pmk

Awesome reply. 10/52, great info, as I was considering maybe 10/50. The TL rider is without doubt experienced at the craft of trials riding. His skills and even his bike are purposely built. The TL is no show winner, but rather the sum of mods based on experience and preference. As a rider, and the sections we ride, he seldom uses the clutch. Like a stump pulling tractor, the machine thumps along, very controlled with little bits of throttle just above idle. His setup is so controlled and predictable, and I suspect the ultra low gearing adds a lot to help this. In regards to my MAR, and my riding buddies. We both have a reasonably light clutch pull, with a soft controlled engagement. Without that, the previous 12/46 and now 11/46 would be impossible to ride sections slow or manage the corners / features. Overall, it just seems, the OSSA is just too fast at times in the technical stuff, and becomes very dependent ypon clutch control while holding a steady throttle. In short, using the clutch to manage speed, grip, and even braking. Understand also, this is simply local events, not a national championship, so if nothing were to be changed, the fun factor still remains. As a lower cost test, I will try a 10/46 setup. Provided the gearing still allows floating the front wheel over or onto stuff, this should be a good indicator to see if it helps.

Thank you for the photo. Folding tip looks good, but yes, the lever is kind of hanging out there. Hope to find something a bit closer to the case, with the folding tip.

Any chance you have a photo of the shifter installed that you could share? I assume the 20mm gap is between the shifter itself and the screw heads? Or is it 20mm between the small cover and the shifter? Thank you for the link.

So, with two events on the 11/46 gearing, certainly better for what they have us ride but maybe not quite there yet. Locally they run two vintage specific classes during an event. An event is focused on the modern bikes, but they offer a vintage B class that rides the intermediate lines. The other class rides the novice line. Without doubt, the very experienced guy that always sees the lowest scores rides well. He is riding a TL125 with modified engine, kind of stripped down to bare minimum, and I beleive has had the frame headtube angle steepened. At the last event, I watched him ride a section. The first portion he seemed to ride in third gear. I say this based on him downshifting twice as he rolled out of the begining portion and into the second portion that involved a right hand 180, into a left hand climb of 6 feet while turning up the steep climb, followed by completeing the left turn as you crested the climb onto the flat. Seems he entered the section in 3, then as he approached the twisty section and climb, selected first. Riding the MAR, the entire section was ridden in first, including the climbs, and to have control required a bunch of clutch work. The TL did see some clutch use, but almost none. Reconsidering going with a 10 tooth countershaft sprocket, or possibly converting to a 50 rear 10 front and using second more, with first gear for these previously described sections. FWIW, his TL is geared so low, the rider accidentally started in gear with clutch out. With barely a kick, the engine fired and it immediately without bog had the front wheel skyward. Just revisiting it as discussion, not saying any one setup overrules a other. Curious on opinions from others that have tried a 10/46 setup, even if they went back to something else.

I see In Motion offers a tip assembly that could possibly be fitted to the oem shift lever. More likely would prefer to find a common shift lever with the same spline shaft diameter and fit that could simply install easily. Anyone ever found a worthy replacement?

2005 Scorpa SY250R, the gearbox is serviced with Shell Rotella T4 15w40, the premix oil I went with Maxima Formula K2 @ 50:1 premix ratio.

Plus, the drain bolt is kind of tilted, so the socket and extension need to be at an angle relative to vertical during removal or installation.

Bad link. Thinking this is the correct spelling and link. http://www.kelleycarbon.com/

Yes, very possible slightly more oil than needed. Agree, a trials bike engine may not be pushed as hard as my 250 KTM. While researching a different oil for the Scorpa, I did have a good conversation with Klotz tech support. As we discussed fuel mix ratios, we both agreed that a key function of the oil is sealing the rings, along with protection to parts needing lubrication. The mix ratios at 80:1 will allow the engine to operate, but he questioned the effectiveness to lubricate rings and thereby allowing a proper seal. As our discussion continued, we both agreed the trials engine being run less at high power did not require the higher flashpoint oils. The lower flashpoint oils will burn off during combustion, running clean, with minimal or no spooge, and can be run at those ratios to promote longer engine life with proper ring sealing. With that said, a deviated away from Klotz products, due to local on the shelf availability. The product I settled on is full synthetic, and the oil manufacturer recommends mix ratios ranging from 24:1 to 60:1. They base this mix ratio range on engine cc. Smaller displacements or sustained high rpm engines ran more oil, while large open class two strokes ran less oil. For a 250, they recommended between 40:1 and 50:1. No doubt I could have gone to 60:1, but decided at this time to first evaluate splitting the difference between Yamahas recommended 40:1 mix of Yamalube, and the 60:1 minimum oil amount prescribed by the oil manufacturer. I mixed only 2 1/2 gallons of fuel, 100ll avgas and the oil. So far it works well, if reasons dictate, next I can try 60:1, or if needed, measure the fuel I have and add more gasoline, but so far, so good. Truly, I believe the low flashpoint will be the key to this oil and ratio burning very clean out the tailpipe, The uncertainty is, will the low flashpoint induce carbon buildup?

