Topic: Proper break in

[aglick87]

I've read several articles on how to break in an engine properly.  The one article stated that nowadays, the best way to break in an engine is to load it down and bury the throttle for the first 20 minutes.  Stating that you only have a limited time to seat the rings properly in the bores.  They claim that this is the best way.  What they were saying is that with today's machining being so flawless, todays motors don't have the burred edges and friction of the motors of old.  The reason I am asking is because I have a cb motor which has 20k miles on it.  I am freshening up the top end with some new rings and a good honing.  I was wondering if I should hammer this motor like the article suggests, since the rest of the motor is already broken in and smooth?  Thoughts?

[Mr. Grimm]

Let us know where that article is. It sounds kinda ridiculous. While it could help seat the rings, other things like the cam and valves will most likely just get chewed on a little more. I've always heard that you should use fresh oil, filter, gas, and bring the engine to about 500-750 rpm faster than the normal idle to maintain good oil pressure and lubricate all the parts equally. Some engines at idle don't pump/sling enough oil to all the parts to keep heat and friction in check. A large fan or strong breeze would also be a necessity, due to the air-cool only nature of these beasts. Then for no less than 100 miles vary your speed so the engine never stays at a constant rpm for over a minute. City driving is great for this. If your  engine tachs at 10,000 rpm, never take it more than half way for the first 200-500 miles. No hard acceleration, and check the oil and temp before and while driving. After 500 miles change the oil and filter and you should be good. If you do a complete rebuild, extend the break-in to 750 miles.

I'm not a professional mechanic, but I've used this process with good results. If nothing else just get the best oil you can afford and keep it flowing at the correct level at regular intervals.

Good luck, see ya on the road.

[Mark M]

Unless you are a professional engine rebuilder I would recomend you don't thrash a recently rebuilt engine on the road, personally I don't have that much confidence in my own building abilities. I have heard the thrash theory and also the more traditional methods. The traditional method would allow you to have confidence in your rebuild with the minimal risk of total destruction should something not be quite purfect. I would also suggest that redlineing a 30 year old engine without a full rebuild might also be asking for trouble. If you think of bike years as a ratio of 6-1 ( most riders think anything over 10years is overdue for pensioning off) then these bikes are now well beyond geriatrics and need a bit of TLC and mechanical sympathy.   

[Chris in Ramsey]

check this:  http://mototuneusa.com/break_in_secrets.htm  or this:  http://mototuneusa.com/break_in_secrets.htm  always seems to be many opinions on this subject