2002 EC125 Connecting Rod Trifercation

[Zman]

I bought back the 2002 EC125 I had a few years ago with a newly added crankcase inspection window in the bottom of the engine. I initially thought it might be a crank stuffer bolt but when I pulled it apart it was much worse. The connecting rod broke and in two places and the carnage was impressive.

I was told that the cases should be able to be repaired. I will know more tomorrow morning. I will need to weld the cylinder to fill the gouge, replate it and get a new piston so I might as well cut the bore bigger and make it a 144cc. That is a pretty easy choice for similar money!

 

[Davehuge]

Wow, to snap a conrod like that must have taken some force.

I guess it didn't happen at idle RPM!

Do you know what happened? Did the big end seize? If so why?

Just interested to know.

Hope you can get it fixed for a reasonable price.

All the best, Dave.

 

[Zman]

The guy said he warmed up the bike for 3 min and then rode it WOT through the gears. It bogged in 1st (probably not warm yet) and ripped through 2,3 and 4. Top end of 4th it locked solid. Both rod bearings looked fine as did the crank bearings. The piston and plug were perfect. Very strange.

 

[Pygmygod]

Sounds like a cold seizure to me.
Went full throttle for too long, too quickly before everything has warmed up to the correct tolerances together.

 

[Zman]

Why are there no witness marks on the piston and cylinder of a bore seizure?

 

[Pygmygod]

Good point Zman.

What do you reckon it is then?

Stress fatigue on the aged conrod?

 

[Zman]

I showed it to my friend Eric who said it was a material failure. He said the Vesrah rods are ok quality but he has seen them fail occasionally.

 

[Zman]

A few weeks ago, I got all of the parts back for the blown up 2002 GG125 and they looked great! This EC144cc is being built for more low end power for my god-daughter.

 

[Zman]

I set the squish at 1mm ~ 0.040 inches and I finished up the engine assembly last night. I put a quick coat of high heat clear on the bare aluminum parts so they stay cleaner. We are going to run this one without the 1cm reed cage spacer for even more low end torque and throttle response.

 

[Harry]

Nice rebuild

 

[Zman]

Break it better or in this case it was broken bigger ;-)

 

[SS109]

That's really nice repair work. Glad you're getting it back together and even cooler it's going to a lady!

 

[Zman]

My 18yr old god-daughter has been riding since she was about 8. She is tall and thin so we needed a light weight enduro bike. She rides well, her riding style is probably better suited for a 4 stroke but 4 stroke size and weight do not leave us many options.

We had a GG EC125 that my son's rode in some enduros and it was a very nice bike with a nice large power band including good low end power. Based on our experience with the EC125, we found and bought her the GG MC125. Unfortunately, the MC125 turned out to be a typical 125MX bike. The MC125 has very limited low rpm power especially in high altitude technical riding, making it a challenge for her to ride.

On a side note, we have a GG MC250 engine in my son's EC250 and it has good low rpm power similar to the EC250 and it rips in high rpm. I am pretty certain the MC125 issues were tied to the lighter flywheel, Messico pipe and MX porting / port timing. As expected the MC125 has a strong mid range and top end power but that is not the way she rides. I have way too many hours invested into finding low rpm power in the MC and while it is much better than it was, it is still a MX125 a it does not suit her riding style.

When I bought back the GG EC125 from the guy that blew it up and found that it needed a full rebuild, I decided a 144cc big bore with the heavier flywheel and FMF pipe would be a great way to finally resolve the low rpm issue for my god-daughter.

At this point we need to swap over the EC 144 engine ignition and pipe to her MC125 and then I will build up and sell off the GG MC125.