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Does reducing the oil effectively make the mixture richer in that there is a higher proportion of petrol in the fuel / oil mix? If this is the case you might be doing several things at once which will counter each other?
I don't know about modern 2 strokes, but the older bikes I play with use pre-mix and there's always a range of opinions on this - certainly there are machines on club runs that often suffer from overheating, generally attributed to running too lean, and then you hear things like "it's supposed to be 24:1 but I put a bit extra (oil) in to be sure"...
MrE-
The conversation seems to be ongoing for the oil ratio thing within trials.
As I understand it, it makes the mixture leaner in the sense that the fuel is less oil-rich.
Various sources from the manufacturer recommend 80:1, but I am certain I saw a sticker or note somewhere stating 50:1.
The bike shop initially told me to use 75ml to 5L which is 66.7:1, and told me some guys run as low as 100:1 which would be 50ml per 5L.
The idea of less oil in the premix fuel means less un-burnt oil making its way into the exhaust. Less smoke, less saturation on the exhaust packing. Less fouling on the plug.
Bearing in mind this is the plug that I pulled out last week, after a few hours of running, there is both way too much sooty deposit, and a lot of unburnt oil on the plug. This is prior to making any changes to my running.
pdlouche
Phwoar, however:
Which seems to be the fashion!!
As for shorter insurance periods, it’s not worth it. I asked about a shorter term insurance to get the second bike insured until the first needed renewal, but it worked out more expensive than any other variation (adding on late, entire new policy, etc).
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Talking of dirt, update on the Sherco. I have had a lot of trouble the past month with it, it bogged and refused to start from cold. After cleaning the plug and carb, it would work for a few hours then bog and refuse to start.
It was something like: seems okay for the first half-hour of practice, second half-hour it gets boggy. Across a week of three or four practices, by the end of the week I wouldn’t like the starting sound. It would take more than two kicks, and overall just sounded and felt wrong.
Two trips to the shop for advice, including a new spark plug and such. The main takeaway was, “the plugs are rarely a nice brown, they’ll be a bit black” and “you really should clean the carb before/after each trial, so if you’re getting three hours practice in a week, that’s more engine hours than a typical trial”.
Okay, okay. 2-smokers need constant babying with a clean plug and jet-cleaning, but after the third week of pulling a black sooty plug out, I was sure it was a rich fuelling issue over anything else. I want a chocolate spark plug, no matter what they say.
So, the correct thing to do is change one variable at a time, by a measured amount, and then check results.
Instead, I turned the fuel/air screw out 1/8 turn, and moved the incredibly rich main jet clip up one notch. Plus, I reduced the oil in the fuel very slightly.
Two one-hour practices, and the bike would start on the first or second kick, idle more comfortably, woke up as far as power delivery, and doesn’t seem to bog over time.
Phew. Getting closer to reliable running.