2001 MZ Kanuni 251 with problems - a real mystery

[daedalus]

We've had problems with this bike for 5 months. It is a 2001 MZ 251 Kanuni.
The bike has:
- difficulty starting
- can barely idle in neutral, cannot idle in first with the clutch pulled in and dies (like when stuck in traffic)
- blackens and fouls the spark plugs
- has begun to recently melt and/or explode spark plugs, sending sparks out the exhaust pipe and then dying
- pops and backfires
- loses power and then regains it, especially after backfiring, but even when not backfiring
- at full throttle, sometimes won't gain enough speed to get out of the lower gears
- we removed the air filter and hose last month, leaving the carb naked on the air intake. What seems to me to be an usual amount of exhaust and mist of gasoline sprays out of the air intake while the bike is running, but as I've never run a bike without an air filter before, I am not sure if this is normal. The last time we put a rubber hose/tube on the carb (but still no air filter), the bike died and wouldn't start.

We took the top off the engine and found that the head gasket was two thin pieces of sheet metal, and one of them was torn. I do not think these were OEM because they didn't seem shapen quite right or large enough. Then again, I now have reason to believe these are in fact the shims, and might be OEM.
We were able to get some flexible gasket paper and cut a new gasket. It wasn't a perfect cut and I had to add a sliver of material to fill in a small gap, but it shouldn't have affected the gasket (it still covered more area than the gaskets we had removed). I then shellac'd it all with black gasket shellac and put the engine back together.
The bike starts better and will sometimes idle in neutral, but still has issues with loss of power and popping and backfiring. It had gotten up to top speed, but as always, after about 30 minutes or so, the loss of power issues started. The bike refused to start after a test drive, and only restarted after cleaning the plug (which was only used for 30 minutes).
The bike has a large coil that might be from a car or truck from which the spark plug wire runs, and a rectifier from another bike (at least it looks like a motorcycle rectifer) that we had installed in Iran. Both get quite hot (the rectifier is missing its heatsink fins), so we had a cut made in the sidecover to allow more air reach to them.
I scraped out some of the carbon deposits inside the engine and attempted to steam clean it by spraying water into the air intake on the carb, but with the exhaust coming out of the carb I'm not sure if much got inside the engine.
The bike is a 2-stroke, but the oil reservoir fell off and we are pre-mixing 4-stroke 20w50 automotive oil with the gas.

If you have any advice, we'd appreciate it.
Thank you.

[airhead]

Hi all. I have been trying to help Daedalus with his broken Kanuni via email, however my ride is a 78 BMW R100 and I am not at all familiar with the MZ. I suggested he contact this forum for possible assistance. A little context is in order: I am in U.S. and Daedalus is in a remote area of Afghanistan trying to continue his journey across the country. Thus I hope you can understand the crude fixes that have been attempted to keep the machine running. He has little chance of getting new parts right now and most fixes and parts must be scavenged or produced on site. The operating conditions are extremely severe.

Any help you can provide is deeply appreciated.

[Houlie58]

Hi Daedalus,

Do you still have the ETZ251?
Have you cured the problems?

[radiograf]

Daedalus wrote;

The bike is a 2-stroke, but the oil reservoir fell off and we are pre-mixing 4-stroke 20w50 automotive oil with the gas.

I think thats the problem, four stroke oil is not formulated as a premix oil, I would not recommend using it in this day and age. He also doesn't say what ratio he's using, too much oil will weaken the mixture, giving some the symptons he's describing.

[Trogolodyte]

Agreed 10w50 engine oil will not burn cleanly and will foul the plug it will also produce excess smoking, you can get good cheap 2 stroke oils fairly cheaply.
I would also check the carb settings

[DAVID THOMPSON]

where this guy was at the time of first posting this question
you could not get much of any thing but shot at

"Daedalus is in a remote area of Afghanistan trying to continue his journey across the country."

above quote from second post
and that was a built in turkey 251
hope god was looking after him 100% of the time
dave

[Trogolodyte]

I agree I hope his god was on his right hand, not nice to serve there at anytime,

daedalus, if you are still watching this thread, please get in touch and let us know you are alright