TS 125 crank seals

[ricklincs45]

Hi Everyone,

am still plodding on (slowly) with the TS - just been looking at replacing the crank seals. Right side one is obvious, just unscrew the mounting plate and out it comes. However, the left side one has me beaten. I'd thought after removing the right one that it was a marvellous design; no need to split the cases. Now I see the left seal isn't held in the same.

I've removed the large circlip which I thought held the seal carrier, but the carrier isn't moving: should it? Neither the Haynes manual or the genuine MZ item are of any use whatsoever. Is it going to be a crankcase half split to change the left seal?

Thanks,

Rick.

[Old Dog]

It is in a holder in front of the bearings. The holder won't come out without splitting the case and from what I understand as it is the same alloy as the case is a pain the proverbial to get back in.I think there is wire clip in front but once out it would be a case of prying out the seal with marking the crank - not unlike the ETZ 250/251/301s

[ricklincs45]

Thank you for that, I half suspected as much. Would have made things MUCH easier if both seals had come out without splitting the cases, but hey-ho.... I guess there's a reason for it

Am slowly losing the will to live with this bike......

[therealche]

Unless I am mistaken both crank seals are inboard of the bearings. on the dynamo side there is an oil seal in a plate , but this is not the main crank seal, it is to keep oil in the bearing ( which I think comes from the gearbox, like the ES and pre /1 TS 250 engines).

[ricklincs45]

Ah

Thanks for that, I did think it unusual to have a seal on the outside of the crankcases; looks like there's no avoiding a case split.

Could anyone suggest or recommend a sealant of any kind to use when re-joining the crankcase halves?

Thanks,

Rick.

[arry_b]

The seals are both on the outside of the crank on almost all small TS engines. Only early ones with the main bearings lubed by the gear oil have internal seals (my 1971 ES150 does this).

The seal holder on the L/H side of the engine is a pain in the backside. Some come straight out, some need persuasion. The last one I had that was stuck, I carefully drilled a couple of small pilot holes in it, screwed a couple of self tappers in and pulled it out with pliers. Needless to say, I had a replacement carrier in my spares, but a new one is only around £8 from memory.

[therealche]

Ah Might have been thinking of my ES... or maybe the ETS! Just looked at a 1983 parts list for the 125/150 and the seals are outboard of the bearings! Now all you got to do is it out!

[therealche]

If you go with splitting the engine , I use Stag jointing compound... Ive had a tin since I started working on engine back when the world were in black and white. Painted on with an artists small brush.

[arry_b]

Copied here for posterity, some advice on replacing the seal PM'd to the OP.

Hi Rick. If you've got the genuine manual, the procedure for getting the seal carrier and bearings out is on page 91 in the bit for the MM125/3 engine. It's not all that clear though even with that!

If it's just the seal carrier that you're trying to get out, it is possible to get it out without splitting the crank cases 50% of the time. I managed to do one last week by removing the circlip, and with a small sharp chisel gently made a couple of ridges on the side of the carrier. I could then lever the carrier out with a screwdriver, and grabbing it with some water pump pliers once it was moving.

Some, however, won't move unless you drift it from the inside meaning you need to split the crank cases. With them split, I remove the circlip and the seal from the carrier, then pop the cases in a low oven for 15 minutes (110 degrees C). The bearings and the seal carrier can then be drifted out from inside to out with little effort.

It's best to make sure you clean any gear oil out of the crankcase half, and wait for any significant other to go out for a couple of hours while you use the oven!

Steve