Best way to break in a fresh engine

[SteveCZ28]

I bought a brand new freshly rebuilt engine for my 85 250r. Im looking for good tips or a good way to break this motor in to last me a good long time.

[tri again]

EXcellent question.
I'm sure there are many wrong ways so thanks for asking.

I want to know too.

[dougspcs]

I think you will find a ton of different opinions about this and none really wrong..just common sense would say don't push it hard for the 1st couple hours of running..

Suggestion would be for the 1st tank to run a little heavier on the oil mixure..maybe 25:1.

Also before riding, start the engine and run with no load(idle or poke the throttle) up to operating temp for 5 minutes, then allow to completely cool down. Repeat again..

Once done..start and run up to temp then take it for a light ride for maybe 15 minutes.

After that and for the next 5 hours of running time..play but don't push too hard.

Once done you should be on your 2nd tank..go to normal oil mixture and back to normal riding!!

Something along this line with your own variation and you couldn't go wrong..I personally would consider the running to temp with no load the most critical!

[atc007]

Very simple actually,,do not bog it,and do not over rev it. It is that simple. If the work was done right and you have good clean oil,and your jetting is on,,or a little rich,,with a oiled air filter,,all will be well. Change your oil after a tank,,because it's a R, won't cost ya a cpl bucks. Then change it again after a few tanks. Then run the pee out of her!

[El Camexican]

The posts above pretty much cover all the basics. If a engine was put together right there is not a lot you can do to hurt it unless you are a board certified idiot. 90% of the engines I’ve built are 4 stroke drag bike motors, so I’ve had to accept so pretty abrupt break-in times. On a 4 stroke the main thing is to have oil on everything, but go easy on the assembly lube as it all gets to the clutch at some point, so I only put this on the cam lobes. When I’m ready to fire up I spin the engine without plugs to get oil up into the cam cover. Then I fire it up and try to keep the revs around 3,000 to 4,000 RPM. Less than that with a low pressure oil system (i.e. roller bearing crank with 7psi at idle) and you can damage the cam lobes. When you think its at operating temperature shut it down and let it cool completely. Check for leaks and re-torque the head (if you want, I always just add a couple pounds when I put them together and leave them). On the second fire up I try to keep them over 3,000 until they are good and warm and then blip the throttle between 4,000 and 8,000 RPM. If it all sounds good I give is a couple good raps to around 10,000 and shut it off. The next time it fires it makes a 10,000 RPM burn out and providing its in a proven chassis it makes full ¼ mile pass. At the end of the day the oil is drained and its as broke in as it’s ever going to get. I’ll add that it is not recommended to use synthetic oil for break-in as the rings won’t seat. Some guys swear by it, but I only use it in my street bike and I waited 5,000 miles before I put it in.

For two strokes it is different. Oil pressure is not an issue, so a pre-mix between 20 & 30 to 1 is fine, but when assembling make sure everything has lots of oil on it, especially the rod bearings and wrist-pin. If someone else put it together, pull the carb, raise the piston and dump an ounce of oil into the crankcase. If you have oil injection do the same and add a pre-mix of 40 or 50 to 1 mix in the tank as well. Personally I think the worst thing you can do to a fresh 2 stroke engine (and an worn in one) is rev them up cold. With all the different metals in play and the perforations in the cylinders and pistons there is a lot of shape changing going up as they come up to temperature. Cold seizures make up the bulk of damage I’ve seen in the 2 strokes I’ve opened up, but I think it goes unnoticed a lot because a lot of guys don’t open up engines until they are blown, or stop making power. At that point the bulk of wear usually appears to be on the exhaust side from the loose piston thrusting against that side of the cylinder, but those faint smears and lines on the intake side were likely there long before the exhaust side damage occurred. That said I recommend that on start up (break-in and regular use) you keep the revs as low as possible and let it come up to temperature. Once the cylinder is getting warm to the touch make sure your radiators are getting warm soon after. (On a new engine if the cylinder is outright hot and the rads are still cold shut it down and wait for the thermostat to open, make sure it’s working). Once the rads are hot to the touch I shut it down and let it cool. Second fire up is about the same and then I start driving. Like has been said above; you never want to lug any engine. Better you cruse around in first gear at 5,000RPM than lug it in 5th at 2,000. As ACT007 recommended a gear oil change never hurt anything. Look for chips and slivers of metal, a few small ones are normal after some use, but a teaspoon of shrapnel means you put something in wrong. After that you can leave it in for an extended period. FYI. Automatic transmission fluid works great in a 2 stroke transmission as well and the clutch plates love it (recommended to me by a tech at Barnett years ago)

