Cylinder removal question:

[FFRDave]

I am doing a top end rebuild on my 2005 Gas-gas EC 250. I am ready to remove the head and cylinder.

I would rather not mess with the powervalve at all, if it can be avoided. I looked at the owners manual parts diagram and I see no parts that move between the base and the cylinder.

< My Honda CR 250 has a little nub that turns the PV open or closed. The nub is in the base and the arm it turns extends through the cylinder to the PV assembly >

Can I just remove the cylinder and leave the PV untouched ?? I would like to Remove the cylinder, wrist pin, old piston; Install new rings, piston, needle bearing, wrist pin, and Reinstall the cylinder. I Will need to do an inspection and replacement of head O-rings.

[Brian VT]

The wire arm that actuates the p.v. can be disconnected at the top and left in place. It's one nut. The stud that this nut is on has been known to snap off. You can minimize this risk by melting the nylon out of the nut before attempting to remove it. I would buy a new "triangle" with stud ahead of time in anticipation of breaking the old one.

[FFRDave]

Is this nut & wire under the rightside PV cover or the left side PV cover ?

Do you have any suggestions for what to use to melt the nylon ? I have a soldering iron, a small butane torch, or a hot air gun.

What "triangle" are you talking about ?

[FFRDave]

The real question here is how to do so minimizing damage potential.

I know that the rules say that you should never strike the cylinder, or pry on it. I also noticed that there are only two 13mm nuts holding the cylinder on at the rear. Have I missed something ?? Can there really only be two, and on the back-side ?! What holds the front area of the cylinder on ?

I understand that I am being a real whimp about all of this. I dont mean to be, but the stakes are fairly high. We have two shops in my local area, and neither of them is willing to work on a Gas-gas. So, if I "F" something up, and cant get it together myself or with your help, I will have to drive my GG over the mountains (250 mi.) in pieces, drop it off, drive home (250 mi.) Wait a week (because I work during the week), and then drive back over to pick it up from the Burlington repair shop. I have some basic skills, but I have to go slow and careful. A little humility is way cheaper than driving a thousand miles in an old GMC pick-up and paying shop fees.

Thanks Brian VT for the tip on that stud under the right hand PV cover. I heated it up with my heat gun until the nylon deformed and that little 8mm nut came right off with no trouble at all.
I did call GoFasters and ordered a new triangle and a couple of gaskets.

[JoshP]

There are 2 bolts on the cylinder base towards the carb side and
then a bolt inside each power valve cover as well. Once you have removed the little nut for the power valve arm now you can pull on that arm to remove it from the triangle looking peice and place it to the right side. It will flex a little but you will not break it. Once all that is off now you can pull up slowly with a little force but hands only on the cylinder and as the piston starts to slide out of the cylinder place your hand under there to catch the piston. You do not need to touch the PV to remove the cylinder although compared to a Honda PV this will be easy to take apart and clean if wanted. I have found that the GG's are real easy to work on alot like a Kawa. GOod luck with it.

[eff]

I've yet to do a top-end on my GG, but it's gonna happen soon. What is the "triangle" you guys refer to?

[FFRDave]

Its the linkage piece between the PowerValve and the PV (somebody called it a Wire, but it looks more like a Rod with a loop in the end to me) actuator Rod that comes from the bottom end.

It is PN ME25616050

I will try to post a photo later.

[PEB]

Get the manual for the off the web, has all the pertinant info. Have confidence, you can rebuild it. I have done numerous top ends and in the last couple years bottom ends with little drama. I rebuilt my 99 after a main gasket failure and then sold it to a guy who used it as a comuter. He told he was buzzing back forth from Granite Falls to Everett on the thing(about 50 miles each way) with no problem. There is no need to remove the head from the jug and a trick I have used the last couple times is to install the piston intothe head then the wrist pin. The head does a nice job of holding the rings in place. Be sure to search on this site and the Smackover board for little hints.

Paul B

Paul B

[FFRDave]

Paul
I did separate the head from the cylinder because I have a water problem. during my last oil change, the oil came out all milkey white (grey). I have read on here that it is most likely a problem with the head gasket o-rings. I suspected the water pump empeller seal. I have a new seal, and I will be installing my new head gasket o-rings.

When I removed the head, I noticed smome marks inside the cylinder. They are on the left and right of the exhaust port and look like scrapes of some kind. The bike has never had any running problems and has plenty of power. The marks are on the piston too. I could still see the cross-hatch marks form the origional machining job at the factory. I could not detect any ridges or gouges on the piston or cylinder, but they are visable. They are each about 1/4" wide and extend the entire length of the stroke.

If someone will tell me how to post a photo here, I will be happy to do so.

[gasgasman]

Leaking head O rings will not cause your oil to be milky.
The oil can be milky from the water pump seal or water entering the transmission from riding through deep water.

You can hone the cylinder with a ball type hone to restore the cross hatch pattern.