2011 GG 300 SD squish, comp, and jetting data

[gasgasman]

Some people say the higher compression will put unnecessary stress on the engine's bottom end.
I've never had any problems with my RB Design's head mod.

[Bikerdad450F]

now to bolt the head back on and re-check the squish, maybe now a .095 " piece of solder will actually squish down for a good reading. I chucked the head up in a 4 jaw and cut .053" (1.34 mm) off of the mating surface, then lightly chamfered the holes, if the measurements happen to come out OK tomorrow, then I'll take it to get hard anodized. wish me luck.

[Jakobi]

Originally Posted by Bikerdad450F

now to bolt the head back on and re-check the squish, maybe now a .095 " piece of solder will actually squish down for a good reading. I chucked the head up in a 4 jaw and cut .053" (1.34 mm) off of the mating surface, then lightly chamfered the holes, if the measurements happen to come out OK tomorrow, then I'll take it to get hard anodized. wish me luck.

Good luck! Most will say just shaving the head down will increase compression too far though.. Hope it works for you.

[GMP]

My 250s have been set up in the high 190s with no problems on pump gas. This is not a lot of compression that would cause a lower end problem, and the bike still revs out very well.

Remember with squish clearance its all about consistancy across the band. A tight, more narrow band will be more effective than a wide band thats tight only on the outside edge. FWIW, Ron just highly polishes the combustion chambers of his modified heads. This has proven fine by me, as after close to 100 hrs on two different bikes all that was needed to clean the head was a wipe with a solvent rag. Clean jetting and Amsoil Dominator oil. Anodizing by nature is a rougher surface, and not neccessary anyway.

[Bikerdad450F]

Originally Posted by Bikerdad450F

2.74 mm of squish ! and while I was at it I took a compression reading. 135 psi. This is with a brass adapter on the gauge, it is bored out inside so I've noticed that my readings are about 10 psi lower than they would be when I don't use the adapter. I suppose the extra volume inside the brass adapter is effectivly increasing the measured combustion chamber volume. I also measured my gasket stack under the cylinder, it is 3 gaskets; 2 green .5 mm, and 1 gray ? .25 mm . 1.25 mm total, and all this cylinder raising and the ports are still not exactly lined up with the piston at bdc. it is about .5 mm from being flush. I intend to leave the gasket stack in place and just machine the head to 1.4 mm squish.

cont... I bolted the head on this morning and squished some solder to 1.40 mm exactly. I removed the solder then did a cold compression test,(WOT, kill switch depressed, kick it till the gauge stops climbing) and got 175 psi, I'm happy with that so I'm going to get the head re-anodized, then move on to other areas like tuning the forks (they were at riders edge for re-valving, good price too.)

[Skidad]

Originally Posted by Bikerdad450F

cont... I bolted the head on this morning and squished some solder to 1.40 mm exactly. I removed the solder then did a cold compression test,(WOT, kill switch depressed, kick it till the gauge stops climbing) and got 175 psi, I'm happy with that so I'm going to get the head re-anodized, then move on to other areas like tuning the forks (they were at riders edge for re-valving, good price too.)

Oh crap that was a tease...hoping for a ride report

Gonna be like a different bike with the head mod and new suspension tweaks. Look forward to the next update.

[Bailey28]

Ummm ride report please!!

[Bikerdad450F]

No ride report till the forks come back, they are in transit. Perhaps monday or Tuesday June-27 or 28th. I am curious what other machining the DB mods include. As stated before. my 2009 EC300 had 2.74 mm of squish at the extreme outer edge of the piston, the measurement quickly tapers to a larger gap as you measure the squish band closer to the center. So if I read all of the info correctly, a minimum "squish band" to "piston top" clearance should be 1.2 mm and ideally between 1.2 and 1.6 mm. So all I did was go to the middle (Conservative, I thought) figure of 1.4mm squish. The bike pumps 175 psi cold now, up from 135 psi. I'm thinking that alone will do it for me, BUT the mystery to me is "what about thinning the I.D. of the squish band"? The engine would be losing compression as a result ofremoving some material from the combustion chamber and raising the CC figure. Wouldn't I be going backwards? Assuming that performance gains are to be had from having a narrow squish band, I assume I would have to re-machine the "gasket surfaces" as well as trim the band to size, in order to keep the 175 psi comp.
Is this sounding correct? I better do some web surfing on 2 stroke head mods. Has anyone heard about those slots that people are machining into there 4 stroke heads' squish zone?

[AZRickD]

You're good at 175. What altitude, btw?

Shoot some oil in the cylinder and your compression will go up (some say that is the proper way). I was 175 dry at 1,300 MSL here in Phoenix.

Ron reshapes the combustion chamber for various reasons including making the charge compress to the center. I wouldn't bother with it

[gasser]

Originally Posted by Bikerdad450F

As stated before. my 2009 EC300 had 2.74 mm of squish at the extreme outer edge of the piston, the measurement quickly tapers to a larger gap as you measure the squish band closer to the center. The mystery to me is "what about thinning the I.D. of the squish band"?

Ron (RBD) has done both a 250 and a 300 head for me and the squish came out the same across the squish band. Those heads, like yours, had a tapered squish before Ron recut them. I am very happy with Ron's work - better running and better gas mileage.