ETZ 250 Seized

[Anonymous]

I have recently bought an ETZ 250. It looks in good condition and it runs very well. However on my third ride while doing about 65 it suddenly tightend up and the rear wheel locked. I immediately applied the clutch but the rear wheel remained locked. I seemed to skid for ever and I thought I was comming off but I controlled it and eventually slowed at which point the rear wheel freed I could hear the engine ticking over so I dropped down gears and pulled away and rode home with no further problem. When I got home I checked the gearbox oil level and that was OK. I rotated the wheel with the bike on the stand and that seemed OK. The clutch drags a bit but I expect that is another matter.
This has unnerved me and I am not going to ride the MZ again until I have found the cause of the lockup. Has anyone else experienced this problem? Any help will gratefully received.

[‘AAA Dummy]

Check your oil pump cable is a.working and b.adjusted correctly,does it smoke much?

[Richard Smith]

I have experienced exactly the same thing,except I came off.
The cause was not the engine,but the rear brake locking on.
I was descending a steep hill,in the wet,and had to brake sharply.The rear wheel locked up and despite releasing the brake,stayed locked and I slithered sideways into the edge of the road,did a textbook “highside”and ended up on my arse.
Investigation found that the extrusion under the engine [where the footrest bar is bolted] had cracked at the weld allowing the footrest bar to flex up and down nearly an inch.This combined with me recently adjusting the brake to give about half an inch of travel,and the greasy road,was enough to keep the wheel locked.
Another thing worth checking is that the brake linings are not too worn.I have not had this on a MZ but on another bike,the brake shoes went “over the cam”and locked the wheel.This is caused by the brake shoes moving too far and the servo effect on the leading edge keeps the brake on.
Hope this helps.

[Anonymous]

Thanks Daniel & Terry, I will check the oil pump cable. My initial thoughts were of a locked brake. Since sending this post I have spoken to the previous owner who tells me that the bike has done very few miles since complete overhaul and has not been run in. So I now think that it was an engine seizure. I also think that the reason that pulling the clutch did not stop the skid was because the clutch drags badly, but I may be wrong.
Today I checked the clutch cable adjustment, both fine and course and it was perfect but the clutch still drags badly. I think the plates will have to come out and be checked. Unfortunately that will wait until next week.

[David Usher]

Check your iginition timing. On a two stroke if it gets to retarded or advanced then the motor will seize. Sorry I cannot remember the way it happens. I found out about this the hard way on a relatively new machine. No lasting damage to me or machine but I did not skid, the Pneumat panniers and the fact I was going up hill meant I was able to sort myself out and get home. I did miss a rally at Hay on Wye however.

[‘AAA Dummy]

I had the same thing happen from a blocked exhaust actually, at a sustained 60-65 im guessing that EGTs got too high and the motor locked up then freed up by the next layby. Had just swapped the exhaust from a very leaky but free flowing one where the bike was noisy but would sit at 80mph happily, swapped exhaust and the next ride top speed was down to 70 and I had the seisure at around 65 after a long climb

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