vertically then it's a big job, so may as well do the crank work too while you're in there.

I'm no tuning expert but I've done a lot of reading around, and a bit of tinkering with mine too. If you want another tuner I'd recommend then talk to Steve Jordan. Whatever you do, you're going to need deep pockets, so unless you're really after making something special, you already know I'm going to say do the cam swap (which oddly needs no further dyno work) and spend the rest on ways to ride it.

[jambo]

Or fit a turbo. I always thought this would be a ludicrous thing to do with an sv and absolutely certainly lead to a motor being blown to bits but a couple of people have managed it. I'm not sure either have done big miles but it didn't seem to grenade.

Jambo

Sent without a real keyboard

[DJ123]

That was an article many years ago in MCN on an SV650 bored out to 800cc vs a ducati (possibly monster). It detailed the work done on the SV but I can't find it now.

[andrewsmith]

To get 85 brake reliable your really having to look at:
new custom crank (900 notes upwards), rods and pistons (about 700), flat side carbs (last set I spotted were around 600 before shipping from the states)

Then what has been already mentioned

[millemille]

Originally Posted by andrewsmith

To get 85 brake reliable your really having to look at:
new custom crank (900 notes upwards), rods and pistons (about 700), flat side carbs (last set I spotted were around 600 before shipping from the states)

Then what has been already mentioned

Is that based on direct personal experience or, like the other posts so far appear , perceived internet "wisdom"?

I ask, because every engine builder I've spoken to says the standard crank - if lightened and balanced with a lightened flywheel - is more than capable of handling that power output reliably and the standard carbs, if rejetted, do not hold the engine back.