HEAT is the biggest enemy of a freshly rebuilt motor.. The ideal thing is to get it hot real fast, and i mean by using rough grit cylinder hones and breaking it in real fast... Its kinda hard to explain,,, bear with me,,, depending on the honing job (i,e. either 120 grit stones or 320 grit stones) your honing will break it in REAL FAST,,, or,,, not so fast.. I like to break it in right away with rough stones... The key is to get it started and bring it up to 2000 rpms for a minute.. NOT KEEPING IT AT 2000 rpms but gradually bringing it up and down, lets say 1500 to 2500 for a minute to get her warmed up!!! It really doesnt make too much of a difference WHICH oil you use for the INITIAL break in because the honing job is SO ROUGH it HEATS THE HELL out of everything RIGHT AWAY!!!! Thats where synthetic oil comes into play... Considering the flash point of conventional oil and the flash point of synthetic oil, the synthetic oil has a much better chance of keeping its lubricity during INITIAL breakin (the first minute) whereas conventional oil goes UP IN SMOKE!!! When an oil goes up in smoke, it LOOSES ALL of its lubricating qualities and when an oil does that the SCRAPING of the new rings on the freshly honed cylinders will ABSOLUTELY DESTROY your cylindrical cosistency( EGG SHAPE)!!! It will also put scratches and marks in your freshly honed jugs (you wont see them, but they are there) and prematurely WORN OUT YOUR MOTOR in the first minute of running!!! The composition of piston rings nowadays will break in almost immediately (within the first few minutes) providing,,,,,, you don't get it TOO HOT (#1) and you DO NOT KEEP IT at ANY SPEED for any length or time!!! UP AND DOWN UP AND DOWN.... NEVER keep it at one speed and after the first minute of 1500 to 2500. the motor should be warmed enough (remember it will get REAL HOT REAL QUICK) to start the bringing it up to 7000 rpm's (WITHOUT THE BELT ON) and bringing it down to 1500rpms... You want to spend around 4 seconds GRADUALLY bringing it up to 7000 and spending another 4 seconds GRADUALLY bringing it down to 1500 rpm.. YOU COULD DO THAT 10 times if you want to.. THE MOST IMPORTANT PART is to SHUT THE MOTOR OFF after you went the 1500 to 7000 up and down and let it sit for about 10 minutes,, You need all the different temperatures to stabilize.. Here is where we get into a little debate,, I LOVE retorquing a motor after waiting the 10 minutes.. Retorquing while its still warm!!!! The aluminum actually expands MORE than the nikasil plating and there is definately a STRUGGLE going on in there between the dissimilar metals You will notice that FAT GASKETS will actually accept a little push on the torque wrench while o ringed and shorter bolts will actually seem even tighter.. not needing a push!!! now that your broken in,,, put the belt on it (AFTER THE MOTOR COOLED DOWN COMPLETELY) and try and drive it up to 7000-7500-8000 (around 30-40MPH) and back down to creeping.. DO NOT USE THE BRAKE to slow it down,,, let the natural drag of the sled do its thing..(it is ACTUALLY good for the motor) it teaches the piston/cyl/rings major and minor thrust surfaces!!! You want to do that about TEN TIMES and SHUT IT OFF AND LET IT GET COLD AGAIN!!! YOU CAN check the torque again (not as important as the 1st warmup) if your ANAL RETENTIVE!!!,, Take the sled out for a ride.. DO NOT DRIVE it LIKE YOU STOLE IT!!!! FASTER, slower, around turns braking,, drive it easy for the first ride,, drive it for a half hour or an hour... DO NOT get on the trail and keep it at 55MPH for a half hour!!!! Up and down,,on and off TWISTY TURNY!!!!! Bring it home and let it cool down again.. COLD not cool... Satrt it up,,,,,,LET IT WARM UP,,, and BEAT THE SHIT OUT OF HER if you want to!!! The motor DOES NOT take 500 miles to break in and the people who tell you that probably have some GOOD REEFER for sale also!!!! (if you like good reefer)..now heres they synthetic oil question,,, SYNTHETIC OIL ALWAYS lubricates BETTER than ANY conventional oil SEMI SYNTHETIC is nothing more than some synthetic additives in CONVENTIONAL MOTOR OIL!!!! ALL CONVENTIONAL motor oil since 1955 has SOME TYPE of synthetic additives in it... THERE ARE ONLY 5 OIL REFINERIES that make 2 stroke oil.. There may be a hunderd brands,,, but it comes from the 5 BIG VATS!!!!! There is only 2 companies that make anti freeze in AMERICA and 1 of them BLEW UP last year!!!! i don't know if it blew up bad enough to cease production,, but there is a DOZEN BRANDS OUT THERE!!! arent there????? USE SYNTHETIC,,, FULLY SYNTHETIC,,, NO bullshit semi additive yamagarbage!!!! (citgo CRAP) Heres the plug... I USE KLOTZ!!!.. You can use whatever oil you like,,,amsoil is FINE,,,,KLOTZ is fine also,, ANY SYNTHETIC with the jaso or the tcw-3 certification is FINE too!!! FULLY SYNTHETIC not semi citgo garbage!!! Did that answer your question??? Gary Oles nosboy
Gary thanks for your input, just getting opinions from all the guys on this site that deal with OIL and MOTORs for these sleds so I have options when the times comes.