High Compression Head

[GMP]

They are all factory anodized so if it was cut after the fact it would be bare aluminum.

[GG27]

Hi, I bought an MC250 head which has catalog part number MC250116000 printed on the packing with CR 250 2001 also printed, while the casting has ME25-30916000 molded on the head. I'm about to change my stock head and I'll check out the differences on squish width and compression and of course the added performance.

[GG27]

I justs opened up my top end for a piston change (about 70 hrs) and had a good look at the difference between the standard EC head and the new MC head I have bought.

Well to my suprise the MC head had a norrower squish width (about 8mm while the EC head has a width of around 13mm!), the same deck height (3mm) and a larger combustion volume compared to the EC head.

I think I'll just keep the EC head and use one 0.5mm base gasket to increase the bottom end. The factory had one 0.5mm and one 0.3mm gasket!

What is your opinion? Is the MC head shaped to increase the hit or what?

[GMP]

All other things being equal, the narrower squish would favor top end. However, its all about effective squish. If the head is cut so that the squish angle does not match the piston dome close enough (higher clearance toward center of head), and the clearance is high overall, a wider squish band will have a narrow effective squish.

[GG27]

Thanks GMP,

Comparing the squish angle, they are equal so I went ahead and kept the original EC head but put in one .5mm base gasket. I still have to run the piston and rings doing a few heat cycles before I can see any difference in the bottom end.

As you stated the MC is shaped for more top end power, how would it compare with the EC head for bottom to mid pull?

[GG27]

Well, I run in the piston and put in a #7 slide,(I was using a #8 slide before) and the bike really has a nice strong linear pull from really low to a health strong mid and top. really pleased now! No hesitation at all with the LTR needle and PV cover working really well.