pmk

I resolved the concern of the chain not having clearance to the nut. Using the lathe, I machined a chamfered edge on the step side of the nut, providing clearance. This could be done with a file if needed. Certainly something to watch for. Possibly not every situation has this clearance issue, but worth checking to prevent a possible problem.

10 tooth sprocket arrived today. Actually, 2 sprockets and 2 stepped nuts, designed to allow clearance for the chain. So, regarding the parts, the Talon sprockets look great. These have a forged in step on the backside, to allow the sprocket to be automatically spaced away from the cases / seal, and it still remains a very close fit. Regarding the nuts, two identically ordered parts, however, dimensionally they differ. One nut is thinner overall than the other. Also, the thinner nut has a shallower step prior to the hex. Regardless, even the nut with the longer step will pinch the chain and totally bind on the master link. The longer step sprocket can clear the chain, provided I install a 2mm shim between the nut and the sprocket. The shallow stepped nut will require more thickness to the spacer. With all this, it seems the easiest solution to allow using the stepped nut will be to modify the nut further, to allow clearance at the chain. So I ask, has anyone run the 10 tooth Talon front sprocket and the stepped nut? If so, what was your solution to allow it to work without contacting the chain?

So with all the ideas posted so far, is there any magic set of angles for steering head angle that works better than others. i openly admit never riding most of those bikes. I do find the MAR turns well, but does sometimes tend to try and tuck the front wheel in a tight turn.When this happens, things kind of stop rolling and the front tire slides unless you straighten the bars a bit. Almost feels as if there is too much offset in the triple clamps.

Narrow yokes? Are we referring to what are also called triple clamps? Narrow vs wide, does this deal primarily with how the front flexes when the bars are turned? Or is there more to it than that?

Jim, that looks pretty sweet. Curious, any idea on how much it weighs? Guessing you also may have steepened the head angle?

I would really like to ride a MAJESTY, if only to compare to my MAR. Months ago, there was a TY175 with Sammy Miller upgrades on it for sale. I was talked out of buying it. Not so sure all those bikes mentioned by Feetupfun would be competeing in the same class. I do know locally, there is a guy riding a TL125, bare bones, modified engine, super low gearing and he mentioned he had steepened the headtube angle, granted he is a very good rider, but that bike simply crawls through sections with super control.

To keep this slightly updated, it was decided to try the 10/46 ratio initially. This makes for a lower cost simpler change to see if the gearing change is worthwhile. The 10 tooth countershaft sprocket was ordered along with the stepped nut. I held of on ordering the flat sprocket adapter, knowing I can easily get that later, and it will be required if I go to a larger rear sprocket. The numbers regarding ratio changes indicate the swap from to 11 to 10 will be a larger percentage change than the swap from 12 to 11. Possibly the 10/46 will be very good. If not, I am leaning towards 10/51 next, which brings second gear to about what was first gear when using the 12/46. Slow speed control with minimal clutch use, in an effort to simply gain a smoother effort while riding sections is the goal. While waiting on the parts, time to go back inside those rear shocks and soften tne damping even more.

I too was not sure which specific machine was being referenced. My OSSA runs super clean at all rpms. Carb is not worn, as it has an almost new Smart Carb on it. Carb tuning is accurate, and simple, since all tuning is accomplished externally. My riding buddy has ridden and compared my OSSA to his, and I should do the same. He stated my OSSA has a smoother lower idle than his with the OKO conversion carb. He also noted my engine pulls cleaner and stronger right off idle into higher power. Maximum power seems the same. I replaced both crank seals with new seals as the resto mod upgrades were accomplished. The rubber intake manifold, airbox to carb rubber boots are both new. The rear silencer was rebuilt and freshly packed, plus is a Krizman style (no screen) spark arrester so it is not clogged. The midpipe was opened and repacked, plus the exhaust header remains tight with no leaks. I did not pull the top end, but the motor is quiet with no rattles and great compression. It starts and runs very well. I keep refrencing back to the purpose built TL125. That bike simply thumps along slightly above idle, even in softer terrain. At 12/46 my OSSA would not do that, with 11/46 it does, guessing 10/46 will do the same, with even easier control, provided I do not simply tip over.

My thought is his bike may be fine. Mine runs super clean, has the power and so forth, but is simply too fast in some sections where the low speed control without clutch use is needed more. If I had to, I could have retained the oem 12/46, and still had a lot of fun. Changing to 11/46, to my surprise became easier to ride slow. My suspicion is that depending upon where you live or ride may influence the gearing choice. Since our local trials club utilizes the intermediate line the same as modern bikes, some features are very tight with the slowest speed needed to roll through them, other sections are not difficult at all. Recently, after an event, my riding buddy and I rode our more modern bikes on some of the sections we rode the OSSAs. For various reasons, the modern bike easily cleaned those sections. One reason that stood out was low speed control. Understanding that the OSSA MAR certainly is not a modern bike, but trying to make the subtle changes to better align it towards the sections we compete on. With trials being new to myself and riding buddy, the learning curve is a bit steep but now easing up. These poste have been a great set of opinions. Some agree with gearing changes, while others may not. All good info though.

Also, nice touch welding nuts to the bash plate mount bracket.

Agree, a 9 tooth is not truly easily viable, but wishful thinking. As for my own machine, yes, the wire harness is routed through a hole drilled near the engine mount and up along the frames downtube. Elaborate, but effective rear sprocket setup. Very nice mod.

Yes, my bike still has the dished rear sprocket in 46t. Considering the 10t as a test, then if viable, either remain with it or convert to a flat rear sprocket setup, adding teeth. I wish they offered a means to install a 9t to test that also. 9/46 would be in the 10/50 to 10/52 range and would be an easy swap to test.

Do not let this topic sway your gear selection. As for how the rear sprocket looks, that TL125 has a huge rear sprocket also with a similar look about it. The photo does inquire my curiousity, any chance for some detail photos of how they did the dished sprocket carrier from an old sprocket. If I do either upgrade the gearing or just replace the sprockets, I will be going to the flat sprocket with the added bearing and hub spacer. Thanks for sharing the photo.

Yes, Vintage B, which does the modern lines along the intermediate course. The 10/46 may happen as a test. Easier to get. Once sorted out, I can decide on what sprocket set to run.

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.