Valve Seals Replacement

[jimmu]

I'm curious if anyone has replaced the valve seals in the head of their 4 stroke Buddy. In an effort to combat oil consumption on my 125 with 17,xxx miles I'm thinking of replacing the oil seals and lapping the valves while I'm at it. Perhaps new rings and a hone wouldn't be a bad idea at that stage as well. Let me know if you have any insight or have experience with this. I'd also like to know if I should get some generic gy6 viton seals or stick with OEM.

[dasscooter]

Upgrade the head instead.

[jimmu]

Also, I've tested the static compression and I have 155 psi (while cold). Is that within spec? What is the spec?

[jimmu]

Upgrade the head instead.

Seals are so cheap tho... I also plan on keeping it a 125cc so what would be the benefit of upgrading the head? Which head do you recommend?

[babblefish]

I would keep the stock head. The quality of PGO castings is very high, as good as any Japanese made castings. Seals are cheap, so I'd just go OEM. If you have the skills or know someone that does, do some port massaging to improve gas flow. If you don't want to remove the head, you can just replace the seals without even removing the head if the correct valve spring compressor is used. The trick is to bring the piston to TDC then stuff the cylinder with light rope through the sparkplug hole. This will keep the valves from dropping into the cylinder. When done, pull the rope out.

Of course, if you're planning on lapping the valves and/or honing the cylinder, then the head will have to come off. Some will say if you're going to all that trouble, just go with a BBK since the price difference is minimal, but keep in mind that PGO's emissions control design is different from everyone else's so a generic BBK will require a little bit of modification to make it work.

[Mikestib1]

Replace the rings, cam chain, valve guides, and seals. Then your good for a long time. 17000 miles at 7000 rpm is a lot for any air cooled motor.

[jimmu]

I think for now I'll just do the valve seals with the head on and monitor the oil. I'd like a definitive answer for compression spec if anybody knows that. I am now interested in some "massaging" of the head at some point, is that something that could be done at home with a dremel or not?

[paracer]

I am now interested in some "massaging" of the head at some point, is that something that could be done at home with a dremel or not?

Yes. There are some good options out there to choose from as a starting point, or you can use your stock head. A Dremel can be used to smooth over the ports and clear some of the restriction around the valves.

I posted about the route I took in this thread: topic29461.html
The real good stuff starts with posts dated 11/3/16.

[babblefish]

I think for now I'll just do the valve seals with the head on and monitor the oil. I'd like a definitive answer for compression spec if anybody knows that. I am now interested in some "massaging" of the head at some point, is that something that could be done at home with a dremel or not?

I did mine with a dremel, but I've done quite a few engines. If you plan on doing the massaging on your own for the first time, good luck. Done right, there is some hidden power to be had, but done wrong, well, generic replacement heads aren't that expensive...

BTW: new valve guides are not available, at least not from scooterloungeonline. New valve guide seals are, however. Cheap at $2.30 each.

Attached is an excerpt from the PGO G-Max service manual showing the compression pressure at 750 rpm. The engines between the Buddy and G-Max should be basically the same, at least the head/cylinder assemblies.

12 kg/cm2 = 170 psi