10 hours ago, manwithtool said:

Anyway, point being too much oil can maybe lead to build up of carbon which is obviously very abrasive, only a problem if it can find it's way into the crankcase or cylinder.

Carbon isn't abrasive. It's a dry lubricant. Have you never rubbed a graphite pencil on something to make it run more smoothly?

Where striate carbon may not be abrasive the stuff it often combines with inside of an engine can become so...  or at least what I have seen would indicate such...

Edited March 30, 20179 yr by jonnyc21

I do know Carbon comes in various forms for Graphite to Diamond and I think one other form.  Anyway I'm goin got stick with 75:1 as I've not had any problems with that ration using the Strawberry Putoline oil.

There is no one correct answer to mix ratio, there are too many variables. My opinions are based on working with 2t engines for nearly 50 years.Most of my knowledge of oil performance was gained on MX and kart engines where the lubricant is worked much harder than in trials engines and lubricant deficiencies show up much faster. All the technical arguments (more power and less wear) favour putting more oil in the fuel. The environmental and oil cost arguments suggest putting less oil in the fuel. In my early days of trial most trials were a lot longer duration than today and involved a lot of roadwork and often a time element, this form of trials needs more oil than the present typical club trial of pottering round a couple of fields for less than 4 hours.

What I did notice on MX engines was a very significant increase in wear rates when the ration was 40:1 compared to the wear rates at 20:1. On air cooled trial engines far more wear occurs at 50:1 than 25:1. On watercooled trial engines I have seen 125cc piston / bores well worn out in under 2 seasons when run at 80:1. Run at 40 or 50:1 and the same or a bit less wear takes about 5 seasons.

Run a larger capacity watercooled trials engine at 32:1 and wear is virtually eliminated but you do have the extra oil costs.

Modern watercooled engines with sealed mains, high silicon cast pistons and tough bore platings can get by on remarkably little oil, but a bit more oil is useful insurance against hard use, water ingress, a stuck open throttle, a carburation fault or running out o fuel.

Run ours at 100:1 fully synthetic putoline and is fine , stripped down the linkages to grease them and shouldn't have really bothered as plenty of grease there.

 

Less lubrication = more wear

On 4/2/2017 at 11:22 PM, dadof2 said:

There is no one correct answer to mix ratio, there are too many variables. My opinions are based on working with 2t engines for nearly 50 years.Most of my knowledge of oil performance was gained on MX and kart engines where the lubricant is worked much harder than in trials engines and lubricant deficiencies show up much faster. All the technical arguments (more power and less wear) favour putting more oil in the fuel. The environmental and oil cost arguments suggest putting less oil in the fuel. In my early days of trial most trials were a lot longer duration than today and involved a lot of roadwork and often a time element, this form of trials needs more oil than the present typical club trial of pottering round a couple of fields for less than 4 hours.

What I did notice on MX engines was a very significant increase in wear rates when the ration was 40:1 compared to the wear rates at 20:1. On air cooled trial engines far more wear occurs at 50:1 than 25:1. On watercooled trial engines I have seen 125cc piston / bores well worn out in under 2 seasons when run at 80:1. Run at 40 or 50:1 and the same or a bit less wear takes about 5 seasons.

Run a larger capacity watercooled trials engine at 32:1 and wear is virtually eliminated but you do have the extra oil costs.

Modern watercooled engines with sealed mains, high silicon cast pistons and tough bore platings can get by on remarkably little oil, but a bit more oil is useful insurance against hard use, water ingress, a stuck open throttle, a carburation fault or running out o fuel.

Worn out piston.  How do you know/can you tell when your piston needs replacing?  

Sherco ST 125 2014