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Hmm, not familiar with either of the electronic systems you have tried but if they don’t use the standard cam to trigger then that blows one theory away. There have been instances of badly machined cams which can trigger at more than one point especially if the points gap is a tad small.
I had a similar problem with a TS150. I am not convinced I ever got to the bottom of it and it seemed to become more prevalent after I fitted a Velleman transitorised gizmo – which reatins the mechanical points.two things I can suggest but try them one at time. Firstly retard the ignition to 2mm btdc and see how the engine behaves. It should reduce the kickback and probably will not have a huge effect on performance though there could of course be a risk of running hotter. If that works then at least you know a cause and may be able to reach a compromise on timing. The other thing to try is a faster idle speed. Slow steady idles are great but they would tend to facilitate engine reversal if the motor is prone to it. My TS150 would reverse whilst ticking over at traffic lights – keeping the speed up helped.
Best I can suggest. If you do ever solve the problem let everyone know how as it will add to MZ folklore.
Peter
Hi Matthew,
Don’t have an immediate solution but before going any further can you confirm what type of electronic ignition you are using. Does it still use the points and the points cam?
Peter
Something not to be overlooked and not mentioned so far in this debate is that changing the premix ratio also affects the fuel supply. Adding more oil weakens the mixture, reducing the oil ratio richens the mixture. MZ took this into account as follows: The 4spd TS250 uses a 140 main jet(33:1), the Supa5 1 135 main jet (50:1) and the ETZ250 (with oil pump) uses a 130 main jet (no oil in the fuel) in what was essentially the same 30mm BVF carb.
That should fan the flames of debate.
Peter
Hi Neil,
As I understand it, the 250 motors went from 33:1 to 50:1 at the time the Supa5 was introduced. prior to that the main bearings were lubricated by gearbox oil so the mixture ratio was only concerned with lubricating the bigend, piston and small end. Don’t think the piston or big end were changed significantly but early motors had bronze bush small ends whereas the later motors had a needle roller bearing. It was this that supposedly allowed a weakening of the oil ratio. Other factors may have come into play, improvements in oil quality and possibly a marketing influence to make the bikes seem more modern in the Western world.
For what it is worth I have always run my ES250/2 on 50:1 even with a 4spd motor but this does have a needle roller small end. It has never seized or given me any problems related to fuel mixture – plenty of electrical problems though but I don’t think lack of oil was the cause!
The 125/150 motors went from 33:1 to 50:1 around the same time as the 250 motors as far as I recall but on what basis I don’t know.
However, in truth the difference is marginal in terms of cost and smoke reduction so I would tend to err on the side of caution over reducing the amount of oil in the earlier engines unless you know for sure the condition of your motor and what type of bearings it is using.
Peter
Hi James,
You can fit an 18″ rim to a a Supa5. I did it a while ago for green laner and one of our Bristol section members has also done it. There were two snags as I recall. The first is the centre stand cross piece which will rub on the tyre if you get to ambition about tyre size and in the same vein, there is not a lot of width in the s/arm.
I got round the former problem by beating the cross tube flatter in the middle section.If have one in my shed with a tyre fitted which you could borrow if you live close enough to pick it up (Nr Bath). My contact details are in the magazine (membership co-ord)
Regards
Peter
Mike,
Have a look at this link from the MZ racing web site. You may find something helpful which can be used on a road bike.
Peter
Not a job I would ever want to tackle again. However, I was reasonably succesfull using the following method. Use some rubber lubricant on the outside of the rubber bush but not on the inside unless absolutely necessary. Push the rubber bush about 1/3 to 1/2 into the fork end then push the metal bush into the free end by hand until it won’t go further. Put the whole assembly into the vice and squeeze the metal bush into the fork end. With luck it will take the rubber in with it squeezing it thinner as it goes. You may have to try this several times before you get it right. The rubber bush elongates and thins down as its pushed into place.
Lubricating the outer part of the rubber bush helps it to slide into the fork end. Not lubricating the inner helps create enough friction to push the rubber bush into place rather than simply sliding the metal part straight through. At least that’s the theory. It worked for me in the end – but never again
Peter
Hi Craig,
There is really only one essential tool for dismantling an ETZ251 engine and that is a proper workshop heavy duty clutch puller. You can buy smaller cheaper ones for very little money but they may not work and could well damage something. The clutch can be very tight. The other really useful tool which can be fabricated from a strong piece of angle iron is a bridge to separate the crankcases. If you look on ebay you will see examples of both tools. Apart from that its common sense but do make sure you heat things up when dismantling and reassembling. A Haynes manual or better still a workshop manual from the Regalia Shop are strongly recommended.
