Base gasket 2011 EC300

[Quigs]

Just a quick question and have done a quick search.

I'm just about to do a top end in my 2011 EC300.

I have a new wossner piston ready to go in and have all new gaskets.

Now I know there are options to what base gaskets you can use.

The current one was a 0.5mm gasket.

I have a bought a Athena top end gasket set and just wondering what your opinions are on which base gasket I should use?

Bike runs well and have good torque but I don't know any different to be honest.

I ride a lot of slow stuff with big climbs most of the time and rarely get the chance to open it up.

[TheLetterJ]

I'm in the middle of the same dilemma. If you were happy with it's performance the way it was, I'd just run the single .5mm

Most references I find say that the ideal port timing (for peak HP) has the piston flush with the exhaust port when at bottom dead center. On my bike it would take in the neighborhood of 1.5mm of base gaskets to get it there. It is generally accepted that dropping your cylinder (thinner base gasket) will gain bottom end while sacrificing top end, while raising your cylinder (thicker gasket stack) will decrease bottom end and increase top end.

I'm personally going to throw the whole stack in (.95mm total) to gain a bit more top end (as compared to my previous .45mm... or was it .65mm? I'll have to check my notes), and have the head cut to regain compression and tighten up the squish. I'm hoping I'll end up with a little more power at both ends of the spectrum this way.

Clear as mud?

[motopsycho87]

I have 3x 0.5mm gaskets totalling 1.5mm runs lovely. Just make sure you adjust your squish and compression ratio to compensate. If you're not going to do this, you are better off getting the squish right and ignoring barrel height. Aim for 0.8 - 1.2mm.

[spooly]

Iv been through the hole base gasket debate and im still not happy..I started with .15 and worked up from that.. now im going to just level the exhaust port with piston BDC.. I did achieve more bottom and mid but it made it a pain to tune. . My two pence is if your a clubman rider like me level the exhaust port and if u want to achieve better squish cut the head.. if you want more snap buy a 250... if you're looking for a tighter squish you'll have to start using race fule.. easy option stick with what works..

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[motopsycho87]

If you want more bottom end, get a RM125 CDI, seriously! the bottom barks, and still revs nice and strong!

[spooly]

Originally Posted by motopsycho87

If you want more bottom end, get a RM125 CDI, seriously! the bottom barks, and still revs nice and strong!

That's one for the books!! Was it just plug and go or did u change jetting etc

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[Zman]

Or go with the GG 250 CDI, or just advance your ignition timing 2 to 3 mm.

If you are going to run a thinner gasket make sure you have no perceivable ridge in your cylinder.

[Jakobi]

As above, however I'll also add. Don't simply go dropping base gaskets to try and tighten the squish without correcting the volume. You'll run pushing compression too high and find the bike runs poorly or needs high octane race fuels.

[motopsycho87]

Originally Posted by spooly

That's one for the books!! Was it just plug and go or did u change jetting etc

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It's a straight swap. I'll do a video comparison once I'm moved. 125, 250 and 300 have quite different timing curves. There's a lot of information on CR500 AND 250 users swapping cdis about. Generally just advancing the stator plate causes a larger loss of high end rpm, with the 125 cdi you gain a hell of a lot of advance at low revs sacrificing a little retard at high. To gain the top end back you would retard the 125 cdi a couple degrees, still getting up to 10 degrees at low revs. I've had no pinging at all and it is FIERCE!

[Zman]

I agree with you assuming the bikes has correct compression for the fuel. Typical GG bikes have lower compression and as noted above most of them need to have the head milled to adjust squish and volume. I have added as much as 5mm of timing (measured at the base plate adjustment screws) for stock GG 250 and 300 bikes with uncut heads. While it does give a nice bump in low end performance it did not make a huge difference in high rpm. I suppose that could be because the GG port timing already is focused on low rpm operation or the older stock CDI units limited high rpm operation.

I fully agree you have to be aware of the detonation and retard the timing or increase octane rating to compensate. Also when you are on the edge of detonation jetting is very important. A richer air fuel mixture will run cooler.

I started another thread a week ago regarding the CDIs and my findings are similar to what you are saying and showing in your graph. The CDI curves make a bike difference in the overall power band. I also found when I used the 125 CDI on my 300 it made a huge difference, but I believe the low rpm timing of the 125 CDI plus my 3mm advanced initial timing was too much and it made the bike prone to stalling at low low rpm lugging up technical hills.

With the stock 2000 brick style CDI on my big bore xc300 (now 327) the bike had a very mellow power band and it would not rev as high as other 300s. With the 125 CDI it came on the pipe right off idle, had a big hit in the middle rpm and revved at least 1000 rpm higher than prior. Off idle I did detect a slight hint of detonation so I switched to a newer 300 CDI that had seemed to be a great compromise between the 125CDI and the original brick 2000 XC300 CDI. I later found I needed to put the initial timing back closer to stock with the newer 300 CDI to regain my very low rpm luggability.