Archive for the ‘Motor – Cam’ Category

XS650: Rocker Shaft Removal   Leave a comment

Have been cleaning up a couple of SR500 heads. Ready for porting, new valves and rocker shaft bushing. Needed to remove the shafts. Rooted around in the odds’n’sods bin.

  • 2 x pieces 6mm threaded rod
  • 1 x long open ended 6mm joiner
  • 2 x 6mm nuts
  • 1 x 6mm dome nut
  • 12 x large 6.5mm washers
  • 1 x piece duct tape

5 minutes. No cutting. A perfectly good 6mm slide hammer.

52c8e8bd-d629-44ef-ac95-4c49409fa2ca

Screw into the rocker shaft. Off you go.

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Same principle for the XS.

 

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XS650: Clear Tappet Covers?   Leave a comment

Like to watch?  Got a thing about control?

leo speed shop at play, feb 2011 … clear tappet covers … take a look …

… four eyes !! …

 

… here’s looking at you …

 

… even has eyes in the back of its head …

 

… think it’ll take LED backlighting ?? …

 

… do the ayes have it ?? …

 

Have they held up to the heat ?

   … the vibration ?
… the oil ?
… discolouration ?
… opacity ?

Wonder what the story is??

Posted March 6, 2012 by xscafe in Motor - Cam, Motor - Head

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XS650: Twingle   Leave a comment

The Urban Dictionary describes Twingle as:

  • A contraction of the words Twin and Single. A twin cylinder motor running a close firing order ignition timing that mimics a single cylinder motor to provide better traction. Most commonly used in reference to motorcycle flat track racing. Referred to as a “big bang” motor when used in reference to multi cylinder machines
  • To twingle : such a state of euphoria that your entire body has the feeling of being asleep, but doesn’t hurt. It’s like when your foot falls asleep but covers your entire body from head to toe, and doesn’t hurt when you walk
  • An internal combustion engine in which more than one piston is actuated by a single connecting rod (often “V” or “Y”-shaped)
  • to play with
  • When an individual, usually a young pre-teen girl, decides to “save herself” for Edward Cullen, forgetting he is a fictional character.These individuals are usually found in groups, and can be heard screaming at the mere sight or mention of said fictional character.
  • The slightly painful tingling, itching, arousing feeling felt in the balls when thinking about, watching, or hearing the “dog-in-a-tub” sexual manoeuvre being performed.

Originally these were 2 stroke, pistons travelling together, sharing a common combustion chamber. One cylinder was responsible for intake. The other for exhaust. When more than one exhaust pipe was used, they came from the same cylinder.

From Wikipedia:

  • A twingle is a 4-stroke twin cylinder engine with an altered firing order designed to give power pulses similar to a single cylinder four-stroke engine. It is well known that four-stroke singles “hook up” better than two-strokes in the dirt. This is because four-stroke singles have half as many power strokes per crankshaft revolutions as a two-stroke single. This creates a recovery gap  during which the rear tyre regains traction.                                   Inline twins with a 360° crankpin offset or flat-twins can be easily converted into twingles by firing both of the cylinders at the same time and installing a camshaft or camshafts that operate both cylinders’ valves in parallel. Because many such engines already employ the wasted spark principle, only the camshaft modification is necessary. The Vintage Dirt Track Racing Association (VDTRA) 2010 Rules have banned vintage motorcycles from being setup as a twingle

This became popular in flattrack racing. ‘Big Bang’ engines. Due to the recovery gap. Banned in ’07 (AMA). Harley riders will tell you this was because of the cost of replacing parts. More likely the Harley lobby was concerned about losing it’s advantage.

Twingling is easily done on our XS650s. A matter of replacing the cam. Ignition is already wasted spark.

 

twingled cam

 

twingle vs standard cam

 

The bloke that made this cam had this to say:

  • This is an XS650 cam which I reground for .060″ more lift intake and exhaust, then parted on a lathe, sleeved, and welded back together 180 degrees out of phase.  This cam will make your XS650 fire both cylinders at the same time! …  This cam was from a 1978 XS650, but should be used with an earlier compression release system in which there is an extra lever on the bar that keeps the left side exhaust valve open.  I tried installing pop off compression release valves, and there still wasn’t enough relief!  I recommend this cam for race use only.  The only way I could get the bike started was on a jumper.  It ran like a demon, with double the torque.  The front wheel would come up in first and second on the throttle!  The problem was that I couldn’t stop anywhere because I’d never be able to get the bike restarted without the jumper.  The sleeve in the cam is 4140 tool steel bored through to accommodate a Boyer ignition.  The weld is extremely strong.  The cam looks a little rough because I reground it on a WWII era tool grinder!  Please keep in mind that I have made race winning cams reground on the same grinder!  This concept was never intended for the street…

Posted October 27, 2011 by xscafe in Motor - Cam, Motor - Head

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XS650: Rephase   3 comments

I first heard whispers about rephasing listening to my older cousins discuss how they could improve their old Triumph race bikes. There are long discussions over at the brit forums.

