loosing the will to live with this project please help

[riess]

hi everyone new to this forum but have been meaning to register since i bought my mz ts150 about four months ago anyway what was thought to be a nice simple project has turned in to a can of worms the engine turned out to have water in the crankcase and the crank was rusty so i ordered a new con rod kit bearing and seals and sent the crank of to have the new con rod fitted and trued cleaned etc now the cranks back iv realised the crank bearings have been spinning on the crank but the crank isent damaged its just that the bearing are a sliding fit rather than being pressed fit question is what exactly should my crank diameter be? its obviously going to be bigger than the bearing diamater so they are then tite! has anyone got an unworn crank from an mz ts that they could mesure for me?

[DAVID THOMPSON]

the electric motor shop i deal with sprays hot aluminium on shafts to make them bigger...

and there is something called bearing fit i have heard of ... and a metal press on sleeve to make shaves bigger
and renew the place where the seal runs...

some one else may chime in on solutions to the problem

dave

[stinkybob]

DON'T PANIC! I've rebuilt loads of MZ engines in my time and this is not that bad a problem.

When I was making Go-Faster sprint MZ engines running on things like alcohol, NOS or purple meths (don't ask) I used to reuse old main bearings and cranks robbed from dead engines because they had minimal resistance being previously worn in (not worn out). Sometimes I'd find that for whatever reasons the bearings would almost be a slip-on fit instead of a tight fit but it never made any difference so long as the sideways movement of the crank is minimal. Sometimes this even meant putting a shim between the crank and main bearing to take up slack and keep things centred. I never had any problem with slightly loose main bearings. The forces on the crank as it's going up and down probably assure it doesn't just slip around in the bearing so long as the bearings are good and have no catchy spots in them.

Also when rebuilding my own cranks I always leave out those little copper shims on the inside of the crank next to the con rod. They don't stand up to abuse and can shred apart sending little copper shards all up through the transfer ports which has the effect of giving your top end an instant rebore in seconds. I would always rebuild the cranks without the copper shims and never had a problem with the con rod being centred. Seemed to me like the piston end kept it centred just fine. The extra clearance at the big end probably helped it lube better anyway. All I know is it works.

I have also reused old con rods where the bottom end was good but the top end was starting to lose it's hardening, usually the first bit to go bad on an MZ crank, which was evident by cracking or even pitting of the inner race area of the small end. I just used bog standard phosphor bronze bushings instead of a needle roller bearing. Contrary to popular belief the bearing doesn't HAVE to be a press fit into the con rod. The slip-in bushings I used worked perfectly fine and in my opinion probably withstand more abuse than a needle roller bearing anyway.

Of course you can get somebody to machine the small end to take a press fit bush if you want but the cost of all that for a road bike is probably about the same as just getting a new crank anyway but I think on a smaller engine for road use a bush would serve perfectly well. I've used them on my 250 road bike engine without any problem so bear that in mind next time you need to rebuild a crank on a budget. I always run more lube than standard in my mix anyway and it's always worked fine for me.

Speaking of which, I've been using diesel instead of two stroke oil for about ten years now it's definitely an improvement. Keeps things cleaner inside. I premix one liter of diesel to one gallon of petrol. Must have viton main seals but I use the same size seals as the output shaft seal for my mains. I just use adapted output shaft seal holders instead of those big old main seals they come with standard but of course that's on my 250 engine so it doesn't really apply to a 125/150.

Oh and 20/50 oil instead of gear oil. Makes the clutch work better and is perfectly fine in the gearbox. Been running 20/50 on my road bike for decades. Got loads more tips but I won't mention them here. (Psssssst- go to Vimeo and search for "Stinkybob" but tell no one!).

Naturally if I admit to any of this in public the MZ Nerds chase me away with burning torches and pitch forks screaming that I am speaking in the devil's tongue but hey- 20 odd years of MZ engine building has taught me a thing or two no matter WHAT the book learned boffins think.

Now I must go crawl back under my rock for the next ten years or so.

