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-   -   Complete Rebuild - EC250 (http://www.gasgasrider.org/forum/showthread.php?t=21160)

RockefellerGG 03-31-2016 09:03 PM

Complete Rebuild - EC250
 
I haven't seen a complete rebuild or walk through on the forum. Maybe I didn't search hard enough. Maybe this will be over-simplified, but I thought it might help someone who needed some motivation or confidence booster.

This EC250 belongs to a friend and fellow forum member. He was riding it a few weeks ago when the engine seized up. While washing it down, he noticed that the carb-to-air boot was disconnected. Here it goes:

Tonight, I'll start with the top end:

I started by removing the water pump cover:
https://drive.google.com/open?id=0B8...mFpSzJjOVE.jpg

The water pump impeller was seized to the bolt:
https://drive.google.com/drive/folde...pshek3brgz.jpg

Gently pried out the shaft seal:
http://i71.photobucket.com/albums/i1...psb0omflcd.jpg

Remove the clutch cover:
http://i71.photobucket.com/albums/i1...psmrl2ptpm.jpg

Remove the right side power valve cover:
http://i71.photobucket.com/albums/i1...psu43zwx8b.jpg

Removed the kick start lever:
http://i71.photobucket.com/albums/i1...psvel7f3vd.jpg

Removed the shifter:
http://i71.photobucket.com/albums/i1...psaheulndz.jpg

Remove the 6 bolts that hold the right side cover on. Gently pull that cover off:
http://i71.photobucket.com/albums/i1...psgq8ewzso.jpg

Removed the lower nut that retains the power valve lever arm:
http://i71.photobucket.com/albums/i1...ps1q5cn44h.jpg

Removed the upper nut that retains the power valve lever arm:
http://i71.photobucket.com/albums/i1...psfhffy0uy.jpg

RockefellerGG 03-31-2016 09:03 PM

Gently slide the lever arm off the posts and down through the hole:
http://i71.photobucket.com/albums/i1...psq6wlu49r.jpg

Remove the two bolts for the thermostat cover and the 6 cylinder head bolts:
http://i71.photobucket.com/albums/i1...psklimdefj.jpg

A view of the head underside. Notice the gouge marks:
http://i71.photobucket.com/albums/i1...psxfvzdseb.jpg

A view down the cylinder. Notice the damage to the top of the piston:
http://i71.photobucket.com/albums/i1...ps5dkahmbk.jpg

Remove the left side exhaust valve cover:
http://i71.photobucket.com/albums/i1...psuoxueckt.jpg

There are 4 nuts that connect the cylinder. 2 are located under the side covers:
http://i71.photobucket.com/albums/i1...psunhwryaw.jpg

A gentle tap with a deadblow hammer helped pop the cylinder off the engine. If you're not doing the bottom end, be sure to stuff a rag under the piston to avoid dropping anything into the bottom end.

Remove the circlip from one side of the piston and gently press the pin out from the opposite side:
http://i71.photobucket.com/albums/i1...psnmoeo0bg.jpg

The piston walls look pretty good. No real signs of blow-by or low compression.
http://i71.photobucket.com/albums/i1...pshm3mmxuf.jpg

This piston top took a beating:
http://i71.photobucket.com/albums/i1...psmkyii3wc.jpg

http://i71.photobucket.com/albums/i1...ps60ax3gnq.jpg

RockefellerGG 03-31-2016 09:04 PM

Notice the big piece of brass that was sitting under the piston:
http://i71.photobucket.com/albums/i1...psmkyii3wc.jpg

http://i71.photobucket.com/albums/i1...psjr7cfaq1.jpg

A couple good gouges in the cylinder wall, right above the power valve:
http://i71.photobucket.com/albums/i1...ps6umugyff.jpg

GGRider01 03-31-2016 09:25 PM

So... what's the verdict here? Foreign matter in the combustion chamber... who knows what's in the crankcase. I hope you document everything if you decide to do the bottom end - love these kind of threads.

RockefellerGG 03-31-2016 09:34 PM

Looks like foreign matter in the combustion chamber based on the gouges in the head and piston. I assume it locked up the piston and destroyed the connecting rod bearing. I don't know what the brass/copper piece is, but I'm sure I'll find out. Lots of slop in the connecting rod:

Not sure if photobucket videos work here, but here it goes:
http://i71.photobucket.com/albums/i1...psodb5u2gf.mp4

With the amount of debris down in the bottom, I'll be splitting cases and documenting. Just not tonight. ;)

RockefellerGG 03-31-2016 10:08 PM

Upon closer inspection, you can see a brass or copper spacer on the left side of the connecting rod. I assume there was one on the right side as well. This is the big piece of debris.

Not sure if a piece worked it's way up into the combustion chamber or if it started from the top down.

Chicken or egg?
http://i71.photobucket.com/albums/i1...pser12zviu.jpg

Jakobi 03-31-2016 10:23 PM

Quote:

Originally Posted by RockefellerGG (Post 165476)
Looks like foreign matter in the combustion chamber based on the gouges in the head and piston. I assume it locked up the piston and destroyed the connecting rod bearing. I don't know what the brass/copper piece is, but I'm sure I'll find out. Lots of slop in the connecting rod:

With the amount of debris down in the bottom, I'll be splitting cases and documenting. Just not tonight. ;)

It looks like one of the thrust washers off the bottom end of the rod.

and from reading further I can see you've found that too :D

barossi73 03-31-2016 11:00 PM

Id say both the chicken and egg are overcooked m8!

Rick 04-01-2016 12:38 AM

My guess is the crank bearing / thrust washer let go.....chicken.....

please keep this thread going!!!

RockefellerGG 04-01-2016 10:32 AM

Here we go! Time to split the cases:


Clutch Disassembly

Start by removing the clutch spring bolts, the springs and spacer:
http://i71.photobucket.com/albums/i1...psjqvdb68p.jpg

Slide out the clutch press plate, the friction discs and steels:
http://i71.photobucket.com/albums/i1...pshx1yaups.jpg

Drive down the safety washer using a hammer and screwdriver or punch:
http://i71.photobucket.com/albums/i1...ps5yjm3nwo.jpg

Remove the clutch hub nut. This is pretty easy with an impact wrench, but you'll need to hold the clutch hub. It can be done with a standard ratchet set, but will take some patience.
http://i71.photobucket.com/albums/i1...ps1cb8lbot.jpg

Remove the clutch hub. The washer may stick to the back. Keep an eye out for it:
http://i71.photobucket.com/albums/i1...psdvjtp3cx.jpg

Lift off the clutch housing:
http://i71.photobucket.com/albums/i1...psjlyhht8l.jpg

Remove the clutch bearings:
http://i71.photobucket.com/albums/i1...ps3bn6cnnt.jpg

Remove the bushing:
http://i71.photobucket.com/albums/i1...psghxqaeqa.jpg

And Washer:
http://i71.photobucket.com/albums/i1...ps9iethfji.jpg


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