Model 116 Alpina is a tractor

[built_to_go]

Hi guys and gals, new to the forums and want to share an observation. 

I was once blessed with both a model 116 350 Alp and a model 85 250 Alp. Both used the stock Amal carb and to my knowledge were set up correctly in regards to timing, fueling etc. 

The model 85 RIPPED and had great midrange and top end power...the thing was like a rocket ship when wound up.

The 350 was more like a tractor, lots of power but not nearly as wicked. It was almost 4 stroke like with a wide, consistent power band I didn't expect out of a larger displacement version of the previous motor. 

Is there one single difference (like the 116s massive, ridiculous flywheel and counterweight) or is it a combo of porting, jetting exhaust etc? 

The 85 is long gone and I love the 116 but I would really like to make this motor a little nastier. 

Thanks in advance! 

[feetupfun]

The same can be said about early to mid 1970s 250cc vs 325cc Sherpa Ts. They both have a similar rated maximum output, but the 325 has much more power at low to mid RPM (from memory they are rated at 21 and 22 horsepower at their peaks)

The reason for this is that the gas volume throughput of both motors is limited by them sharing the same size carby and the same size exhaust system.

My Alpina M138 350 is also an amazing tractor like the M116 at low to what would be mid-RPM on most other big two stroke bikes of the era so I know what you mean. It doesn't stop you going fast in the bush though, because it has enough gears spaced apart enough to suit the power spread. I find that it is the suspension that limits how fast I am game to go in the bush (so I can still hang on)

I'm currently rebuilding a M85 and am greatly looking forward to riding it too. I expect it will be much more like my Sherpa T 250 in handling and motor than the M138, because the early Alpinas share frame and steering geometry with the early Sherpa Ts, while the M138 is longer and has the Pursang triple clamps

[scot taco]

I think the early model sherpa t 325 also had a different head/squish design than the late model 325 and that the early ones were a bit more of an animal so maybe that could make a difference along with the carb and exhaust if the alpinas shared the same head.

I know the later model big bore Alpina also had a different exhaust port height compared to a sherpa t but not sure about the 250.

 My 199a is deceivingly fast through the woods because it is smooth,but like feetup said,when a get up into 4th  gear and spool it up I can run out of enough brakes pretty quick.

A bigger carb would maybe give it some more bite but you might run into trouble with the sizing for the boot going to the air box.