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

[wideguy]

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:



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]

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.

[andrewsmith]

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.
It was something I looked at last year. But it was based on using a blown motor. With your exhaust system get the bike dyno'd prior to tuning the motor.
From memory Rictus had a 700 kit in a curvy and it liked to drink oil.

As a side, get onto JHS Racings website as they're doing a set of forged pistons for 200

[carelesschucca]

First question has to be why do you want 85bhp from an SV engine?

[johnnyrod]

Forsooth, chucca, an to some extent it depends how it's measured.

My mate has a 700 kit on his (built by a well-known spannerer, shall we say) and it drinks oil too, but that doesn't mean they're all like that.

I'd love to tell you what extra power comes beyond pipe/filter/cam swap/ignition advancer/dyno time but not yet had my bike in to somewhere to get the set-up adjusted for the latest changes. As it stands it shows 81bhp on a Dynojet dyno which will be a lot less on a Dynapro. It's faster than it was, noticeably so. You're really getting into specialist territory where experience and quality of work come into their own. So far I've been bolting on go-faster bits, plus a bit of dyno time, and then these new heads (not yet bottomed, as noted).

I would post this in the racing section too, and also ring all of the tuners listed above and ask them all the same questions. You won't get all the same answers.

[jhsracing]

Reliable 85bhp at the wheel from a curvy sv is easy. We have been doing it for years. But you have to select the correct parts.
We would recommend for road use every thing can be done with the engine in place.
83mm forged piston kit with XG rings not XC as these will allow oil to be used.
Cylinder heads gas flowed properly.
Camshafts regrind to give a longer duration and higher lift (not injected cams these don't have enough of either)
M4 full system
Dynojet kit with big airflow filter (not K&N) must be the BMC RS Type.


85BHP TO 90BHP no problem. Depending on mileage possible valves and valve springs and up dated cam chain adjusters.
Hope this helps.

[rowdy]

I'd love to tell you what extra power comes beyond pipe/filter/cam swap/ignition advancer/dyno time but not yet had my bike in to somewhere to get the set-up adjusted for the latest changes. As it stands it shows 81bhp on a Dynojet dyno which will be a lot less on a Dynapro.

Not read the thread, just the last couple of posts and found this point interesting. Any idea what sort of figure percentage wise the difference between a dynapro dyno and dyno jet is?
Genuinely interested, as when I got my full m4 system the founder of dynapro came down and set my bike up on a friends dynapro, and it was making 72bhp.

I am also interested to know at what revs an sv will make peak power. I didn't receive a print out so don't know what figures mine made at what point. What I do know is that Mark only went up to 10400rpm, and after the dyno run I told him that the rev limiter kicks in at 11400rpm. He told me there were a few k3's that slipped through the net with this 1000rpm higher rev limit set in the ecu, but I am guessing the peak power would have dropped off before the lower rev limit.

Anyway, back to the crank, mine did end up snapping, although this was after going through a phase of taking it up to the rev limit and popping wheelies which didn't help the crank one bit!

[jhsracing]

Dyno power outputs that's a big subject !


ALL dyno's will have a degree of positive and negative feedback but what I have seen is that operators of Dynapro dyno's seem to be very quick to run down the Dynojet dyno but do seem to forget these are the industry standard within the motorcycle trade. (that's my view)
As to power output from a k3 sv650 machine your figure is acceptable and where it should be at but a lot of factors can be brought into play,such as tyre pressure, chain tension, air temp and air supply and exstraction of the dyno room. There is loads of data on this subject on the net if you want to do some research.
hope this helps
james

[andrewsmith]

Between a few people who've had bikes on Dynojet and Dynapro it was between 5 and 10% difference.
The dyno operator's bike was measured about 7% between a Dynojet and Dynapro units (wasn't measured on his dyno), and the firm are car rolling roads mostly with a bike dyno on the side

[johnnyrod]

Around 5-10% sounds about right, but as James says, there are a load of corrections and influencing factors, plus you do a set of runs back to back and you'll get a variation in numbers straight away. What you're after is optimising the performance and the seeing the gains with the mods, rather than aiming for a specific number.

