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About pmk

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  1. Wanted to add some details about this countershaft sprocket change. Initially when built and during my rebuild, the 73 OSSA MAR came with stock gearing of 12/46. After some use, rides, I made a change to 11/46. This was a very noticable change. The downside being tight sections or some climbing required use of the clutch. Most recently, I installed a 10 tooth countershaft sprocket. Initially, I rode the 10/46 setup in my yard, prior to yesterdays event. The change from 11 to 10 was also very noticable. With the 10 tooth, the low speed control is improved. The need for using the clutch is almost never. The good of the 10 tooth was low speed control. Steep climbs were not a problem, and my riding buddy commented there was no tire spin at all. A secondary benefit it how improved the rear braking has become. The downside of the 10 is how quickly the engine revs out. Riding between sections, this is a non issue. The main drawback so far has been when using the throttle to lift the front wheel. With the 11 or 12 tooth, the engine had a longer pull and could keep the front wheel lofted longer. Understanding the lower gearing not being able to hold the front end up as long, timing becomes a bit more important. At the event yesterday it was a learning curve, for various reasons and my mistakes were my own. The bike certainly did not struggle. For now, I plan to run the 10 but if I deem needed, will go back to the 11.
  2. 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.
  3. 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?
  4. 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.
  5. 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?
  6. Jim, that looks pretty sweet. Curious, any idea on how much it weighs? Guessing you also may have steepened the head angle?
  7. 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.
  8. 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.
  9. 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.
  10. 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.
  11. Also, nice touch welding nuts to the bash plate mount bracket.
  12. 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.
  13. 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.
  14. 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.
  15. 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.