Yamaha TRX850 Enthusiasts Forum

Hi,
I’m new to posting on here, however have been modifying and tinkering with my TRX for years.
I have a question though, during the last engine tear down the cam tensioner got stuck and didn’t apply enough/any pressure to the chain which allowed the chain to slip on the crank. As a result the crank is now missing a number of teeth.

I have sourced a replacement from Germany, which is apparently from a 4UN motor, the same a mine, however, on closer inspection the conrods that are still attached have 3VD on them.
It looks like a 270 crank which I know was on the later TDM bikes which have the 3VD number for the rods although this was on the 180 engine.

I’m full aware that the TRX is a parts bin bike and shares multiple parts with other machines like the 3VD, so I’m not saying that this is a 3VD crank just because the rod are.

My question is, is there anyway of identifying the exact crank, short of side by side comparison, to ensure this will work as a replacement. I really want to avoid pulling the motor apart only to find this out.

All help / advice is greatly received.

Say safe, many thanks, Steve.

Rods are the same on all 850-engines, all marked 3VD116500000. So if it's apparently from an 4UN engine you are all good. Crank itself should be marked 4NX, the cylinder block 4UN. That's the 270 TDM/TRX crank.

You can cross reference any TRX-parts at http://www.motorcyclespareparts.eu or similar site.

3VD conrods is correct as already mentioned.
But honestly I doubt if the crank teeth are torn because of the tensioner. It is more likely the cams got stuck in their bearings in the cil.head. This does occur if the cam caps bolts are bolted too tight or in wrong order.

Tarwetijger I think you are right about the reason for missing tooths. I know about two cases when the timing chain slipped for one or two tooths due to big slack (bikes were with 100k km mileage) but then only one part was damaged - valves.