Two-stroke oil premix ratios: Is less more? Is more less? Is more more? Is less less?

[Fabian]

Yes, castor oil is ancient technology - those plants have been growing in the ground for longer than i have lived.

When used in an internal combustion engine, it generally makes a filthy mess of things and if used incorrectly, it does do the things you have described ""carbon deposits, stuck rings, etc"" but when using good quality first pressing degumed castor oil, it provides some serious levels of lubrication with sensational thermal absorption qualities, whilst at the microscopic level, even burnt castor oil still provides lubrication.

I've been flying radio controlled nitro powered helicopters for years, and nothing tollerates heat quite like it - sure, the synthetics are good as they avoid most of the mess and filth and burnt crud that you have to live with when running castor but if wanting to squeeze down the oil ratio and still have good piston ring to bore seal, there is a blended castor/synthetic oil available.

Yes, lean is lean but a simple plug check will tell you all you need to know and you can adjust your jetting if it's outside of normal air/fuel ratios.

Just like yourself, i get all my fuel from the same can of mix at 20:1 - lawn mower, leaf blower, trimmer, motorized bike, generator, etc.

There is a good video on youtube of the assembly process in one of the Chinese factorys producing motorised bicycle engines- they certainly don't treat our engines with any kindness, but when a worker has been on the assembly line for 18 hours straight, would you be able to concentrate or care about quality control.

The thing that stuck in my mind was a lady on a work station bashing in the crankshaft bearings into the reciever with a hammer - she just simply smacked the bearing into the hole - if it went in straight or on a misaligned angle, it just got passed on to the next work station - "YIKES", make that "DOUBLE YIKES"

Fabian

 

[arceeguy]

I too have been racing RC cars and planes for years. Yes, there is castor oil in model engine fuel because it has excellent lubricating qualities for that particular application. (High RPM, ringless ABC engine) High revving model car engines typically have a life span of under 50 hours, and are often torn down and cleaned out several times between rebuilds. Same goes for helicopter engines, and ducted fans. I use a pure sythetic for my airplanes, as they run at much lower rpms. Castor oil (IMHO) is not suitable for bicycle engines or any two stroke that isn't for racing.

As far as the assembly process goes, I believe the video was posted to illustrate the crummy conditions of that particular factory. I think most of them are similar. It is always a good idea to give each engine a "once over" before starting them. Remember these are just the final assembly factories, we haven't seen the equipment they use to cast and machine the individual components. From what I can tell, most "out of the box" engine problems are due to crummy assembly, not an actual defect in the components.

 

[Fabian]

I happen to have a blown engine (bottom end conrod bearing from typical over rev) and want to rebuild the thing with quality high speed roller bearings.

Can you give any suggestions as to what manufacturer and part numbers i should be looking at.

Fabian

 

[arceeguy]

Sorry - I don't have any information regarding the bottom end. I have sold dozens of engine kits and assembled bikes, and haven't seen a bottom end failure...yet. Do you have the proper equipment to split the crank and press it back together properly? How does the crank journal look, was it torn up when the bearing shredded?

 

[Fabian]

I haven't yet disassembled the engine.
Bottom end connecting rod bearing failure seems to be quite common. It's great to see you have not experienced this particular type of failure.
When at my local Walmart type store (Bunnings in Australia) i happened to come accross a kid who installed a 2-stroke Chinese motoried bicycle engine kit.
On average his engines were lasting him 3 weeks and his bike had the 4th engine installed - every one with the same failure - bottom end bearing, but that's from over revving the motor as he freely admitted.

I've put up a thread asking if someone could post thir step by step photos on engine strip down and reassembly.

There's nothing like a well presented photo tutorial to use as a guide.

Cheers Fabian

 

[Skyliner70cc]

Not using castor in our HT engines is a big mistake. Used in small percentages it doesn't have the problems normally associated with it. I've been running at least 20% castor in my engines oil for past 4+ years with no varnish problems or stuck rings.

You can use synthetic in your rc airplanes but I'll stick with my castor blended fuels. I've got engines 30+ years old.

 

[Fabian]

Same here Skyliner

I'm still flying one of my smaller helicopters that's 5 years old, and on the original engine; nothing has been changed or replaced.
It sits in the air revving at 16,000 rpm for as many tanks of fuel as i care to put through the thing.
I've used nothing but straight degummed first pressing castor oil and have never had a stuck piston ring or excessive carbon deposits on the inside of any of my engines.
What i will say though is that all the filth and carbon seems to be magnetically attracted to the outside of my engine, particularly turning my lovely tuned chromed pipes a disheartening filthy brown and black colour.

I've learnt a neat trick over the years to slow down the carbonisation of castor oil on the outside of these motors - spray straight alcohol onto the external parts of the engine as soon as you've finished the flight - the castor oil just washes away, at least a good quantity of it.

Fabian

 

[StrontiumEthics]

So exactly which ratio is good to use? Currently I just started on 32:1 . I live in new york where its fall right now temps are like 60 fahren. Should I use more oil?