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Thread: ST4S - SPS racer

  1. #41
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    Nope.
    '01 996R, '94 888 SPO Ltd, '88 851 Adamo racebike, '91 ZX-7R K1 homologation, '89 NSR250 MC18r5k, '01 Derbi GPR50/75, '71 CB450/500 cafť.

  2. #42
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    Jun 2007
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    Quote Originally Posted by stiglarsenDK View Post
    Building 2 more engines with the same recipe .. St4s w 996 sps left side...

    I have sourced all the 996 (2000) parts and some RS flywheel, rotor and stators parts as well.

    The RS flywheel is not having starter feature ... hmm .

    Did some parts weighing and come up with -2.3 KG rotation and - 2.6 KG static, hence we are talking 5kg !

    Iím tempted to take out the 5 kg as itís for racing ... Iíll need a roller starter ... (if any advice here, please share does and doníts
    Ah Flywheels. Flywheels are an energy storage device that can double as harmonic balance to reduce inherant vibrabration. Iíve run a 250 with and without, and a 900 bevel with and without. What power you put in due to rotation momentum, you get back. So itís all about acceleration and deceleration time. I would suggest strongly the factory race bikes have a bead on this already and so wouldnít deviate from what they use.
    There was a car guy on the net writing about lightening flywheels and his conclusion was as the power used to drive them was relatively small, they were the very last thing he would consider in performance enhancement. Considering how much torque your going to develop I doubt youíll be able to notice the difference. Of coarse a couple of dyno runs will give you the definitive answer.


    My conclusion from running without on a 250 was the acceleration gain was relatively small, at the cost of increased vibration. Vibration itself saps power to a degree, and increases the chances of things becoming loose. Not to mention fuzz hands and feet and in the case of the 250 an uncomfortable sphincter (yep at 13000rpm itís nasty). This time on my twin iím Going half way between zero and full flywheel, to reduce hand fuzz. (I have weighted clipons already)

    Seeing how your looking at all of this, consider reading up on ceramic bearing. The good ones are expensive, but there are gains to be made as they can run closer tolerances because heat is not an issue. Smooth is fast.


    As for using starter rollers, that depends on how much you value the cash you spend for track time, versus your desire to be Carl Fogarty. If it snuffs out for some reason like a run off, thatís the end of your laps. At least you stand a chance If you can fire it up again out on the circuit. In hysterical racing forgetting to turn on fuel taps is rather expensive!
    Griff
    To infinity and.......

  3. #43
    Join Date
    Apr 2013
    Location
    Perth, Australia
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    122

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    Quote Originally Posted by stiglarsenDK View Post
    Building 2 more engines with the same recipe .. St4s w 996 sps left side...

    I have sourced all the 996 (2000) parts and some RS flywheel, rotor and stators parts as well.

    The RS flywheel is not having starter feature ... hmm .

    Did some parts weighing and come up with -2.3 KG rotation and - 2.6 KG static, hence we are talking 5kg !

    I’m tempted to take out the 5 kg as it’s for racing ... I’ll need a roller starter ... (if any advice here, please share does and don’ts

    As mentioned by others, great looking project!

    You say "racer" (rather than track bike) so I'll give you my experience with my 749R/999RS race bike, and an HRC'd CBR1000RR with no starter.

    It really is a double edged sword. My 999RS engine was supposedly AMA-spec so it came with all the (unfitted) starter parts but was set up as a "normal" RS. I went to fit the AMA-RS starter parts only to find the crank was a run of the mill RS so not drilled for oiling the starter parts. Bugger.

    But in playing around with it I got pretty well acquainted with the differences. For those who haven't seen one this is a normal RS flywheel. It's not the best pic but basically it is just a wafer, approx 2mm thick:



    With this flywheel there is a small spacer that fills in the real estate where the starter gear would normally sit. So you actually lose a helluva lot more than just the reduced flywheel weight.

    The AMA-RS flywheel was a fair bit meatier (to support the starter gear/sprag) etc but still substantially lighter than the 749R flywheel, the starter gear is lightened and the alternator rotor is also lighter than a 749R unit. So all up it is very lightweight compared to even the lightweight stuff on a 749R, but a true RS setup is in a different league, especially when you factor in the H-beam Ti rods, lightweight Omega pistons and short stroke lightweight crank.

    But on track it is sensational. The throttle response is amazing, giving you exactly what you want exactly when you want it, and the bike is noticeably more agile with less rotating mass. It is just a beautiful thing, not at all vibey, with awesome drive off the corners.

    The downsides rear their ugly head when you are not circulating.

    I remember being stuck on a grid with a delayed start after someone crashed on the warm-up lap, watching the temperature gauge rising....waiting....rising....waiting....nervous times! I've also stalled once on the grid, which screwed that race result even though I was able/allowed to push start the IL4 after everyone had buggered off.

    Same for a red flagged race and you are waiting on the dummy grid: is it practical for your offsider to bring the starter to the grid? If not you are stuck with the bike running again, getting hot, chewing fuel when your rules probably say there is no refuelling allowed.

