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1/4 mile sprinting on an xs650

Discussion in 'The Garage' started by jay760, Oct 23, 2018.

  1. jay760

    jay760 XS650 Junkie

    Thought I would start a thread on my bike, I had been watching sprinting for a few years before I had a go, I took my 750cc xs650 down and got a time of 13.68 without even topping 100mph, took a break for a few years then joined the nsa and have been taking part ever since, when I first started it was on an engine I built while in Australia, 707cc and web camshaft it was quicker than the 750 engine but not by much web.jpg
     
    MaxPete, Jim, Superjet and 3 others like this.
  2. jay760

    jay760 XS650 Junkie

    Over the next couple of years the bike to on a few different guises but was basically the same bike, until I found a top end on eBay for not much money it included a ported head, unknown cam with 750 barrels and pistons these were fitted to the 707cc engine, the bike by then had a champion tank and seat unit 002_zps7e48505f.jpg
     
    Mailman, MaxPete, Stardust83 and 5 others like this.
  3. CBJamie

    CBJamie BIKE ADDICT

    001.JPG Love the old Tracy body I have one on a CB750
     
    MaxPete, Jim and gggGary like this.
  4. jay760

    jay760 XS650 Junkie

    WP_20151128_002.jpg
    A different Tracy body went on, I also changed the frame to an xs2 frame to save weight, about this time I managed to save enough to buy kibblewhite valves, guides and springs.
     

    Attached Files:

    Mailman, MaxPete, peanut and 4 others like this.
  5. jay760

    jay760 XS650 Junkie

    I didn't get on with the Tracy body, found the seat was too high and too far back the front end was lifting all the time, so now I have the latest version of the same bike 20180915_151615.jpg
    With just a small alloy tank and cafe racer seat,
     
  6. jay760

    jay760 XS650 Junkie

    That's the brief history with quite a bit missed out or it would have gone on forever, now to the present, I need to emphasise that I am not a mechanic, engineer or have virtually any disposable income, so I either have to look long and hard on eBay for bits people have missed or try and work out if I can afford them,
    Being around 200lbs my main competition in my class weighs around 60lbs lighter than me and goes through the 1/4 at just below 11.5 sec so I'm always looking for some way to get closer if not beat him, so want to do some work on my present engine, I have another engine which will come in for the start of next season, 533 rod euro engine, I managed to get some je pistons though not sure if they were originally designed for the xs as they have a wide lip around them 20181021_154825.jpg
    Will use the head with the 1mm over Kibblewhite valves 20181021_154842.jpg 20181021_154901.jpg 20181021_154922.jpg
    With a megacycle 250-40 cam
     
    MaxPete, gggGary and Jim like this.
  7. peanut

    peanut XS650 enthusiast & inveterate tinkerer Top Contributor XS650.com Supporter

    great story Jay.............. I shall be following this with keen interest.
    Sounds like a great way to get into racing with a minimal investment and on a tight budget but like everything once you're hooked it probably becomes a bottomless money pit :)

    If you ever get any video of any of your runs stick em up....I would love to see them.

    Don't forget the cheapest way to increase horsepower is always weight loss first. ....... so ...less do-nuts and pasties :laugh2:
     
  8. peanut

    peanut XS650 enthusiast & inveterate tinkerer Top Contributor XS650.com Supporter

    kinell...:eek:

    Great run...engine sounds fantastic ... The stretched out position is certainly helping stability and keeping the front end down.
    What was that annoying 2stroke demented wasp sound coming from lol
     
    MaxPete, gggGary and Jim like this.
  9. CBJamie

    CBJamie BIKE ADDICT

    That small alloy tank and simpile seat should save you a few pounds. I just really like the looks of the Tracy bodies. I bought my Tracy bodied 750 from a guy that was drag racing it, the whole machine was drasticly lowered. Seat heigth was 22" and only had 2.5" of ground clearence. I converted it back to a cafe' streetbike. Though its still very low. Your XS sounds great, have you thought about doing a rephase? I know its expensive but you'll get higher RPM's and a wider power band.
     
    MaxPete and gggGary like this.
  10. jay760

    jay760 XS650 Junkie

    I have thought about rephasing just to see what the difference would be, but it would take a long time to afford how I would want it, I do have another engine in bits I may slowly get it built as a rephase.
     
    MaxPete and CBJamie like this.
  11. If that Tracy body is for sale, please let me know. I could make the long journey from Wiltshire to Somerset with some minor planning ;)
     
    MaxPete likes this.
  12. jay760

    jay760 XS650 Junkie

    20190114_130255.jpg Picked up an old race fairing, just about finished mocking it up in place, hopefully it will increase speed/times
     
    MaxPete, TwoManyXS1Bs and 59Tebo like this.
  13. peanut

    peanut XS650 enthusiast & inveterate tinkerer Top Contributor XS650.com Supporter

    pity there isn't a college near you that has a wind tunnel you could use .;)

    Incidentally what squish and compression are you running on this engine ?

    I was amazed to read recently about the huge increase in power that can be had by closing up the squish to the minimum or slightly less. I cannot find a reference to the stock squish at the moment but Howard at Smedspeed has this to say about a 880cc engine .
    http://www.smedspeed.co.uk/tech.html
     
    MaxPete and TwoManyXS1Bs like this.
  14. jay760

    jay760 XS650 Junkie

    As I have said I'm no mechanic or engineer, the main thing I worry about is parts hitting, I put solder wire in to see if it gets crushed that's as far as it goes, compression is somewhere around 11.5-1, I have started using nf fuel additive I had been looking at race fuel but don't use enough to warrant the cost.
     
    MaxPete likes this.
  15. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Jay, streamlining starts to become significant at about 60 mph (100 kph). Expect your 0-60 (or 0-100 kph) times and distances to remain about the same. Beyond those, expect improvements...
     
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  16. jay760

    jay760 XS650 Junkie

    That's what I'm hoping, I'm not the smallest person in the world so getting my bulk behind something has to help, at the end of last season I was less then 1/2 a second behind my competition who is about 50lbs lighter than me even at my lightest weight I would still be about 30lbs heavier,
    I did ask him if he would take the bike up the strip to see what it would go like with a lighter rider but he wouldn't, so will never have a like for like comparison between the bikes.
     
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  17. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Uh-oh.
    Better not read my BBQ postings...
     
    MaxPete, gggGary and jay760 like this.
  18. peanut

    peanut XS650 enthusiast & inveterate tinkerer Top Contributor XS650.com Supporter

    that looks the business Jay ...reckon even I could get behind that.
    When and where is your next run ?
     
    Last edited: Mar 17, 2019
    MaxPete and TwoManyXS1Bs like this.

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