Archive for the ‘Frame – Forks’ Tag

XS650: SR500, Velorex Sidecar   1 comment

Once upon a time I had this nice little SR500.

my 48T SR500


I got it into my head to build a sidecar – to take my son to school. Started collecting bits. And ideas. (I did consider using the XS650. Decided against it as the SR and the Velorex match pretty well. Both light and manouverable.)


making a start … leading link forks, box section swingarm and front disc brake … ended up reworking the forks – added an extra 1cm castor (nachlauf)


Got hold of a Velorex 562 sidecar. How to connect? Collected a lot of ideas.

  • Original Velorex frame clamps. Too much point load on the frame. And they work loose.
  • Mount points welded directly to frame. Weakens frame. Point loading.
  • Subframe. Bolts directly to frame. Sidecar mounted to subframe. Load distributed. Solid.

Sounded good to me. What about TÜV (MOT) certification? Could make my own subframe but I’m not a ticketed welder. Visited my local friendly greycoat (TÜVler). Fixed his brown-eye on me and shat on my ideas. Some people simply have no imagination. No sense of adventure.

Found a list of Gespannbauers (sidecar builders). Rang around. Karl Schmid from Mickhausen near Augsburg was the most approachable, and fitted into my time frame. So, off I went. Beginning of September. Said he would try to have it ready by the end of the month. OK by me. Spent the next week constructing at Automechanika – Automobile industry Trade Fair. Stand handover Monday. Home late. Phone rings 08.00 Tuesday morning “TÜV is on Friday. You can pick it up then.” Hang-on? It’s not even midmonth! I’m not ready! Cant believe it’s early. Kool!!

Commitments, illness, work, rugby meant I wasn’t able to get down there for a week. Got a train ticket, €39 to Schwabmünchen. Left Frankfurt at 05.30. 20 minutes late. By Stuttgart the train was getting pretty full. Ah, yes, 1st day of Oktoberfest. God I love girls in Dirndls. Nothing quite like it. Eye candy.

Was picked-up at the station. Sweet.


finally there


half workshop half house … nice


Smells just like a metal workshop should.

Karl Schmid: Gespannbauer


there she is … waiting


Took my time getting home. 650km. The first 3 hours in driving rain. Forgot to switch back from reserve and ran out of gas in the middle of nowhere. Great way to meet friendly strangers. Took the sideroads. No map. Using the sun position – when I could see it. And geography. Had a great day. Perfect way to meet my new toy. Glad I took 3 pairs of riding gloves. Meant dry warm hands. Mostly. Uses more gas, be careful cornering, no need to put your foot down when stopped.


front on


rhs … the boat is sitting on the original frame podests … it is possible to rework these and lower the body 30-40 mm … lower centre of gravity … adding an MZ torsion bar (bike swingarm to sidecar swingarm) helps handling too


you can see the body mount podests on this frame


as a reference: this velorex frame has been heavily modified – cross bracing, lowered body mounts, bolt on lower frame mount points, extended rear, self-made shock tower, self-made extended swingarm


lhs … have some longer konis I may swap into the forks – lift the front a little


324mm konis up front, from my guzzi … replace the series SR shock 316mm … feels better


connected – front view … exhaust pipe is very close to the lower car mount – i have now ground the mount to give more free space for the pipe


connected – rear view … the lower rear sidecar mount, seen here has been shifted to the rear of the sidecar to leave space to kickstart … the upper rear mount is just on the limit of being restrictive, my boot heel hits the bar if Im not careful


front – upper … boxed over the frame


front – lower … bolted to the front engine mount


rear upper, subframe fixed to the shock mount, sidecar mounted off the subframe … you can see the lower sidecar mount point going off to the left … rear lower subframe mount uses the footpeg mounting points (will take photos of these and post as well)


right hand rider footpeg now welded directly to the subframe … subframe mount uses the frame points previously used by the footpeg


sidecar brake cable … attached to footbrake rod – pulls against the alu block


brake cable mounted to the swingarm shock mount


nice bonus – the front lower sidecar mount serves as a perfect footrest – very comfortable riding – need to practice braking with my heel


Fully certified (TÜV)!!

Now I’m ready to take my 6yo son to school.

off to school


I’ve now ridden this a couple of thousand km. Not bad for a month.