Afraid I don’t know where you can beg/borrow one, you really need to make contact with an MZ owner in your local area. Suggest if you have not already done so that you contact your local section rep Dave Gillespie who can probably put you in contact with someone close who can help. Dave’s details are in MZ Rider.
Hope that helps
Peter
Hi Peter, I am a great believer in always looking at the last thing you did when something has gone wrong. I suspect what you have is clutch drag caused by the thicker new plates and no doubt some new oil. Its not unusual for the 250 motors to be hard to get into neutral and always seems to get worse if the motor is disturbed. With the bike on the stand the back wheel can spin so the clutch does not have much effect dragging or not.
You may just have to get used to slipping the bike into neutral before coming to a halt and if you forget then you will just have to hold the clutch in until you can pull away again.Since you state that the garage road tested the bike I am assuming that the clutch does actually work, its just an issue getting neutral.It will probably bed in over time ( but do make sure your clutch is adjusted properly)Regards
Peter
Hi Derek,
Welcome to the madhouse. They should provide damping. Assuming you still have original MZ shocks then both front and rear are very easy to strip if you have the correct tool or can make one up. First you need to compress the spring to remove the collets; the spring, cover etc then just pull of. The top of the damper unit is a threaded (RH) collar and once undone the innards pull out. The collar has two slots for the tool to engage, at a pinch and with care you can use a pin punch. Your manual will show the tool if you want to make one.
You may get away with simply refilling with fluid (about 70cc), more likely you will need to replace the top seal which is a standard size and can be purchased from any bearing stockist. Cannot remember the exact size its something like 15x10x7 but you can measure it easily enough when you have it stripped.
best of luck
Peter
PS: The rear is normally adjustable for preload and its common for the adjuster to seize. Heat, lubricant and patience are required but they can usually be saved. Don’t try using too much force on the alloy handle it will break very easily.
Hi John,
The TS125/150 motors are prone to clutch drag even when otherwise in perfect condition. When cold they will often want to jump back into neutral and try to drive the bike when in gear even with the clutch fully disengaged. Try running with some thinnish oil in the gearbox for a while. There’s nothing special in the box that needs heavy grade gear oil so it won’t do any harm. I run mine with SAE30 mono bought for the motor mower and 20/50 would probably be ok.
PeterFHi Pete,
Your symptoms do sound like an air leak. provided the manifold screws are tight then the crank seals are the most likely culprit. I would guess it was the generator side and its easiest to start with that as you only need the minimum of tools.Job can be done in frame as follows.
1.Remove dynamo stator – 2 screws and note where wires go. Extract rotor, you need a long threaded 8mm bolt to pull it off the crank.
2. Inspect seal for obvious signs of leakage or damage but since its sucking inwards there may not be much.
3. Remove the circlip which retains the seal. There are two types, early ones are proper flat circlips, later are just wire.
4. remove seal by carefully drilling two small holes near the edge of the seal 180degrees apart. Do this carefully as you don’t want to damage the plate behind the seal.
5. Screw in two self tappers – gently again and they may well force the seal out. If not, once they are firm use pliers to pull the seal out.
6 Fit new seal – inner side to engine.
7 fit circlip and dynamo bits – job done.Probably best to get the seals from TheMZshop but if you are confident in ordering such parts they can be bought for less from a bearing stockist such as Simply bearings. Spares book will give you the sizes 72 x 30 x 7 from memory.
There is a better seal for the drive side with double lips but these should not be used on the generator side.
If that does not do the trick then you may have to tackle the drive side which does need special tools. However its less likely to go as it runs in oil. Come back for more help if necessary.
Peter
I suggest before buying a new clutch centre that you double check the state of the taper on the crankshaft as well. This should be smooth and there should be a number of horizontal grooves (4 I think) running down the taper. If these are no longer present or in any way worn then the crank has suffered as well. You may find you can still get round this with a new clutch centre and by using a smidgeon of bearing fit to hold it in place. But be warned that if it works it will be the devil to get off again probably needing heat to softer the adhesive.
By the way fitting a key into the crankshaft is neither necessary nor desirable. The taper is what provides the grip. A keyway is primarily to provide a positive location for things which need to be lined up correctly e.g. the dynamo stator to ensure timing is correct. Keys don’t provide a secure drive except perhaps in very low stress applications and on an MZ with a worn taper would almost certainly fail quite quickly doing even more damage. Not a good investment for this application.
PeterF
