Need help on top end rebuild

[gasgasman]

If you can't snag your finger nail on the grooves, you can use a ball type hone to clean up the cylinder.
I use one on my cylinder to knock the glaze off when I'm doing a top end.

[rpduc]

Thanks GGman. I was just talking to my Duc mechanic and he suggested the "dingleberry" hone too. That would be cool if I didn't already have a new Vertex "A" piston. At least I think I'd need an oversized one and prolly end up costing me as much as the replate.

Glenn, or anyone, I tore apart the powervalve and there is NO washer on the left side as shown in the exploded view in the Powervalve info in Tech Articles. There is a shoulder machined onto the end of the left side PV "cylinder" but no washer. I assume that would be that the missing washer you mentioned. Is that shoulder there on those bikes with washers too?

Also the "hat" shaped alu (?) bushing on the right side is SLOPPPPPY loose on the "shaft" and there is probably 2mm of end gap between it and the bearing if you push the bushing tight one way or the other. I hope that makes sense...

Oh, and one other stupid question. I pulled the nipple for the PV drain off and I thought it was plugged. It has just a pinhole opening in it. Like the drill didn't quite make it all the way through. Is that thing supposed to be that way or should I drill it out the rest of the way?

[GMP]

Ross,

OEM piston supplier has changed throughout the years. Up to '03 or '04 it was Wiseco, then Wossner, and Vertex. Thats why I said make sure you specify Vertex rings because "GasGas 250 rings" could be one of three parts! The same Vertex piston has always been OEM in the TM250, and I beleive available from Vertex through a distributor.

I was refering to the "hat" or shouldered washer on the right side. Those parts were hand press/tight slip fits on both of my previous bikes, the '07 PV has not been apart yet. I do not remember a shoulder on the left side drum valve, or the "hat" being a very sloppy fit on the right side drum. The drums do have a lot of axial play and clearance to the cylinder, so they can function when fouled, like a military firearm. I have a pic on my home PC somewhere of my '03 PV parts during disassambly, I'll try and find it tonight. I don't think any of this was changed from '03.

The drain nipple on the lower left side has a small hole from my experience, and some came with tubing zip tied shut, to limit oil dripping for emmisions reasons as the EC bike is street legal in Europe. The right side vent on the cylinder is also your trans vent and should have a larger hole.

[GMP]

Here are the PV parts from my '03:

[rpduc]

Thanks Glenn,
Yup, looks like mine. (big surprise)

That alu "hat" spacer on the left was only 4 bucks so I just had Mark at GF send it. We'll see if it fits any tighter than what's in there now. If I push the bearing tight up to the shoulder on the shaft I have about what you show in the pic for space for the hat spacer slide back and forth.

The "missing" washer I was talking about is shown on the parts diagram between the drum and the two bearings on the right. I don't 'spose you remember if you had one in there... I ordered that too since it was so cheap and I guess it should be in there if it's on the parts list? I don't know if the PO had this apart but if he did it would not surprise me if a few parts were missing...

[GMP]

I'm pretty sure its in there. Its been awhile but I would have noticed if it was missing, if things go smooth you tend to not remember.

Get the bearings too, cheap and not worth cleaning. On my '00 I had a the right side bearing go bad and it rattled a lot more than normal. The bearings only operate over the same arc of rotation, and are lubed by spooge oil. The bearings on my '07 appear to be the sealed type, at least on the outside.

That bike must have been apart before because '05s did not come with Wiseco pistons as far as I know. Once its been potentially hacked, anything is possible.

[rpduc]

Get the bearings too, cheap and not worth cleaning. On my '00 I had a the right side bearing go bad and it rattled a lot more than normal.

Yup got the bearings, GF had Vertex rings, wrist pin etc. and all gaskets. I also ordered swing and linkage bearing kits. I was surprised to see that the big internal bushing on front of the linkage was cracked??? All were well lubed and free, but the cracked one made up my mind. Bit of a struggle banging out the swingarm bolt...

Carb is off to RB Designs, suspension done late last fall. She should be like a new bike. I'm tuned for spring.

[gaspipe]

I had Millenium replate the cylinder on my 300 this winter. Send them your new piston when you send the jug, and it'll be honed just right when you get it back. Turn around was under two weeks door to door.