EC 125 piston cross over and Jetting

[GSP]

Hi Guys, after many years of temptation I have finally become part of the Gas Gas family. I have just collected an 05 EC125, in fair condition, she has no compression seems to have been neglected for a while. After some research, I went and purchased a piston kit for an 98' YZ125, as it mentioned in a few places that it could be used without any problems, and out here in Africa it is literealy half the price of an OEM. There are however a few differences in the pistons, the OEM has a flat top where as the YZ has a dome top, the OEM has 4 tiny holes down the one side the YZ has only 2, and lastly the YZ has a window or port on one side, not sure if any of this will infulence things, Is there anybody who has expereinced similar who can offer some help. I am also looking for help with the jetting, we are at about 2000m ubove sea level, and the bike currently has a 168 main and a 65 pilot.
Any help would be greatly appreciated regards GSP

 

[GMP]

The older GG 125 I have experience with is an exact crossover with the '98 -'00 YZ125 piston. I've done two top ends on it so far and it works perfect. Sometime after that they went to a flat top and almost certainly the head is different to match. The holes are for lubricating the exhaust port bridge.

Sounds like it won't work in the '05. I'd bet there is something that will though as I doubt GG uses a custom piston. The bore and stroke is still the same, and same as other 125s. Time to do more research.

 

[jayc]

Hi Guys, after many years of temptation I have finally become part of the Gas Gas family. I have just collected an 05 EC125, in fair condition, she has no compression seems to have been neglected for a while. After some research, I went and purchased a piston kit for an 98' YZ125, as it mentioned in a few places that it could be used without any problems, and out here in Africa it is literealy half the price of an OEM. There are however a few differences in the pistons, the OEM has a flat top where as the YZ has a dome top, the OEM has 4 tiny holes down the one side the YZ has only 2, and lastly the YZ has a window or port on one side, not sure if any of this will infulence things, Is there anybody who has expereinced similar who can offer some help. I am also looking for help with the jetting, we are at about 2000m ubove sea level, and the bike currently has a 168 main and a 65 pilot.
Any help would be greatly appreciated regards GSP

I did the top end on my '02 125xc recently with a Wiseco '00 YZ piston - I popped it in as it comes out of the box, and it works fine. As for jetting, your pilot seems extremely rich - I am running a 45. The 168 main sounds OK - that's what is in my bike now, although the 168 is still a little on the rich side.

There's a bunch of people around that are running mains way up in the 185-205 range in their 125s. If you want a 20HP bike that smokes like a mosquito truck, that's definately the ticket - my bike came with a 195 and would barely run at WFO, just bog and belch smoke at 10,000,000 cu.ft/min. I worked my way down to the 168 and now the bike near tears my arms off (at least for a 125).

JayC

 

[GMP]

You can't assume that is true as a general statement. There are many variables. The needle taper structure in particular will dictate the main choice. The '01 runs awesome with a DGH needle and a 190 - 195 main @ 1000'. What I learned jeting this thing from scratch is that low end goes completely away if its just a little lean, its a dramatic difference when jetted just rich enough. Stock, it was very unimpressive and I'm sure the reason for a less than stellar reputation, at least for the older bikes.