I initially was lazy and used my KTM premix. 40:1 klotz r50. The jetting was not happy and the high flashpoint was very spoogy. Researched various brands and products offered. Currently running 50:1 mix ratio with a low flashpoint oil. Jetting and spooge sorted by just this change. So, 50:1 in my 2005 SY250R. I was told by others use 80:1, but was not comfy at that mix, simply a personal opinion not something I tested.

Waiting on a quart of expired high temp epoxy, then plan to make a headpipe heatsheild, silencer guard, and a pair of case guards. Debating on the waterpump guard. Thinking fabricate from aluminum and either weld on or use fasteners if clearance permits. Answering your question, never seen case protectors offered, but not saying they did not exist.

b40rt, curious, regarding setting up the suspension on these vintage machines, is your thought they should retain heavier damping, or should tne damping be lightened? Maybe not so little damping to fully mimic a modern trials machine, but maybe it should. From some easy simple rides at tne house, the lightened damping so far in the forks and shocks seems an improvement, just concerned that there is an edge of too lighly damped I prefer not to cross. FWIW, using the sometimes referred to push down test, the MAR at the moment has the forks reacting slightly faster than the rear shocks, when applying pressure onto the footpegs.

FeetUpFun, my OSSA came to me with oem shocks. I gave the oem shocks to my riding budding so we could try to build 2 good ones from 4 less good shocks. Show bike so fluid in them was less of an issue. Somehow I thought when I measured the Curnutts came in at 10mm longer but who knows. Ironically, comparing modern vs old, yes, new stuff is more advanced, but travel wise, these Curnutts have 4.7" of shaft travel so this gives the MAR just under 5" of travel. Not quite modern but more than the 3.5" ish they did come with. Hope tomorrow I can make my last mod for a bit. With like it will be pretty good, and the event Saturday could be proof of the pudding as they say.

Honestly, is 99% out mean it is accurate or incorrect. My guess is that yes, back then, all the brands were kind of designed to be a bit more damped. Riding the same bikes, in more modern sections, granted nothing crazy, seems less damping may be a bit better. Not so little to bounce around on the rear wheel, but just a bit more lively. The oem Betor forks came around easily and do feel much better with a fluid change from Mobil 1 ATF to Maxima 5 wt fork fluid. This was a drop in viscosity to about 16 cst from around 33. The rear shocks as I first built them up, I also used Mobil 1 ATF as back in the 70’s per the Curnutt rebuild instructions, they wanted type F ATF. I have since tested the original pistons at 5 wt Maxima fork fluid, and stayed with that, but have been enlarging the drilled ports in the piston. I enjoy working on suspension of all types. Ironically, not having even a simple rebound adjuster makes me appreciate having them on modern stuff.

Not sure what is stock length on a TY. On the OSSA MAR, if remembering correctly, the Curnutts are 10 mm longer than stock. Curnutts are 350 mm and not shortened, but could be easily. Too much experience working on suspension for mx and woods bikes and none on trials bikes is adding to the learning curve. Eventually, I will find the setup. If you do plan to possibly make a fluid change to alter damping, be cautious since true viscosity is very random when stated as a weight. I will add a link to Peters V chart, that list many fluids by cetistokes, which is an easy and better way to make changes. http://www.peterverdone.com/wiki/index.php?title=Suspension_Fluid

This past week I was talking about rear shocks and the forks on my and my friends OSSA MARs. His bike, he wants to replace the rears, currently the modern Betors. He is in email conversations with NJB, decided Rock Shocks are a bit more than he cares to spend. I did suggest he have a look at the Majesty shocks and also fork springs. As for myself, my OSSA has vintage Curnutt shocks on it, freshly rebuilt. New to trials, but not suspension tuning, I am learning that although these vintage bikes when new had very noticable damping, they are not as lightly damped as modern bikes. Saying that, I am learning that even though I am not hopping the MAR around, it is overdamped in the rear. With that, I have swapped to a lighter rated fluid, and even have been drilling the pistons for added flow. Time will tell if I am headed in a good direction or need to buy new shocks.

One point not mentioned in the previous oil discussion, is flashpoint of the oil. Yes the oil, however much or little is mixed with the fuel is headed somewhere. Most likely out the exhaust. High flashpoint oils seem better for and recommended for high rpm, higher output engines. Lower flashpoint oils tend to burn cleaner, and are oftened recommended to run a lower premix ratio, the higher the intended rpm. Oils that do burn, may produce carbon over time, while high flashpoint oils tend to remain wet. Synthetics of high flashpoints tend to leave a strong but easily cleaned oil layer, while castor oils tend to gum up unless run hot and often. With current technolgy, coatings, and exotic materials, plus some very high quality oils, the time may be near for mix ratios even higher tha 200:1. Sometimes though, our comfort level and instilled experienceholds us back. Admitting, I even consider oil inexpensive vs engine repairs, provided the engine performs correctly. Not debating anything, just sharing info.

