Quick question - original top end set-up

R

rossi

New member
A quick question for those who have had the top end off their engine. How was it set up by the factory?

I am currently refreshing the top end on my recently bought EC300 (2010 6 days). The base gaskets were stacked to 1.1mm to match the exhaust port height and the holes in the head steady plates had been elongated to reach the cylinder head. This suggests to me that the motor has had a proper set-up for piston timing and squish. This impression is supported by the opinions of people who have ridden the bike and saythat it performs better than other 300's they have ridden. However, the previous owners confirm that no work has ever been carried out on the engine. For an untouched bike, it seems to have a non-standard set up. Anyone come across this before?
 
My 2010 EC300 Racing had 1.3mm of base gasket stack to time the ports towards top end. It also had 2.6mm+ of squish clearance. What's your squish?
 
To save a trip to the store, you can also use a drill to twist multiple thinner solder strands together to wind a consistent rope.
 
Jakobi said:
My 2010 EC300 Racing had 1.3mm of base gasket stack to time the ports towards top end. It also had 2.6mm+ of squish clearance. What's your squish?
Click to expand...

Squish with the new Wosner piston measures 1.8mm. It seems that somebody may have been here before me - strange as the original owner says he never did anything to it.
 
Every engine is a bit different. Tolerances vary between all parts involved (gaskets included).
 
1.8 is super dreadful. Just not as bad as some. Machine the head to get it down to 1mm without screwing around with gaskets will retain the same power character but be better in every way. BUT. You MUST carve some out of the chamber or the compression ratio will be way too high even with race gas. Heck probably with methanol.
 
ARGHH!

So I had everything ready this afternoon to machine the head. We turned down the hex section of an old plug to serve as a mandrel, screwed it into the head and mounted it up in the chuck. As soon as we turned the lathe on it was clear that something wasn't right as the head was bobbing up and down. A closer inspection revealed the plug hole has been drilled about 1mm off centre.

Without a chuck large enough to grip the outside of the head I don't see any easy way of machining the head to reduce the squish.

Now to plan B:

Remove the barrel and re-install with thinner base gaskets.
This will alter the port timing to give more bottom end, which is fine because that is where I am lacking when climbing hills. Obviously I can't go as close on the squish as I would like as this will push the compression too high.

I am going to have a look at motopsycho's pics though and see if i can relieve some of the compression by adding some Singh grooves. This won't give me much but it will hopefully give me enough to close the squish a bit. Fortunately I am not using the bike on the road but we have some pretty long, steep, full throttle fire break hills here in Cyprus.

I may also have a look at the power-valve flap. Another thread from motopsycho has a description of how he filed back a step on the flap which gave extended top end. To my thinking this will effectively raise the top of the port a fraction which the flap open to compensate for the barrel sitting a fraction lower.
 
That socks. A sparkplug is not much to grip hold of.
So as a check. . .no. . . That's just odd. Surely they would have turned that thread and drilled/tapped the spark hole at the same time.
Sorry out of ideas.
EBay?
 
On one of my GG 250 heads the spark plug was drilled a degree or 2 off perpendicular which was a nightmare to cut the face for squish. I wonder if they mill the heads at the factory with a 4 jaw chuck or some tool that holds the head from the head stud holes?
 
Zman said:
On one of my GG 250 heads the spark plug was drilled a degree or 2 off perpendicular which was a nightmare to cut the face for squish. I wonder if they mill the heads at the factory with a 4 jaw chuck or some tool that holds the head from the head stud holes?
Click to expand...

That sounds like mine, looks ok from the top but when you look at it closely the hole is clearly not central inside the dome.
 
I've been trying to think of a clever way to build a mandrel to tool. But it doesn't make machining he face possible.
If you search different country's wreckers people must have another head and pretty small to post.
 
For the moment I have removed 0.86 cc from the head by filing some Singh grooves copying Motopsycho's pics. I have crunched the numbers and removed base gaskets to set the squish at 1.5mm which should hopefully be OK. It turns out that my squish was originally even wider (2.2mm) as I had been been using a vernier to measure the piston depth and the height of the flange on the head, but discovered my vernier is out - measurements now taken properly with a micrometer and solder.
 
(F5) said:
I've been trying to think of a clever way to build a mandrel to tool. But it doesn't make machining he face possible.
If you search different country's wreckers people must have another head and pretty small to post.
Click to expand...

I just bought a nice steel piston stop and am using it as a mandrel.
 
Update -

With the Singh grooves filed in the head removing 0.8cc the engine is now running with a single 0.3mm base gasket.

Less than ideal for the height of the exhaust port, and slightly greater than 1mm squish but is it like riding completely different bike. Torque off the bottom end is fantastic and it pulls seamlessly into the power band.

Running 50:1 98 RON (Euro) with motorex fully synthetic, the central plug insulator is a perfect match for a bar of milk chocolate and absolutely no sign of detonation.

Fuel range is improved - I haven't done more than 1/2 a tank in one go yet but it looks like it will be good for close to 100km. Jetting is also consistent from 0 - 2000 m (N1EF#1, 165, 35)

I'm not sure why but the bike also seems to be a lot smoother with less vibration through the footpegs

The only gripe is the burble on the transition between closed and partially open throttle which makes the throttle an off / on / more affair rather than feeding in smoothly on the initial opening. Now that everything else is working I can experiment with the needles though.
 
rossi said:
Update -

With the Singh grooves filed in the head removing 0.8cc the engine is now running with a single 0.3mm base gasket.

Less than ideal for the height of the exhaust port, and slightly greater than 1mm squish but is it like riding completely different bike. Torque off the bottom end is fantastic and it pulls seamlessly into the power band.

Running 50:1 98 RON (Euro) with motorex fully synthetic, the central plug insulator is a perfect match for a bar of milk chocolate and absolutely no sign of detonation.

Fuel range is improved - I haven't done more than 1/2 a tank in one go yet but it looks like it will be good for close to 100km. Jetting is also consistent from 0 - 2000 m (N1EF#1, 165, 35)

I'm not sure why but the bike also seems to be a lot smoother with less vibration through the footpegs

The only gripe is the burble on the transition between closed and partially open throttle which makes the throttle an off / on / more affair rather than feeding in smoothly on the initial opening. Now that everything else is working I can experiment with the needles though.
Click to expand...

Needle will fix it now.

Been posted numerous times.

Squish, float height, jet and forget..

I chased myself around in circles for a long time before I worked it out. On my 2013 the head was sent off immediately following the break in ride.
 
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