301 will not increase RPM under laod

[qcs]

Guys,

New to the site and just purchased a 1994 MZ 301 ETZ, as a short track bike. Plans are to work on most aspects of the machine, starting with suspension, weight reduction, wheel swap (to 17"), etc.

Problem is that at this point the bike will not increase RPM ander load. Not too bad in 1st gear, where RPM will go to around 7K. Second gear will alow around 5.5. Third and up, RPM will not go over 4K-4.5K, no matter how much throttle is opened. It feels like choking.

Carb is Bing 84. Took it apart and cleaned it completely. These is some wear, but jets seem to be OK, float height is fine and the unit seems, altogetehr, in a satisfactory state.

Ignition is the original electronic PVL. Seems that timing is OK. Voltage on the coil at runing is 14.4. I see spark, although weak, with ignition on and the plug out, but the voltage on the coil is pretty low (probably drops on the way, ignition switch, etc), but seems OK at running.

Plug is new and looks OK after running. I can not see any signs of fouling or overheating.

I did not replace the foloowing yet:
Coil
HT wire
Plug boot

I did not check compression yet, as I do not have the specs.

A couple of questions:
1. Any other things I should look at?
2. What are the coil specs? How can I test the coil?
3. In case that I am looking for an aftermarket coil, what should be its specifications? As far as I understand my PVL is running the same coil as the points, so any coil, which can work with points might be suitable. am I correct in assumiong this?

Sorr to have my first post filled with tech issues.

Thanks for your assistance.

[djsbriscoe]

Hi,
As the engine seems to be reving freely in first gear maybe the problem is elsewhere. I would suspect clutch slip as this makes more sense.
Have you looked at the clutch plates and springs? Is the clutch free play set correctly? What kind of oil is in the gearbox, maybe flush it and replace with fresh oil?
Check these first.

Then again I could be completely wrong and it may need an "italian tuneup" (a good long fast ride to burn any c**p out of the exhaust).

David.

[qcs]

Thanks David.

My experience with a slipping clutch is that the RPM will go up, but the speed will not increase. In this case, RPM does not go up under load and the bike seems to choke.

[qcs]

OK, some more info:

1. HT cable repaled.
2. Plug boot replaced.

Still no significant change.

I did not replace the coil but measured its resistance:

Lead 1 to Lead 15 (I suppose this is the primary): 5 Ohm.
Lead 1/15 to HT outlet (I suppose this is the secondary): 9.5K Ohm.
Lead 1/15/HT-outlet to ground: Infinite.

What next?

[rodge70]

is this a 2 stroke and if so have you tried running it without the baffles in?

[qcs]

Meaning exhaust baffles? I did not take the muffler off.

BTW, it is a one piece, so should I take the whole thing off? would you think that the exhaust is blocked?

[rodge70]

not familier with this bike but usualy baffles are removeable on most 2 strokes,well ones i've had in the past,may find an access hole in rear of exhaust that holds baffle in place,good luck.

[manumensa]

Hello Ari:

A original MZ ETZ 301 have 23 PS (max. power) at only 5500rpm.
Model ETZ 251 (21 PS 5500rpm) and 301 have the same gearbox ratios. The 251 sprocket 21/48 and 301 22/48 teeth. Perhaps long mileage blocked the exhaust,
also new piston and rebored barrel in the first miles or very wear, front brake caliper dirty and pad blocked the wheel......
I think you have too much expectation about the 301 power

Best Regards, Manuel

[qcs]

Thanks Manuel. I am aware that it is not a 1000RR

Having said that, the bike is choked and will not travel faster than 100 km/h, while it should probably do about 30 km/h more at top speed.

I will try to clean the exhaust. any good ideas on how to do this?

Thanks,

Ari

[qcs]

OK. Cleaned the exhaust. Washe it a couple of time with Soda Caustic. A lot of dirt cam out.

As far as the results: more or less the same.

What next?

[manumensa]

Oh, sorry Ari, we forget air filter.

Same for all ETZ models. Dirty close soon pores paper filter and the engine don´t breath.

My friend Pedro, he worked in a MZ dealer, found a solution using a base Citroen 2CV (I don´t remember well the car model) filter. It never clog because have a plastic mesh. Of course paper is a best filter but have a very short life 100% ok.


Saludos, Manuel.

[mzman]

Try starting the bike with out exhaust,if it works the exhaust is blocked.A well used tip for clean out a mz 2 stoke exhaust in the uk is to take the exhaust off and seal one end with a potato.Put in a corner a way from the kids and fill up with caustic soda and leave for 3 days .Pour the caustic a way and remove the potato then hose a way with water.I hope this works for you .

[iceman]

Try starting the bike with out exhaust,if it works the exhaust is blocked.A well used tip for clean out a mz 2 stoke exhaust in the uk is to take the exhaust off and seal one end with a potato.Put in a corner a way from the kids and fill up with caustic soda and leave for 3 days .Pour the caustic a way and remove the potato then hose a way with water.I hope this works for you .

Very important to remove the potato...

I was also thinking air filter clogged try it without air filter...John