Anyone know if the later Yamaha YBR 125 engine with Fi is a straight swap with the wee Scorpa 125/143/163 engines.?

Cheers.

Quite likely, but the FI won't work without a battery I suspect and fitting that would be problematic. That would also scupper the electric start which would be an even better consideration for us old gits.

It's in,had to swap the electrics though.

Blank off the casing where the starter goes.

Carb/ manifold bolts straight on.

See how it goes tomorrow.

Surely it has road gearing ???

They all do,,standard they run 10/11 front 57 rear sprockets to get round this but you really only have one usable trials gear.

This isn't a problem as they have so little power anyway.

Rode a trial today ,everthing in first,just rev it a bit more.

Ran perfect.

Soo, what DID YOU GAIN WITH ALL THIS?

Eh,the original engine was knackered.

You don't think i swapped it because I had nothing better to do?

I couldn't get an old style engine.

Edited October 14, 201312 yr by breagh

Surely it has road gearing ???

I suspect the internal ratios are all the same on these motors although I haven't had a look in either one myself.

Maybe the TTR engines have their own gear sets, a quick look at the online parts fiches might answer that.

Edited October 18, 201312 yr by craig10

On 10/18/2013 at 12:38 PM, craig10 said:

I suspect the internal ratios are all the same on these motors although I haven't had a look in either one myself.

Maybe the TTR engines have their own gear sets, a quick look at the online parts fiches might answer that.

2021 Sherco ty 125f Adventure.  This bike is fitted as standard with a Jianshe Yamaha YBR 125 engine, made in China.  I had serious issues with the kickstart and gearbox mechanisms, so  I have now replaced the entire bottom end (apart from the flywheel, stator and flywheel engine case) with the complete bottom end from a Japanese made 2006 YBR 125.  I retained the up-rated 150cc barrel and piston.  I also kept the complete Jianshe-Yamaha head. I can detect no difference in performance between the two motors.  

Differences include: the two stators are different.  The old flywheel is 300g heavier than the new one.  The crank shaft cam chain sprocket on the old motor has one tooth less (or more) than the new one.  They are not compatible, so you have to change BOTH for one or the other (the ratios remain the same).  

 

 

 

Edited September 18, 2025Sep 18 by stpauls

On 10/12/2013 at 9:50 PM, 2stroke4stroke said:

Quite likely, but the FI won't work without a battery I suspect and fitting that would be problematic. That would also scupper the electric start which would be an even better consideration for us old gits.

Just stick the carb off the old engine onto it.