I have 10 46 gearing is that ok ballpark for trials riding, I am a beginner. Thanks

Couldn't tell you I'm afraid,  just starting out myself. Literally just got it running properly yeaterday after an engine rebuild. Done a few road trials in the chair of a 1950 Norton and thought I'd like have a go myself. 

taken yesterday after getting the idle sorted. Electronic ignition fitted and airscrew adjusted. Starts beautifully and sits and ticks over like a dream.

There's loads of more knowledgable people on this site.

Are you sure it's 10 on the front?  10:46 is very low geared, 11:46 is the usual gearing.  A 10 tooth Bultaco front sprocket was never commonly available, they aren't available any more

I ran my 199 on 11/47, worked a treat for me.

I and quite a few other ran 11/39. Puts first gear where second is on standard gearing. Quite a few riders found they never needed original first gear and the 11/39 made 3rd gear ace for hill climb sections and 4th ideal for moorland crossing, and a decent 5th for road work.

11/46 is the correct gearing for your bike and should be fine, never seen a 10t front sprocket and I certainly wouldn't recommend gearing the bike up by putting a smaller rear sprocket on it, would make the bike a nightmare in any tight sections.

Cheers Greg

Just try it and see how it is for you. I have three Sherpa`s and I run 11/42 on all of them but I do ride on the clutch so I just find the higher gearing makes first a lot more usable but you do have to use the clutch in the tight stuff. You chain will wear out faster with a ten tooth front though. Graham.

18 hours ago, fastfred said:

I have 10 46 gearing is that ok ballpark for trials riding, I am a beginner. Thanks

FYI Mine has 10/48 fitted and it idles in first at far less than crawling pace which will make tight sections easy but I do hold up the traffic with road work !

Just for reference, Sherpas have been delivered from the factory with basically the same first gear ratio since the M91/92 series

M91 1/2 chain   14/52 gearing  33.5:1  1st gear ratio

M92 1/2 chain   13/52 gearing  36.1:1  1st gear ratio [325 was geared down one tooth]

M124  up to and including M191  5/8 chain  11/46 gearing  37.7:1  1st gear ratio

Internal ratios changed from here on to provide higher top speed in 5th & 6th on 199B

M198/199  13/46 gearing   37.6:1  1st gear ratio [you can change the gearing on these models to 11/39]

                   11/39 gearing  37.7:1   1st gear [same ratio , smaller back sprocket]

M198A 199A 198B 199B    11/39 gearing  37.7:1  1st gear

Hope this clears up any confusion as the gearing really depends on which model you have,

Cheers Greg

 

Edited January 4, 20179 yr by sherpa325

Thanks, you guys certainly know your bunions. I can't count, it has a 12 front sprocket. So 12 46. What do you reckon? I will use for trials but may get road registered to get to local trials?

4 hours ago, sherpa325 said:

Just for reference, Sherpas have been delivered from the factory with basically the same first gear ratio since the M91/92 series

M91 1/2 chain   14/52 gearing  33.5:1  1st gear ratio

M92 1/2 chain   13/52 gearing  36.1:1  1st gear ratio [325 was geared down one tooth]

M124  up to and including M191  5/8 chain  11/46 gearing  37.7:1  1st gear ratio

Internal ratios changed from here on to provide higher top speed in 5th & 6th on 199B

M198/199  13/46 gearing   37.6:1  1st gear ratio [you can change the gearing on these models to 11/39]

                   11/39 gearing  37.7:1   1st gear [same ratio , smaller back sprocket]

M198A 199A 198B 199B    11/39 gearing  37.7:1  1st gear

Hope this clears up any confusion as the gearing really depends on which model you have,

Cheers Greg

 

Super info, thanks. Mine has 10/48 would that make a huge difference overall?

20 hours ago, sherpa325 said:

Internal ratios changed from here on to provide higher top speed in 5th & 6th on 199B

As I understand it,  Sherpa 5-spd.internal ratios were changed to provide a wider spread of ratios, by lowering the intermediate ratios.

(Compared to the previous set-up)

As top gear remained unchanged and is direct (1:1), higher top speed in 5th.  would result only from changing the secondary ratio.

Having re-assembled the gearbox recently that makes sense as thinking back it did seem to me that 5th gear was 1:1

These are the overall ratios with standard gearing as delivered from the factory  11/46 [M159]  11/39[199A & B]

            M159                   M199A              M199B

1st        37.7:1                37.7:1                37.7:1

2nd      29:1                    29.3:1                29.3:1

3rd       22.4:1                22.3:1                22.35:1

4th       13.7:1                13.7:1                16.4:1

5th        9.9:1                   8.4:1                 11.4:1

6th                                                              8.4:1

You can see 5th is taller on the 199A gearbox and all other ratios are near identical on the 5 speed boxes. Fourth and fifth are different on the six speed box  

The reason the bikes have a higher top speed is the changing of the final ratio from 11/46 to 11/39 which still keeps the first four gears the same overall ratio, but allows an overall taller top gear. The change also obviously uses a smaller rear sprocket as well, so less likely to be damaged.

 

I'll stick with the 12 46 to start with. I'm a road racer and crap at trials so I'm going to be calling off a lot anyway