Here is a video of my latest fire up (2 stroke). You’ll notice I can’t get it to idle on its own (I did not know the idle adjustment was built into the choke), so I just keep it running at low RPM until it got hot and then I shut it off. Second start is the same, but I took the rad cap off as I was concerned I had an air lock and the third fire up I’m revving it up pretty good. This particular engine had a tight crank due to one of the main bearings being slightly out of place when I first assembled it, so I was hoping the heat cycles would set it right and I think it worked (thanks again Mosh). So with less than 15 minutes of “Break-in” time I’m making top end chops to check the plug.

http://www.youtube.com/watch?v=VZnhAPvOh8s

One way to know when your engine is broken it is the temperature it runs at. Fresh engines run hot, very hot in some cases. You’ll notice this fades away after a few fire ups and that’s when you know things have worn in and friction (the cause of most engine heat) is reduced. I’ll add that RPM variation is a must to keeping any engine happy and healthy. Go ahead and keep the revs a few thousand under redline (as most manufactures suggest) but don’t do it for too long as you need to give the parts a good stretch in order to get the upper few thousands of the bore to wear in. The longer you wait to do this the more of a ridge the rings will encounter when you do rev it out (you’d be surprised how much longer things get at high RPM and hot)

And finally DON’T deviate from what the manufactures suggest on new vehicles. With all the new electronics on things nowadays I imagine they can tell if you hit redline two blocks off the lot and that could effect your warrantee.

Good luck!

[SteveCZ28]

Thanks for all the recomensations guys. Sadly I have 2to machines to break In. Ny 85responses r and my banshee Haha. Banshee puked on me 4th of july. And my r never did run right since ice owned it and I noticed chunks of meta in the crank bearings. So ill have to mix up some rich fuel for both bikes and do some tinkering.

[Mosh]

You will get a varying degree of tips for break in, like someone said and almost none are wrong except that "run it like you will ride it". In other words the only one I dont like is run the snot out of it right off the bat.
I have built a few and generally I run at 30-1 for the first tank.
I just start them up and let them run in the shop for about 5 minutes just gently burping the throttle off idle up to around 3000 Rpm at times till they get warm, then I shut them down and let them cool down back to about 100 degrees for about 20 minutes while I check for leaks and stuff.

Then I repeat that process one more time. These are heat cycles to help your gaskets and bearings and rings, seat in. You will also find out if you have carb issues or idle midrange jetting to deal with during this process. If all that is or feels good, the third start-up I take them out and run them for 15 minutes at gentle throttle ranges with low loads just barely hitting the power band, then shiffting. Once again pay attention for jetting issues. If it bogs or goes into a phantom stall when you load the engine, you better go back and find out if you are lean before anymore run time is attempted.
The main thing to avoid is running at a steady idle or RPM. Vary the throttle and rpm and dont hold a sustained RPM or heavy load for more than a few seconds.

I ride them like that above about 2 times while letting a cooldown cyle go in between.
Generally the 5th time I run them I start taking them up to half and 3/4 throttle letting them rev out a little more.