  • Have added a longer set of shocks to the forks-a bit more height (not too much)-needed to alter the sidecar settings slightly.
  • The rear shocks are far too weak. Tried a set of SR500 konis – still too weak. Looking for a better solution.
  • In retrospect I might design the subframe somewhat differently. As a 1 piece there is structural integrity and load-spread across the whole frame but the thing will need to be removed to repair things like clutch, kickstart, oil pump. A 2 piece subframe, although loading the front and rear of the frame separately allows access to the right hand case. Just how strong is the original frame?
  • I will add a rollbar and 4 point seatbelt.
  • Am glad I didn’t use the XS650. The Velorex is light and flies easily. Great for freaking out cagers that follow too close.
  • Had forgotten just how physical sidecar riding is. Body position is critical when racing through corners. My 6 yo son is becoming a good monkey.

Couple of updates …


VM32SS carb from an early XT500, rejetted … large increase in torque for minor loss of top speed (-10kmh max.) … purrfect fit … have ordered a new boot


Have exchanged the carb. Taken the BST34 flat slide out. Put a VM32SS round slide from an early XT500 in. Direct fit. Mates to both the carb boot and air filter

no problem.

Starting point : 41mm single wall head pipe … K & N filter insert, open carb boot.

  • Pilot Jet 25
  • Main Jet 260
  • Needle Clip position #4
  • Float at 21mm (float was twisted-one side sat higher than the other)
  • Cables are different, (both 2 cable system) … shortened the BST push cable outer and used it as a VM pull cable, added a second nut to give myself adjustment at both the carb and handlebar.

I love the difference. Not quite as much top speed (I rarely travel more than 100-105kmh anyway) BUT there is a noticeable increase in torque from idle. Pulls great through the complete rev range. Fuel consumption is better too.

Exchanged the std Velorex lights for LEDs. Figured it would be easier on the batteryless electrics I run. Had halogen blinkers on the left hand side. Load-independant blinker relay. Seems to work with halogen front and LED rear but not halogen left and LED right. Appears to require the same combined load on both sides. Swapped the halogens for LEDs and all was well. Except for the headlight the bike now has LEDs all round.


LED rear


and LED front


Have booked the bike in to have the subframe modified. Never liked the front top mount – headstock. Transfers the stress directly to a known weak point. The square section tube under the oil tank. Cracks along the weld – both sides.


subframe top monut, front … at headstock … clamped to known weak point – leads to cracking along the welds


Had a front brace made up. Clamps to the frame. Bolted up through the steering head – 2 bearings keep the steering operating. Brace back to the subframe.


brace from the rhs … can see the frame clamp, the bearing housing under the steering head – there is a bolt through this from below attaching it to a block inserted into the lower yoke (this is held in place with the bolt coming down through the top – could also have been cemented in place)




front brace – rhs – showing link to subframe – note, this is all easily removeable, clamp releases, link unbolts from brace, brace separates from bearing house


my other three-wheeler … shop hack … sharing space with the XS

A common SR500 rear wheel problem is the wearing out of the rear sprocket carrier. If this isnt regularly greased via the provided grease nipple the wear accelerates. Result? Sloppy rear wheel. The added stresses imparted by running a sidecar exacerbates this problem.

This can be rectified by machining the carrier  ID to fit 1 or 2 bearings and reducing the existing stem in the hub. I tried contacting an SR500 forum member here in Germany but he never replied. A pity as he provided a nice 2 bearing modification. While looking for a solution I found complete a rear wheel, already modified, on fleabay. New bearings, brake shoes, carrier dampening rubbers. For cheaper than used wheels usually go for. Score!

complete rear wheel – already modified – single carrier bearing and reducing spacer


rear sprocket carrier – machined to fit a bearing – reducing spacer fitted – i have covered this with the plastic cover found on XT500s – lube as normal using the grease nipple provided


rear view of sprocket carrier – can see both the bearing and reducing spacer … fits as normal to the hub



XS650: Fork Rake Adjustor   Leave a comment

From Cheney Engineering:


rake adjustors…top, bottom or both


These give you the ability to quickly change your rake.

  • Insert one adjustor in the top of your fork head: -can position this for a +0.50 or -0.50 degrees over 30″
  • Add an adjustor in the bottom of your fork head: -gives an adjustment of ~ +1 or -1 degree over the 30″

Each Adjustor comes with Adjusting Offset, Race and Bearing.

You need to supply the diameter, thickness and length of your fork head.

Your stem probably requires machining to fit the bearing. Or buy one of theirs and press it into your bottom yoke.

