Flat Top Piston

[papatrx]

For years I have been thinking about trying a CR250 flat top piston in my bike but have never gotten around to it since they have different wrist pin heights and the space plate customization I would have to do. I know some people have shaved the head on the domed trx piston but the extra heat build up in the center of the piston always concerned me. Now Wiseco makes a flat top piston for the trx250r with the wrist pin 5 mm higher like the 87 -89 models with the 130 mm rod. They have added about 20 grams of weight over the pro-lite to the top of the head to help with heat containment.

My question is have any of you tried this setup and what did you cut the squish angle on the head to? I know some of the CR guys are running 5 to 6 degrees and want to know what is a good number for the trx cylinder and also are you using the small dome head or the large one and how much change did you make to the dome to get compression back up?

And finally have you had any issues with extra heat build up since the flame is now traveling down the center and not being pushed out to the side walls?

[beerock]

I was just looking at wisecos catalog and there making a flat top piston for the trx now.

[papatrx]

Exactly, I have been thinking about this for a while now and about 6 months ago also noticed that Wiseco offers it, which now is really making my little peabrain start to work. I know that with the flat top, the squish needs to be changed to now match the flat area, but what are the recomendations from someone who has tried this. I know most of the CR guys with flat tops run from 4 - 6 degrees of angle

Also, I need to reduce the head chamber volume to get my compression back up while reducing the squish angle.

I assume that the flame travel should be much better since it is not going to be pushe out to the sides also creating better heat transfer, but that is my assumption.

I also assume that the bottom end will be much crisper but what about up on top? The nice thing is with the flat top the port timings will be exact, no rolling through the champhered edges.

I have many unanswered questions about this and am looking for help from anyone, if you know of anyone that's done this I would love to contact them.