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Old 04-08-2010
Junior Member
Join Date: Apr 2010
Location: Chestertown, MD
Posts: 6
Default 250 Yamaha OX66

Hey guys, do any of you have the original owner's manual for a Yamaha 250 OX66? I ask because I recently had one rebuilt (includes new pistons, bearings, rings, seals, gaskets, performance reeds and thermostats) and wanted to know the break-in sequence. Here is my understanding at this time:

1- Mix oil in with gas 50:1 to run in addition to the oil being mixed by the oil tank and pump
2- First 15 minutes at high idle
3- Next 45 minutes up to 1800 rpms changing speed every few minutes
4- Hour 2 up to 2400 rpms changing speed every few minutes
5- Hour 3 up to 3000 rpms changing speed every few minutes
6- Hour 4 through 12 up to 4000 rpms changing speeds every few minutes
7- After the 12th hour, speeds of all rpms can be used, re-torque the heads and change the plugs

My understanding with 2-strokes are that short bursts of WOT are required throughout the break-in sequence.

One more thing, we are having a problem in the rigging process with oil overflow. First, when the remote oil pump is activated and filling up the onboard oil tank, the float does not activate causing oil to overflow. So, we replaced the float on the onboard oil tank and still, the remote oil pump remains activated causing the overflow. Could the CDI Unit be the problem? Please let me know your thoughts. Thanks in advance.
21 Contender w/250 Yamaha OX66
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Old 04-09-2010
Super Moderator
Join Date: Dec 2009
Location: Lake Placid, Fl
Posts: 10,359

Here is breakin schedule and oil transfer trouble shooting chart.
2 StrokeBreakin.JPG
Oil Transfer Chart.JPG
Yamaha Outboard Parts
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