First Top-End Rebuild on a 2007 EC250

[speedy08]

Hello, I am looking to do my first top-end rebuild on a 2007 EC250 that I picked up a week ago. Previous owner stated that it was on its original piston/rings. Starts and rides fine, but there is strange vibration noise. It sounds as if there is some rattling/vibration noise around the engine area. Maybe the Rekluse or the Power Valve? What else could it be, a bearing?

I thought that this would be enough for a top-end and fresh start.

I have a few questions.

First, a "B" is stamped on the back of the cylinder head. I am assuming this is the piston size that I need to order?

Second, is it as simple as replacing the piston, rings, gaskets or do I need to consider a replate, bearing change, etc?

Third, I noticed that the Power Valve is completely coated in carbon. Should I just pull it out and clean it with contact/carb cleaner?

Fourth, do it all myself or take it to a GasGas expert 2.5 hours away?

Any other tips or suggestions?

Thanks for the help guys!

[Rick]

I'm sure others will jump in.......

First, a "B" is stamped on the back of the cylinder head. I am assuming this is the piston size that I need to order?
Yes....allways a good idea to have the bore checked.

Second, is it as simple as replacing the piston, rings, gaskets or do I need to consider a replate, bearing change, etc?

Yes, doing a topend it pretty straight forward, wrist pin bearing, make sure you lube it with some premix before install, you don't want it dry. Get all the proper gaskets, the base gaskets come in different thickness, so make sure you get the correct gasket. Reed valve block gaskets as well, however not required to be removed for a topend job. But, I would remove and inspect and replace if the reeds are flaking on the edges, or not closing all the way. Inspect the bore, being such a new bike, one would not think that it would need to be replated, but you know.

Third, I noticed that the Power Valve is completely coated in carbon. Should I just pull it out and clean it with contact/carb cleaner?
Yes, check those little bearing in the power valve area. They should rotate freely and smooth. Clean or replace as needed. Take the p/v flaps out of the cylinder, and clean them. I use a wire brush with cleaner, to remove all carbon, I strive to get a polish like surface to prevent and carbon from building up. Once the bearings are cleaned up, put all back together and the operation should be very smooth and fluid. If there are any "rough" spots, in the movement of the flaps / valves figure out where fix it. It should be like "butter".....as my son would say

Fourth, do it all myself or take it to a GasGas expert 2.5 hours away?
Only you can answer that question....however there is a ton of great guys here on this site that can and will help you out. A topend is easy if you've done it before, but can be a little over the top for some. Having the proper tools, and space to do it makes things much easier. My approach to bike maintenace is much like a doctor, clean tools, clean work space, clean shop towels, all layed out ready to perform an operation. Being clean, neat and organized makes any job that much easier.....but, that me!

Any other tips or suggestions?
Yes, take your time, and prepare.......meaning, perform searches on this site using "key words" and you will find an answer to your questions. Print out the thread, that way you have the info out in your work area when performing your tasks, or drag the lap top out to the shop if you have WIFI? I have a binder full of threads from this site on broken down by parts of the bike, engine, frame, suspenion, ect, ect, comes in handy. Better than any OEM manual.
Good Luck, have fun and when in doudt....ASK!

[speedy08]

Thanks for your time and help Rick!

Upon measuring the bore, could it be possible that I need to jump up a piston size, say from a "B" to a "C" for proper clearance?

Should I be worried about any of the little or big engine bearings? Any simple tests to perform?

[Rick]

Speedy,

Upon measuring the bore, could it be possible that I need to jump up a piston size, say from a "B" to a "C" for proper clearance?
Yes, but measuring would be required to ensure proper fit, so the piston does not seize.

Should I be worried about any of the little or big engine bearings? Any simple tests to perform?
The wrist pin bearing should be replaced. The big end bearing should be inspected, there will be some side to side movement, but no free play, of the up and down type motion. Make sure you put a few drop of premix oil on the big end bearing for start up. A lite coat on the piston / rings as well.

Hope that helps

[speedy08]

Going good so far.

Removed the top end tonight. Inside of the cylinder looks great, I can see the cross-hatch marks, and no dings or strange marks of any sort.

Big-end bearing looks and feels good, has some side to side movement but no play when I move the crank up and down.

Going to BeaverCreek Cycle tomorrow in Lisbon, Ohio to pick up my new piston, rings, gaskets, etc. I am taking the cylinder with me as asked by the shop owner

Hopefully tomorrow night I will get to drop the new heart in, bolt it back up, add coolant, etc.

Now as far as the break-in procedure goes, does anyone have any recommendations?

Look forward to riding all day on Saturday

[Stoby]

Is this your first gasgas?Because you might just be hearing the normal noises they make ,I thought something was wrong with my 300 when i first got it 3 yrs ago but its just how this one and every other one ive ridden 200,250 sounds.I'm sure others will agree they make some noise
Stoby

[dank]

people have different viewes as to how to break them in. some say gently, others say not so gently. someone once explained in a thread on this site that the piston rings and cylinder are relatively rough when they are first put together, and dont fit snuggly together (not close to the exact words but the general idea is the same.) it is important that you properly warm the bike up before you do any hard riding on it. the person that posted the above idea said that to get them to properly fit together you need to ride the bike hard, as hard as you would race it, because the rings need to match the cylinder for when it is being used at its maximum potential. however, others say that it should be gently worn in, by using smooth gently throttle control. both hold solid logic, but my personal vote is with the first idea. just passing on what i (think) i remember.

[Rick]

Every has there own flavor on this topic!

I like to give it a good warm up for about 10 minutes. Cool down the cylinder to touch, then another warm cycle, go for a ride, no deep sand, or long hard pulls.

[speedy08]

Thanks guys for all the help.

Finally had a few free days to finish the bike.

I pulled the power valves out and gave them a good cleaning. There was quite a bit of carbon. As others have mentioned, oven cleaner works great. Just be careful to not leave it on anything aluminum too long. Gave the parts a good polishing too.

Put the new Athena piston and all the other new parts in (the wrist pin circlips gave me a short headache ), bolted everything back up, added coolant, gave her a few kicks and she purred to life.

I let her warm up for some time and then took her for a short ride in the back field. I will run a couple heat cycles, and then once broke in I will ride it like I stole it!

As a side note, this is my first GasGas and I am really impressed with the bike!

[Jakobi]

So did this fix the noise/rattle you first went chasing?