[DAVID THOMPSON]

i think i just got a short lesson on how to make an old mz go stinky FAST

which makes the best one to restore ts or etz

i use bikes as a daily driver ..building it so it stays together is the goal

dave

[stinkybob]

Twenty years ago it was hard to get some MZ parts but these days it looks like you can get anything now. Lots of old stock and new parts seem to be hitting the internet. It's a bit like the situation with Vincents. There was a time you could only get spares through owner's clubs and secret parts hoarders known only to a few but my mate says you can now readily get anything you want for them. He says you could literally build a whole brand new Vincent out of new bits if you wanted. I've seen it going that way with MZ spares now.

Having said that I know from past experience that the 12v ETZ line is very easy to maintain and use daily. I used to courier on my 250 so it got a lot of use. It held up just as good as any other Jap bike and was easier and cheaper to fix. None of the seals and bearings are hard to get, they're all bog standard bits obtainable from your local bearing shop.

The 12v ETZ alternator system is really good. It's robust and long lived if you change the MZ regulator for an electronic one. I used to use a Lucas NCB403, found on older BMW cars and other stuff, but different companies make the exact same thing and they're not expensive. And anyway having 12v means ease of bulbs etc. You can't just nip into the local petrol station for a 6v bulb anymore and 6v coils and stuff are harder to readily get these days if you're in a hurry. On the 12v system any car coil you can bodge onto it seems to work fine. I've been running a Lucas coil off a Metro for like 15 years now.

There ARE some really good 12v conversion kits for old TS models, and I've had one and it worked great, but they're a bit expensive and more complicated and harder to get spares for than a bog standard ETZ 12v system.

Luckily the engine mounts on all TS and ETZ 250/300 are the same so I've got a 12v ETZ engine in my TS frame no problem. Unfortunately it's not the same on the 125's. The TS has a different mounting to the ETZ so it's a real hassle to fit a newer engine into an older MZ125.

I used to have an ETZ 150 and found it amazing for a small bike. If you want to use a small MZ every day with minimal hassle that's what I'd go for. You could get a 125 on L plates and put a 150 top end on it if you were sneaky and nobody would ever know.

It's also unfortunate that these days people are asking silly money for MZ motorcycles, even those later ETZ models that use to be two a penny. Luckily I got mine when they were virtually give-away prices and I'd never pay what they're asking these days. But if you're mechanically minded then you might still be able to pick up a non-runner cheap. And one thing to remember is that no matter WHAT they tell you is the reason why it won't run they're all WRONG. It's the main seals. I've known people replace the entire electrical system, carb, and allsorts before giving up and all I had to do was bung in some main seals to make it run. This is a common MZ trait and is often overlooked by people with a troublesome MZ so they throw money at new carbs and stuff before getting frustrated and giving up, but once you know these things an MZ is in my experience the most capable and dependable bike I've ever had. But I can build them in my sleep, which is a trait not much in demand anymore.

[paulatradese-6]

stinkybob, I have a cart load of 15/50 oil that I need to use for something. Looking at your info. I think it might be O.K. for an etz gearbox?

[stinkybob]

When I first started with MZ's it was the first two stroke I'd had since I was like 12 years old and that was just a lawnmower engine minibike. So when I first got an MZ all the MZ nerds told me you MUST use heavy gear oil, like EPA90 or something, or your engine would explode and send you cartwheeling down the road in a ball of fire smashing into a busload of nuns and orphans killing and maiming everybody and you'd be condemned to Hell for all eternity, but after eventually looking at the internal workings of an MZ engine myself I switched to bog standard cheapo 20/50 about 15 years ago. In my opinion it makes the clutch work better and I have never had an oil related clutch or gearbox problem since. I've used 10/40 before as well without problem (somebody gave it to me) so I'd say your oil is fine for an MZ. They're not rocket science. They're like two wheeled tractors. You can fix them with a rock and pointy stick. In my experience they are very forgiving of curious maintenance, obscene bodging and dubious upkeep. You wouldn't believe the things I've done to my bike over the years. I can't count the number of times people have told me "That'll never work because..."

[suzukix7]

Just bought some 20/50 oil for mine too.....It's wilkos oil at £3 a litre

[paulatradese-6]

Cool, next oil change in goes the 15/50.