Top end break in, heat cycling

[rpduc]

Well I finally found time to get the MC back together with replated cylinder, new Vertex piston etc. She fired up on the 3rd kick. as per instructions from Millenium I just let it idle for ten minutes and shut it down.

I now will commence with the break-in procedure recommended in the owners manual unless some of you characters have a better suggestion.

I was surprised by something in the manual when looking up the recommended break-in procedure.

"Below 0º C. do NOT use 100% synthetic oil"

What is the logic there? I used Amzoil Dominator in my MC for a couple rides last winter out on the ice. -10º C. The jetting was corrected per the manual and it ran fine. When I pulled top end there was some scoring on the piston. It may have been there even from the P.O. but I'm just curious if anyone has thoughts on this synthetic oil theory.

 

[jostby]

2 stroke or gear box oil?

 

[jiauka]

There is absouletly no need for heat cycling any modern engine.

There are 30 different ways to break it in, because there are different ways for differnet people.

Search for "mototune" break in, it is aimed to 4 strokes engines, but is also good for 2 smokes.

My favourite break-in method is to warm the engine to operating temperature idling it about 2 minutes and riding without too much load on the engine (better downhill) for about 5 to 10 minutes, then ride the bike normal and doing some full throtle runs at full load (better uphill).

The most important part on ANY breakin method in warming up the bike first.

have fun,

j.

 

[rpduc]

2 stroke or gear box oil?

The premix oil.

Since the first machine listed on the Dominator bottle is snowmobiles I'm not going to get too worried about it, but I sure am curious why GG would recommend against a full synthetic for cold temps...

There is absouletly no need for heat cycling any modern engine.

Thanks for that opinion. Care to elaborate on theory?
Not to argue, just curious why GG would recommend it in the manual then?

 

[2 strokes 4 life]

I would say you dont need heat cycles in any modern engine because of the materials the engine is made of. Unlike a cast Iron block aluminum does not need seasoning or any of the junk.

 

[widebear]

Heat cycling is only important on engines with super tight tolerences and crisp jetting or guys who like to put B pistons into A cylinders without measuring.Ive heat cycled, pulled off the jug and removed the high spots with 800 grit wet dry before re assembling. Re platers will typically avoid many potencial seizure/ warranty problems, because they did'nt measure the piston either by finish honing to a much larger than o.e. piston to wall clearances.I'd be very suprised if your replated jug came in at 1.5 thou piston to wall.But mistakes still happen, piston production tolerances vary, so that heat cyling from the re platers perspective will identify any potencial problems with their work at idle, a mild squeek where things are salvagable, replace the piston and clean up the nikasil as opposed to a catastrophic redline lock up were everything will be totally destroyed.

 

[rpduc]

I'd be very suprised if your replated jug came in at 1.5 thou piston to wall.

I did the 10 minute idle thing per Millenium's reccomendation and ran it around the parking lot at my shop for a couple easy 10 minute sessions with cool downs on Fri. I sent Millenium my new piston and the cyl. was supposed to be honed to spec accordingly. I didn't actually measure it but I've heard nothing but good reports on their work.

Sat. I took it up to some kinda crappy trails beat up by too many fricken quads (the only ones open yet here) and after a thorough warm up pretty much rode the snot out of it for three hours. Ran great. The RB carb mod also seems to have cleaned up the throttle response. We'll see as the season progresses.

 

[GMP]

Most people don't have the tools to propely measure a cylinder. The error induced in hack metods is often greater than the total desired clearance. I laugh when I see someone go at a cylinder with a caliper. Thats why I say unless you have these tools or go to a shop that does don't bother. What widebear describes is the best way to do a top end but how many of us actually do that? I just do the initial idle for 10 min cycle, then several short hard runs with cooldowns. My stuff looks fine when taken down.

 

[widebear]

Of course what you say makes perfect sense Glenn. And the fact is 99 times out of a 100 its gonna work just fine ,running a large clearence, should not cause a problem unless you plan on keeping the bike a very long time , 2 stroke sleds run 7 thou for those minus whatever cold starts. But I have seen my share of problems just ask cactusreid, re
; his husky 450 and the resulting frustration because of sloppy work ethics. Now on a 4 stroke to much piston to wall using a slipper piston is a certain death sentence but thats another topic. I use a machine shop in town here and for the price of a box of donuts for his staff plus I enjoy hanging out there he has a flow bench, lots of knowledge and the contract to flow the heads for Ktm Canada's race team motors, why would'nt I.

 

[GMP]

Why sure, I'd be off to the bakery too!

We have a nice three point bore mic here in the machine shop at work. Its regularly calibrated and kept out of the hands of hacks. With this you can get good numbers. I'm sure a better tool than most bike shops have.

Somewhere on TT, there was a pic of a CRF450 slipper piston that decided it was time to go sideways in the bore.