Rowdy, peak power is usually just around the redline, as the torque curve is fairly flat, hence the power curve (torque times revs) climbs all the way. Even the drop-off at higher revs is slow compared to the rate of revs rising so the power curve continues upwards. You should have had a printout, but you can see plenty on t'internet anyway for various SVs.

James I've still got a K&N, not the first gen crap one, the next one, what sort of difference (%) do you reckon the BMC RS is worth?

[yorkie_chris]

Personally, I'd be looking for a set of flatslides for best hassle to gains ratio.

[jhsracing]

Around 5-10% sounds about right, but as James says, there are a load of corrections and influencing factors, plus you do a set of runs back to back and you'll get a variation in numbers straight away. What you're after is optimising the performance and the seeing the gains with the mods, rather than aiming for a specific number.

Rowdy, peak power is usually just around the redline, as the torque curve is fairly flat, hence the power curve (torque times revs) climbs all the way. Even the drop-off at higher revs is slow compared to the rate of revs rising so the power curve continues upwards. You should have had a printout, but you can see plenty on t'internet anyway for various SVs.

James I've still got a K&N, not the first gen crap one, the next one, what sort of difference (%) do you reckon the BMC RS is worth?
The BMC 205/10RS is by far the best filter but getting them now is hard work. We haven't had a batch mad for a long tine so the only option is to modifie a BMC 205/10 race filter which can still be bought.
james

[jhsracing]

Personally, I'd be looking for a set of flatslides for best hassle to gains ratio.
Flatslides bring their own problems. We are talking about a road machine here to it has to be user friendly. Once the CV carbs are modified they work really well.
james

[jhsracing]

It was something I looked at last year. But it was based on using a blown motor. With your exhaust system get the bike dyno'd prior to tuning the motor.
From memory Rictus had a 700 kit in a curvy and it liked to drink oil.

As a side, get onto JHS Racings website as they're doing a set of forged pistons for 200
We are also having a special at present on conrods. http://www.jhsracingstore.co.uk/PBSCProduct.asp?ItmID=15374278
But please do remember we have loads of parts which we never advertise as we just don't have the room nor time to. Just contact us we will try our best for you.
james

[andrewsmith]

We are also having a special at present on conrods. http://www.jhsracingstore.co.uk/PBSCProduct.asp?ItmID=15374278
But please do remember we have loads of parts which we never advertise as we just don't have the room nor time to. Just contact us we will try our best for you.
james

I wish I had the cash to stick a set of rods and pistons and a set of naughty cams in

[MOTO-TECH]

We are the European distributor for Spears Racing parts & have been winning Supertwin championships here in Ireland for some time now.
We can easily reach 85 plus bhp with reprofiled cams, Spears/CP standard bore, high compression pistons, Carrillo A beam rods - lighter than H beams & good for 90bhp per rod, heads gas flowed & set up on dyno.
There is no machining of heads or cylinders required.
Flat slides are the answer if you are looking for maximum power, but aren't as flexible as CV's.
Feel free to give me a call if you want a chat about your engine.

Brian
www.moto-tech.biz
2014 Adelaide Masters Champions.

[rowdy]

Dyno power outputs that's a big subject !