    What compression is your 98mm bore 996 going to be? I learnt the hard way how difficult it is to start a big twin with 104mm pistons and 14:1 compression. Being Nigel-no-mates at the track I bought an electric starter with a foot switch so I could start the thing without any outside assistance.



    It is plenty grunty....but not as grunty as the RS engine, and all the bike wanted to do was climb over the back of it even when strapped down.

    An ex-WSB mechanic informed me an RS needs to be spun up to 100kph in top gear, using the rear wheel as a flywheel to overcome the compression. Righto then, and I set about changing the drive sprockets on the starter and sped it up as much as I could, close, but no cigar.

    So I built this:





    A 6.5hp Chonda (Chinese-Honda copy), with integral 2:1 reduction drive, go kart rim and tyre....and it works like a charm. Even ticking the electric start option (brilliant!) it was dirt cheap, as was the rim and the kart shop threw in an old tyre for free! It works well enough that during dyno tuning we stopped taking the bike off the dyno to start it and just cranked up the (heavy!) dyno drum using the starter, what a lil' champion, lol.

    I take it you'll also be running a slipper clutch? You'll need something like a 4-spring Corse unit with a pin for locking the slipper action, for obvious reasons.

    Another thing to think about is the battery: with no starting capacity required you can run a ridiculously small battery which opens up all sorts of placement options. You could easily mount a tiny battery up front where the Corsa bikes put the ECU.

    Bottom line, I highly recommend the lightweight RS gear on track....just as long as you can live with the downsides off track.
    Last edited by seven4nineR; 03-17-2019 at 03:03 AM.

  4. #44
    Join Date
    Feb 2011
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    Denmark
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    644

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    Quote Originally Posted by seven4nineR View Post
    As mentioned by others, great looking project!

    You say "racer" (rather than track bike) so I'll give you my experience with my 749R/999RS race bike, and an HRC'd CBR1000RR with no starter.

    It really is a double edged sword. My 999RS engine was supposedly AMA-spec so it came with all the (unfitted) starter parts but was set up as a "normal" RS. I went to fit the AMA-RS starter parts only to find the crank was a run of the mill RS so not drilled for oiling the starter parts. Bugger.

    But in playing around with it I got pretty well acquainted with the differences. For those who haven't seen one this is a normal RS flywheel. It's not the best pic but basically it is just a wafer, approx 2mm thick:



    With this flywheel there is a small spacer that fills in the real estate where the starter gear would normally sit. So you actually lose a helluva lot more than just the reduced flywheel weight.

    The AMA-RS flywheel was a fair bit meatier (to support the starter gear/sprag) etc but still substantially lighter than the 749R flywheel, the starter gear is lightened and the alternator rotor is also lighter than a 749R unit. So all up it is very lightweight compared to even the lightweight stuff on a 749R, but a true RS setup is in a different league, especially when you factor in the H-beam Ti rods, lightweight Omega pistons and short stroke lightweight crank.

    But on track it is sensational. The throttle response is amazing, giving you exactly what you want exactly when you want it, and the bike is noticeably more agile with less rotating mass. It is just a beautiful thing, not at all vibey, with awesome drive off the corners.

    The downsides rear their ugly head when you are not circulating.

    I remember being stuck on a grid with a delayed start after someone crashed on the warm-up lap, watching the temperature gauge rising....waiting....rising....waiting....nervous times! I've also stalled once on the grid, which screwed that race result even though I was able/allowed to push start the IL4 after everyone had buggered off.

    Same for a red flagged race and you are waiting on the dummy grid: is it practical for your offsider to bring the starter to the grid? If not you are stuck with the bike running again, getting hot, chewing fuel when your rules probably say there is no refuelling allowed.

    What compression is your 98mm bore 996 going to be? I learnt the hard way how difficult it is to start a big twin with 104mm pistons and 14:1 compression. Being Nigel-no-mates at the track I bought an electric starter with a foot switch so I could start the thing without any outside assistance.



    It is plenty grunty....but not as grunty as the RS engine, and all the bike wanted to do was climb over the back of it even when strapped down.

    An ex-WSB mechanic informed me an RS needs to be spun up to 100kph in top gear, using the rear wheel as a flywheel to overcome the compression. Righto then, and I set about changing the drive sprockets on the starter and sped it up as much as I could, close, but no cigar.

    So I built this:





    A 6.5hp Chonda (Chinese-Honda copy), with integral 2:1 reduction drive, go kart rim and tyre....and it works like a charm. Even ticking the electric start option (brilliant!) it was dirt cheap, as was the rim and the kart shop threw in an old tyre for free! It works well enough that during dyno tuning we stopped taking the bike off the dyno to start it and just cranked up the (heavy!) dyno drum using the starter, what a lil' champion, lol.

    I take it you'll also be running a slipper clutch? You'll need something like a 4-spring Corse unit with a pin for locking the slipper action, for obvious reasons.

