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Thread: Project 2

  1. #1
    Join Date
    Aug 2008
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    Default Project 2

    So, I have anouther project... well a collection of parts which dosent quite reach the full sum of a bike but its not that far off. Whilst its all tucked away in the spare room I have had to make assurances that the house and Project 1 888/S4RS will be finished first.

    Its a retired race bike from the Bott serise early 90s, was once owned and raced by Roy Armstrong. It started out I beleve as a 851 Kit bike, though relations I beleve Roy had with the factory over the years the bike became kitted with some rather nice parts.

    Ive managed to get most of the parts but not all, this just to reminde you was a race bike by Roy not a corsa/racing.

    I was unable to purchase the cases but strangley most other parts of the engine. However this is the where I seek the advise. I have G&421 cams close ratio box cylinders and pistons & crank and rods with 20mm pins.

    I also have a set of race cases period correct (not really wanting to use these), but as its a race bike and not a corsa to restore in all there beauty I am pondering the build for the engine. I have accsess to a new unsed late sp5 cases or should i go for ST4S with 996sps cams. Im not likley to be srceaming it around a track and looking for that 12 thou on the rev counter but would like a strong & fast motor for the eventual track day exploration.

    Mr R, Brad anyone with an opinion I would be greatful as Project 1 is nearing compleation. (But alas not the house)

    Thanks
    Surfking

  2. #2
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    Project 1 is nearing completion................have I missed something ?????

    My tuppence worth.............why not a 996 engine 110 Hp and 70ft/lbs of torque as standard. Plenty around , easily tuneable and won.t cost the earth. Slots straight in , 996 SPS double injection , larger exhaust.

  3. #3
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    Default

    As I understand you seem to noted cases thorough the ages, in that they got better as they were improved throughout their life cycle.
    Whatever you do, balance the crank assembly, 300 miles was the expected life for a race Corsa in 1992.
    To summarise I think you need to ask yourself what you are going to use it for and asses the risk of damaging the cases given the use you choose, personally I'd fit the period piece if not for race use.
    celeresracing.blogspot looking-back-at-2016-classic-tt
    Power tends to corrupt and absolute power corrupts absolutely.

  4. #4
    Join Date
    Jan 2015
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    Chicago
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    Cut the baby in half--use a 996 now, but put a period motor together for the future.
    '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 café.

  5. #5
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    Quote Originally Posted by surfking View Post
    Im not likley to be srceaming it around a track and looking for that 12 thou on the rev counter but would like a strong & fast motor for the eventual track day exploration.
    Haven't you kinda answered your own question? If you are not going to be racing and constantly exploring the 12krpm mark any of the above options would be fine wouldn't they? It just depends on how you picture the bike in your head.

    After much umming and aahing I picked up a rebuilt 999RS engine to replace the cooked unit in my 749R race bike, but only after talking to a couple of RS experts in your neck of the woods. They both pretty much said the same thing: treat an RS like a road engine and it will outlast and outperform a modified road engine treated like an RS. An RS at WSB level makes 190 odd hp at 13krpm (13.5krpm if you are Chili and never look at the tacho, lol), but needs rebuilding every 500km's. I'm happy with my RS making a relatively unstressed 168rwhp at 11.5krpm, should last ages....whereas a 999R built to make that sort of grunt is going to be living on borrowed time.

    It's like that "90% of the wear happens on start up" mantra is turned on it's head for race engines: 90% of the stress occurs in the last 10% of the rev range.

    Sorry, this is a long winded way of saying if you just run a real world redline rather than a BSB/WSB-spec redline even the old race cases will be relatively unstressed, especially if they are sand cast.

    I'm a romantic but it seems kind of a shame to have most of the bits to build a very cool old race bike and put an St4S engine it. But "needs must", what constitutes a "strong fast motor"?

    EDIT: apologies for the waffle, it's a quiet nightshift!

  6. #6
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    st4s.
    Brad The Bike Boy

    www.bikeboy.org

  7. #7
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    Got NOS late 888 cases sourced, crank with 20mm, waiting for barrels & 94mm pistons with 20mm, close ratio Gears, Cams G/431

    So still collecting parts need to start thinking about the heads, I have some notes somewhere for the what he ran when he was racing, i think 37/31 but will have to check.

    Nick
    Surfking

  8. #8
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    Default Pistons & Cylinders

    Got the heads sorted, late corse type with machined front for clearance. But want to look at making 1 926so need to sort pistons and cylinders, want to remain on 64mm crank etc with 20mm pins.

    There is many bits of info on here but just trying to drill down to facts. Has any one used these? or have experience or point of view. Am I on to the right thing? is the pin to the piston crown too high?

    Appreciate feed back

    https://www.ebay.co.uk/itm/KIT-PISTO...19.m1438.l2649

    Have drawing can't post again!! will try to add
    Last edited by surfking; 05-19-2018 at 03:09 AM.
    Surfking

  9. #9
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    The 96mm 955cc pistons are designed to be run with a 66mm stroke 916 crank.
    They have a different deck height to the 96mm items intended for a 64mm stroke 851/888 crank.

    Steve R

  10. #10
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    Quote Originally Posted by Mr.R View Post
    The 96mm 955cc pistons are designed to be run with a 66mm stroke 916 crank.
    They have a different deck height to the 96mm items intended for a 64mm stroke 851/888 crank.

    Steve R

    Thought that was the case, where should I look for 96mm/926 any ideas Mr R? would really like to stick on the original crank & rods with 20mm end.
    Surfking

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