CG250 Head - A Closer Look.

[JerryHawk250]

More aggressive like you did. I have some abrasive buffing wheels coming in tomorrow so I can polish it out. https://www.amazon.com/gp/product/B075PVWJXX

[Megadan]

Originally Posted by JerryHawk250

More aggressive like you did. I have some abrasive buffing wheels coming in tomorrow so I can polish it out. https://www.amazon.com/gp/product/B075PVWJXX

I bought those exact ones lol. They work good for polishing up the exhaust side, which I just finished doing.

[JerryHawk250]

Originally Posted by Megadan

I bought those exact ones lol. They work good for polishing up the exhaust side, which I just finished doing.

For the price I couldn't pass them up.

[JerryHawk250]

Originally Posted by Megadan

I bought those exact ones lol. They work good for polishing up the exhaust side, which I just finished doing.

Picture updates????

[Megadan]

I get home tomorrow. I will try lol

[Megadan]

Here Jerry. I tried to show it, but Cameras don't do a good job of showing the finish. It's a lot more shiny than it appears lol. This is my finished product after a bit more work. I trenched out the sides of the valve guides and blended them in more with the bowl. No more ridges!

[BlackBike]

Surely you will feel a little crisp-ness in the throttle now. That looks like a nice air molecule slide to me

[Megadan]

Originally Posted by BlackBike

Surely you will feel a little crisp-ness in the throttle now. That looks like a nice air molecule slide to me

Oh, I think it will be a bit more than crispness. Full on burned and crunchy. I will let these similar angle before and after shots speak for themselves.

I tried to get the angles exactly the same, but not quite perfect. Close enough to make a point though. I still have a little more I want to do on the intake side, but for the most part I am done.

[pete]

the shape looks good..
keep at the finish... you will get there..it takes time..

[Megadan]

Originally Posted by pete

the shape looks good..
keep at the finish... you will get there..it takes time..

I am not too worried about the finish. It's smooth to the touch, but the camera shows a lot of the imperfections you can't see with your own eyes, mostly small scratches. It's the shape of the port that matters the most. Obviously, I will still work at it a little bit, but it's 99% there at this point.

[JerryHawk250]

Looking good .

[ben2go]

The ports really opened up nicely. A regrind cam would help but with a single lobe, how much would it really help. Would it be possible to play around with offsetting the cam sprocket? I'm not sure if it uses a key, a pin, or some other means of keeping them together and in time.

[Megadan]

Originally Posted by ben2go

The ports really opened up nicely. A regrind cam would help but with a single lobe, how much would it really help. Would it be possible to play around with offsetting the cam sprocket? I'm not sure if it uses a key, a pin, or some other means of keeping them together and in time.

I don't doubt that the right cam profile would help. Sharing a cam lobe doesn't mean you can't get more out of a new cam profile. CCW surely managed to get a lot more out of their engine with one. (23whp from a counterbalanced cg250 is nothing to snort at).

For me, it's more a matter of useable power. I want to try and keep a flatter power curve. That is why my intake porting is a little less aggressive than the exhaust side. Even if that means I sacrifice a little peak hp, I am okay with that. These engines already have a larger than necessary intake port, so simply focusing on smoothing transitions and reducing the pinch point at the valve guide is more than enough.

The exhaust side is the greatest restriction in these heads, bar none. Being able to evacuate the exhaust from the cylinder as quickly and efficiently as possible will make more room for fresh air and fuel, which will increase the efficiency of the intake side. The roof area on an exhaust port is the best place to perform porting for making more power, and also where these heads need the most work. You will notice that the majority of my porting work focused on opening up that exact area.

[BlackBike]

Meg...can you get an app that will measure g force or some kind of hp simulation so you can take road measurements? Saying this since it seems you indicated previously that the dino fell thru. I think this would be a good way to at least quantify what you have done. No, it would not be accurate/ perfect and all that but just like a inaccurate bathroom scale, as long as you use the same one you know what you have gained or lost.

[Megadan]

Originally Posted by BlackBike

Meg...can you get an app that will measure g force or some kind of hp simulation so you can take road measurements? Saying this since it seems you indicated previously that the dino fell thru. I think this would be a good way to at least quantify what you have done. No, it would not be accurate/ perfect and all that but just like a inaccurate bathroom scale, as long as you use the same one you know what you have gained or lost.

My plan is to try and get this bike into the dyno sometime in Feb. or March, and then install the head and tune the carbs. again. I can do without a before/after dyno of basic bolt ons, because realistically we all have a rough idea of what a bolt on CG250 can produce in terms of power. I refuse to let the head work go unquantified, because that is a bigger unknown.

I think the only thing I will leave out is a dyno with the VM30 carb. The VM26 will be far easier to adjust the jetting for and get back on the road. Plus, I think it would be more realistic in representing what most Hawk/Bashan/TT owners would want to do. The VM30 will require a lot of tuning from scratch.