05 ec200 squish, cc's, jetting

[Zrt1200]

Sense I am new to GG bikes and I have read probable 12 hours on various things to improve these bikes in this section of the forum it's now time for some questions and I hope you guys can help me out.

Lets start with squish gap. My 200 has a squish gap of 1.5 to 2.0mm and from checking the solider I would say the squish width is at 8.5mm.

From what I have read it should be in the 1.1 to 1.5mm range for pump gas fuel?? I use 90 octane on (R+ M)/2 octane rating

My cranking compression is 145 PSI after 5 kicks with the throttle at WOT. The top end was rebuilt and has approx 3 hours of riding on it.

I know our 99 YZ250 is at a 180PSI after 5 kicks and it runs just fine on our 90 octane.

Has any one CC'ed there 200 head after correcting the squish either Installed or Flat plated?? And what kind of cranking compression are you getting out of it??

I also just went through my carb to see what it has for jetting.

180 Main Jet
42 pilot jet, Air screw is set at 1.5 turns out
#7 slide cutaway
CCL needle in #4 clip

Thanks in advance.

 

[Zrt1200]

I just checked my base gasket and noticed I have a aluminum shim between gaskets. So I measured the thickness with a set of calipers and I have .060" or 1.5mm of base gaskets.

 

[(F5)]

Yes, I'll check my notes when I'm downstairs in a while. Pressure gauge is so unreliable when you get up in comp on a small engine that I won't use them. Should ideally get to say 0.9mm. But you will 100% have to cut some material out of the chamber to get ratio to a usable number. I measure on the bike, far more accurate. Can't flatplate due to stepped design anyway.

Do a search to my thread on doing my 300 head and read up. Helped my 200 a lot too.

 

[(F5)]

OK here we go. With squish reduced to 1mm it was 15:1. Too high. I cut it till it was 15.2cc on the bike level and up to 2nd plug thread from bottom. This was 14.1:1 and I was running on 1\2av gas 1\2 91. Hmm you may have to cut some more out for your gas. We run RON though.

 

[barossi73]

If he cuts head and corrects squish based on cc,wont his comp guage still read 145ish?relative to the yz at 180
Not denying the benefits of the squish mod just wondering wether its worth checking comp again or wether the bore could be the culprit (assuming the topend was piston/rings only).whats a normal comp reading for gasgas?iv never checked mine but id expect 160-180?

 

[Zrt1200]

Thanks F5. I will have my boy help get the bike's front lifted tonight and check CC volume. Before I checked this post I Googled GG200cc head volume and this came up. I have search for hours for a post like that on the search engine.

http://www.gasgasrider.org/forum/showthread.php?t=14052&page=4

Read Page 4 post #35 & #36.

And here is F5's thread he was talking about....

http://www.gasgasrider.org/forum/showthread.php?t=16560

 

[Zrt1200]

I little Update. I thought my squish was from 1.5 to 2.0mm but it turns out my solider was not thick enough. I had to go to 1/8" solider and the actually squish is .060 to .100" or 1.5mm to 2.5mm.

I then proceeded to check my installed CC volume with this large squish gap. The installed CC volume is 15.0 cc to the bottom of the plug hole.

Actual Squish width is 10.2mm's.

But what baffles me is why the piston dome is 6mm from the top of the cylinder?? Is it normal to have the piston 6mm below the top of the cylinder??

 

[Zrt1200]

A few more pics

 

[Zrt1200]

And a few more pics

 

[Rick]

I little Update. I thought my squish was from 1.5 to 2.0mm but it turns out my solider was not thick enough. I had to go to 1/8" solider and the actually squish is .060 to .100" or 1.5mm to 2.5mm.

I then proceeded to check my installed CC volume with this large squish gap. The installed CC volume is 15.0 cc to the bottom of the plug hole.

Actual Squish width is 10.2mm's.

But what baffles me is why the piston dome is 6mm from the top of the cylinder?? Is it normal to have the piston 6mm below the top of the cylinder??

If I read correctly you mentioned a small spacer / extra thick gasket was between the case and cylinder base??? I would imagine some was tinkering with port timing......

 

[(F5)]

The head dome fitting down into the cylinder centralises it quite nicely without having to use dowels. Also it removes the sealing surfaces and o-rings away from the edge a traditional head interfaces with the cylinder. None of which is possible when you had to account for rebores. Took a while to move away from the old constraints.

I measure two threads up from bottom of plughole as it accounts for the inside of the plug. Think it was .1 or .2 of a cc. I'd checked it but that was over 20yrs ago.

 

[Zrt1200]

The head dome fitting down into the cylinder centralises it quite nicely without having to use dowels. Also it removes the sealing surfaces and o-rings away from the edge a traditional head interfaces with the cylinder. None of which is possible when you had to account for rebores. Took a while to move away from the old constraints.

I measure two threads up from bottom of plughole as it accounts for the inside of the plug. Think it was .1 or .2 of a cc. I'd checked it but that was over 20yrs ago.

I know what you are saying but 6mm seems excessive. You could do it with easy with 2mm.

 

[Zrt1200]

The head is all done. Squish is set at 1.14mm / .045" with a installed CC of 16.8cc. Compression Ratio is 12.87 to 1. That should be good for 91 octane may be a touch less.

I will give a ride report after I get it back together and it quits raining.

 

[Zrt1200]

I got it back together tonight and ran it around. Wow what a difference. The bike now idles as its should and it comes up on the pipe a Lot Faster than is did before. It's night and day difference. There was no Detro at all so all's good on 91 octane fuel.

My cranking compression did lower by 16lbs down to 129PSI which I figured it would when I add'ed 1.8cc volume.

I am going to have to pull the cylinder off as I noticed the cylinder walls has some good size scratchs and I could tell a big difference in kicking the bike when there was still a little grease on the rings vs only 15 minutes of riding. I had a buddy run the numbers through his program and he said it should be around 150psi - 155psi cranking compression so I am loosing some power. I will get it fixed but in the mean time I have a few other things to do to it.

 

[Zrt1200]

Just wanted to give a Update. I just tried some 89 Octane R+M/2 and I get a very slight detro ping lugging the engine at a real low RPM and or in deep sand at lower RPM's. I have the timing set to stock so I hope this helps the next person out.