Jump to content
Sign in to follow this  

2012 Connecting Rod Seized

Recommended Posts

My 2012 engine seized with 68 hours on it.  After digging into it, I found that the connecting rod is seized within the crank.  The crank spins freely, but the connecting rod is griding away as you try and rotate it within the crank.

 

Are the OEM cranks really only good for 68 hours?  This seems like low time to me. 

 

I always run OEM parts, but this has me reconsidering.  Any thoughts on throwing in another OEM crank or go with Hot Rods?

Share this post


Link to post
Share on other sites

I had my crank rebuilt with a HotRods rod kit at 112 hours on my 2009. The crank was working fine but I split the cases and did the bottom end bearings and I thought I should rebuild the crank at the same time. There was no failure just run time. So far the bike has worked as well as before. I normally stick with oem but the rebuild made sense in my situation.

Share this post


Link to post
Share on other sites

The time is relative to how the bike is ridden.  That being said, there is a chance the bike could blow with only 2 hours on it...  MFG defects can and do happen on mass produced products.

 

For me, I went Hot Rods but I really don't think you can do wrong going either way.  Some will tell you to stick what worked for them, but it may not work for you.  

Share this post


Link to post
Share on other sites

Nobody ever believes me but I know what I'm talking about. The Honda manual says to replace the piston every 12.5 hours. A crank will need replaced about every three piston changes. Obviously Honda is being safe (Yamaha is 15 hours) and this applies to a very skilled rider but the point is well made. High level pro changes the crank every fifteen hours - slow Joe every 60 hours. Good rule of thumb.

Share this post


Link to post
Share on other sites

It all has to how the bike is ridden also a bike that is idled around a lot and lugged can have a failure sooner as the forces on the bearings can be greater @ lower rpms Harleys were known for rod problems because people wanted to tune them to idle very slowly it stated in the service manual that this could be hard on the rod bearings it also goes for cam lobes @ lower rpms .There also may have been some fuel dilution going on with the oil this seems to take away from the life .I s upose if every body read the owners manual and actually believed the engineers and what they say about parts change intervals they would never by a ra ce bike extending the time to double of what they say is a probably pushing it .

  • Like 1

Share this post


Link to post
Share on other sites

Thanks guys. As far as riding type, I ride mostly mx with some dessert tossed in. Im slow Joe and dont run it hard. The last few rides, however, were in supermoto trim on a big road course. Im sure this didnt help things any. I probably had 3 hours of supermoto before it seized.

Any reason to think supermoto hours are going to be harder on the engine? Im a little gun shy to take this new one back to a road course if that's harder than mx.

Share this post


Link to post
Share on other sites

It all has to how the bike is ridden also a bike that is idled around a lot and lugged can have a failure sooner as the forces on the bearings can be greater @ lower rpms Harleys were known for rod problems because people wanted to tune them to idle very slowly it stated in the service manual that this could be hard on the rod bearings it also goes for cam lobes @ lower rpms .There also may have been some fuel dilution going on with the oil this seems to take away from the life .I s upose if every body read the owners manual and actually believed the engineers and what they say about parts change intervals they would never by a ra ce bike extending the time to double of what they say is a probably pushing it .

Ron whats your opinion?

 

OEM or hot rods in a situation where you need a new crank?

Share this post


Link to post
Share on other sites

Nobody ever believes me but I know what I'm talking about. The Honda manual says to replace the piston every 12.5 hours. A crank will need replaced about every three piston changes. Obviously Honda is being safe (Yamaha is 15 hours) and this applies to a very skilled rider but the point is well made. High level pro changes the crank every fifteen hours - slow Joe every 60 hours. Good rule of thumb.

12.5

WHAT!!!!!  your shitting me?

Does it really say that, i have never looked. I just always used 35-50 as a good number

but then again I'm barley a c rider

Share this post


Link to post
Share on other sites

12.5 Hours - look it up for yourself! Its right in the Honda service manual. But remember this is a high level rider. Also, take note that power drops off rapidly after several hours of use. Even a great rider may get more time out of the piston but the power performance will suffer. This is why cast pistons are the preferred choice in two strokes as their dyno numbers stay high longer than a forged piston. They both start with the same power but several hours later the casting will be the better performer of the two - not talking about four strokes here!  Not going to argue this point I know it for a fact.   

Share this post


Link to post
Share on other sites

Nobody ever believes me but I know what I'm talking about. The Honda manual says to replace the piston every 12.5 hours. A crank will need replaced about every three piston changes. Obviously Honda is being safe (Yamaha is 15 hours) and this applies to a very skilled rider but the point is well made. High level pro changes the crank every fifteen hours - slow Joe every 60 hours. Good rule of thumb.

this is bull.

  • Like 1

Share this post


Link to post
Share on other sites

The lower rod bearing is a weak link in this  motor.

KTM has gone to a plain big end bearing. I'm not sure if this is good or not. They do seem to be more reliable than Honda cranks.

Plain bearings hold up quite well in road racing engines which KTM has expanded into and no doubt learned a thing or two about.

On the other hand road racing engines are subject to much different loads than Motocross engines.

Edited by nesc103y

Share this post


Link to post
Share on other sites

The lower rod bearing is a weak link in this  motor.

KTM has gone to a plain big end bearing. I'm not sure if this is good or not. They do seem to be more reliable than Honda cranks.

Plain bearings hold up quite well in road racing engines which KTM has expanded into and no doubt learned a thing or two about.

On the other hand road racing engines are subject to much different loads than Motocross engines.

Plain bearings have better load carrying capacity and rpm capabilities compared to caged roller bearings. However, their weakness is oil contamination. They can't handle dirt or low oil pressures like a traditional caged roller bearing. It will be interesting to see if this design is a viable alternative to a cage need roller bearing.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×