DT125R FORUM

The bore looked ok when we rebuilt it 2 moths ago, but it now has small rust pitting on the edges of the barrel. The piston won't rise with the barrel off.

I'm sure it was in neutral, and had the bike on a paddock stand, so even if it wasn't the rear wheel should have spun around.

By the mains do you mean the main crankshaft bearing? i.e. this:
http://www.ebay.co.uk/itm/Yamaha-DT-125-R-1988-2004-Genuine-Koyo-Mains-Crank-Shaft-Bearings-Set-/131753167760?hash=item1ead19cb90:g:RucAAOSwvgdW6ASL

Thanks!

Hello!

So I have a 1998 DT125 which needed an engine rebuild. I've messed it up and after a bit of advice.
I sent the barrel away to get it rebored, and refitted everything with a new piston, new rings and new gaskets. After doing this, the engine wouldn’t start, it had a coolant leak and was left for about 2 months. I stupidly thought that I could just repair the coolant leak at a later date, give it a kick and it should fire up, but was busy so didn't get around to it.

When I came back to it (a week ago), the engine wouldn’t kick and has seized. Upon opening up the engine, it appears coolant has got into the barrel, past the piston and into the lower part of the engine. With the barrel off and the piston still in place, the engine will still not kick, and it looks like there is now surface rust on the bottom end. So I think that coolant has got into the bottom end and sat there for a while, hence to bottom end is now seized.

I’d like advice of what to do next really?
I will happily rebuild the top end again, but need advice of how to free off the bottom end so the engine will turn.

Thanks very much,
Olly