The manuals suggest a 50/50 mix of coolant and water. Myself, keeping it simple, I replaced the coolant with what I use in the KTM. 70% distilled water, 30% coolant safe for aluminum, and the applicable amount of Water Wetter for the batch I mixed.

Agree, possibly overfilled and simply venting the excess. You might consider routing the overflow hose outside the bash plate and then watch for any signs of coolant, just to ensure it is not a waterpump seal or drain, gasket, etc.

Agree on checking the small adjuster at the lever. I am going through a 2005 SY250R I recently purchased. That engine, in the Scorpa chassis has a funky adapted hydraulic clutch setup. You might ensure no pebbles or debris are fouling the engines clutch arm movement.

6 volt AC voltage regulator arrived Friday. For my setup, I am running a 6 volt 10 watt headlight, and a 6 volt 5 watt tailight. I did not bother adding the brake switch and brake light or horn. The MAR apparently has 3 generator output coils besides ignition. The higher output yellow lead on my machine is for the headlight in original setup. Another coil was for the tail light, and the third for brake and horn. With my combined electrical load at 15 watts, the headlights coil, rated for 30 ish watts is more than needed. The original design, like many other 60’s and 70’s designs, utilized 6 volt AC to drive the headlight. By design, they matched the headlights requirement, to the ouput coil capability, and things worked. Voltage would climb and fall, but it worked. Same on tne other output coils. A couple weeks ago, when I first powered the lights, all was good, until I the rpm increased. Because increased rpm drove the output to max, and the bulbs could not consume the power, voltage rose until the bulbs burned out. I decided on getting. Kedo 6 volt AC voltage regulator. AC only, and no rectified DC as there is no battery or horn. If you plan to use a horn or flashers you might need DC for those to operate correctly. The Kedo regulator is supposedly a reproduction for a Yamaha XT500 and others. Electricity is not brand loyal, so it was an easy hookup. The regulator has a single yellow wire, that coincidentally matches tne OSSA yellow 30 watt wire. The regulator case is aluminum pot metal and must be grounded. In simple terms, the regulator is basically a controlled leak. Set in the 6 volt range, as voltage increases with revs, the regulator holds the voltage steady, bleeding excess to ground via an internal variable load. I mounted the regulator on my resto mod MAR to tne left side feame and headtube gusset. One small 6mm hole. The hole itself was burnished to remove powdercoat, and then to be certain, I verified low ohms from the burnished area to the engine center case. The reading was bouncing between 0.0 and 0.2 ohms. The wire hookup had me retain a single bullet female connector on the oem yellow output harness. For my homemade chassis harness, I installed a male bullet connector where I placed two wires. One wire ran off the lights, while the second ran to the regulator. The regulator arrived with a bullet connector crimped to the lead, so I simply made a match there with no mods. To save money in case this did not go as planned, I only installed a tail light bulb. I expected that for the cost it was smarter if it popped. Also, at 5 watts required, if the voltage was not regulated, it would fail easily. Fired it up, set the switch for lights and the tail light illuminated. With rpm increased, the tail light did not fail. AC voltage checks were bouncing about, but never above 7 volts. Ideally, this will not be exceeded at full revs. Installed a new headlight, and tested again still working. Not exactly sure if or how this could help others, especially if you must run power from all three output coils. But did want to share if needed.

Interesting about the reeds and water pump housing. On my SY250, reeds in it now are fibreglass with no true stoppers. The water pump housing is stock, but I did get the 2005 Scorpa options catalog with the bike. They show a slightly different housing where the fwd hose spigot extends more towards the radiator.

Ordering parts today. Expect good results and a simple solution. Not expecting lights to be superb for higher speed night riding / driving, but acceptable for daytime road use and night rides at slower trials speeds.

Reviving an older topic. The other day, I wired the 73 MAR for lights. The bulbs I used were 6 volt. No plans to ride at night. The first run the lights operated fine until I reved it while riding. both headlight and taillight failed. Checked the voltage and found far more than 6 volts AC. I operated both lights off the one designated wire for the headlight, yellow I believe. Since my headlight is 15 watts and the tailight is minimal the system was not heavily loaded except at idle. So with this said, it becomes apparent I need a voltage regulator. The easiest method would be to find a proven single wire style, that simply bleeds off excess voltage to ground. My KTM had a regulator like this, but was 12 volt. i can find many low cost regulator / rectifiers that are 4 wire. Guessing two feed wires, 6v AC and ground, and two outputs of 6v DC power and ground. Not sure if it is possible to utilize only the input side to regulate 6v AC, and cap the rectified outputs. Price is good at $10 delivered. Any thoughts.

Rode a bit more. Will give the 11/46 a chance. Not bad, just considering a bit slower in first could be a benefit and allow second to work better. Time will tell after the upcoming event.