• Announcements

    • Bryan Bosch

      Buy/Sell/Trade/Wanted   01/18/2018

      Checkout our robust classifieds for amazing deals on bikes, parts, accessories, gear & apparel 

Sign in to follow this  
Followers 0

How to Break-In An Engine

Ron Hamp


Engine break-in is not the same as it was when our grandfathers were putting their Triumphs and Harleys together 40 years ago. In the old days, the metallurgy required alloys with lots of nickle or chrome for parts like rings and camshaft components to maintain any reliability. The machining processes were not as good as today and surface finishes were made purposefully rough to allow parts to eventually mate. Piston technology in some engines was to use zero clearance and split skirts to keep the engines quiet. Oil was good enough in those days to compress the skirt and still maintain an oil film, but there were also high spots that would protrude through the film and the engine would need to be run slow at in break in to keep from overheating the parts and causing complete failure.

Today's engines have much harder cylinders and steel aloys, piston rings have surfaces like moly that offer less friction and mate to the cylinders very quickly. Cylinder bores and camshaft tolerences are near perfect, very round & smooth bearings and crankshafts have the same qualities, so the break in period is not what it used to be.

Now days, in a brand new engine, the parts that need the most attention are the cam shaft and lifters. These are the parts with the highest load and require the surfaces to mate, removing microscopic peaks that can damage the lobe or lifter, so lots of lubrication is required. A faster engine speed is required for cam break in to form a better hydraulic oil surface. The faster surface speed of the lobe forms a thicker wedge of oil, allowing the peaks to be worn away. This process only takes a few minutes.

When rebuilding an engine, I think it is important to lubricate the components. The piston and rings should have some lubrication, but this should be very light so that it doesn't burn and form a glaze before the ring has had a chance to mate with the cylinder. I have had good results with Total Seal Quick Seat which is tungsten disulfide and I also put a dab of oil on the piston skirt. This slight amount of lubrication alows the high spots to gradually come off and be floated away with the oil and into the filter. In contrast, no lubrication can cause theses particles to be transfered to a softer surface like the piston and ring, causing unwanted wear to the cylinder as the piston rings are being forced against the cylinder with over 2000 psi.

Engine break-in very short for the latest generation of engines. I warm them up to temperature while going through the transmission gears, making sure every thing is working. I then let the engine cool down and check the oil & coolant levels, also checking for any leaks. After that, I start the engine, let it warm up to temperature and its wide open from there. I heard a story from a freind that worked for Rob Muzzy where one of the mechanics was asking him how he wanted this road race engine broken in. His reply was like your new chainsaw: fill it with gas and oil and start cutting wood.

Who is Ron Hamp?


Some of Ron's Work


Sign in to follow this  
Followers 0

User Feedback

There are no comments to display.

This is now closed for further comments

  • Similar Content

    • By Kieran Black
      I have freshly rebuild my top end on my 2009 yzf250, new intake valves piston and rings, cam chain. I put it all back together ran mint, but after starting it up for about the 3Rd time a loud knocking noise from the engine appears, the bike is still running fine although a very obvious loud knocking noise. valves are all inspect aswel. note, the knocking id only at one certain compression stroke its past TDC its a short stroke but quite a difficult one, never had even put it in gear so i dont think it is the trans. i also ripped out the cams a couple times thinking that was the problem and once i put it together it ran mint for about 4 seconds then knocking came back. I originally thought it was the exhaust cam decompression sticking but after inspection was not making the nosie. I took the flywheel off and checked if I had put it wrong, but no. have just tore apart the clutch side cover and all teeth are fine. I am at a point where I don't know what to do next. please any advice is much appreciated.
    • By raymondthebodeau
      These are pictures of a 2006 honda crf 250 right side case half. In the kick starter mechanism housing, there is a small piece of aluminum that bridges across a hole in the case. It broke off, and im wondering if anybody else has seen this before, and will it be an issue? I dont think it serves a purpose, but i would like a second opinion. Thanks!

    • By Supermotofool
      Now that I am rebuilding my 2001 DRZ400S due to a crash.. I want to be sure that when it happens again the bike will not be completely totaled.  I cannot find any axle sliders for it because it does not have hollow axles. The only thing I have been able to find are engine guards that mount to the frame so I will for sure be getting those. So I just have questions on how to get axle sliders mounted on my bike, and I also will probably be getting a handbrake sometime in the near future. Would I be better off just swapping to an SM swingarm? 
      I wish there was a document listing all the spec differences between the SM and S models. 
      Any help would be great.
      Best regards.
    • By Hewie
      Hoping someone with a lot more experience than myself might be able to help me out. 
      Make: YZ450F 2012 model EFI
      idles for a minute or two and then stalls when hot and I back off the throttle it stalls after stalling when hot, takes lots of kicks to start again, when i remove the plug and dry and clean it the bike will start more easily What I had done to it before it started this:
      bike seized due to  chain tensioner wore out and travelled up into the cam chain and head. replaced piston and cylinder (aftermarket Athena installed) assembled head with new valves and springs new cam chain set valve clearance replaced clutch (basket as well) After less than 10 hours, the stalling was happening too frequently to ride without losing my calm so I took it to the shop again. They spent seven hours trying to diagnose the fault with no results.
      reset cam timing and checked flywheel key found small amount of water in oil cleaned injector and air mixture screw checked crankshaft position sensor checked coil and cap replaced spark plugi inspected TPS, APS, atmospheric pressure sensor and kill switch It was getting too expensive to leave at the shop any longer so I am trying to have a crack at it myself. Does anyone have any ideas? I'm going to try to do a compression test or leak down test this week. Also, has anyone made up the test harnesses for this engine?... I'm not keen to buy a gytr tuner to test the sensors again if I can avoid it.
      Any help would be greatly appreciated.
    • By Kor3y101
      Hey guys!
      So after chasing down an issue of fuel being in my Oil, it turns out the float needle isn't leaking and the carby is functioning as it should. It was an issue with the Accellerator Pump causing fuel to leak over as the throttle was constantly being turned to try and start the bike whilst it had a valve issue. 
      So, I have since replaced the filter and dropped the oil twice. However it is still a bit too diluted and smells of fuel. I had left the dipstick off to try and vent the frame. I know there isn't more fuel getting Into the oil as the level isn't changing and it isn't getting worse. 
      What is the best way to flush it all out? Buy 5L of cheap car oil, warm the bike, drop the oil. Rinse and repeat? Or use an engine oil flush additive? Or both? 
      I know I need to get another oil filter again, should I put that in after I have flushed it out, or before? The current filter has had 1 oil gone through it and dropped and is currently on its second lot of oil. It has done maybe 20km since then.