Engine break in, what pipes to use?

[yz400ex]

I am rebuilding my RMK 800 engine from the crank to the pistons. Everything will be new. My question is whats the best way of breaking this motor in since all the bearings and pistons will be new? Also is it safe to run an aftermarket pipe during this break in time or should the stock pipe be run? 1 last thing is does anyone recommend an oil to use for break in or just run the same oil I normally would?

Sorry for so many questions. I have rebuilt motorcycles and atv's from the crank up, but this is a first for me on the snowmobile crank and since there is no real crankcase oil, I am just wondering what the preferred method of all this is? If anyone can help, please let me know. Thank you

 

[sled_guy]

Pipe doesn't matter as long as it's jetting right.

If you don't use a dino oil to break it in then the breakin period will take longer.

I usually mix the first tank at 50:1 along with the injector. No big azz hard pulls, no steady state cruising, vary the throttle and revs for the first tank. For the first couple of miles I check the coolant close because Polaris' are infamous for having air bubbles that cause them to over heat if you've had the whole system apart.

After the first ride I go at it like I stole it. But it will still finish breaking in over the next hand ful of rides... not uncommon for performance to increase after 200-300 miles on a motor when it gets fully broke in.

sled_guy

 

[F-Bomb]

I agree with Dan pipe makes no difference if your on a known state of tune. All of mine have been "broken" I mean BROKE IN in with all kinds of aftermarket add's without failure. I don't build the motors but I do BREAK them in. (In the old drag racing days I 'broke" one about every ten passes..so I had lots of experience)

I don't know if this is snake oil or not but I have religiously added a small amount of energy release pre fire up to all of my engines. If you get a chance I dress the sleaves and rings with a very light rub down. Like I said I don't know if it is a waste of a few dollars but the facts are since 2003 on five different sled motors I've done the exact same break in procedure and every single one has been an absolute performance standout for their rated cc and expected HP.

hand turn the system several times without spark plugs listening and feeling for non normal binding....
put it together for running double check your oiler setting (now the biggie..lots of guys put mineral as opposed to synthetic on their first break in tank. I've read all kinds of arguements concerning burn and ring pressure settings that lead me to believe this is sound thinking. I've done straight Redline synthetic right from the start 3 times and ran what ever comes from Polaris as the initial tank oil (it's supposed to be a mineral based break in formula) no additional oil mix in the fuel only on heat soak series not on field break in. (you are always going to have some residual in the tank but I try to heat soak with a 50-1 mix and run in the field straight fuel.
fire and keep it running but not much above idle for a few seconds with the h2o cap off. Listening and watching for problems. All is sound cap on and then reving in and out idle to pre-engagement and watch as it heats to hot say 140-160. Naturally cooled off and then one more time just like that. Then the third time with the front of the sled elevated dramatically to burp the coolant system (have your kid be real busy wiggling the coolent bottle hose while you do this). Cool to room then stand or raise the track...keep a steady stream of water on your hifax and heat soak the engine again from idle to blurps of 7000 ish...being really busy on the throttle but spend 5 - 10 seconds at medium RPM's..no more. Heat soak to 180 coolant MAX! I do this procedure 2 times then remove mix fuel replace with straight and take the sled to the field and run it on the trail for 10-15 miles at varying RPMs and never full past about a couple seconds (eye on heat and make sure everything is fine...and it's making RPM as designed). Then your good to go....my best runner to date had about a 45 second full 8150 hill pull as it's first real full throttle run. 3 uneventful seasons on a big bore top with a 6000 mile plus bottom crank and it rips to this day.

 

[yz400ex]

This is why I ask about the pipes.. I am thinking of buying some SLP twin pipes.. right now my sled has been running stock pipe, but the crank busted.. now that is getting all fixed and since I will be breaking it in, I was wanting to know if I should run the stock pipe since it is already tuned for it, or run the twin pipes and try and tune before break in.. To me it sounds like the only way to go with the twins from what you guys are saying is if I already had the sled setup to run to make sure it was tuned right to ensure proper break in and then switch to the twin pipes once the break in is completed.. Right?

 

[XC700116]

Yeap that'd be right, In your shoes I'd run the stocker and then once the motor is broke in put your twins on and tune it. That and you won't get your best tune out of it with the engine being borken in and running extra oil, ect and you'll have to re visit your tuning later on again once the motor is broken in.

Also I'll second sled_guy on the oil thing, I have tried to break in a motor 1 time with synthetic in it (Klotz) and I got to rebuild it again about 25 miles later. the oil was too slipery and the rings didn't seat causing a cold sieze. I always break in a new motor with a mineral based oil normally one injection tank full of it before I switch over to synthetic along with the first tank of gas mixed 100:1. A lot of guys do 50:1 on the premix but I just make sure the injection is working well before I ride it and go from there, that's a personal preference thing too.