Break In Engine Break in, run in

Discussion in '2-Stroke Engines' started by llopart, May 9, 2008.

  1. llopart

    llopart New Member


    I just have mounted a F80 engine few days ago. It's awesome, goes nice. The only thing is that on low rpm and riding...I mean, when the engine is giving power at low rpm (not idle), the engine makes a strange metallic noise, like something is eroding the cilynder. That is specially noticeable when I release the gas and rpm decreases. Is that normal during the break in/run in?

    I want to correctly run in the engine, and sometimes I full throtle for few seconds, or just go uphill with the engine still cold, I know this is not good, so I'd like to know what you did to break in your there a quick way, or the only option is to do 500 km at 20 kph? I just can't mantain that speed....

    Thanks a lot!!

  2. relaxxx

    relaxxx Member

    My HT80 CC also sounds horrible at low RPM. I don't know if it's the clutch or what but something just howls at a a certain low rpm and the bike rattles like crazy. When I crank it up, it all goes away!! I just can not break this thing in at the recommended speed, it's torture! What I would like to know is just how bad is it to run an extra 5-10 MPH than the lousy 15MPH break in. From the sound and feel I can't help but tell myself it's just as good if not better to break her in at 20MPH than 15MPH
  3. Ghost0

    Ghost0 Guest

    Unless there is something really wrong with your engine, and I don't thing there is. The noise you are hearing is probably coming from the gears on your clutch. They should be lightly greased. Putting some sound deadening material over the clutch cover will help.

    In my opinion there is nothing wrong with breaking your motor in at a higher speed. I believe the key to a good break in is varying the speed. I would just cycle between slow to fast and then back again. I would just try not to top it out for too long. Again, just my opinion.
    Last edited by a moderator: May 15, 2008
  4. Simonator

    Simonator Guest

    That's how I did it. I varied the speed alot for the first few tanks. On the first tank of gas, i tried not to run the motor for more than 10 minutes at a time. The key is to not let it get too hot. I did not top mine out during the break in period, but i come close.
  5. datz510

    datz510 Member

    I just got my HT livefast 70cc build done tonight and started the break in process. Mine runs and idles very very smoothly. No strange noises or anything. I've been running it for short 10 minute jaunts around the neighborhood at around 15 mph, varying the speed, but never full throttle. We'll see how it does. So far, so good though.
  6. SirJakesus

    SirJakesus Guest

    Yeah just vary the speed, don't top it out for too long (just tap its higher revs) and don't bog the motor EVER! and you should be fine. Give it some breaks dont run it for more than 20 or 30 mins at a time and try to avoid running when the weather is really hot.
  7. Mountainman

    Mountainman Active Member

    My engine came in today -- I mounted the Subaru on my mountainbike -- a few test rides up and down this old dirt road -- double checking here in regards to break in period ( there was nothing said in the manual ? ) Yes, to vary my speed and not long or hard on the top end.. Tomorrow is THE BIG RIDE -- slight problem here -- it has been hotter than heck !!! Not the best for breaking in -- will be taking many time outs for cooling off periods... I am reading 500 mile break in for 2-strokes --- does that hold true for my 4-stroke ? Happy Riding from Mountainman
  8. With any engine the break in period is really only to bed the rings into the cylinder, typically a single cylinder 2 or 4 stroke motor has ball race main crankshaft bearings and a roller race conrod (bigend) bearing which really need no beading in.
    Piston rings are not held against the bore by ring tension alone but by a small amount of combustion going behind the ring to push it into the cylinder wall.
    So constant revs, contsant idling or constant load are really not ideal to bed the ring, if it gets to hot the ring ends can "but up" and distort the ring which leads to combustion gasses passing the ring.
    To get good beding you need to pull the motor to load, which makes the ring push hard against the cylinder wall, then slow it down again to let the ring sit back in the ring groove and only be held against the cylinder by ring tension.
    On a 2 stroke motor the oil/fuel ratio is also important during beding, a tad more oil is ok but to much can also lead to unburnt oil to stay in the ring land and carbon up and may lead to bore glazing.