EC250 to 300

[GG27]

Hi, I know this question has been asked many times in this forum but I'll ask it again.

Since I'm about to change piston on my EC250, I was thinking if its worth going to a 300 conversion or just spend the extra money on improving the 250. I can rebore my carb to 39mm and add a power now and set my squish to 1.4mm with some good port matching? I really like the 250 screams from mid to top but just want that little more off-idle pull. I'm also looking for a lighter 2-K-2 ignition.

Thanks

[GG27]

Any opinions will be much appreciated

[MattR]

You could have 3 scenarios. A full 300 conversion, a hybrid 250/300 conversion, or 250 makeover. The full 300 conversion is probably the most expensive (new cylinder, head, PV, piston, CDI). The hybrid 250/300 would be similar in price to the 250 makeover (like you described). The hybrid would be a pick & choose thing... 300 piston, cylinder, head, and PV, but with the 250 CDI and ignition. The 250 makeover could be done in increments such as head and porting mods first, then carb mods, then ignition swap, etc.. until you find the sweet spot.

For me, I would choose the 250 makeover. You keep the great traits of the 250 bike but improve on it's qualities.

[GG27]

Thanks Matt for your reply.

I think that the PV is the same for both 250 and 300 so I won;t have to change it. About the cdi, I have a strange feeling that the cdi on the 250 and 300 '08 models is the same, which makes my 250 so "soft" of the bottom. The parts catalogue has the same number for all EC and MC models now? The color of my cdi is black.

[tm_enduro]

It seems to me that the factory team uses a 300 crank and 250 piston. This has also been a favorite combo of KTM racers. There was a company a few years ago that specialized in stroker kits (relocating the crank pin, installing a long con rod, and adjusting the deck height, etc).

[widebear]

Originally Posted by GG27

Thanks Matt for your reply.

I think that the PV is the same for both 250 and 300 so I won;t have to change it. About the cdi, I have a strange feeling that the cdi on the 250 and 300 '08 models is the same, which makes my 250 so "soft" of the bottom. The parts catalogue has the same number for all EC and MC models now? The color of my cdi is black.

I think the power valve flappers are different unless the cylinders 250-300are completly independent castings, the 300 one should be narrower to compensate for the extra bore dia, cdi's are the same as far as I can tell and a recent post on the subject confirms this view, that if working properly they ramp up to full advance right of idle. The reason your bottom end is softer is because of elementry physics and that huge ign rotar.You understand theres a reason fat men make better door crashers than great sprinters!

[GG27]

Widebear, maybe your right about the PV differences, although the parts list has the same item for both 250 and 300's.
I'm still searching for a 2K2 ignition since as you say Fat Guys can't be sprinters. So I'll go ahead and get my piston and rings changed with head squish tightened and port matching.

Thanks again

[Ud_luz]

Have you played around with the ignition timing too? If you pull the ignition cover and flywheel off you'll see a small metal plate under one of the stator screws preventing you from rotating it. This plate may be removed allowing you to adjust timing. Just a few degrees +/- can make quite a difference.

I'm more interested in trading my 2K2 for a 2K3. Let me think about this one a bit.

Later, Bill.