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Old 03-09-2015, 11:07 AM
  #11  
Fuelman
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Join Date: Dec 2001
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Breaking in any two stroke ABC, ABL or AAC engine, which has a tapered bore sleeve requires a hot break in. What I mean by hot is; operating it at design operating temps. The bubbly rich idle method which a lot of car engine manufacturers recommend is detrimental to their longevity. Using a low oil content fuel only magnifies the issue.

Using low oil fuel, like the 6 percent you mention has multiple effects. First you are running it at leaner needle settings since there is more fuel per induction stroke than there would be in a higher oil fuel, say 14-16 percent. Second, the greater methanol content (in a low oil fuel) has a greater cooling effect as it vaporizes, making it a little more difficult to get to optimum operating temps where the top of the sleeve expands to a near zero clearance with the piston. At these near zero clearances, the oil is critical to keep the piston and sleeve from scuffing, and since you are running it at leaner needle settings in the first place and have a low oil content to begin with, it is a very tricky balance to keep the engine operating in its sweet spot without accelerating the wear.

We have not even talked about the effect of low oil content and leaner needle settings on the crank pin or connecting rod wear.........

I had a couple test buggy's, Losi XXX NT's that I had stock engines last 20 gallons. To be fair, I broke them in, completely differently than what the instructions suggested and routinely ran high oil content fuels like I would for two stroke airplanes in them, and tuned them to the fuel, plug and weather conditions/ temperatures instead of using a digital temp meter.
There is way too much miss information out there propagated by the RC car manufacturers.