SYM XS125-K Engine Swap possibilities?

[CraddyMcPatty]

Got me a SYM XS125-K (Yamaha YBR 125 Clone) back in April of 2024, and felt that it didn't have any engine damper/crankshaft damper on it (It shakes like hell when it reaches 4000RPM+).

So was wondering if maybe an engine swap would be mechanically possible without too much hassle with an engine such as the one from a 2008 Yamaha YBR 125? Almost like a retrofit style 'upgrade'.

Alternatively if anybody knows any (preferably trustworthy) engine dampers that are compatible with the SYM XS125-K motor, please show and tell.

[jeffyjeff]

Although similar, the XS125-K is not a clone of the YBR. Starter motor location is the most obvious difference. Also the SYM bikes in my Google search are carbureted and the YBRs post 2006 are fuel injected. Swapping out your engine for a YBR will not likely be "plug-and-play".

SYM (Taiwan) has a better reputation than mainland Chinese motorbikes, in my experience. If your bike was mine, I would undertake a serious diagnosis as to the cause of the vibration. The shaking over 4000RPM will not be solved by some bolt-on aftermarket part. Your motor likely has an internal balance weight (gear or chain driven) that is timed to the crankshaft and driven at twice crankshaft speed. If that balance weight was somehow misassembled or otherwise jumped time, that could cause your condition. However, your vibrations could also be caused by something as simple as a loose, cracked, or broken motor mount, or perhaps misalignment when the engine was fit into the frame. Worth checking into.
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History shows again and again how nature points out the folly of men - BOC

[CraddyMcPatty]

[jeffyjeff]

If it was wrecked before, that is even more suggestive that a cracked or broken motor mount could be the cause. Your problem might not be internal at all, and if not, should be easier to find and fix.
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History shows again and again how nature points out the folly of men - BOC

[jeffyjeff]

If it vibrates when revving in neutral, that suggests to me a cause within the engine. But if it mainly vibrates when riding at speed, I would look more closely at an external cause.
____________________
History shows again and again how nature points out the folly of men - BOC

[CraddyMcPatty]

[WD Forte]

I dont know the Sym but expect you could shoe horn a YBR lump in there, but you'd also need a YBR ECU to make it work.
The wiring harness from a YBR donor would make it a lot easier too.

As to the physical fitment viability, I have no idea what the Sym looks like and cba to look it up, its your job to show us
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bikers smell of wee

[CraddyMcPatty]