For Lozza and other 2 stroke riders who use Castrol R and other Castor based oils I would suggest you read this for some handy hints especially on page's 4&5 for 2 strokes on getting the best out of your castor based premixes.
http://www.castrol.com/liveassets/bp_internet/castrol/castrol_australia/STAGING/local_assets/downloads/r/R30_40_M_B861.pdfJi,
This is an extract out of the A747 Product Data Sheet, "For some competition applications, particularly for very high engine speeds (typically greater than 15,000 RPM), Castrol A747 is the prime recommendation (see the Product & Technical Data SheetB1109/95/1).
.............Now, when was the last time your Maico reached or exceeded these RPM?? It would turn into a West German stick grenade on two wheels.
Heavy oils need HIGH RPM (and resultant extreme air flow & turbulence) to be pushed through the mechanical componants of an engine, and you need this extra viscosity for them to stay inside the crankcases long enough to do their task of lubing the bearings down under. At your engine speeds they will only STEAL power and lead to "Oil Hangup" (a real term in lubrication not something I have come up with) in your exhaust system frustrating you. We see this same phenomena as an example in industrial refrigeration compressors when the client puts in heavy oil against my advice to compensate for wear and take up clearances (Doesnt want to spend the $ on a rebuild) and then his electricity bill and maintenance costs skyrocket from oil drag and lubricant hangup throughout the system. Then he blames me that my oil is no good!
The Universal law of spending money is that the more money you spend on something the better it will be and perform. Not so with many things and especially so with 2 stroke oils.
Ji, the builder of your engine would have thought that to protect his rebuild then the costs of protection will be passed onto his customer for the life of the bike, you and your wallet...........and one way of getting around this was with expensive oils as an insurance policy to reduce any warranty exposure.
These oils are expensive not because they deliver better performance for your Maico but because of small (read : uneconomical pain in the A$$) blend sizes at the lube plant, and also base oil & additive costs purchased in uneconomical volumes including sometimes most singnificantly sponsorship costs of race teams etc that add about 50% to the price of the product. This is true with tyres and other parts where a large proportion of the production is given away free to racers and the humble riders like us pays the costs for this policy.
In your case you are using a too heavy oil for your application that is not atomising properly into fine enough molecules................. read the bottle, "Not to be used in conditions under Zero Celcius".........that is enough to tell you that you are loosing heaps of performance by using this product from what I can determine in 2 areas.
Detonation can be caused by some 4-5 factors (not limited to Ignition timing, preigintion by hotspots/carbon, fuel octane, overheating, lean jetting, incorrect fuel mixture/contamination etc) but one possible cause in your particular case is that the heavy oil at the low to moderate RPM you are running at is creating a moment (nanosecond) during the ignition cycle where the air fuel mixture contains globules/molecules/particles/droplets whatever of oil that quenches the flame front, prevents full and efficient fuel burning in the time allowed (~34 degrees of crank rotation) leading to detonation. It is why these heavy oils are for small engine HIGH RPM use only, Go Karts, road racers around 15,000RPM. The bike shops generally dont really care what you buy as long as a sale has been made and the average guy at the counter would have zero product and more importantly application knowledge for a 2 stroke that their shop perhaps havent sold in 15 years. That scares me as the buying decision is left to the punter with the bike!!
It is EXACTLY like when you have misfuelled your car with Diesel Ji as diesel has a heavier viscosity and density and also a higher flash point. What is happening inside your Maico is also like when you have a worn engine in your car and you have engine oil going into the combsution chamber past the rings or valve guides increasing the compression ratio causing detonation. I would like to add here that the local Volvo car dealer swears on 2 litres of diesel in a tank of petrol as a very good injector cleaner. In fact injector cleaners use diesel/heating oil as the carrier for its additves.
Also synthetic 2T oil is a very good injector cleaner for diesel engines (like 300ml per 75litre tank full in your 4WD when filling up) and I have a website that discusses that if anyone is interested. Perhaps a good home for any spare oil that riders may have when changing their type of oil.
So when you have A747 ,as in your case, you have two ingredients in the air fuel mixture when the plug goes off that have different flash points fighting with each other and the higher flash point hi-vis product overwhelmes the fuel component (that makes the power) like a fire extinguisher......it is like spraying foam over an oil fire.............great loss of performance.
Another area that is of concern in a 2 stroke engine that run these heavy oils is the phenomena of "Puddling". As in mud puddles you see on the track. Low speeds/RPM's and/or heavy 2T oils create puddling in the bottoms of your crank cases where the low speeds cannot move the oil through high air speed of the descending piston and centifugal forces from the flywheel towards the cylinder and up through the intake tracts. This is what is also happening in your bike. It is not just oil in the "puddle" but a large % of fuel as well.
Regardless of what oil you use you will get puddling for example if you left your bike idling for hours on end, but heavy oils exacerbate that.
Outboard manufacturers have solved this issue by drilling a hole at the base of the crankcase and fitting a one way valve to drain out this oil and redirect it towards the bearings. Understand that an outboard engine has a vertically placed crankshaft and with multiple cylinders as in a V6 there is a lot of oil buildup at the bottom crankshaft outlet. This happens when trolling slowly and when you open the throttle on the older engines without this drain valve the engine creates a cloud of smoke, runs rough, fowls your plugs and upsets the greenies birdwatching along the shoreline who then ring their Member of Parliament.
KTM are looking at direct oil injection (as well as direct fuel injection into the cylinder) for future 2 stroke models where you will have a system similar to VRO on outboards (Variable Ratio Oiling) where according to the RPM and load on the engine an exact amount of oil the computer (ECU) tells it to will be injected to the bearings. I think it would be an advanced system like the old Suzuki CCI method. At idle you may have 150:1 and at wide open throttle or at redline 32:1 or something like that. This will reduce emissions and make them more greenie friendly in the Government.
By the addition of more fuel into your mix, will, as you have found fixes one thing and brings on a new issue. The solution in your case if you are a Castrol fan is to use Castrol Power TTS that is the correct viscosity at 25:1 as base line, if this works well for you then try 20:1 with this oil. Similarly for users of MC-1 try a switch to Bel-Ray H1R Synthetic 2-Stroke Racing Oil or Bel-Ray Si-7 Synthetic 2-Stroke Oil and Motul fans who are using 800 try a batch of 710 at richer ratios.
You will find these oils will remain in the exhaust gas stream more to be expelled out into the atmosphere (horrible thing to write if a greenie from the EPA is reading this!) rather than condensing, dropping out of the gas stream and adhering to the internal surfaces of your exhaust system perhaps pooling at the lowest part of your exapansion chamber where it bends up again. Your packing may last longer too.
Ji, I would share this knowledge with all your other "experts" that you have spoken to AFTER you have tried my above advice first to make sure it works for you. It should solve many of the issues that you experienced.
I dont own a CZ but I know several others that do and and being the crafty, passionate and meticulous enthusiasts that they are, they run 20-25:1.
Below is the link to the legendary Gordon Jennings article about 2 stroke oil premix ratios written in 1978,
http://cid-407d7ef0965d3991.skydrive.live.com:80/self.aspx/Pure%20Enduro/oilpremix.pdf
