S3 head mod Q???

[redrider]

I have a 2011 250 and a 300.

Has anyone put a 300 S3 head mod on a 250?

I ask because of the mapping difference for the 250 and the 300. I've heard of fellas putting the S3 250 head on a 300, but not the other way.

Any thoughts on the subject?

[hannesd]

can't work unless you get the head cut to fit "in" the 250 cil bore.
the head sit a little in the bore and since the 250 has a smaller bore...
but it can be done if you make it fit, as goes with everything, just gotta make it fit...
but why not just cut your original head then?
adjust squish and correct CR?

Hannes.

[Jakobi]

The S3 head is a 2 piece item. You have the anodized outer, and then the actual chamber insert. The outer is the same for both. If you buy the correct insert for the cylinder it will fit (ie 250 insert on a 250 cyl, or 300 insert on a 300 cylinder). The powervalve and spigot will fit in both cylinders too.

So if you have 2 cylinders, and an S3 head, all you need is the correct insert for each one. Make sense?

[redrider]

Guess I should have said the complete cylinder and head mod. My bad...

Jakobi, I read some of your thread on the 300 convert to S3 250 and wondered if anyone was converting the 250 to a 300 S3. The reason I ask is I assume the 250s have a different mapping program than the 300s. Wondered how the 300 S3 conversion (with the 250 map) would compare to a 300 to 300 S3 mod......if at all.

My 2011 6 days 300 has the RB des mod for squish and the carb mod as well. My 2011 EC 250 is factory (right now).

[Jakobi]

I thought that they used the same cdi for both models. I'd have to check the parts fiche to be sure. Bolting the 300 top end onto a 250 won't cause any issues, but why would you want to own 2 x 300's when you could have one of each capacity?

[redrider]

Honestly, I'm just curious if there was an advantage one way or the other. I believe the KTMs have a different cdi 250 vs 300 so I wondered about the GGs.
My 300 is in need of a bottom rebuild and I'm still trying to decide who to have do the work. Which is what got wondering about the S3 mod etc.. The 250 is great as is....currently racing it since the 300 is down.

Any suggestions on a rebuild guy? Clay Stuckey recommends a fella in Tennessee I think, but if I do the S3 mod will I have to have that head shaved by RB des as well? (If the squish measurement is too high)?

[Jakobi]

I have a spare stock EC300 head laying around.. it would need to be modded.. but probably cheaper than buying an S3 and then modding.

Rebuild wise I have no idea whats local or close as I'm in Australia. Cooksey crank gets some great reviews. Considered doing the rebuild yourself and just having someone else do the crank?

[redrider]

I have considered it, but don't have the time at the moment. Trying to rebuild a jeep, race, work etc. I may have RB des. do the crank but haven't decided. Need to do something quick so I have the bike back after the summer break.