They also have some nice trick stuff to adjust your offset-

  • Offsets provide the ability to make incremental adjustments to move your forks closer or away from your fork steering stem. Offsetting forks farther from the steering stem transfers more of the engine weight to the rear wheel…provides better hook-up. By modifying your offsets, you can improve your rear wheel hook-up. The trick is getting the right amount of offset for each style of track.

…and for dealing with shorter inverted forks.

XS650: Fork Brace   3 comments

I have a wife and kids. A home. Some toys. And my bikes. We live ok, are not well-off. Cash is always tight. Whatever I buy for my bikes is a compromise. That cash could, simply put, be used for other things.

So. Bang for my buck?

Good question.

I have an answer. It’s not a single item however.

There is a list. Needs prioritising according to your pocket and your bike.

If it’s not broken don’t fix it.

My basic list includes:

  • tapered roller steering head bearings…if needed
  • new fork oil, and seals when needed
  • swing arm roller bearings or bushes…always needed
  • rear shocks…anything is an improvement
  • check wheel bearings
  • look at the tyres
  • fork brace

Note that none of these are related to the motor. All affect handling. Directly.

I always keep my eye out for cheap fork braces. You hardly ever buy a bike with one on it.

Basic pattern is:

  • 35 x 55 x 185…’77-on
  • 35 x 55-58 x 185…’76
  • 34 x …………………….up to ’75 -i don’t have one here to measure

The later 35 x 55 x 185 version is shared with several other models. Some are:

  • SR500
  • XS750
  • XS1100
  • XJ550..80
  • XZ550S..82
  • XJ400..82
  • XZ400..82

’76 models are also found in ’80 Suzuki CM400L

The 35mm models produced that I know of are:

Daytona..japan..i have these…i like the foil shape, although i turn it around, to push down as i go forward


motoline … 35 x 55 x 182-185 … forged .. 500g


Motoline – certified for:

Yamaha XS 500 650 750 SR 500 XJ 550 XJ 650  XS 400 TR1

Kawasaki KZ650B KZ750E KZ750B Z1F KZT00A KZ550B KZ440A

Suzuki GS400 GS1000 GS850 GS450

Honda CB400T CX500 CB1 CB750F CB750G

Tarozzi…can fit the boot or gaitors over these


Telefix…also boot and gaitor friendly


AME…simple, clean


and the old standby .. hooped


Any of these will strengthen up the front. Remove the fork flex. The results are immediately noticeable. Careful, it will uncover other problems.

Where do you stop?

Posted January 19, 2011 by xscafe in Frame - Forks, Frame - Handling

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XS650: (Un)Sprung Weight   Leave a comment

Some would say I’m coming unsprung. Some that I’m unhinged. Others don’t even see me. Me? I can get along with myself most of the time. And that’s all that really matters. In my own way I’ve found my balance. The theory of multiple intelligences makes sense to me.

It’s not so clear cut however when it comes to my bike.

My grandfather always quoted the 4 B rule. You don’t lend your Bundle, your Better-half, your Bike, or your Bum. As for my Bundle? What the Better-half doesn’t get the Bike does. And my Bum spends a lot of time on the Bike.

Which brings me closer to my point. Your bike is basically for you. You ride her. You put your trust into the bond you have with her every time you ride. You. Your bike. The road. The conditions.

Really, she is set-up for you.

Parts of the matrix making up your ride experience. Your mass. Your type and style of riding. Determiners of basic geometry:

  • Rake. Neck height. Trail. Wheel-base. Fork length. Centre of gravity…All factors in how she handles.
  • Tyre size. Rear shock angle. Spring rates front and rear. Preload. Compression dampening. Rebound. Oil weight….factors relating to how well she handles surface variations and cornering.

Major considerations are Sprung and Unsprung Weight.

Force the wheels up and down. What moves is Unsprung weight. Your suspension forces this into contact with the road. Reduce this weight and your suspension has less work to do keeping it all in contact with the ground. Releases the suspension for the other part of its’ job. Dealing with the G-forces experienced in cornering, acceleration and deceleration. Giving you , the rider, a softer ride:…

  • Front Wheel:  tyre, tube, valve, rim, spokes, hub, wheel bearings…
  • Brakes: rotors, calipers, caliper mounts, pads, hoses … drum, shoes, linkages…
  • Forks: lower legs, guard, brace, damper rods, fluid, axle, speedo drive…
  • Rear: tyre, tube, valve, rim spokes, hub, sprocket, cush drive, axle, adjusters, rear of chain, rear of swing arm, brakes-disc or drum, drum plate lock, end of chain guard…

Sprung weight moves with the frame. Held by your suspension, isolated by it from the road. Includes: motor, transmission, you-the rider. With gear. Mass. Means energy.

