Easiest/Cheapest way to get some more bottom/mid grunt

[Zman]

To clarify, you can change the base gasket below the cylinder to improve the low end power. The head gasket on a GG is a pare of Orings and they should not be modified.

You should be able to measure the thickness of the base gasket without disassembly of the engine. Very often that gasket may hang outside of the engine so you can put a caliper on it or trim off a loose piece with a razor blade. If this gasket is already the thin gasket (0.014 inches), you will need to get the head machined to reduce the squish measurement.

[swazi_matt]

Originally Posted by Zman

To clarify, you can change the base gasket below the cylinder to improve the low end power. The head gasket on a GG is a pare of Orings and they should not be modified.

You should be able to measure the thickness of the base gasket without disassembly of the engine. Very often that gasket may hang outside of the engine so you can put a caliper on it or trim off a loose piece with a razor blade. If this gasket is already the thin gasket (0.014 inches), you will need to get the head machined to reduce the squish measurement.

What are the implications of doing this if it makes the edge of the piston higher than the exhaust port at BDC?

[Capz85]

The last mod I did was to install the lectron carb, really improved bottom end very responsive at low revs

[memphis2857]

To answer your question about how to get squish corrected. You will measure your squish and then send it off to someone like Ron Black of RB designs. He does great work with a reasonable turn around time. He will mill the outer edge of the head down to lower the squish clearance. Then he will reshape the combustion chamber to compensate for the loss of volume. You can have a machine shop do this but they may or may not reshape the combustion chamber. If they don't it will in turn raise your compression ratio and you may end up having to run race fuel. I went the S3 route to get squish corrected but it is the same as having your squish cut without reshaping the combustion chamber. I had a calculated compression ratio of 14:1 which made me run race fuel. I didn't mind because it is readily available and can be had for $6/gal. The extra compression also helped tremendously with low end but my over rev suffered quite a bit.


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[Jakobi]

Originally Posted by memphis2857

To answer your question about how to get squish corrected. You will measure your squish and then send it off to someone like Ron Black of RB designs. He does great work with a reasonable turn around time. He will mill the outer edge of the head down to lower the squish clearance. Then he will reshape the combustion chamber to compensate for the loss of volume. You can have a machine shop do this but they may or may not reshape the combustion chamber. If they don't it will in turn raise your compression ratio and you may end up having to run race fuel. I went the S3 route to get squish corrected but it is the same as having your squish cut without reshaping the combustion chamber. I had a calculated compression ratio of 14:1 which made me run race fuel. I didn't mind because it is readily available and can be had for $6/gal. The extra compression also helped tremendously with low end but my over rev suffered quite a bit.


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The 250 by design has a higher compression ratio than the 300, so simply reducing the squish through base gaskets or machining the mating surface will most likely reduce in too much compression.

A good machinist/2 stroke tuner will also match the angle of the squish band to the dome of the piston as well as reshaping the bowl to achieve a desired volume/compression ratio.

[Zman]

There is no significant problem with the top of the piston being above the bottom of the exhaust port at BDC because the piston spends so little time at that location and because the majority of the exhaust has already left the cylinder by that point in time.

That being said, I would not put in a thinner gasket if there is any perceptible ridge in the top of the cylinder as it will catch the ring at TDC because the thinner gasket will allow the piston to no go higher in the bore.

[barossi73]

Also wouldnt go thinner on base gasket if you dont know what your squish measurement is already.if a previous owner has already cut it...changing thickness has a small effect on port timing,but as you are changing compression also its hard to isolate the benefits.

[Jakobi]

Originally Posted by barossi73

Also wouldnt go thinner on base gasket if you dont know what your squish measurement is already.if a previous owner has already cut it...changing thickness has a small effect on port timing,but as you are changing compression also its hard to isolate the benefits.

Hard to isolate the benefits yes.. However reducing the squish, moving the port timing in that direction, and increasing compression all favour the scenario of getting more bottom end.

Unfortunately, they all come with trade-offs and the net result could be something along the lines of an engine that needs to run rich/high octane fuels to keep the pinging away under load.. as well as sacrificing your top end and over rev.

The ideal scenario is to set the ports where you want them for a decent spread of usable power. Leave some room to move in the squish clearance for any fine tuning of the base gasket stack in either direction (1.2-1.4mm is a good range to work with), and same for the volume/compression ratio. It does however involve the most work/cost compared to simply changing a gasket. IMO it provides the best outcome though and the savings in time and effort trying to get the bike to run well is well worth the coins.

[adriano.ro]

Originally Posted by Zman

To advance the timing, you do not need to take of the flywheel. The timing plate screws are easily accessible behind the flywheel cover.

If you don't hear detonation, advancing the timing a few degrees is not risky. I have done it on 8 different GG bikes from 125 to 300cc engines. If you hear detonation you retard the timing until it goes away.

In my ec 300 2009 is just impossible to touch some screw of ignition plate,flywheel cover up all screws.

[stian]

Originally Posted by adriano.ro

I need to take off the flywheel for timing adjusting?

The stator is behind the FW, so yes. Also, you have to take away the lock-plate that holds the stator screw for adjustment.