Trials Australia Forums

I think all the Alpina`s use a single row primary chain and as far as I know the 250`s use a single weight and all the 350`s use a double weight.. I know the last ones do the M 212 and 213 also the M115, M116, M137 and the M138. They are the only ones I have seen the inside of. The are supposed to have a primary chain tensioner and they are easily available. It was recommended to remove the tensioner from anything that revs hard but to leave it on the Sherpa`s and Alpina`s as it is supposed to smooth them out at low revs. The through gear change happened in 1976 when the Americans ruled that any motorcycle sold in the USA had to have left side gear change. Graham.

I just cleaned the top of the barrel and it has 157 stamped in it. When I bought it it had a massive rear sprocket. A bastard son welded up out of two sprockets.

Will count the teeth ASAP.

That is very interesting. My Engine number and year list has a M157 as a 1975 125 cc Sherpa T. The 158 and 159 came out over here in 1976. Graham.

According to my research, it's to do with the ports and could be from anything.

I'm fairly resigned to the fact that this is either an Alpina or a Lobito engine.

Here's the stamp….


Here's that rear sprocket…..


Somebody asked to see the bottom of the engine


And this is where we are at….


What's it like doing trials on a Alpina/Lobito with sherpa chain and sprockets I wonder???

Ian.

That sprocket has 52 teeth. If I get a 50 tooth I'm wondering if that'll gear it down enough.

It means I can live with my current transmission and proceed with he rebuild.

Otherwise I will have to risk buying a Sherpa transmission on Ebay and they could come from anything.

I'd be taking the word of the random who ripped it down and could end up with another Alpina/Lobito (Or anything in between) gear set.

On the other hand if it works out then it's as close to a proper Sherpa tranny as possible and the strange engine number then becomes useful.

I.

If you get a 10 tooth sprocket for the front you can use a much smaller rear to get the same gearing.
You should be able to work out what gearbox it is by putting it in first gear and measuring the ratio between sprocket and clutch. There are specs available for the gear ratios of Alpinas and Sherpa Ts gearboxes

157 is listed as Sherpa T 125 on one list as Graham said. My 4 other lists don't include that # at all.

Have you measured the bore?

If its the later 125 short-stroke engine it should have 54.2mm bore & central exhaust port, but if its the earlier long-stroke 125 engine it would be 51.5mm bore ( for standard bores)

I had a look on a USA list I have and it has a 157 as a 1975 Lobito T 238. Prototipo or Prototype. So it might be a Lobito 250. If it is it is very rare over here I think. I`ll ask around some Bultaco experts! Graham.

Maybe you have a 158 motor if you look in a parts book, cylinder part number is 157.10-026 so that's why yours would be stamped 157
If you don't have parts book look up manuelsoler blog spot there is one there for 158/159

Here's the link http://sherpamanuelsoler.blogspot.com.au