YZ 125 right side crank seal?

[Renegade90]

So just a few questions for you experienced guys. My 98 yz125 I use in the woods smokes a little more than what I’d expect. I use to have the factory carb on the bike and the slide screws were locked up good, it ran pretty darn rich and loaded up super fast. So I switched to a lectron which I absolutely love the bike runs a whole lot better and doesn’t really load up unless I put around for a really long time which seems acceptable, and doesn’t smoke at part throttle. So here’s the other end, I run 32 to 1 yamalube 93 octane fuel, I change my trans oil every 4 hours with gear saver, I’m pretty consistently down 100cc’s after those 4 hours. My guess would be when I go wide open that initial burst of smoke which is a blueish tint is probably trans oil? My guess is this is the RH crank seal and for some reason it either mildly weeps or weeps when the motor gets spun up? I have the seal already and planned to change it this weekend. Any other opinions, suggestions, or advice on changing the seal would be greatly appreciated. Also just to add I do topends at 25 hours and I always get for bottom end play and the bike thus far has had zero over 3 topends. Thanks again guys.

[YZDOC]

Sounds like you have it diagnosed. I would add the clutch lock tab and right gasket if you don't have those handy before you open it up. Gasket likes to leak around water transfer. 

[Renegade90]

Thanks man. I didn’t even think about that, luckily I have a gasket set in the tool box just incase I ever needed them. Is the drill and screw method still the best way to pull those seals? You’ve been a God send on here!

[YZDOC]

1 hour ago, Renegade90 said:

Thanks man. I didn’t even think about that, luckily I have a gasket set in the tool box just incase I ever needed them. Is the drill and screw method still the best way to pull those seals? You’ve been a God send on here!

Crank has a steel collar on it, pull that and you can get under the seal with a seal pry bar, or equal, just don't mar or scratch the case. 

https://www.manualslib.com/manual/196053/Yamaha-Yz125k1.html?page=18#manual

Number 2 on this page.

[Renegade90]

Now that’s looks easy thanks again. I’ll try to set something against the pry like a wrapped up tight rag or something.

[markmc2]

I just did one myself, easy. U have a clutch holder tool? Don’t leave your gear wedge in there after reinstalling the gears...like i did. Got lucky, no damage, found it in there 10 hrs later. Check your shift lever bearing while in there.

[Renegade90]

49 minutes ago, markmc2 said:

I just did one myself, easy. U have a clutch holder tool? Don’t leave your gear wedge in there after reinstalling the gears...like i did. Got lucky, no damage, found it in there 10 hrs later. Check your shift lever bearing while in there.

I do have a clutch holder tool.  As far as I’m aware I can access the seal with the left side cover off.

[markmc2]

Right side off for right seal

[Renegade90]

4 hours ago, markmc2 said:

Right side off for right seal

That’s what I meant lol. Had a little moment there. I appreciate everyone’s help very much. I’ll try to tackle it this weekend or next weekend depending on time. I believe I’ll go ahead put some new clutch plates in it while I’m in there, I’ve had a spare set forever.

Edited April 19, 2019 by Renegade90

[Renegade90]

Well little late replying but if anyone stumbles on this post hopefully they gain some insight. I got the job done weeks ago and it went well. I used a rolled up cutout of a soda can as a gear wedge, worked wonderfully. I replaced my clutch hub and basket while I was in there, the basket probably can be cleaned up and used as a spare but the hub is grooved pretty darn bad. I have no idea how many hours total were on them, but I’ve put 78hrs on the bike since I bought it 3 year ago. The only thing hard in this job was getting the old seal out. I used a seal pry and wrapped a rag tight around the seal bezel, I did no damage to it but someone has slightly marred it in a few spots in the past, luckily it did indeed seal. Realigning the power valve gear took some patience too. The bike now runs with minimal smoke, just a mild thin puff when I’ve been in the low revs for a while or when I first open it up after being warmed up which is what I totally expect. The bike feels snappier and more crisp then ever the last few rides. I’m going to change the trans oil a little early (normally I do it around 4hrs) and check the level, but I can already tell a difference. For reference if someone stumbles on this the bike is a 98 yz125 woods ridden, lectron 38mm carb, 32:1 93 octane, mixed usually with yamalube, but also Motul 710. I’d imagine this procedure is still nearly the same for any new yz125 as well.

[markmc2]

Good deal!