Heat cycle the head gasket?

Discussion in 'Touring Models' started by the draggin, Jul 7, 2015.

  1. the draggin

    the draggin Active Member

    I have seen this commented before but can't seem to pull it up now any help would be appreciated.
  2. Jack Klarich

    Jack Klarich Expert Member

    Proper break-in is critical to realizing maximum life and performance of your engine kit! We can't stress this enough. Follow these steps to the letter. Ignore any alternative methods you may read about on the internet!

    Minimizing heat is absolutely essential to successful break-in, and excessive heat will damage your pistons and forever condemn your motor to be a mediocre performer. The reason for this is that neither your rings nor your cylinder bores are perfectly round on initial assembly. Therefore, the rings are actually only making contact with the cylinder walls in a few places. The tension of the rings is concentrated in these places, increasing friction and heat. This condition exists until the rings have a chance to carve the cylinders into their shape. While that process is taking place, however, the rings and the pistons are very vulnerable to damage from excess heat. You can learn more about this phenomena by researching "ring microwelding". It's a very real risk to your engine!
    The assembly lube you put on the rings and pistons is to help combat ring microwelding. Yes, we know that some shops recommend minimal or even no lube at all to better assist the break-in process. We don't subscribe to that theory. Your rings are at much greater risk of microwelding than they are of failing to seat. They will seat just fine. You need to pay attention to the possibility of damaging them.
    On your initial start-up, run the engine no longer than 10 seconds. Use a clock with a second hand or a stop watch. Don't guess! Shut it off and allow it to cool completely to room temperature. A little bit of patience now will go a long way to providing you with a strong motor that lasts a long time.
    For your second heat cycle, run the motor no longer than 20 seconds. Again, time it properly, don't guess. Allow it to cool completely.
    Repeat these heat and cool cycles with run times of 30 and 40 seconds.
    You're now ready for your first ride. Keep the rpm's down as much as possible and keep air flowing across the cylinders. Ride it no more than a mile, shut it down, and let it cool completely
    For your second ride, treat it similarly gently. Keep your rpm's below 3500 and keep air moving across the cylinders. Ride it a couple miles and let it cool completely.
    For the next 50 miles, do not exceed 3500rpm and avoid using full throttle. Vary your speeds, allowing the engine to pull and then decelerate gradually. This reversal on the rings, from pressure to vacuum, assists in the seating process.
    For the next 500 miles, stay below 4000rpm, avoid using full throttle, and keep the heat down.
    Once you're past the 500 mile break-in period, change your oil. During break-in, the rings have carved the cylinders into their shape and the shavings have been captured in the oil, so you want to change the oil to get that stuff out. Use any high quality 20W-50 oil formulated for air-cooled V-Twin engines.
    Have your bike professionally dyno tuned. Proper tuning is critical to maximum power, long life, and good gas mileage. It makes no sense at all to spend thousands on motor work and then leave power on the table, and put it all at risk, because you didn't spend a couple hundred on a proper dyno tune.
    You are now ready to enjoy the full power of your new engine kit!
  3. the draggin

    the draggin Active Member

    Thanks, will use this approach to ease it back into use.
  4. dolt

    dolt Senior Member Contributor

    I am not a fan of heat cycling. One or two 10-20 second heat cycles is fine to check for leaks or noises that indicate something is amiss. The quickest way to seat the rings is to get on the bike and ride. Keep rpms under 3500 but get some good pulls through 2d and 3d gear; you need to load the motor. It takes heat and compression to seat the rings and they can be seated in less than 50 miles of riding.

    If you plan to dyno tune, a good dyno operator can seat the rings on the dyno as well.
  5. nfusion

    nfusion Active Member

    I followed s&s beak in for my big bore kit which I purchased from them and my engine is still running like a champ
  6. motor

    motor Active Member

    Jack I know you are knowledgeable and a great asset to this site ...But you wrote these break in tips like this is the way and the only way. Not the way I do it .I have rebuilt more engines in my life than I can remember and have had very few failures. No failures from ring microwelding .I'm of the belief if built properly soft break in is not required .I just don't dog the things(engines of all sorts) until I have some time on them. I do change oil and filter after the initial bench run and a couple times in the first 1000 miles ,then just settle in to regular service . So we can agree to disagree on this one