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Yamaha XS880 rephased

Discussion in 'The Garage' started by howardsmed, Oct 7, 2020.

  1. howardsmed

    howardsmed Ragged trousered Philanthropist

    This racing season was short for us, only four races. In 2020 we fielded an 880cc rephased XS650. Raised inlet ports, larger valves, 87mm wiseco pistons, and new design cam, ductile iron liners and other parts designed by me. The engine goes well, we had it dyno tested at Richard Albans TTS in Northampton, where we test all our engines. 90hp rear wheel at 7500rpm, and 65lbs/ft torque. Richard congratulated us on building " a very high performance tractor".

    This engine isn't even pushing the red line up, it will run happily on super unleaded fuel. It is the culmination of five years of CRMC sidecar racing efforts, last year Steve Mann's bike won the trophy, this year we are in a different class racing bigger engined BMW airheads. As a potential street bike engine, in a lightweight chassis, it would be fun.

    Howard ( ex Smedspeed) but still in the game
     
  2. Paul Sutton

    Paul Sutton Still Looking Good Top Contributor

    Impressive! :bike:

    Edit: My apologies, I enquired about the oil situation but deleted it as I did not want to detract from the thread. Howard has been running Mobil-1 Extended Life 10W-60 for a long time in standard XS650 engines and encountered no issues. This oil has 1300 ppm ZDDP plus other additives.

    See Entry 7 for his comments today.
     
    Last edited: Oct 7, 2020
    Bewarethemoon likes this.
  3. howardsmed

    howardsmed Ragged trousered Philanthropist

    Steve Mann 1st came to me around 6 years ago, I built him a mild engine for a sidecar road race bike, lat year he stripped it for the owner who races in France. It was in superb internal condition, BUT the engine has a proper filter, and runs synthetic all the time. We built many 750 engines, each one getting more powerful. The best we got was 76hp rear wheel again on TTS dyno. max power at 8300rpm.
    We cant catch the BMW airheads, they are 1070cc, and 107hp, again on the same TTS dyno. But we have a good time chasing them, our engine was £5K, their cranks alone are more than 1/2 that !!
    the solution and one of the main power additions are the lifted ports, now at 12 degrees. The port is not much larger, just much straighter, we actually fill some of the port with epoxy.
    There are a few more hp lurking in the engine, retarding the cam timing will yield a few more at the expense of lost bottom end power.
    We will see how it goes.
    What is surprising is how little we have had to add to go from the stock 38hp to 90hp
     
  4. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    I'd love to see some pics of that.
     
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  5. howardsmed

    howardsmed Ragged trousered Philanthropist

    Of the engine or the bike ?

    the engine build work is the same as my 880, it can be found on Smedspeed website.

    the bike can be found on the CRMC website
     
  6. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    I was referring to the port work. Thanks, I'll check out your website.
     
  7. howardsmed

    howardsmed Ragged trousered Philanthropist

    When Yamaha designed the XS650, they specified 20/50. They specified a mineral oil too. That was the industry standard at the time. With the passing of time, mineral oil and 20/50 are now quite hard to obtain, thinner oils ( of the same strength) mean quicker and more effective lubrication of parts furthest away from the oil pump, and when fuel economy is sought ( which it has to be by law now) less internal drag
    Yes I run, as do may others 10/60 in my 650s. I run 15/50 too in my TDM and Buell and old Airhead BMW, but all synthetic.
     
  8. howardsmed

    howardsmed Ragged trousered Philanthropist

    The port work isn't on the website, some things are secret. Suffice to say that once we finished the inlet porting, the flow was still good at .515 lift.
    I designed the cam based on the flow bench figures
     
  9. howardsmed

    howardsmed Ragged trousered Philanthropist

    Here's the dyno sheet. It is a racing engine, that's what it is supposed to do, The big carbs make it slightly fluffy at low rpm, just like an old Bevel Drive Ducati, BUT bear in mind its blisteringly fast and the sidecar is 150kg and a rider AND a passenger another 140-150kg.
    There have been a lot of 840 and 880 engines built in the past. The engineering work is complex, finding the right cam is equally hard, but it can be done, its here in black and white. Many people say they are very torquey, but nom more power than a 750. Hmm think that might be wrong.

    All available at Smedspeed XS650 SMEDSPEED 90 hp xs880.jpg
     
  10. Paul Sutton

    Paul Sutton Still Looking Good Top Contributor

    Thank you Howard for the oil update. It gives us another oil option should the need arise and its also great to know there are other users also satisfied with this Mobil product.

    Thank you.
     