    Another thing to think about is the battery: with no starting capacity required you can run a ridiculously small battery which opens up all sorts of placement options. You could easily mount a tiny battery up front where the Corsa bikes put the ECU.

    Bottom line, I highly recommend the lightweight RS gear on track....just as long as you can live with the downsides off track.

    Thanks for all the comments here, i recon that less flywheel is not always better, and not having a starter feature is not always a good thing either...
    The 999 AMA-RS fly with starter provision ; pls check foto
    This and the no starter RS flywheel has 8 pick up features ??? where the normal 2 sensor sps need 4 ... I guess it can be explained with a different cpu/controller.

    Anyway the AMA-rs flywheel unit may work after chopping the 4 extra taps off ? ;-)
    Attached Images

  5. #45
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    Apr 2013
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    Perth, Australia
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    Quote Originally Posted by stiglarsenDK View Post
    Thanks for all the comments here, i recon that less flywheel is not always better, and not having a starter feature is not always a good thing either...
    The 999 AMA-RS fly with starter provision ; pls check foto
    This and the no starter RS flywheel has 8 pick up features ??? where the normal 2 sensor sps need 4 ... I guess it can be explained with a different cpu/controller.

    Anyway the AMA-rs flywheel unit may work after chopping the 4 extra taps off ? ;-)
    Yes, that's exactly the AMA-RS flywheel setup I have. You've done well to find it, they are very thin on the ground.

    Luckily using the 749R ECU/harness for the 999RS I only needed the single CPS looking at the timing gear so didn't have to worry about the pick ups on the flywheel. Machining off the unwanted pick ups would be no problem at all....just make sure to pick the right ones in relation to the timing mark, lol.

    To be honest I don't think it's possible to make the rotating components of a Ducati twin too light for track work, especially if it is a road based engine. The reduced rotating mass helps in every single aspect. It is not like a +200hp 4 cylinder with a tiny stroke (V4R is just 48.4mm) and light switch power delivery. Corse went out of their way to lighten every single rotating component for a reason....and even now the V4R crank is 1.1kg's lighter than the V4S, with a shorter stroke, so imagine the difference in gyroscopic forces at 16000rpm! It's obviously a bit different for something that is going to be pottering through traffic and around town.

    But yeah, a lack of starter does make for many more complications. When I was starter-less more than once I found myself looking at that beautiful lil' button on other peoples handlbars with outright lust in my heart, lol.

  6. #46
    Join Date
    Feb 2011
    Location
    Denmark
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    Default Flywheel options

    Quote Originally Posted by seven4nineR View Post
    Yes, that's exactly the AMA-RS flywheel setup I have. You've done well to find it, they are very thin on the ground.

    Luckily using the 749R ECU/harness for the 999RS I only needed the single CPS looking at the timing gear so didn't have to worry about the pick ups on the flywheel. Machining off the unwanted pick ups would be no problem at all....just make sure to pick the right ones in relation to the timing mark, lol.

    To be honest I don't think it's possible to make the rotating components of a Ducati twin too light for track work, especially if it is a road based engine. The reduced rotating mass helps in every single aspect. It is not like a +200hp 4 cylinder with a tiny stroke (V4R is just 48.4mm) and light switch power delivery. Corse went out of their way to lighten every single rotating component for a reason....and even now the V4R crank is 1.1kg's lighter than the V4S, with a shorter stroke, so imagine the difference in gyroscopic forces at 16000rpm! It's obviously a bit different for something that is going to be pottering through traffic and around town.

    But yeah, a lack of starter does make for many more complications. When I was starter-less more than once I found myself looking at that beautiful lil' button on other peoples handlbars with outright lust in my heart, lol.
    A small progress on the flywheel case.

    Have modified the AMA 999 RS (chopping off the extra 4 Pick up features not needed for the P08 box)
    Except the need for an aprox 3mm thick spacer between the crank gear and flywheel spacer, its all a perfect fit. super light, I’ll keep my starter (will try to lose those 2kg myself next summer) The center pos flywheel in last foto is from an 996SPS , the right hand side is the std ST4s (no pick up on flywheel) I’m thinking using the rs rotor/stators for both engines as for track use.
    Last edited by stiglarsenDK; 03-27-2019 at 01:32 PM.

  7. #47
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    Thanks for the picís Stig, the last one in particular is really interesting.

  8. #48
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    FYI Nichols Sportbikes still have an alloy SPS flywheel available. Expensive though

    https://nicholssportbikes.com/product/nmi-sps-flywheel/

  9. #49
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    Quote Originally Posted by Speedmade View Post
    FYI Nichols Sportbikes still have an alloy SPS flywheel available. Expensive though

    https://nicholssportbikes.com/product/nmi-sps-flywheel/
    Hi, yep have one of those alu ones as well.. I have seen some where a similar alu flywheel give up, and spitting out the alu splines .. ;-( not sure if a real issues ? But super light ! Here with std st4s big rotor
    Attached Images
    Last edited by stiglarsenDK; 03-28-2019 at 01:01 PM.

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