WOT?
06-08-2012, 09:57 PM
#1
Thread Starter
WOT?
I just purchased 2OS engines (always bought used) I was reading the break-in info from the manual,,,,,,,,Start it rich atWOT?Is that right? Seems to me that sounds like sudden death for any engine. any input would be helpful
THXTAZZZZ
THXTAZZZZ
06-08-2012, 11:00 PM
#2
Moderator
RE: WOT?
Yes, that's right. The engine needs to get up to its normal operating temperature with the extra lubrication of a rich mixture. So you under prop it (the manual recommends the right break in prop) and run it full throttle for the first couple of tanks to burnish the piston and liner together. Adding some extra castor oil to your fuel for those first two tanks gives you some added protection against overheating and lets your run a little faster (leaner setting) to make sure you don't get too cool.
06-09-2012, 07:00 AM
#4
RE: WOT?
Agine Yes (if it is an ABC or ABN engine) It is neccessary on the first few starts to get it up to operating temps quickly so the bronze sleeve will expand to a greater degree than the high nitrate alum piston to reach that perfect clearance.
Concerning the thermal cycling. Yes my personal preferance is to introduce many cycles during break in process. It is my belief that the true breakin process occurs during the cycles from ambient temps to operating temps and that will hasten the process over just endless static runs with no cycling.
John
Concerning the thermal cycling. Yes my personal preferance is to introduce many cycles during break in process. It is my belief that the true breakin process occurs during the cycles from ambient temps to operating temps and that will hasten the process over just endless static runs with no cycling.
John
06-10-2012, 07:31 AM
#6
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RE: WOT?
According to all my OS manuals the two stroke is broke in at full throttle but with the needle valve opened enough to make it four stroke. While at this rich setting the rpm's are raised and lowered via the needle valve. Rich to lean and back to rich at 10 second intervals.
If a four stroke engine, the same technique rich-lean-rich-lean while observing the smoke. Lots of smoke.
If a four stroke engine, the same technique rich-lean-rich-lean while observing the smoke. Lots of smoke.
06-10-2012, 08:16 AM
#7
RE: WOT?
ORIGINAL: acerc
the two stroke is broke in at full throttle but with the needle valve opened enough to make it four stroke. While at this rich setting the rpm's are raised and lowered via the needle valve. Rich to lean and back to rich at 10 second intervals.
the two stroke is broke in at full throttle but with the needle valve opened enough to make it four stroke. While at this rich setting the rpm's are raised and lowered via the needle valve. Rich to lean and back to rich at 10 second intervals.
Precisely - Ditto's
OS's specified technique works very well indeed. I have also been using this technique for some time particularly with competition engines, its effective and it works.
The only thing I add is thermal cycling the engine every few minutes (Stopping, a short break and restarting). This for the first five or six minutes of the engines first runs.
John
06-10-2012, 07:43 PM
#8
Moderator
RE: WOT?
The whole idea is to have the engine at operating temp but not higher. If you run a new engine with an optimal fuel mix it will overheat and either shut off (if you're lucky) or be damaged. The up and down needle valve routine is all about letting friction do it's magic for a few seconds then flooding it with oil and fuel to keep it lubricated and cool enough. Don't run a new engine at a 4 cycling rich mix for long though or you'll ruin the liner's fit by breaking it in too cold. Dub Jett wrote up an alternative method that I use that (IMO) is far more fool proof. You put extra oil in to bring the lubricant up to around 30% and run the engine about 1k rpm off peak and propped to turn the rpms you expect to fly at.