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  11. howardsmed

    howardsmed Ragged trousered Philanthropist

    Many years ago, when we were all running HD Evo engines, a good friend and I started using the new Castrol Syntron X in our bikes, all the nay-sayers proclaimed the roller bearings in the crank would skid, and the big ends would explode. Well they never did, and now Harley and S&S wont warranty an engine unless it has synthetic engine oil in it, my how attitudes have changed. The same is for the XS650, NO the big ends wont explode, YES the oil will prevent scuffing if there is borderline lubrication. I ran my XS1 on the dyno, it had Mobil 1 10/60 in it, the clutch didn't slip either.
    The Silkolene 15/50 fully synthetic is excellent too. we use it in the race bike
     
  12. Jack

    Jack XS650 Junkie Top Contributor

    Impressive output for sure! Don't know what your doing in preventing case failure where others have failed exceeding 75 HP.
    Knew a guy in Michigan who built a water cooled XS 900 plus CCs to compete with Harleys on dirt with custom home built babbitt bearing automotive titanium type crank with ti rods, same type of head work,re angled valves with aluminum combustion caps, BIG ports raised etc. Cases had to be stock but rules allowed inner mods to stiffen cases which he did. Output at rear wheel was 100 plus HP.
    Any chance you have a video of your beast?
     
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  13. howardsmed

    howardsmed Ragged trousered Philanthropist

    Yes we are particularly pleased. We know exactly why the cases haven't broken and I will tell you. The engine is 277 rephased, so the inertial torque forces ( which are huge, see my website for the calculations) are almost wholly mitigated, Phil Irving approached all the British bike manufacturers in the early 60s and suggested they should be 270, but was rejected as it gave an uneven firing order. (odd as Phil Irving designed the Vincent ) the crank Is perfectly true, the forces that the cases see are actually less now than on a standard 360 engine. The broken cases conversations are regurgitated stuff from the flat track racing days of the 70s, no one actually breaks cases these days, or if they do they are not doing it properly.
    To ensure the cases have as little metal removed for the cylinder liners, we specify ductile iron, this allows for a very thin section where they go into the cases. the cases are also bored very quite close to the liners, and then de-burred, polished and shot peened. we have never broken a set of cases too date.
    The ports on our engine are smaller than standard where it counts. we use valves from a very old firm who make for F1, The 750 engine we raced did three seasons before put back into the garage, it hadn't gone bang, it was just superseded. ( poor thing all that hard work just to be pensioned off)
    Yes I do have a video, but this site doesn't allow for MOV files !
    The race season is over now, we have some ideas for the engine, but all the big hp gains have been had. we could go up on valve size, retard the cam timing and add a bit more compression, but we wont have the tractability

    I can send you the video if you send me your email

    Howard
     
  14. Wordman

    Wordman XS650 Addict

    880? Wow! How do you get 880cc?
     
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  15. Jack

    Jack XS650 Junkie Top Contributor

    Howard.......I know of only one race team"The club racer" who have experienced case crack failure at the rear mount,as to what cause it they
    never posted the reasons. Small ports can and will reward you with sufficient flow gains( where you want this gain occur) and velocity which in return will reward you with power gains. Looking forward to the video and Thanks.
     
  16. SomervilleXS650

    SomervilleXS650 XS650 Addict XS650.com Supporter

    Really cool stuff, thanks for sharing Howard. And thanks for the edit above Paul highlighting the oil recommendation.

    I'll preface this question with a disclaimer that I am NOT intending to hijack this into an "oil thread"....but does anyone have any insight into the Mobil-1 Extended Life 10W-60 that Howard and Paul Sutton are discussing and it's apparent lack of availability in the US? I went to check it out after reading through the thread and all searches seemed to direct me towards EU/UK websites.
     
  17. howardsmed

    howardsmed Ragged trousered Philanthropist

    Hi Wordman

    The 880cc conversion uses an 87mm piston, it has to use a 533 type crank, which has 140mm rods, the cylinder HAS to be a Heiden big fin item. The cylinder liners are a Smedspeed item, made especially for the conversion from ductile iron

    I have built around six, the race bike is the most powerful, but only because it is a race bike
     
  18. howardsmed

    howardsmed Ragged trousered Philanthropist

    Yamaha modified the rear mount two or three times over the years, so they too were aware of a problem, very big bore engines crack the cases where the cam chain blade is, but we machine a radius there, and then shot peen the area. A little diligence early on saves a whole bucket of £££ later.
    I have a BMW R80ST, ( I know, I know, why would anyone want one ?) I bored it to 980cc, and used the small port heads but with the larger 44mm valves , it too will live on very high velocity not sheer flow numbers. I always set the engine up so sonic choke occurs around a 1000rpm short of the redline.
     
  19. howardsmed

    howardsmed Ragged trousered Philanthropist

    Hi Somerville

    the Silkolene 15/50 synthetic is also absolutely 1st class.
     
  20. Jack

    Jack XS650 Junkie Top Contributor

    Howards race sidecar looks amazing,sounds great for a rephase and workmanship is top notch. 90HP strapped between two XS wheels
    would definitely be an thrilling experience :bike:
     

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