ALL dyno's will have a degree of positive and negative feedback but what I have seen is that operators of Dynapro dyno's seem to be very quick to run down the Dynojet dyno but do seem to forget these are the industry standard within the motorcycle trade. (that's my view)
As to power output from a k3 sv650 machine your figure is acceptable and where it should be at but a lot of factors can be brought into play,such as tyre pressure, chain tension, air temp and air supply and exstraction of the dyno room. There is loads of data on this subject on the net if you want to do some research.
hope this helps
jameswas chatting to a mate the other day and he was saying you can gain 1bhp depending on the chain used, and could feel a drop in power when the chain needed adjusting. As I mentioned, the guy that was operating the dynapro was the guy that made them, so I guess he would think they are better than dynojet dynos, but he wasn't bragging about his dyno or slating any other at the time. As for the power mine was making, he said he had dyno tested a lot of sv's at mini twin events and that mine made good power and was at the limit for legality were it to be a mini twin race bike.

Around 5-10% sounds about right, but as James says, there are a load of corrections and influencing factors, plus you do a set of runs back to back and you'll get a variation in numbers straight away. What you're after is optimising the performance and the seeing the gains with the mods, rather than aiming for a specific number.

Rowdy, peak power is usually just around the redline, as the torque curve is fairly flat, hence the power curve (torque times revs) climbs all the way. Even the drop-off at higher revs is slow compared to the rate of revs rising so the power curve continues upwards. You should have had a printout, but you can see plenty on t'internet anyway for various SVs.

James I've still got a K&N, not the first gen crap one, the next one, what sort of difference (%) do you reckon the BMC RS is worth?
It would have been nice to have had a printout, but like you say it was not about chasing numbers, just to fine tune the bike to the exhaust.
A friend of ours had just got a dyno from mark, primarily to test engines for go kart racing. The wife had arranged for me to ride up to Steve Jordan and get a full m4 fitted for a birthday present, and then to take it back down to our friends to have mark come over with his box of tricks, plug it into the ecu and fettle it, and to show our friend how to use the dyno, so wasn't able to get before and after figures.

[yorkie_chris]

Flatslides bring their own problems. We are talking about a road machine here to it has to be user friendly. Once the CV carbs are modified they work really well.
james

They sound awesome and have a lot of character. I've never had some on an SV but did have on an exup thou, they were ace once you'd got the hang of starting them.

Can you get CVs to give that same instant response? I've never managed to.

[MOTO-TECH]

You won't get the same response from CV's as you can from well set up flat slides.

Brian
www.moto-tech.biz
2014 Adelaide Masters Supertwin Champions.

[jhsracing]

Oh yes you will. The cv carbs as I said have to be modified to get great results without sheading loads of money.

[jhsracing]

was chatting to a mate the other day and he was saying you can gain 1bhp depending on the chain used, and could feel a drop in power when the chain needed adjusting. As I mentioned, the guy that was operating the dynapro was the guy that made them, so I guess he would think they are better than dynojet dynos, but he wasn't bragging about his dyno or slating any other at the time. As for the power mine was making, he said he had dyno tested a lot of sv's at mini twin events and that mine made good power and was at the limit for legality were it to be a mini twin race bike.


It would have been nice to have had a printout, but like you say it was not about chasing numbers, just to fine tune the bike to the exhaust.
A friend of ours had just got a dyno from mark, primarily to test engines for go kart racing. The wife had arranged for me to ride up to Steve Jordan and get a full m4 fitted for a birthday present, and then to take it back down to our friends to have mark come over with his box of tricks, plug it into the ecu and fettle it, and to show our friend how to use the dyno, so wasn't able to get before and after figures.


To be honest just fit the full system and don't touch the ECU it does not return the results and you are only changing the basic fueling.
jh

[yorkie_chris]

Oh yes you will. The cv carbs as I said have to be modified to get great results without sheading loads of money.

What do you modify on them?

[jhsracing]

What do you modify on them?


We go through the carb from inlet to exit. Bellmouths, machining inlet face to aid airflow into the carb. Emulsion tube modified,of course the use of a dynojet kit is required, the butterfly is modified and the shaft machined again to aid flow rate,the exit of the carb into the manifold is where the real work is at with a much bigger radius and rubber modified. Of course none of this is minitwins legal, but we have done a lot of this work for road customers and specials builders.
james