Lower Rod Bearing Seizure Causes, with pics

[CrazyBRONCOguy]

Recently had the clutch side lower rod bearing sieze on me and was wondering what you all thought of what may have happened?

It was a hotrods crank. the engine is on its way to Herr Jugs to get rebuilt and new jugs ported.

I had 30 minutes on the engine maybe, though the crank is approximately 4 years old. It was not trued and welded.

I've read that marks on the intake side may mean that there was not enough oil, do those look like that may have happened? The other side looks fine. It had enough compression at one point to make the electrode come out of the plug. I have never seen that happen before. Another thought I had was the side had a bad plug in it that was leaking and made it run lean?

Another thing that may help is this engine has had the rod let go on that side at one point, before I bought it. hence the non-stock crank.

 

thanks for any input

 

-CrazyBRONCOguy

[Nieskes]

What do you mix your oil at?

[CrazyBRONCOguy]

32:1 I was using Golden Spectro at the time. I will be using amsoil dominator in the future.

these pics may help too

Im just really wanting to make sure I dont have this failure again

Edited June 22, 2013 by CrazyBRONCOguy

[421alkybanshee]

Needs to be trued and welded!

32:1 Klotz benol oil, and you will have no problems

[joey83]

Did you do a leak down test?

And I think the electrode burning off and plug backing out is a seperate issue. But somebody will chime in with more knowledge than me.

If you are sending the entire motor to Herr it should come back ready to rip. That woukd take all the guess work out of it.

[WINDYCITYJOHN400]

What happened to cause the rebuild? Did something let loose or melt down with the previous combo?

If so, you might have had junk in the bearing and after firing up this new combo....30 min of ride time trashed the bearing, heated the rod, transferred heat to that cylinder and lead to the detonation that killed the plug and did all the piston/dome damage.

 

Hard to tell with pictures, but everything looks pretty dry. Was assembly oil used on everything, crank pre oiled thru the oil galleries, ring lands oiled, etc? 

 

Last thought - I bought a used motor that had loose cases. (The crank wobbled on the bearing supports.) You could do a leakdown test and get a positive result, then once riding and the motor was reved up....the crank would wobble and I'd get an airleak thru the crank seal. I gave me fits because I was chasing jetting due to the positive leakdown results. Check the cases/crank for trueness and correct fit when it's apart.

[CrazyBRONCOguy]

The previous engine I was just not happy with the performance, so I had it ported more aggresively. Not builders fault at all I didnt know exactly what I wanted.

Your saying that the dome and piston damage is from detonation instead of the rod having enough slop to let the piston hit the dome?

 

Cannot say on the pre-oiled, I dropped the banshee off and picked it back up from the person who built it. Upon me taking it apart I did see that the snap ring and washer came off the Idler gear, to one goes between the kickstart and clutch basket. while that's not good Im dont think its completely related to what happened.

 

I did not do  a leak down test on this engine as per above, it was suppose to be ready to go.

 

The whole engine should be at Herr Jugs this week sometime getting a port job and rebuild, but I have another engine I want to put togethor as a spare.

Edited June 23, 2013 by CrazyBRONCOguy

[oldskool]

Detonation is whats going on with piston and dome which transfers to rod and crank. Compression,squish and octane all play a part in this

[CrazyBRONCOguy]

Kevin at herr jugs said in his opinion it was eithier a crank that became untrue or the oil ratio was off in the fuel. I have ran the same fuel in other machines with no issues.

 

Anyways thanks for all the input, gives me some ideas of things to look out for and I also plan on building a back up engine with the pistons and jugs from the pics.