250 EC head mod

motorex · #1 02-13-2011, 05:26 PM

I have attained alot of GG knowledge threw this site and have some to give back now. There is a guy on KTM talk who does head mods. He has been getting very positive reviews. Since I was putting a new piston in my 250XC I sent my head to him. After i got it back I was most impressed. I asked him (Mike) if he could do a GG head and he said he could do same thing. So I sent it to Mike, while putting a new piston in my sons 250EC. I did take a pic of the head before it left and compared to what i got back. The combustion chamber is much smaller. 1st thing you notice is the kicker takes more force to turn the engine over. My 250 has much meater power now and you certainly notice the difference. My son commented that not only did his bike pull harder but seemed to run cleaner. Its the best $150 I ever spent. And thats for both heads. Web site is cycleplayground.com

One more little tidbet is the front pads from a 07 YZ250 fit on the front of my sons 07 250EC.

case-racing · #2 02-13-2011, 05:55 PM

can you post the pics please, i run a 300 in a quad and in need of a full rebuild, living on the wrong side of austalia doesn't help either but cheers for the heads upon a good service provided.

motorex · #3 02-14-2011, 11:28 AM

Quote:

Originally Posted by case-racing

can you post the pics please, i run a 300 in a quad and in need of a full rebuild, living on the wrong side of austalia doesn't help either but cheers for the heads upon a good service provided.

No. I just took a pic of the head before. Didnt take one after. My orange 250 is much like my old 300 now with bottom to mid pull. But it still retains the smoothness of a 250 and revs out better than a 300. I havent ridden my sons EC yet, but he is very pleased with his bike.

GMP · #4 02-15-2011, 09:27 PM

Sounds like he just milled it and upped the compression. Did you measure original squish and compression, and specify new compression and/or fuel ? Squish should be about 1mm across the band for a 250 regardless of the compression. With the correct squish and not too much compression you can gain low end not loose top end.

motorex · #5 02-16-2011, 12:15 PM

On the work order I asked for overall power increse. I already knew his standard head mod was supposed to run on pump premium. I can say the GG head was cut. The bowl looks to be half the size it was before. I dont recall squish but I know he stresses the importance of that.

Such a good power gain. Why wouldnt the head come that way from the factory? Not just the GG but my KTM as well. Are they keeping compression that low to avoid possible detonation?

GMP · #6 02-16-2011, 12:39 PM

First, its impossible to get an accurate squish clearance across the band without providing initial measurements, so it sounds like he took a guess. The idea in not only to reduce squish, but to cut the head precisely across the band to match the piston dome and maintain that clearance. This is why RBD requires a solder crush sample. As far as compression, again initial data so the final head volume can be adjusted. Basically its done like this: Head milled to bring squish at inside band to spec, band angle cut to even squish across band, head bowl volume adjusted for desired compression.

Compression should be about 200PSI max for pump fuel in a 250. The reason the bikes(all bikes) come set up loose is because as crappy as fuel is here its worse in other places.

Mine runs hard across the range with best gains off the bottom, and is great on gas. Compression is 192 PSI. I'd be interested in what you ended up with.

motorex · #7 02-16-2011, 05:28 PM

I was in a real hurry to get bike together Sat so we could ride Sunday. I never even thought about checking the compression. I have a nice guage and will check both bikes. The only solder I have is .88mm. I will have to aquire a piece of larger sized solder and I will see what the squish is too.