crank noise

[erioni123]

hey doing a rebuild now and i have the barrel off and when i spin it by hand it makes a grinding noise is this okay ? i think it should spin without any noise
https://imgur.com/gallery/PVuO4DT

[MadGyver]

@erioni123 Hi. It's not ok,it should spin freely and noiseless. You have to check/replace crankshaft bearings and the bottom big end bearing. I would change them all to be in piece of mind.

[SpookDog]

@erioni123

Ditto, definitely not. New main bearings and seals…

[erioni123]

@SpookDog i see koyo main bearings the pop up a lot when i search on google are they any good

[SpookDog]

@erioni123

They’re the ones to get. There is a type to get though, don’t get the ‘cs’ type (I think!)…

CRB023

These are the ones to get I think…

[Calum]

PJME is your friend. Make sure you get the right clearances as well. C3 IIRC.

Yamaha DT125R Crankshaft Main Bearing LH

Yamaha DT125R Crankshaft Main Bearing RH

I always replace all other gearbox bearings whilst you're there, but that's just me and my OCD.

[erioni123]

@Calum is there any way to split the cases without a case splitter as someone said that you can but i dont think you can

[Calum]

I've never used a case splitter. What is a case splitter?

[erioni123]

@Calumhow do i split the case tho, the cank case how do i split it apart to change the bearings

[Calum]

Undo the bolts, dismantle the clutch/generator and then gently tap the casings apart. I use a rubber mallet.

[erioni123]

@Calum how do you tap them apart like there is no place to hit it

[Calum]

There is a spot where the starter motor goes. And there is a piece up top near the inlet manifold.

It literally only needs a gentle tap.

The other good technique is just use the flywheel puller. These can be had on eBay for next to nothing and can even be made from scrap metal. It's well described in the Haynes.

[SpookDog]

@erioni123

I don’t mean to offend.
Are you sure you’re up for this? Is this the first engine that you’ve worked on?
There are certain tools you need to dismantle the engine. Not to mention the damage you can do trying to remove bearings, even after you’ve successfully dismantled the casing…

[erioni123]

@SpookDog its my first time splitting cases but im not sure if i will do it myself maybe i'll have someone do the rest of the work just to be safer, but i saw that people use case spliters its a tool made for spliting them

[SpookDog]

@erioni123

Like Callum said, use a flywheel puller to push the crank in and separate the cases. DO NOT use a screwdriver or chisel, please!…

A rubber mallet is usually enough for me…