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

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.
 
Zman said:
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.
Click to expand...

What are the implications of doing this if it makes the edge of the piston higher than the exhaust port at BDC?
 
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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memphis2857 said:
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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Click to expand...

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.
 
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.
 
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.
 
barossi73 said:
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.
Click to expand...

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.
 
Zman said:
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.
Click to expand...

In my ec 300 2009 is just impossible to touch some screw of ignition plate,flywheel cover up all screws.
 
The stator plate has slotted screws for adjustment. They are located outside of the area covered by the flywheel. You have access to them after you take off the ignition cover you do not need to remove the flywheel.
 
My flywheel cover all screws,is like this from below. I saw some flywheels smaller that mine,in that case you can work at timing.
 

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adriano.ro said:
My flywheel cover all screws,is like this from below. I saw some flywheels smaller that mine,in that case you can work at timing.
Click to expand...

You have an aftermarket flywheel weight attached to your flywheel. That will need to be removed before you can perform the ignition timing adjustment.

Eric
 
I stand corrected. Yes it appears the larger 2k3 ignition prevents access to the screws. On the smaller ignitions you can get to them directly.
 
Didnt mean to imply the benefits werent there with base gasket,just that its hard to isolate the port effect as youre changing 2 things at once.i fully intend having my head cut next rebuild...but will leave base gaskets as they are(its a 200 so i dont want to lose too much top!)more interested in cleaner fueling,easier jetting from squish correction and am wary of the cylinder lip meeting the top ring (esp if ive just forked out for head machining,and new piston,that would suck)
Oops im in the wrong thread...
Nope,right thread,wrong page.too many open tabs
 
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95Jersey, I agree with most opinions on squish, I've had a couple 300's where you could drive a bus between the head and piston, 0.130 clearance, where as desired measurement would be more like 0.042-45. RB does great head work, I've also has a carb mod done by RB, good stuff, There is also the rm125 cdi box, not sure if those pertain to an 014 300, ignition curve in those boxes are way more aggressive, did that on an older 250 with head mod, OMG..
Measure your head to piston clearance and jet the bike correctly.
 
Suggest first you check if the PV is adjusted without slop, but the new ones are a little different to mine. If they aren't under control of the arm the valve will open too far with just pressure.

Then irrespective do the head mod. Worked wonders on my 200 and my 300. The compression gets way too high, on the 300 you have to remove quite a bit of metal. Search and read my head mod thread, well the first few pages, I get in a spin with a faulty coil later.

Oh yeah on my 200 I pulled the 2nd gasket. Still had enough top end zing for me. On the dyno after the mod timing was left at std position after some fiddling.
 
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