New cylinder head

[Kent A]

I've finally finished the combustion chamber inserts for the cylinder head that I bought from France earlier this year. The combustion chamber that came with the head was useless so I designed two chamber inserts of my own instead. Both are designed for 1,2 mm squish height and slightly higher compression ratio. The only difference between them is the installed height, one is designed to use the standard cylinder base gaskets and the other one allows the cylinder to be raised 0,5 mm to mimic the exhaust port timing of the EC250.

In the picture the "useless" combustion chamber sits to the left and the two home made chambers are placed in the centre and right side of the picture.

I'll install the new parts after I return from my Christmas vacation and post a report as soon as I've ridden the bike again.

Kent

EC 300 2006

[Dave]

Very nice! I'm looking forward to your ride report.

[Brian VT]

Too cool.
I program a 3 1/2-axis (ho-hum) CNC wood router at work but I dream of someday getting, or having access to, metal-working machinery and
making one-offs like that for fun and function.
I hope the results of your work are favorable and I look forward to your report.

[RBD]

In the picture the "useless" combustion chamber sits to the left and the two home made chambers are placed in the centre and right side of the picture.

Kent A,

That is a nice head you have there, looks like the actual head casting has two water spigots? Also the chamber on the left that you called useless (the one on the left), did it come with the head? It kind of looks like a blank chamber that is to be machined to your own specs....?

I hope your chambers work the way you want them to, but hey, having removable chambers lets you experiment and have the advantage of swapping chambers for different riding styles.

My hat is off to you, at a boy.

Ron

[Kent A]

Ron

I found the French manufacturer of this cylinder head while searchig the net. The head is not cast, it's machined from aluminum. The water spigots are threaded into the head.

I also thought that the picture they sent med showed a blank insert but they claim that they've "invented" the combustion chamber design. I'm no expert but none of the features of their combustion chamber makes sense to me.

I expect to make a few more inserts of my own as soon as I learn how to calculate squish velocity.

Kent

[Kent A]

I've finished the combustion chamber inserts and installed the cylinder head on the bike. The cylinder is now raised 0,5 mm by means of a 1,0 mm base gasket instead of the standard 0,5 mm gasket.

The exhaust- and transfer ports now line up much better with the piston now that the cylinder is raised. On the EC300 the transfer ports are shrouded slightly by the piston at BDC and lifting the cylinder helps a bit.

With my +0,5 mm insert the squish measures 1,24 mm around the edge of the piston and CCP (Cold Cranking Pressure) is up slightly (5%).

I have yet to ride the bike after installing the new head but may try to go for a spin tomorrow if it's not too cold.

Kent

[iancp5]

Well, how'd it go?
Or was it too cold?

(edit)
Oops forgot the time difference you may be riding as I wrote!

[Kent A]

It was a bit on the cold side today so I just took the bike for a short ride around the block to check for leaks. Everything seemed OK and the bike runs fine. I expect to be able to hit the trails next weekend for some proper testing. I'm also waiting for a GG SM 250 thermostat that I've ordered. I'm tired of relying on covering the radiators for cold weather riding.

Kent

[Kent A]

I managed to pinch a nerve in my back the first time I took the bike out for a "proper" ride with the new cylinder head. Two months later my right foot is still tingling like it's asleep but at least I'm able to ride again.

Today I finally got to ride the bike in the woods. The cylinder head modification really has made a big difference. With the extra 0,5 mm cylinder base gasket, squish set at 1,2 mm and raised compression ratio it's a lot more powerful than a std GG 300. It really comes alive when "on the pipe" and there is more overrev than before. It's just about as powerful as is practical för the tight woods riding that I do most.

The new cylinder head also allows me to run the "shorty" Doma silencer with the pipe without loosing power down low.

Here's a list of the mods so far:

LTR jet kit
VF2 reedcage (no spacer) set at low tension, instead of the std VF3
Raised cylinder (0,5 mm) to simulate EC 250 port timing
New cylinder head with interchangeable inserts, now running an insert that offsets the raised cylinder and maintains the desired 1,2 mm squish with slightly higher compression ratio.
Doma pipe and silencer
LTR powervalve cover

I'm very happy with the way the squish modification has changed the bike. The two mods that make the most difference are the VF2 reedcage and the cylinder head/squish adjustment.

Kent