Is it necessary to change every engine bearing on a rebuild?

I'm currently in the middle of giving my two stroke motor a full overhaul because the big end rod bearing is worn.

I'm just curious how many of you replace every single bearing in the engine while it's split or if you only replace them if they show signs of wear/damage?

Normally, all trans bearings live as long as the engine. I just check and any play,rouchness/signs of damage, then replace. Crank bearings I change every time the crank is changed or rebuilt as well as if there is any signs of play, roughness or damage.

William has it right..

I would also like to add that changing out any good Honda bearing for new CHINA made JUNK is WRONG! WRONG! WRONG! I'd rather have a 20 year old Honda bearing with 100,000 miles on it than a brand new China made, soft, improperly machined, not heat-treated, out-of-round, piece of you know what.

If you do end up changing ANY bearings, please, ONLY use genuine Honda, or bearings from another WELL KNOWN, HIGH QUALITY, manufacturer. Beware ANYTHING that comes out of China. Do not trust ANY China made internal engine parts-EVER! In my business we are seeing more China made junk coming to our parts counters and it really is just useless garbage. But, people want the lowest price.. They never factor in what it costs to tear an engine down a second time to replace the China junk they installed the first time because it saved them a little money over genuine, quality, parts. Trust me I've used a "complete bearing kit" to replace all of my bottom end bearings. The last time I had my engine apart those "new" bearings were already so sloppy that I had to change them out again. Luckily I caught them before they failed. I was replacing my crank and decided to check those bearings again since I had the cases split. Now, I only have HONDA bearings in my bottom end again. Try and find FAG, or Timken bearings. SKG is now CHINA made so beware. They might be good, but why gamble on something so hard to replace if it fails shortly after install?

1 hour ago, Kawabuggy said:

William has it right..

I would also like to add that changing out any good Honda bearing for new CHINA made JUNK is WRONG! WRONG! WRONG! I'd rather have a 20 year old Honda bearing with 100,000 miles on it than a brand new China made, soft, improperly machined, not heat-treated, out-of-round, piece of you know what.

If you do end up changing ANY bearings, please, ONLY use genuine Honda, or bearings from another WELL KNOWN, HIGH QUALITY, manufacturer. Beware ANYTHING that comes out of China. Do not trust ANY China made internal engine parts-EVER! In my business we are seeing more China made junk coming to our parts counters and it really is just useless garbage. But, people want the lowest price.. They never factor in what it costs to tear an engine down a second time to replace the China junk they installed the first time because it saved them a little money over genuine, quality, parts. Trust me I've used a "complete bearing kit" to replace all of my bottom end bearings. The last time I had my engine apart those "new" bearings were already so sloppy that I had to change them out again. Luckily I caught them before they failed. I was replacing my crank and decided to check those bearings again since I had the cases split. Now, I only have HONDA bearings in my bottom end again. Try and find FAG, or Timken bearings. SKG is now CHINA made so beware. They might be good, but why gamble on something so hard to replace if it fails shortly after install?

Thanks for the information. I only ever trust bearings that are recommended by manufacturer or have made in Japan stamped onto the race personally. I swear by KOYO or SFK bearings with previous experience!

Edited by Joemi

You are gonna pay to have the crank pulled apart and reassembled and not replace a $20 bearing?  That makes no sense.  If the crank is coming apart, replace every bearing associated with it, along with the seals.  

I replace every bearing and bushing that is within the cases if the engine has unknown hours or has several hundred. I look at as I don't want to split the cases again for a long time and especially not because a $20 bearing failed. I also only use OEM bearings/bushing within the cases. Do it once, do it right!

 

I do not replace trans bearings just because I'm in there.  No need.  Excellent point above about good used stock bearings VS replacements of unknown quality.

Main bearing, crank seals and a crank if necessary.  Unless something very bad happened to the trans those bearings will be fine.  This is a situation where the less you screw with the better off you will be.

Not mentioned yet, but NTN bearings (stock in Kawasaki, not sure of other makes) are the best bearings made. This is, at least, the opinion of a local bearing distributor.

On 12/08/2017 at 8:45 PM, CDNSXV said:

You are gonna pay to have the crank pulled apart and reassembled and not replace a $20 bearing?  That makes no sense.  If the crank is coming apart, replace every bearing associated with it, along with the seals.  

I had this state of mind but it's more like £80 and a 2 week wait for KTMs strangely sized final drive bearing... 

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