After about 6 mild runs and about 2 hours of total run time, I run them at about 75% power and throttle for about 30 minutes. Then recheck for leaks and change the trans oil.
After that I start hammering on them pretty much to their potential, once again paying attention to top end jetting. But I still do not rev the snot out of them for more than a second or so.
At that point you have used around a 1/2 tank on a 2 stroke, then I mix down another can of fuel back to 42-1 and top off the rich gas tank and just ride them at that mix (or your prefered mix) and they are ready. You may have a burble on the top till you get the gas thinned back to 42-1. Once you are at you final mix do your plug chops and jet accordingly. One key to lean top end jetting is if the bike will rev out very hi on the top, but you dont feel much torque or pull from the engine.

If you feel that it is revving too cleanly and laying over or not pulling torque, go up a step at a time on the main till it burbles or misses on the top end, then come back down one step at a time on the main till the burble is gone. Or you can lean your needle also, if that main jet adjustment is that close for top end jetting to get rid of a burble. Then do you plug chops for a final check.

Some argue not to use synthetic 2 stroke oil for break-in and I can see the point of why.
But I have always broke them in on my main oil Castor 927. I have never had a issue using my main oil brand for break in.
Our Banshee got almost 10 years (still runs good, just burning some coolant from the head gasket)
My R has almost 4 years on it
Her R has 2 years on it
My bigbore Z has 4 years on it. All with no issues. Jetting is crucial, and 2 strokes dont like WOT for steady hard loads sustained times. (For duners heavy steady loads are hard to avoid in the sand, So I see alot of them stirring the gearbox alot to vary the engine load).The dunes are very hard on a machine due to the load of the sand and the way it can get in an engine if not sealed well.
I never rap them down the roads WOT for more than a 4 second burst. I feel varying throttle ranges in conjuction with proper jetting is the best you can do to keep a 2 stroke alive for a long time.
Really, a proper built and jetted atv engine only needs about 3-4 hours of mild run time till break in is finished.
The main thing is Wiseco pistons always like to expand before the jug does during warm-up, so letting your bike warm up before riding, is key to avoid cold siezing. That way the jug and piston expand together to their happy point.

Generally if you are going to have an engine failure due to assembly, it will happen within the first few hours of run time, unless you have bad jetting or dont let the piston warm-up before you ride it.

[SteveCZ28]

ok what oil would you reccomend i break the engine in on. and then what oil do i switch to when broke in....as in oil to mix with my gas.

[Tri-Z 250]

I'm a frim believer in heat cycles...with a rich frist tank of fuel(1gal). I use a fan for cooling between cycles as the bike sits(not running). I do a progression style break in. 30% never out of 3rd(10-15 mins, just to bring it to temp check plug) cool down; 40-50% same as frist break in routine...cool down; 50-60% forth gear(if you have the room) but continue to shift out at 60% go 15-20 mins, cool down. Check plug again by now I mix the fuel as I'm going to run it for life(just add if your not through the frist gal). Ride it normal..WITHOUT lugging the motor too much...ride for 20mins with 2 full hole shot runs 80%... one at temp and the last minute of the cycle time...cool down check plug...you should by now have the jetting pretty much spot on(correct if not)....The next cycle is up to you...30mins tops on a track or open non muddy trail ride(DO NOT rip it down the street...you will stand a chance of locking it up at topend death runs). Let the bike cool and ride for 30mins more again do not lug or stand on the topend too long. After that she's solid and ready for wear. Large open fields are great for this but it will take a full day of wanting to pin it just to see...take your time.

[El Camexican]

ok what oil would you reccomend i break the engine in on. and then what oil do i switch to when broke in....as in oil to mix with my gas.

There is less 2 stroke oil on the shelves these days. I can remember when there were 10 flavors at the bike shop, now the main bike dealer in Laredo has to order it in for me pre-paid. I'd suggest that you pick one that your local dealer carries and stick with it. Just make sure it's an established name brand bike oil and not some fangled new stuff brewed in some guys basement. I'll add if you end up unable to find that same brand at some point don't be scared to mix another in your tank, it is not the end of the world as some would have you belive. I don't like doing it, but I don't like pushing my ride either. What you don't ever want to mix is fuels i.e. aviation gas (don't run it in any circomstances!) race fuel with pump gas etc. 87 with 92 is not a problem in a bind.