Some are both, one end fixed to the frame, the other tracking the wheels:…

  • fork spring, swing-arm, shock absorber, coil spring, suspension linkages, some rear guards, chain guard, rear chain or drive-shaft,…
  • Weight split isn’t 50/50, division has less to do with center of gravity than centerline from the pivot point…
  • unsprung swing-arm rears are lighter than the sprung front.

All of it you need to push.

Then you have Rotational Weight, which can be either sprung or unsprung.

Why is this important? Well, if you’re my dog, and something moves, you nail it or bite it. Even better, both.

There’s inertia. The resistance of any physical object to a change in its state of motion or rest. Want to move something from rest? Change its’ velocity? Or direction? Stop it? Acceleration and deceleration. Find some energy.

Do this around a pivot. Angular Momentum.

Things that go round are kind of a double whammy. They need to be accelerated forward, and rotated.

Every gram of mass in the tyre or rim has the same effect as two grams in the frame. The tyre’s angular intertia is approximately equal to its linear inertia.


Cruising? Weight is pretty much irrelevant. Air drag followed by frictional forces due to rolling resistance of tyres, bearings, etc.are your primary concerns.

Hardtails…no suspension, zero effect.

  • Rotating mass affects acceleration.
  • Total mass requires work to accelerate, decelerate, change direction or elevation.
  • Extra unsprung mass has a negative effect on a bikes’ ride.

That is why rotating weight is an issue. Rotating weight includes anything that turns: .. wheels, tyres, brakes. Also, engine parts: the flywheel, crank, clutch, cam, transmission, chain, …..

When accelerating you put energy into two things beyond that needed for a constant speed for the given riding conditions…

  • acceleration, F=ma. (linear momentum). Mass of the bike, wheels and rider.Rectilliner acceleration, Increasing kinetic energy
  • rotational acceleration- (angular momentum).extra to the energy required to accelerate in direction of travel.

Though static weight matters, pursuing rotating weight matters more.

Minimum weight is just that. Minimum. Should your bike be lighter, add ballast. Where you want it. Low.

Light has it’s advantages. Rotating weight has more.

There are practical advantages aside from better acceleration and deceleration.

Look at the variables. Type of track. Your style. How much brake you use. How much the course will require. What and where are the G-forces. Reduce rotating mass, you could use smaller brakes. Lightness means the whole range of components get an easier time. Tyres. Shocks. Springs. Brakes. Rider.

Smaller brakes are easier to manage, generate less heat. The weight can go elsewhere.

You could go to the effort of laser cutting new crank discs from modern lightweight materials. Expensive. While you’re at it do it right. 270°. 256 crank discs were commonly drilled and filled with lead, from factory. When these plugs started falling out they stopped. Cranks are finely engineered. Be careful. A well balanced crank is what you really want. Drilling for lightness is a compromise between structural integrity and performance. Crossing the finish line last is better than not at all. Cheaper too.

Running total-loss? Have a range of rotors, drilled, for different weights. Swap them in and out to suit. Could even have several sets of wheels, having different diameters and weight distributions. For that matter, if sharing a bike it could be a good idea to have several sets of forks, and rear shocks, all having different spring ratings, dampening profiles, preloads, actions. Even different length swingarms. If your forks are a little longer, moving them up and down in the triples trees gives easy geometry adjustment. Several sets of triple trees-predrilled for different rakes, trails, wheelbases. Doesn’t take long to swap any of these in and out for individual riders.

Short-tracks are easier. Narrower rev range. Cornering is more predictable. Easier set-up. Larger tracks, are a little different. Corner and straight combinations. Rpm. Velocity, Cornering dynamics. All more complex.

With lighter rotating components, you get up to speed at a faster rate.

Start at the front. Reducing weight with the largest parts first. Drilling shafts is expensive and the gain is very close to the centre of rotation. Little gain for the cost.

Lower friction bearings. Lighter grade oils changed frequently. These may give better results than taking components to their structural limits.

How far do you go? There are breaks. And there are breaks waiting to happen. Always at the wrong moment. Strain, power loss, or vibration. Vibration will literally eat horsepower. Rear wheels never see it.

