Hi All,  has anyone had trouble with small end bearings for DTs?  I ordered an part from Yamaha here in the UK for my ‘76 DT400 but it is slightly too small. The guy at Yamaha assures me it’s the correct equivalent number, but it just don’t fit. Any ideas please?

What is the part number you think that you need?
What is the part number you received?

What do you mean by it is too small?
Won't fit over the wrist pin?
Fits on the wrist pin but is too loose inside the rod opening?
Bearing not wide enough?
What is the rod casting number? Is it a Yamaha rod or some off-brand?

Not sure I'd call it "trouble" but several members here have reported 250/360/400 aftermarket replacement rods that have a larger opening in the small end of the rod.  This requires a small end bearing with a larger OD.

I couldn't find a part number...  but if you can answer DEET's questions perhaps he or one of the other real experts can help.

Looks like the part number might have been changed from 93310-21854 to 93310-218A6 and it is not unknown for superseded part numbers not to fit.

Best to provide answers to DEET's questions first, though. 

If the PO already did a crank repair, it could be that a connecting rod used has bigger diameter at the small end of the rod. Thats also the case with my rebuild crank. The mechanic i gave it to said this con rod set was easier available and also the needle bearing at the small end is easier to get.. Didn´t prove that and couldn´t avoid, as the crank was already finished before he told me. Anyway, runs fine. No idea about he bearing size, but should be standardized. The order No of my con rod kit is WYA-22072b, no manufactor name written on the bill. hope this helps

Thanks for the replies guys and sorry it’s taken so long for me to get back….it’s school holidays here and I have to pick my moments to hide in my man cave!
the original part number is 93310-21874 and the equivalent that Yamaha supplied is 93310-218A6 (in fairness the guy was really helpful and did loads of research and sent another bearing….that was exactly the same as the one he’d already sent!).  It fits over the wrist pin fine and is the correct length but is about half a millimetre to small in the con rod.  I can’t see a part number on the con rod as it’s still installed, it just say 5x5 on one side and 0 on the other.  I’m not sure I even need to replace the bearing as a can’t feel any vertical movement when I put it all back together. I just thought it would be best as I had the head off anyway and have had a re-hone and new rings.
on another note, I hade the head powder coated and it looks brand new. I’m thinking of sanding off the tips of the fins to make it look original but I’m worried about damaging the powder coat or allowing moisture/oil to get under it.  Any experience with this?

How does the powder coating go with getting rid of heat. Just thought it'd be thicker than a splash of rattle can paint but could be wrong. You say the head but is that head & cylinder both done. Bet it looks great. Pics please sometime if pos.

The bearing you need is 93310-418E9-00

Had to check a dozen times before replying (and I'll still probably be wrong ), but should that be 93310-418E9, DEET?

Yessir... I must have hit the gap between the 8 and 9 on my keyboard....