33 minutes ago, woody said:

10/52..?  Really or was that a typo for 10/42.  I found 10/42 about as low as I would want to go,  10/52 would be far too low for me to even use first

I went and counted the rear yesterday (before I had anything to drink). It is a pretty big sprocket and yes it is slow in first but it's never troubled me. However I don't actually like the way it looks (so big) and now with this discussion am thinking of fitting a smaller rear and giving that a go

2 hours ago, feetupfun said:

I went and counted the rear yesterday (before I had anything to drink). It is a pretty big sprocket and yes it is slow in first but it's never troubled me. However I don't actually like the way it looks (so big) and now with this discussion am thinking of fitting a smaller rear and giving that a go

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.

3 hours ago, lineaway said:

Yes, if you are still running the dished sprocket.

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.

36 minutes ago, pmk said:

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.

The new sprocket was machined to provide a half-width recess to match a half-width recess machined on the original dished sprocket. I then drilled 6mm holes and bolted the two pieces together.

An alternative is to machine the teeth off the dished sprocket and weld a new sprocket on.

These photos were taken while I was preparing to fit an extension piece outboard of the sprocket to reduce the bending moment on the axle

and here is what it looked like after fitting the extension piece

and this photo is to illustrate why no-one makes a 9T front sprocket for OSSAs. This shows a 10T sprocket

 So do you not have the electrics going out of the front of the engine and up the frame, instead of under?

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.

Edited December 26, 20178 yr by pmk

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

 

 Yeah, I shorted out the original motoplat pretty quickly on my Ossa. But I rode very large rocks and cased hard frequently. November 1974.

 

4 hours ago, lineaway said:

 So do you not have the electrics going out of the front of the engine and up the frame, instead of under?

The reason that there is no stator in the photo is because I took that photo when I had the stator out to drill the hole to run the wires out at the front/top.

4 hours ago, pmk said:

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

Thanks but that is how it came to me. Maybe MkII MAR brackets come like that.

I think someone told me previously that I had those brackets fitted backwards. Again, that is how it came to me and I've had no reason to change it around yet.

12 hours ago, feetupfun said:

I went and counted the rear yesterday (before I had anything to drink). It is a pretty big sprocket and yes it is slow in first but it's never troubled me. However I don't actually like the way it looks (so big) and now with this discussion am thinking of fitting a smaller rear and giving that a go

Gearing is very subjective but on a trials bike no use whatsoever if too high, does the engine run nicely at low rpm or does the carb need attention, maybe a worn slide, incorrect jetting or crank seals. All of these things if not right will make the bike less rideable also can you try another bike to make a comparison.

Your OSSA looks to be in good original condition but some things must have worn or aged from when it was new.

Edited December 26, 20178 yr by trialsrfun

1 hour ago, trialsrfun said:

Gearing is very subjective but on a trials bike no use whatsoever if too high, does the engine run nicely at low rpm or does the carb need attention, maybe a worn slide, incorrect jetting or crank seals. All of these things if not right will make the bike less rideable also can you try another bike to make a comparison.

Your OSSA looks to be in good original condition but some things must have worn or aged from when it was new.

Are you referring to my OSSA (the green and white one as shown in the photos) or pmk's OSSA?

1 hour ago, trialsrfun said:

Gearing is very subjective but on a trials bike no use whatsoever if too high, does the engine run nicely at low rpm or does the carb need attention, maybe a worn slide, incorrect jetting or crank seals. All of these things if not right will make the bike less rideable also can you try another bike to make a comparison.

Your OSSA looks to be in good original condition but some things must have worn or aged from when it was new.

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.