Power to the wheels is always very important. The more power getting to your tyres, the faster you’ll go. Assuming you and your bike can handle it.

Unsprung vs sprung weight have the same efect on acceleration and top speed.

Lighter wheels, tyres, brakes, rotors have gains due to the lower ammount of power required to rotate them. Lighter springs can be used. Frames are less disturbed by surface irregularities. Gains frequently, improperly attributed to unsprung weight.

Weight removed from unsprung components such as rear wheels may affect traction if the wheel is not under control.

Require precise control of wheel movement? A low percentage-45:55-of unsprung weight is an advantage, giving faster lap times, higher top speeds. Because traction is improved.

Unsprung:sprung ratios affect wheel control. Especially on uneven and road racing surfaces. Of lesser importance for dirt track and little value for drag racing or hardtails.

The rest is up to you. How much are you prepared to spend? Reliability vs performance. Strictly racing? Maybe you sacrifice reliability for performance.

The lightest and fastest bike is only as good as it’s rider’s training and technique.

Together you move this.

You. Your body weight. Your motor. United. With machine.

Bio-mechanic body language.

XS650: Steering-head Bearings   1 comment

Many of our girls have been steadily rolling those kms by year after year. Others have been doing regular service on flattracks, in sidecross, as offroaders etc..

Today, as we uncover these grand ol damen, years of riding and often neglect have taken their toll. A common complaint is ‘positive click’ steering, great when you only want to go straight.

positive click steering…dry

Original balls and races are commonly replaced with tapered roller bearings. The upper and lower have differing dimensions so dont mix them up.

bearing dimensions


  • Upper:  25 x 48 x 15.2
  • Lower:  30 x 48 x 15

tapered roller bearings


A word of advice. The roller bearing races are not as wide as the ball races. Makes it difficult to tap them out when replacing later. Before pressing the roller races in, cut 2 notches in the steering head race seats. Top and bottom.

If you dont do this you might have to weld tabs on the races so you can get them moving before removing them next time.

handy tool…actually for my downhill bikes


I had one of these lying around. I use it for my and my mates Downhill bikes. Pack the new races with those you removed, they’re the same OD so will clear the insides of the steering-head end flanges. This works great too.

a bit of old threaded rod…use the old races as spacers


If putting your machine together from bits n pieces don’t mix the early and late triple trees. They both take the same bearings. The early are for 34mm fork tubes. The later for 35mm tubes. The earlier shaft is shorter too.

early and later stems…early is threaded all the way and shorter…wont fit into a later steeringhead


The tapered roller races are somewhat narrower. This could be a problem if needing to remove them. Something like this may come in handy.

removing races




Now, if you’re serious about handling, are looking for that exstra little handling advantage, steeringhead and swingarm bearings will be one of the first places to look for results.

This is all well and good, and for the average rider, gives positive results for sure.

Problem is that the stem bearing seats themselves are often found from new to have up to 0.1mm play between them and the bearing ID.

And, as the roller races are so thin, they get squeezed out-of-round when pressed into the steering head. This is what gives the infamous clacking sound commonly heard in roller bearings. Point loading. Not good. Run a 48mm ream around the inside of the race-seats to rounden them up – no tight spots. If necessary spin a little off the outside of the races – just so they can drop into place. Glue with something like Loctite 638. Work quick. Get the triples in before the glue sets – insures the races are in line.

up to 0.1mm play from new…easily 0.15mm with wear


Emil Schwarz produces precision bearings with this in mind. Bearings are pressed onto steeringhead nuts and tightened down for a perfect form fit. No tolerance. No play. Use Type 5 for the XS650.

upper bearing


Emil Schwarz also produce precision swingarm bearings. Couldn’t find a listing for the XS650. They provide an installation service and state….

Wir geben eine 100.000 km Garantie auf Spielfreiheit dieses Lagerumbaus !!!

We give a 100,000 km No-play Guarantee on this modification!!!

They sure believe in themselves.

XS650: How to lower those forks   Leave a comment

I have been meaning to put this down in print for quite some time now but then I found this. It runs you through the process very well so I will simply link to it at Chop Cult.

Hugh ‘Punkskalar’ … XS650: How to lower those forks

Hughs' own

17mm bolt used to hold the internals - later models

17mm socket modified to fit earlier fork internals

... like this

Posted January 10, 2011 by xscafe in Frame - Forks

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