Jump to content
Sign in to follow this  

piston break in

Recommended Posts

i just am curious what peoples views on breakin in a piston(new top end) are:thumbsup: i for one ride it like normal after i replace the piston, i have tried babying it and it doesnt seem to help at all

Share this post


Link to post
Share on other sites
i just am curious what peoples views on breakin in a piston(new top end) are:thumbsup: i for one ride it like normal after i replace the piston, i have tried babying it and it doesnt seem to help at all

Maybe you can't tell if it helps or not, but I can garuntee you it doesn't hurt to baby it.

When I "break in" a new top, I:

1) Kick it over and keep it running until the top end is too hot to touch

2) Once cooled, I run it through the gears, not on the pipe, gently

3) Once cooled I run it throught the gears again, but way more agressively

4) Finally, it's done.

I'm not saying all of this needs to be done, but I have never had any harm from this, it works for me.

MAX!!!

Share this post


Link to post
Share on other sites

okay now i feel like a liar, most of the time when i do a top end i start the bike up and mess with the fuel mixture bike hits temature, then i usally "lug to mid power band around in second and third then i usally let the bike cool down and make sure everything is tight... :thumbsup: my friend babys his for almost a whole day riding!:ride:

Share this post


Link to post
Share on other sites

When my bike was a 125cc(now 144cc) I put a new piston and ring in my bike once after a race day and had a race the next day, thought I would just take it easy in practice but they decided no practice laps that day to save time(race was a 5 moto format 3 the day before and 2 day of break in). Long story short I had to break it in in full moto and every other compression test after breakin before was 10psi lower then the full moto breakin. Not sure if I could make myself do that kind of breakin all the time but makes you wonder if easy breakin is the way to do it.

Share this post


Link to post
Share on other sites
Not a heck of a lot to break in, basically just seating the rings.

Take a shake down run to check your work, then run it like normal.

:worthy:thats what i have been trying to tell my friend

Share this post


Link to post
Share on other sites

There are so many thoughts on whats right or wrong. dry assembly, use lube, change premix oils add extra oil etc etc and the list goes on.

I do know that you can't go wrong if you run it through the heat cycle. Assemble the bike, start it and let it get up to operating temp while blitzing the throttle lightly to prevent build up. Shut her down cool for a few hrs and then do it again if you choose. I do this on every rebuild. Heat cycles are important.

Share this post


Link to post
Share on other sites

I do a wet rebuild then start the bike and let it run untill warm two times with about a half hour break in between then on the third start up I rev it high a few times then it's go time during the heat cycles I can feel the difference in the throttle response as the rings are seating!!

Share this post


Link to post
Share on other sites

If you use a cast piston ie OEM, then heat cycles are of no use. Simply get it up to temp varying the throttel constantly and ride it like normal. Most of all DO NOT baby it, ride it hard. The rings have a very small widow to seat, after a very few minutes that's it they are seated and the compression they achieve will be it until the next top end. This is all assuming you roughed up the cylinder by ball honing or cleaning out the aluminum build up in the cylinder before re-assembly.

Now if you have a forged piston ie Wiseco, then heat cycles would be a good idea to get the piston to conform to the cylinder without creating significant rub spots. Warm it up until the radiators are hot to the touch by varying the throttle constantly and then let engine cool to ambient temp (at least one hour) then do this again and let cool again. On the third time let it warm up varying throttle constanty then go ride the bike just below the pipe for 10-20 minutes lugging the engine the whole time any time you cannot lug the engine pull in the cluch and vary the throttle like you did during the warm-up then back to loading the engine. Loading is important to create the pressure necessary for the rings to seat well. Let it cool again. Then ride it like you stole it.

I personally always did a dry install on the top ends and never and I mean never had a blowby issue with my top ends. They always achieved good compression and lasted a long time (65-75hrs of motocross use).

Just remember the first time you kick over the engine fuel is supplied to the piston, with that fuel comes lubrication (pre-mix). So your piston is never without lubrication even when it first starts after a dry installation.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×