Then I forgot all about it.

Some years ago I bought an old Special from a bloke in the Hunsrück. Don’t really know why. On a whim. An ebay joke-bid. Low kms. Clean. Been sitting for some years . MMM. As usual. The missus wasn’t happy. As usual.. And it sat. As usual.

Then I put my back out. Time on my hands. Found the aussie 650 site. Yes Terry, I know. You didn’t force me to read. And it got me off my arse. Actually I like the Yamahas. The only new bike I’ve ever bought was a ’77 XT500. My daily rides are my SR500 and SRX600. Growing up with British bikes you learn to think that‘s all there is. Later I was introduced to Italian bikes, falling in love with a ’75 Ducati 750. And with Guzzi Le Mans. They all, however, share one thing in common. They’re Thumpers.

Anyway reading that site opened my eyes to the versatilty of these bikes, and reintroduced me to rephasing. This little gif said it all.

 

360° crank

 

270° crank

 

Changing the crank set up so the pistons dont travel together. Rephasing doesn’t so much give a power increase. Rather it uses the existing power more efficiently. The torque wasted overcoming the inertia of having both pistons stationary at TDC and BDC is made useable

  • power saving
  • less vibration, the motor runs smoother
  • better responsiveness
  • slightly torquier
  • if you do this weld the pins to the flywheels…balancing helps too

 

split crank…you want another #2 disc

 

and one of these 90° offset centre pins

 

#2 disc modified…dont forget to renotch for the cam chain gear locator … this is only necessary when doing a 277° rephase as the sprocket is relocated onto the splined rephasing shaft for a 270° and is positioned properly when re installed

 

to be assembled so

 

and so

 

to look like this

 

so right leads left…makes timing easier as you can use the original marks

 

tolerances

 

tolerances

 

mmm

 

There are 2 ways of doing this
277°

  • split the crank at the centrepin-rotate the right hand side 3 splines and press back together…277° rephase

270°

  • split the crank, replace the 2nd flywheel from the right with a slightly modified 3rd flywheel (remove 7mm from the pin boss where the cam sprocket seats … Distance between centre flywheels is 54mm, unmodified flywheel is 25mm cam sprocket is 11mm leaving 18mm for the modified flywheel therefore 7mm is removed. This just happens to be from the end of the bearing mounting section to the bottom of the circlip groove.), use a 270° pin and press together 90° out of phase…270° rephase.

Was talking with Heiden a while ago. They were tying to explain their new method. I couldn’t exactly understand what was being said. What I did get was that they use an offset pin…do the 277° swap and a 3° offset pin to get the rest. Saves sourcing and machining the other crank disc.

These require a suitably modified camshaft and ignition system…a good time to consider installing a permanant magnet alternator. Originally I used a modified points plate

Yamaha missed a golden opportunity to produce a truly extraordinary motor by turning this idea down. Todays TDM.

Anyone interested in spending the effort wont be disappointed. Virtually all modern-day parallel twins are built this way.

Last time I went home I took with me the bits necessary to do this. Airport security and check-in were not happy. Complete 533 crank. Already set-up. Back home we get 447 motors. Rephased 256 cam. That hurt, I had around 8 or 9 of these. All got destroyed trying to weld them together. Except for that last one. What a waste. And a modified points plate. Fortunately I had my 2 year old with me and got to use his baggage allowance too.

My initial test ride was the Scenic Drive. This winds its’ way along the Waitakere Ranges west of Auckland, separating it from the west coast. A nice ride. Couldn’t get the smile off my face. Had to turn around and run again. This time taking the Piha Kare Kare road. To the beaches. In the old days this used to be gravel. Great for testing. What a blast. Couldn’t stop. Back. To Huia and Whatipu. Then. Shot across the city. South and East. Through Kawakawa Bay, Orere, down the Kaiaua Coast road, stopping for fish and chips at my cousins. And along the Coromandel Coast Road to the commune at Coro. There I changed the oil, got super wasted and spent the night. Next day across the Hauraki Plains, out to Port Waikato and down the back way to Raglan. Then time to go home. Had forgotten my poor son. Although he was with my family he doesn’t speak english. He was not happy. Ouch.

