Hi, just bought a ty125, been getting it ready to ride so done all the servicing bit n bobs. Went for a 15 min run and on return the reg plate is black with oil. I took the plug out and all the plug threads are coated in oil, do I assume the clutch side seal has gone? If so what is the procedure to repair this

If the clutch side crank seal goes allowing gearbox oil into the motor you can normally smell it

A definitive test for the crank seal letting oil in is to look for a reduction in oil contents in the gearbox with use

 

It's normal to have oil on plug threads

It's normal to have all sorts of gunk, yes just like that, come out the end of a 2 stroke exhaust

 

Best way to test is with a 2-stroke leak down tester.

But yes, if clutch side it would lower your trans fluid level- although it wouldn't take much oil to make a huge mess.

Ordered a full seal kit and a clutch/flywheel holding tool

Now need some tips on removing the seals if anyone has done this before

Cheers

Gary

Gary, Don't know where you are located, but as stated above that looks pretty normal for a 2 stroke when it can exhaust

directly onto a surface, if your silencer had a turned out end so it wouldn't blow straight as it is now , you probably wouldn't

see such a mess.

 

What mixture are you running?

Does the bike run pretty good as is?

The pipe itself is subject to a build up over time & needs cleaned out.

I am not familiar with seal replacement on a TY,  but its not fun on any brand.

 

Have a nice day

Larry

Hi larry, i am in norfolk uk. I am re living or trying to re live my youth. I bought the same model and year new in 1994, so exactly the same. I suspect the seals as the gunk on the back is really thick oil, this was from 15 mins running, back in the day i dont remember it being like this, also the plug is wet with black oil, again should not be like this. I changed the oil a few days ago and topped it up last night, so putting all these things together made me think of the right hand seal. I would dread to think what it would be like after an hrs running.

The motor starts first kick, ticks over very well but feels lumpy and was down on power when riding it. When going into 5th it lacked pull, when going into 6th it was completely gutless

On the 250s the seals can be changed without splitting the cases, I can't remember if the clutch needs to be removed or just the primary gear

 

First thing to check if you do the seals is that there is a o-ring behind the primary gear or the spacer/sleeve to seal against the crankshaft, a lot of kits don't have the o-ring & it is needed to completely seal the crankshaft assembly

 

Removing seals involves screwing a small self tapping screw into the seal a small way the using vise grips to work the seal out

Edited March 8, 201610 yr by tony27

 If the primary side seal went, it would look like a mosquito fogger. Not just a little oil.

Started to strip the side off ready for the parts coming, it looked like the seal is in backwards as i could see the internal spring, but the pic does not really show what i seen, it was evident someone gas been here before.

Question what direction are the idler gear and clutch basket nuts

Dont seem to be able to post a pic now

A

Seal not in backwards as a double lip and spring seal. I bought the clutch n flywheel tool that is brill, got it all stripped and the seal out, i noticed that the oring was missing from the bike, so assume this has been causing the issue? The seal kit has this oring, looking at the dwg it shows the seal, then the o ring then the spacer, so does the oring sit on the shaft and the spacer buts it against the casing, or does the oring go on the spacer and but against the seal, i dont know, help please

Cheers

Gary

The o-ring is to seal the inside of the spacer to the crankshaft, without it there is nothing to prevent oil etc migrating along the shaft. It's a strange design but seems to be common to most Yamaha 2 strokes for quite some time, my 81 YZ465 has it as well & the YZ490s are the same so the idea stayed around until the 90s