125-200cc wre 125

my 05 wre is due it's mot soon, the engine seems great, in 20,000 miles and 9 years it's only had 3 pistons and ring sets done. How long do the bottom end bearings last in these engines? As my gear lever seems to have ground of it's teeth so I keep having to put loctite type glue on the lever and retightening it or the lever flops around everywhere or falls off. So I'm thinking, if I have the engine split [which you have to do to put a new gear selector shaft in right?] would it be worth doing the bottom end bearings and crank too? Or will it last the life of the bike if I use a good oil every 1000 miles? I know some jap road bikes can do 50,000 miles plus on the same engine parts but on a little 2 stroke thumper I'm not so sure.

find out about cost,availability if there are any noisy gruanchy bearings in the cases replace them.
the bottom end may be good but do examine it carefully. ive had cases apart and not replaced mains and the engine goes for an age.
if in doubt swap it out.
oh and any up and down movment in the conrod big end its game over they have a spec of side to side movment.
check that very closely again if in doubt take it to some one who knows

if your splitting the cases anyway i would replace everything and keep your receipts, you will need to buy flywheel puller,gaskets and bearings and seals as well as the shifter shaft anf shifter, if you can get hold of a second hand electric oven to heat up the cases this will make removal/installation of bearings much easier, oh and get the workshop manual and cleanout and re grease swing arm bearings and starter motor and would buy a swing arm bearing kit and give the frame a paint, in other words a full rebuild.
the expensive part would be the con rod kit you will have to take it to a shop to install the new conrod and bearing be careful not to knock or drop it once rebuilt as it can easily be thrown out of whack.

if it's a long job I might not bother replacing it, what's the worst that can happen if I never changed the rod/ bearing? Would it eventually just wobble around too much and not run/ seize? When I had the top end off I pulled at the rod and it moved such a tiny bit side to side, it didn't move up and down at all

You do not have to split the cases to change the selector shaft ! Just remove the clutch case and the complete clutch, pull the old item out, fit new and box it all back together again. Takes longer to get the old gasket material off than it takes to do the shaft replacement. There are plenty of 125s out there with more hours / miles on them than yours that have never been apart and still run fine.

Are the teeth worn off on the gear lever, or the shaft? If it's just the lever, I'd replace it ASAP, before it also destroys the shaft. If it's the shaft, you're going to want to replace both.

If there was no play in the bearing when you had the top end off, I'd probably run it, but that's just me.

yeh if the conrod has a major malfunction it could junk the engine but thats worst case. lol oh and the get very rattaly before this happens sounds like a washing mashine with pea grit in it.
ive not taken 125 apart so yes you may not need to split cases.

double check no play in the conrod if barrels still off and run it.

thanks for the replies, the old gear lever had it's teeth worn out so much before that it wouldn't grip the shaft when I was 15 miles from home, got stuck in 4th gear. Put a new apico lever on instead, but that one has come loose four times now. I've put my finger on the end of the shaft and it has got teeth on it but they're not very deep, I think the old lever probably took some of the metal along with it. I'll ask for a new shaft and lever to be out on before mot if it's that easy to do. And when I had the top end off, that was 6000 miles ish ago, before it had a new piston and ring too, it doesn't make any funny noises or rattles tbh so I'll leave it alone