I was converted. My son was concerned.

Bits can be sourced from Daryl promctun@bigpond.net.au ph: aus 03-9330-4909 …  and Heiden -not on their site-u need to ask for these

Webcam will regrind your stock cam to any of their profiles, and for a rephase motor. Megacycle will do this too, they need to know which piston you lead with & what profile you want. See Heiden also for billet cams. If anyone in kiwiland is reading, contact orb, he will point you to a grinder.

The crank was split and reassembled using a press. Safe. Controlled. I have seen photos where this has been done on the garage floor. It can be done. I’ve seen similar in Africa, Sth America, Asia, India etc.

Don’t know about you. But. I like my eyes.

 

if these get loose i dont want to be in the way

 

there are parts of me that wish i’d never seen these 2 photos..hugh says ..’The 2 picture you posted of a crank being split and pressed together are mine. I did that several years ago when no one else in the US was willing to build a crank for me, nor had anyone had any real experience doing so that they wanted to share. Low budget, and not a highly recommended method, but it worked and has worked for over 10,000 miles now. I do recommend welding the crank at all pressed joints though, as they tend to seperate at high rpm’s.’

 

Vibration was noticeably less. Was not an XS any more. Neither sounded nor responded the same.  Begged to be cut loose. Yamaduc.

Generally crank vibration depends on such-like: balance factor, stroke and rod ratio. She will run smoother the closer you get to a balance factor of 50 to 53%. I didn’t balance mine. Pressed her together. Mic’d her up and slammed her gently into the cases. Ride.

I want to do this to my ride here too. Wont tell the wife unless she notices. Time to start collecting the bits again. This will complement the 750 well.

Interesting. Was talking to Jerry Heiden this morning. Was saying he doesnt like, or more to the point, is not as fond of the 270° conversion. Too time consuming for the extra gain? Says he has been having problems matching crank parts. Seems there are variations in castings and machining between the years. Puts the balance out. To minimise the problems you need to get the extra crank parts from a machine as close as possible to your production run/engine nr. All for only a 2% gain. Or stick to a 277° rephase. He welds them up. But not fully. 2 x 1cm tab welds. Makes it easier to resplit.

Posted January 25, 2011 by xscafe in Frame - Handling, Motor - Cam, Motor - Crank

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XS650: Hydraulic Cam Chain Adjuster   Leave a comment

You met Steffi the other day, he had a crank problem remember, well, he had another problem. He does a high annual mileage-80K in 3 years. This means maintenance and that means time. Now Steffi is not lazy, he’s Swiss, think time -clocks man clocks- time is for riding, ticking for cam chains. Minimise your timing problems and you have more time. Cam chain, valves and ignition-in that order.

He already builds an electronic ignition for the XS650 and there are valve adjusters available that will minimise work there too. So he started playing with hydraulically damped cam chain adjusters. The idea is not new but this application is.

As the motor rotates so does the cam chain 2:1. Rotation and counterpointing 4 stroke dynamics associated with firing set up primary and secondary oscillations in the chain. Add secondary and tertiary oscillations from the sprung chain adjuster and constructive and destructive interferrence sets up vibration esp at idle. Ok this isnt the prime source of XS650 vibration but it does lead to unnecessary chain wear, subsequent effect on valve and ignition timing and a lot of chain chatter.

Steffi came up with these hydraulic dampers for our XS650s

HSKS for ’76 on models

HSKS ’74-75 comparison with an OEM

This is a self contained hydraulically damped cam chain adjuster…has an internal oil reservoir which is pressurised when you install it…and controls the chain oscillations reducing cam chain noise considerably and is supposed to reduce cam chain wear…it is fitted and adjusted just like the stock one, you just do it up slowly to allow the hydraulic damper to adjust until the pin is level with the end of the nut, even if the hydraulics fail it will work the same as the stock item on the spring only.

As a bonus the better managed cam chain has a positive effect on cam-based ignition systems eg Pamco.

Available from Twins Inn in Germany. Wolfgang speaks English but also has a day-job. Best to contact via email webmaster@Twins-Inn.de

Posted January 10, 2011 by xscafe in Motor - Cam

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