301 jumping out of gear

[atreyu]

Hi All,

My 301 engined Supa 5 started jumping out of 3rd gear about 5 miles from home this evening. It was fine and then coming off a roundabout it popped out, was a complete nightmare to get back into 3rd and then after a second it jumped out. Ended up jumping 2nd to 4th gear.

The clutch adjustment doesnt seem brilliant so I'll look into that at the weekend, however from searching the forum it seems to point at a worn selector drum? Is this right? Or could it be the dogs on the 3rd gear?

Has anyone had the selector drums from ost2rad? http://www.ost2rad.com/MZ-Spare-Parts/C ... 250-1.html

[DAVID THOMPSON]

could it be the dogs on the 3rd gear

or the shift foot lever not rotating the drum all the way into 3rd gear position


on some bikes there is a spring loaded ball bearing that holds the drum in gear positions
and that may be weak or where the ball sets is worn down

this stuff is made so many different ways its hard to say what is going wrong

one thing i noticed about mz bikes the guys that designed them went to a different school of engineering
to others ....they work good but built different than most others based on my fun with a rotax powered saxon tour
dave

[mr_luke]

My ETZ had this problem when I got it. From what I understand, it's normally down to a worn or mismade selector fork, which doesn't hold the gears in place properly. The dogs on the gears are 'undercut' slightly, so they pull each other into mesh, but once the fork is too far gone, these dogs wear and start to round off.

The selector drum in mine did show some signs of wear, but nothing very major at all. The dogs on the gears were nicely rounded off, and the fork was completely knackered - about half of its thickness had been worn away and it was badly blued from the heat. I replaced the 1st/3rd selector fork, the 3rd gear pinion, and the 1st/3rd sliding gear.

That solved the problem. All the bits came from Ost2Rad and were absolutely fine. Good luck!

[atreyu]

Thanks for the replies guys, keep any help/info coming!

Looks like it might have just been on it's last legs on my ride out yesterday. I'll adjust the clutch as per the manual but it's looking like it will be a rebuild job!

[therealche]

An engine rebuild isn't that big a job on an MZ. Used to be able to do a Supa5 or an ETZ in a weekend even with compulsory beer breaks! The only special tool you really need is a clutch puller

[atreyu]

Well as I had a day off work today I've taken the clutch off and found the positive stop "roller" spring to have come off its little peg, also the countersunk screw holding the thick washer which is screwed onto the end of the selector drum was also loose.

Now I'm wondering whether to stick it back together and try it again or to go ahead and rebuild the rest of it anyway, It was running pretty good

[therealche]

I would replace the spring (http://www.themzshop.co.uk/product/return-spring_wm/) and put it all back together. Use threadlock on the screw holding the end plate on. Clean the taper on the crank and the clutch with alcohol before you stick it back on. My favourite way of locking the engine to tighten the tacho drive nut on was using nylon rope down the spark plug to pack the combustion chamber, use a ring spanner and a big hammer to shock the nut tight, but I'm sure everyone has their own favourite method. If the gearbox still doesn't select properly you have only lost a day, if it works you've saved the time and cost of a full rebuild